Dehydrogenation apparatus and steel sheet manufacturing system and steel sheet manufacturing method

Abstract

The present invention provides a hydrogen removal device for a steel sheet, a manufacturing system for a steel sheet, and a manufacturing method for a steel sheet, which can produce a steel sheet having excellent hydrogen embrittlement resistance without changing the mechanical properties of the steel sheet. The hydrogen removal device includes a housing portion that houses a steel sheet coil in which a steel strip is wound in a roll shape, and a vibration application device that applies vibration to the steel sheet coil housed in the housing portion in such a manner that the frequency of the vibration of the steel sheet coil is 100 to 100,000 Hz and the maximum amplitude of the steel sheet coil is 10 nm to 500 μm.

Description

Technical Field

[0001] This invention relates to a dehydrogenation apparatus and a steel sheet manufacturing system for producing steel sheets suitable for use in industries such as automobiles, home appliances, and building materials. In particular, this invention relates to a dehydrogenation apparatus, a steel sheet manufacturing system, and a method for producing steel sheets with excellent resistance to hydrogen embrittlement due to low intrinsic diffusible hydrogen content. Background Technology

[0002] A particular concern with high-strength steel sheets is hydrogen embrittlement, caused by hydrogen intrusion into the steel. When annealing steel sheets using continuous annealing or continuous hot-dip galvanizing equipment, a mixture of H₂ and N₂ gases, often used as reducing or non-oxidizing gases, is introduced into the annealing furnace. Hydrogen from this H₂-N₂ mixture can intrude into the steel during annealing. Additionally, in automotive steel sheets, hydrogen is generated by corrosion reactions occurring in the automotive operating environment and intrudes into the steel. If the diffusible hydrogen intrusion into the steel is not sufficiently reduced, hydrogen embrittlement can occur, potentially leading to delayed fracture.

[0003] Various methods for reducing the amount of diffusible hydrogen in steel have been studied previously. For example, Patent Document 1 discloses a method to reduce the amount of hydrogen trapped in steel by performing an aging treatment after annealing and elongation rolling. Another method for reducing diffusible hydrogen is to leave annealed steel sheets at room temperature for an extended period to allow the diffusible hydrogen to detach from the steel sheet surface. Patent Document 2 discloses a method to reduce the amount of diffusible hydrogen in steel by holding cold-rolled and annealed steel sheets in a temperature range of 50°C to 300°C for 1800s to 3200s.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6562180

[0007] Patent Document 2: International Publication No. 2019 / 188642 Summary of the Invention

[0008] However, the methods described in Patent Documents 1 and 2 can cause changes in microstructure by maintaining the heat after annealing, making it difficult to apply the methods to other steel plates. Furthermore, the method of placing the steel plate at room temperature requires long-term placement, resulting in low productivity.

[0009] The present invention was made in view of the above circumstances, and its object is to provide a dehydrogenation device for steel plates, a steel plate manufacturing system, and a steel plate manufacturing method that can manufacture steel plates with excellent resistance to hydrogen embrittlement without changing the mechanical properties of the steel plates.

[0010] To achieve the aforementioned goal, the inventors conducted repeated and in-depth research, discovering that by applying vibrations at a specified frequency and maximum amplitude to the steel plate, the amount of diffusible hydrogen in the steel can be reduced, thus suppressing hydrogen embrittlement. Specifically, it is known that by subjecting the steel plate to micro-vibration at a high frequency and a small maximum amplitude, the amount of hydrogen in the steel plate can be sufficiently and effectively reduced. This is presumably due to the following mechanism: By forcing the steel plate to undergo micro-vibration, repeated bending deformation is applied to the steel plate. As a result, the lattice spacing on the surface expands compared to the thickness of the center of the steel plate. Hydrogen in the steel plate diffuses towards the steel plate surface, where the potential energy is lower, due to the wider lattice spacing, and escapes from the surface.

[0011] This invention is based on the above-mentioned insights. Specifically, the essence of this invention is as follows.

[0012] [1] A dehydrogenation unit having:

[0013] The containment section contains steel sheet coils that are wound from steel strips, and...

[0014] The vibration attachment device applies vibration to the steel sheet coil housed in the aforementioned housing portion in such a manner that the vibration frequency of the steel sheet coil is 100 to 100,000 Hz and the maximum amplitude of the steel sheet coil is 10 nm to 500 μm.

[0015] [2] According to the dehydrogenation device described in [1] above, the vibration auxiliary device is configured to have an electromagnet having a magnetic pole surface that is separated from and opposite to the surface of the steel sheet coil, and the steel sheet coil vibrates by an external force applied to the steel sheet coil by the electromagnet.

[0016] [3] According to the dehydrogenation device described in [1] above, the vibration auxiliary device is configured to have an oscillator that contacts the steel plate coil, and the steel plate coil vibrates by the oscillator.

[0017] [4] The dehydrogenation apparatus according to any one of [1] to [3] above, wherein it further comprises a heating section for applying the vibration while heating the steel plate coil.

[0018] [5] A dehydrogenation device, comprising:

[0019] Unwinding device for unwinding steel strip from steel sheet coils

[0020] A plate-passing device for passing the aforementioned steel strip through a plate.

[0021] A winding device for winding the aforementioned steel strip, and

[0022] A vibration amplification device that adds vibration to the steel strip in the aforementioned through-plate device in such a way that the vibration frequency of the steel strip is 100 to 100,000 Hz and the maximum amplitude of the steel strip is 10 nm to 500 μm.

[0023] [6] According to the dehydrogenation apparatus described in [5] above, the vibration auxiliary device is configured to have an electromagnet having a magnetic pole surface that is separated from and opposite to the surface of the steel strip in the through plate, and the steel strip vibrates by an external force applied to the steel strip by the electromagnet.

[0024] [7] According to the dehydrogenation apparatus described in [5] above, the vibration auxiliary device is configured to have an oscillator that contacts the steel strip in the through plate, and the steel strip vibrates through the oscillator.

[0025] [8] The dehydrogenation apparatus according to any one of [5] to [7] above, wherein it further comprises a heating section for applying the vibration while heating the steel strip.

[0026] [9] The dehydrogenation apparatus according to any one of [1] to [8] above, wherein it further comprises a vibration damping part to prevent the above vibration from being transmitted to the outside of the dehydrogenation apparatus.

[0027]

[10] A steel plate manufacturing system, comprising:

[0028] Hot rolling mills are used to hot roll steel billets to produce hot-rolled steel plates.

[0029] A hot-rolled steel sheet winding device winds the aforementioned hot-rolled steel sheet to obtain hot-rolled coils, and

[0030] The dehydrogenation apparatus described in any one of [1] to [9] above processes the hot-rolled coil into the steel plate coil.

[0031]

[11] A steel plate manufacturing system, comprising:

[0032] A cold rolling mill is used to cold roll hot-rolled steel sheets to produce cold-rolled steel sheets.

[0033] A cold-rolled steel sheet winding device winds the aforementioned cold-rolled steel sheet to obtain cold-rolled coils, and

[0034] The dehydrogenation apparatus described in any one of [1] to [9] above processes the above-mentioned cold-rolled coil into the above-mentioned steel sheet coil.

[0035]

[12] A steel plate manufacturing system, comprising:

[0036] A batch annealing furnace is used to anneal cold-rolled or hot-rolled coils in batches to obtain annealed coils.

[0037] The dehydrogenation apparatus described in any one of [1] to [9] above forms the annealed coil into the steel plate coil.

[0038]

[13] A steel plate manufacturing system, comprising:

[0039] The uncoiling device before annealing unwinds cold-rolled steel sheets or hot-rolled steel sheets from cold-rolled coils or hot-rolled coils, respectively.

[0040] A continuous annealing furnace is used to continuously anneal the above-mentioned cold-rolled or hot-rolled steel sheets to produce annealed steel sheets.

[0041] Annealed steel sheet winding apparatus, which winds the aforementioned annealed steel sheet to obtain annealed coil material, and

[0042] The dehydrogenation apparatus described in any one of [1] to [9] above forms the annealed coil into the steel plate coil.

[0043]

[14] A steel plate manufacturing system, comprising:

[0044] A coating apparatus forms a coating film on the surface of hot-rolled or cold-rolled steel sheets to produce coated steel sheets.

[0045] A coated steel sheet winding device winds the aforementioned coated steel sheet to obtain coated steel sheet coils.

[0046] The dehydrogenation apparatus described in any one of [1] to [9] above is used to produce the above-mentioned coated steel sheet coil.

[0047]

[15] The steel plate manufacturing system according to

[14] above, wherein the plating device is a hot-dip galvanizing device.

[0048]

[16] The steel plate manufacturing system according to

[14] above, wherein the plating apparatus includes a hot-dip galvanizing apparatus and an alloying furnace thereafter.

[0049]

[17] The steel plate manufacturing system according to

[14] above, wherein the plating device is an electroplating device.

[0050]

[18] A method for manufacturing a steel plate includes the following vibration addition step: a steel plate coil in which a steel strip is wound into a coil is subjected to vibration in a manner in which the vibration frequency of the steel plate coil is 100 to 100,000 Hz and the maximum amplitude of the steel plate coil is 10 nm to 500 μm, thereby producing a product coil.

[0051]

[19] In the steel plate manufacturing method described in

[18] above, the above-mentioned vibration additional process is carried out by keeping the steel plate coil at 300°C or below.

[0052]

[20] A method for manufacturing a steel plate, comprising:

[0053] From the process of unwinding steel sheet coils into steel strips,

[0054] The process of passing the above-mentioned steel strip through the plate, and

[0055] The process of winding the aforementioned steel strip to form a product coil.

[0056] The above-mentioned through-plate process includes the following additional vibration process: the steel strip is subjected to additional vibration with a vibration frequency of 100 to 100,000 Hz and a maximum amplitude of 10 nm to 500 μm.

[0057]

[21] In the steel plate manufacturing method described in

[20] above, the above-mentioned vibration additional process is carried out by keeping the steel strip at a temperature below 300°C.

[0058]

[22] The method for manufacturing a steel plate according to any one of

[18] to

[21] above includes a step of hot rolling a steel billet to produce a hot-rolled steel plate and a step of winding the hot-rolled steel plate to obtain a hot-rolled coil, and then making the hot-rolled coil into the steel plate coil.

[0059]

[23] The method for manufacturing a steel plate according to any one of

[18] to

[21] above includes a step of cold rolling a hot-rolled steel plate to produce a cold-rolled steel plate and a step of winding the cold-rolled steel plate to obtain a cold-rolled coil, and then making the cold-rolled coil into the steel plate coil.

[0060]

[24] The method for manufacturing steel plate according to any one of

[18] to

[21] above includes a step of performing batch annealing on cold-rolled coil or hot-rolled coil to obtain annealed coil, and then making the annealed coil into the steel plate coil.

[0061]

[25] The method for manufacturing a steel plate according to any one of

[18] to

[21] above includes the steps of unwinding a cold-rolled steel plate or a hot-rolled steel plate from a cold-rolled coil or a hot-rolled coil, the steps of continuously annealing the cold-rolled steel plate or the hot-rolled steel plate to obtain an annealed steel plate, and the steps of winding the annealed steel plate to obtain an annealed coil, and then making the annealed coil into the steel plate coil.

[0062]

[26] The method for manufacturing steel plate according to any one of

[18] to

[21] above includes a plating process in which a plating film is formed on the surface of a hot-rolled steel plate or a cold-rolled steel plate to produce a plating steel plate and a process in which the plating steel plate is rolled to obtain a plating steel plate coil, and then the plating steel plate coil is made into the steel plate coil.

[0063]

[27] In the steel plate manufacturing method described in

[26] above, the above-mentioned plating process includes a hot-dip galvanizing process.

[0064]

[28] According to the steel plate manufacturing method described in

[26] above, the above-mentioned plating process includes a hot-dip galvanizing process and a subsequent alloying process.

[0065]

[29] In the steel plate manufacturing method described above

[26] , the plating process includes an electroplating process.

[0066]

[30] The method for manufacturing steel plate according to any one of

[18] to

[29] above, wherein the product coil is composed of a high-strength steel plate having a tensile strength of 590 MPa or more.

[0067]

[31] The method for manufacturing the steel plate according to any one of

[18] to

[30] above, wherein the above-mentioned product coil comprises a base steel plate having the following composition, wherein the composition, in mass %, contains C: 0.030% to 0.800%, Si: 0.01% to 3.00%, Mn: 0.01% to 10.00%, P: 0.001% to 0.100%, S: 0.0001% to 0.0200%, N: 0.0005% to 0.0100% and Al: less than 2.000%, with the remainder consisting of Fe and unavoidable impurities.

[0068]

[32] According to the steel plate manufacturing method described in

[31] above, wherein the above-mentioned composition further contains, by mass %, at least one element selected from Ti: 0.200% or less, Nb: 0.200% or less, V: 0.500% or less, W: 0.500% or less, B: 0.0050% or less, Ni: 1.000% or less, Cr: 1.000% or less, Mo: 1.000% or less, Cu: 1.000% or less, Sn: 0.200% or less, Sb: 0.200% or less, Ta: 0.100% or less, Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.0050% or less, and REM: 0.0050% or less.

[0069]

[33] The method for manufacturing the steel plate according to any one of

[18] to

[30] above, wherein the above-mentioned product coil comprises a stainless steel plate having the following composition, wherein the composition, in mass %, contains C: 0.001% to 0.400%, Si: 0.01% to 2.00%, Mn: 0.01% to 5.00%, P: 0.001% to 0.100%, S: 0.0001% to 0.0200%, Cr: 9.0% to 28.0%, Ni: 0.01% to 40.0%, N: 0.0005% to 0.500%, and Al: less than 3.000%, with the remainder consisting of Fe and unavoidable impurities.

[0070]

[34] According to the steel plate manufacturing method described above

[33] , wherein the above composition further contains, by mass %, at least one element selected from Ti: 0.500% or less, Nb: 0.500% or less, V: 0.500% or less, W: 2.000% or less, B: 0.0050% or less, Mo: 2.000% or less, Cu: 3.000% or less, Sn: 0.500% or less, Sb: 0.200% or less, Ta: 0.100% or less, Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.0050% or less, and REM: 0.0050% or less.

[0071]

[35] The method for manufacturing steel plate according to any one of

[18] to

[34] above, wherein the above-mentioned product coil has a diffusible hydrogen content of 0.50 ppm by mass or less.

[0072] According to the present invention, it is possible to manufacture steel plates with excellent resistance to hydrogen embrittlement without altering the mechanical properties of the steel plate. Attached Figure Description

[0073] Figure 1 This is a diagram illustrating an example of the configuration of a vibration attachment.

[0074] Figure 2 (A) and (B) are schematic diagrams illustrating examples of the arrangement of the electromagnet 63 of the vibration attachment 60 relative to the steel sheet coil C in various embodiments of the present invention.

[0075] Figure 3 (A) and (B) are schematic diagrams illustrating how a magnetic field is generated from an electromagnet 63 in various embodiments of the present invention.

[0076] Figure 4 This is a schematic diagram illustrating another example of the configuration of a vibration attachment.

[0077] Figure 5These are schematic diagrams used to illustrate an example of the configuration of the dehydrogenation apparatus equipped with the vibration auxiliary device 60 in Embodiment 1. (A) is a perspective view of the dehydrogenation apparatus, (B) is a view of the dehydrogenation apparatus taken from side a, (C) is an example of a view of the dehydrogenation apparatus taken from side b, and (D) is another example of a view of the dehydrogenation apparatus taken from side b.

[0078] Figure 6 This is a schematic diagram illustrating an example of the configuration of a dehydrogenation apparatus equipped with a vibration auxiliary device 70 according to Embodiment 1.

[0079] Figure 7 This is a diagram showing an example of the configuration of the dehydrogenation device equipped with the vibration auxiliary device 60 in Embodiment 2, viewed from the winding axis of the steel sheet coil.

[0080] Figure 8 This is a diagram showing an example of the configuration of the dehydrogenation device equipped with the vibration auxiliary device 70 in Embodiment 2, viewed from the winding axis of the steel sheet coil. Detailed Implementation

[0081] The embodiments of the present invention will be described below. The present invention is not limited to the following embodiments. In this specification, the numerical range indicated by “~” represents the range of values ​​described before and after “~” as a lower limit and an upper limit. In this specification, “steel plate” is a general term including hot-rolled steel plate, cold-rolled steel plate, annealed steel plate obtained by further annealing them, and coated steel plate with a coating formed on their surface. The shape of “steel plate” is not limited and includes either steel plate coils or unwound steel strips.

[0082] This dehydrogenation device applies vibrations at a specified frequency and maximum amplitude to the steel plate to reduce the amount of diffusible hydrogen in the steel. According to this dehydrogenation device, since there is no need to heat-treat the steel plate, the amount of diffusible hydrogen in the steel can be reduced without altering the microstructure of the steel plate.

[0083] Furthermore, in the manufacturing method of this steel plate, vibration is applied to the steel plate with a vibration frequency of 100 to 100,000 Hz and a maximum amplitude of 10 nm to 500 μm. According to this manufacturing method, since there is no need to heat-treat the steel plate, the amount of diffusible hydrogen in the steel can be reduced without changing the microstructure of the steel plate.

[0084] The reason why the resistance of steel plates to hydrogen embrittlement can be improved by adding vibration to the steel plates is not yet clear, but the inventors speculate as follows.

[0085] That is, the steel plate is subjected to forced vibration under specified conditions. Due to the bending deformation caused by this forced vibration, the lattice spacing of the steel plate repeatedly expands (stretches) and contracts (compresses) in the thickness direction. Diffusible hydrogen in the steel is induced to diffuse towards the lower potential energy of the tensile side. Therefore, with the expansion and contraction of this lattice spacing, the diffusion of diffusible hydrogen is promoted, forcibly creating a diffusion path for diffusible hydrogen connecting the interior and surface of the steel plate. When the lattice spacing near the surface of the steel plate expands due to the forced diffusion path, diffusible hydrogen is less likely to escape further through the surface to the exterior of the steel plate, where the potential energy is more favorable. It is speculated that this forced vibration of the steel plate under specified conditions sufficiently and effectively reduces the diffusible hydrogen in the steel, thus effectively and easily suppressing hydrogen embrittlement of the steel plate.

[0086] The following will be divided into (1) a dehydrogenation device that applies vibration to steel sheet coils and a method for manufacturing steel sheets, and (2) a dehydrogenation device that applies vibration to unwound steel sheets while unwinding and rewinding them, and a method for manufacturing steel sheets.

[0087] <Implementation Method 1>

[0088] The dehydrogenation apparatus of this embodiment is a dehydrogenation apparatus having a housing section for housing a steel sheet coil C formed by winding a steel strip, and a vibration addition device for adding vibration to the steel sheet coil housed in the housing section at a vibration frequency of 100 to 100,000 Hz and a maximum amplitude of 10 nm to 500 μm. In various processes of steel sheet manufacturing, steel strip is wound into a steel sheet coil.

[0089] Furthermore, the steel sheet manufacturing method of this embodiment includes the following vibration additional step: vibration is applied to the steel sheet coil in which the steel strip is wound into a coil, with a vibration frequency of 100 to 100,000 Hz and a maximum amplitude of 10 nm to 500 μm. In various steps of steel sheet manufacturing, the steel strip is wound into a steel sheet coil.

[0090] In the dehydrogenation apparatus and steel sheet manufacturing method of this embodiment, by applying vibration to the steel sheet coil, the amount of diffusible hydrogen in the steel can be reduced, resulting in a steel sheet with excellent resistance to hydrogen embrittlement. It is believed that, particularly in the steel sheet coil, when bending deformation is applied to the steel strip, the lattice spacing on the radially outer surface of the steel strip expands, thus easily forming hydrogen diffusion paths towards the radially outer side. In this embodiment, by applying vibration to the steel sheet coil, since a slight bending deformation is further applied to the steel strip, which is already in a state of expanded lattice spacing on the radially outer surface, diffusible hydrogen in the steel can be reduced even more effectively.

[0091] [Vibration Addition Device]

[0092] (Vibration attachment 60)

[0093] Vibration can be added using a vibration attachment device. In one example, the vibration attachment device can be configured to cause the steel sheet coil to vibrate by an external force (gravity) applied to the steel sheet coil by an electromagnet. Figure 1 An example of the configuration of a vibration attachment device is shown. In one example, the vibration attachment device 60 includes a controller 61, an amplifier 62, an electromagnet 63, a vibration detector 64, and a power supply 65. Figure 3 As shown in (A) and (B), in one example, the vibration attachment 60 has an electromagnet 63 comprising a magnet 63A and a coil 63B wound around the magnet 63A. The electromagnet 63 has magnetic pole faces 63A1 that are separated from and opposite to the surface of the steel coil. It should be noted that "the surface of the steel coil" here refers to the surface of the steel plate located at the outermost periphery in the radial direction of the steel coil C.

[0094] The electromagnet 63 has a magnetic pole surface 63A1 that is separated from and opposite to the surface of the steel sheet coil C. Preferably, the electromagnet 63 has a magnetic pole surface 63A1 that is separated from and opposite to the surface of the steel sheet coil C in a manner that is radially perpendicular to the steel sheet coil C. Thus, as... Figure 3 As shown in (A) and (B), the magnetic field lines are directed along the radial direction of the steel sheet coil C, enabling an attractive force to act on the steel sheet coil C. Examples of the shape and arrangement of the electromagnet include... Figure 2 (A) (B).

[0095] Figure 2 In (A), cubical electromagnets 63 are spaced apart at predetermined intervals on the surface of the steel coil C, extending along the width direction of the steel plate. This allows for the uniform application of an external force (attraction) along the width direction of the steel coil C, achieving uniform vibration in that direction. Furthermore, by arranging multiple such electromagnets 63 along the through-plate direction, sufficient time for applying vibration to the steel coil C can be ensured. Figure 2 As shown in (A), the electromagnet 63 has a magnet 63A and a coil 63B wound around it, the axial direction of the coil 63B being aligned with the thickness direction of the cold-rolled steel sheet S. In this case, depending on the direction of the current flowing through the coil 63B, as... Figure 3 As shown in (A), the magnetic pole face 63A1 opposite to the steel sheet coil C becomes the N pole, or as... Figure 3 As shown in (B), the magnetic pole face 63A1 opposite to the steel sheet coil C becomes the S pole.

[0096] Figure 2In (B), multiple cylindrical electromagnets 63 are arranged at predetermined intervals along the width direction of the steel sheet, with their bottom magnetic pole surfaces separated from the surface of the steel sheet coil C and facing each other. This allows for the uniform application of an external force (attraction) along the width direction of the surface of the steel sheet coil C, achieving uniform vibration in the width direction. Furthermore, by arranging a row of multiple such cylindrical electromagnets 63 along the through-plate direction, sufficient time for applying vibration to the steel sheet coil C can be ensured. Figure 2 As shown in (B), each electromagnet 63 has a cylindrical magnet and a coil wound around it, the axis of which is aligned with the thickness direction of the steel sheet coil C. In this case, depending on the direction of the current flowing through the coil, as... Figure 3 As shown in (A), the magnetic pole face 63A1 opposite to the steel sheet coil C becomes the N pole, or as... Figure 3 As shown in (B), the magnetic pole face 63A1 opposite to the steel sheet coil C becomes the S pole.

[0097] To uniformly apply vibration to the entire surface of the steel sheet coil C, it is preferable to arrange a plurality of electromagnets 63 at uniform intervals along the circumference of the steel sheet coil C. In one example, a plurality of electromagnets 63 may be arranged at intervals of 1° to 30° between each other at the central corner of the steel sheet coil C along the circumference of the steel sheet coil C.

[0098] exist Figure 3 (A) and Figure 3 In case (B), by allowing current to flow through the electromagnet 63, an external force (attraction) acts on the surface of the steel coil C. The current flowing through the electromagnet 63 is either a DC pulsed current or an AC continuous current. When a DC pulsed current flows through the electromagnet 63, the steel coil C vibrates due to the intermittent attraction acting on the cold-rolled steel sheet S. When an AC continuous current flows through the electromagnet 63, the magnetic pole face 63A1 opposite to the steel coil C switches between the N and S poles each time the current direction changes, but the external force (attraction) always acts on the steel coil. In the case of AC, the magnitude of the external force (attraction) acting on the steel coil also changes according to the time-varying current value, thus causing the steel coil C to vibrate.

[0099] Figure 1The vibration detector 64 shown is a laser displacement meter or laser Doppler vibrometer positioned at a predetermined interval from the surface of the steel sheet coil C, capable of measuring the frequency and amplitude of vibrations on the surface of the steel sheet coil C. By positioning the vibration detector 64 at the same height as the electromagnet 63 within the steel sheet coil, the maximum amplitude of vibrations in the steel sheet coil C can be measured using the vibration detector 64. The frequency and maximum amplitude detected by the vibration detector 64 are output to the controller 61. The controller 61 receives the frequency and maximum amplitude values ​​output from the vibration detector 64, compares them with set values, performs PID calculations on the deviations, etc., to determine the frequency (frequency of a DC pulse current or the frequency of an AC continuous current) and current value of the electromagnet 63 in a manner that causes the cold-rolled steel sheet S to vibrate at a predetermined frequency and maximum amplitude. Additionally, considering the amplification of the amplifier 62, it determines the current value applied to the amplifier 62 and provides a command value to the power supply 65. The power supply 65 is a power source for the coil through which current flows through the electromagnet 63, receives the command value input from the controller 61, and provides a current with a predetermined frequency and current value to the amplifier 62. Amplifier 62 amplifies the current value supplied from power supply 65 at a specified amplification rate, providing a command value to electromagnet 63. As a result, a current with a specified frequency and current value flows through electromagnet 63, enabling the steel sheet coil C to vibrate at a specified frequency and maximum amplitude.

[0100] (Vibration attachment 70)

[0101] In another example, the vibration attachment is configured to have an oscillator 72 in contact with the surface of the steel sheet coil C, through which the steel sheet coil C vibrates. Figure 4 Figure A shows another example of the configuration of a vibration-assisted device. (See reference...) Figure 4 A. The vibration attachment 70 includes a controller 71, an oscillator 72, and a vibration detector 73. The vibration attachment 70 is configured to have an oscillator 72 that contacts the steel sheet coil C, through which the steel sheet coil C vibrates.

[0102] The oscillator 72 is not particularly limited as long as it is a general piezoelectric element, and its shape and arrangement are not limited, but for example... Figure 4 As shown in Figure B, the steel coil C can be vibrated by making a flat, plate-shaped vibrator 72, with its long side along the width direction of the steel coil C, into surface contact with the surface of the steel coil C. To uniformly apply vibration to the entire surface of the steel coil C, it is preferable to arrange a plurality of vibrators 72 at uniform intervals along the circumference of the steel coil C. In one example, a plurality of vibrators 72 can be arranged at intervals of 1° to 30° between each other at the central corner of the steel coil C along the circumference of the steel coil C.

[0103] Figure 4The vibration detector 73 shown in Figure A is a laser displacement meter or laser Doppler vibrometer arranged at predetermined intervals on the surface of the steel sheet coil C, capable of measuring the frequency and amplitude of the vibration of the steel sheet coil C. By arranging the vibration detector 73 at the same height as the oscillator 72 of the steel sheet coil C, the maximum amplitude of the vibration of the steel sheet coil C can be measured using the vibration detector 73. The frequency and maximum amplitude detected by the vibration detector 73 are output to the controller 71. The controller 71 receives the frequency and maximum amplitude values ​​output from the vibration detector 73, compares them with set values, performs ID calculations on the deviations, etc., to determine the frequency and current value of the DC pulse current flowing through the oscillator 72 in a manner that causes the steel sheet coil C to vibrate at a predetermined frequency and maximum amplitude, controls a power supply (not shown) to provide a DC pulse current of the predetermined frequency and current value to the oscillator 72, and thus, the oscillator 72 vibrates at a predetermined frequency and amplitude, thereby enabling the steel sheet coil C to vibrate at a predetermined frequency and maximum amplitude.

[0104] [Dehydrogenation unit]

[0105] Figure 5 An example of a dehydrogenation device is shown in the figure for reducing diffusible hydrogen in steel by applying vibration to steel sheet coil C through vibration attachment device 60. Figure 5 (A) is a perspective view of the dehydrogenation unit 300a. It should be noted that... Figure 5 (A) only shows the few rows of electromagnets 63 closest to the front, as seen from side a of the dehydrogenation unit 300a. Figure 5 (B) is a diagram showing the dehydrogenation unit 300a viewed from side a. (See diagram for example.) Figure 5 (A) and Figure 5 As shown in (B), the dehydrogenation apparatus 300a includes a receiving section 80 for accommodating steel sheet coil C, and an electromagnet 63 for applying additional vibration to the steel sheet coil C housed in the receiving section 80. The number and arrangement of the electromagnets 63 are not particularly limited. Figure 2 In this example, multiple electromagnets 63 are arranged to surround the steel sheet coil C. It should be noted that, although... Figure 5 (A) to (D) are not shown, but each electromagnet 63 is connected to an amplifier 62, a power supply 65, and a controller 61. A vibration detector 64 is further connected to the controller 61, and the electromagnets 63 apply additional vibration to the steel sheet coil C. By arranging multiple electromagnets 63 around the steel sheet coil C, it is possible to uniformly apply vibration to the steel sheet coil C. It is assumed that... Figure 5(A) In the case where the electromagnet 63 is arranged to surround the steel sheet coil C as shown, the surface of the steel sheet coil C vibrates due to the electromagnet 63. It is assumed that in the steel sheet coil C where the surface vibrates, the vibration propagates towards the inner periphery of the coil via the air present between the steel sheets, or the vibration propagates directly from the outermost surface of the coil towards the inner periphery, ultimately reaching the innermost part of the coil. It should be noted that, as shown, the receiving section 80 can receive multiple steel sheet coils C.

[0106] From the viewpoint of uniformly applying vibration to the entire surface of the steel sheet coil C, it is preferable to arrange multiple electromagnets 63 along the height and width directions of the inner wall of the dehydrogenation device 300a in a manner that surrounds the steel sheet coil C. Figure 5 (C) shows a diagram of an example of a dehydrogenation unit viewed from the side (b). Figure 5 As shown in (C), the electromagnets 63 can be arranged at uniform intervals along the height and width directions of side b. Additionally, Figure 5 (D) shows another example of the dehydrogenation unit viewed from the side (b). The electromagnet 63 only needs to apply vibration to the steel sheet coil C, for example... Figure 5 As shown in (D), it can be a rectangular tube shape with a rectangular cross-section. In addition, an electromagnet 63 can be placed in the hollow part divided by the steel plate coil C to add vibration from the inside of the steel plate coil C.

[0107] It should be noted that since diffusible hydrogen is released from the end face of the steel coil C, the efficiency of reducing the amount of diffusible hydrogen in the central part of the steel coil in the width direction is considered to be lower compared to the end of the steel coil C in the width direction. Therefore, it is preferable that the electromagnet 63 is specifically provided near the central part of the steel coil C in the width direction.

[0108] It should be noted that, as shown in the figure, a coil holding section 90 is appropriately provided within the dehydrogenation device 300a. The shape of the coil holding section 90 is not particularly limited; when the steel coil C is placed with its winding axis parallel to the bottom plate of the dehydrogenation device 300a, such as... Figure 5 As shown in (A), the coil holding part 90 can be a pair of rod-shaped members that clamp the steel sheet coil C from both sides to prevent the steel sheet coil C from rolling within the dehydrogenation device 300a. Figure 5 As shown in (A), the coil holding part 90 can be a pair of rod-shaped members having a concave arc-shaped upper surface that follows the arc drawn along the outermost periphery of the steel coil C. Additionally, although not shown, the steel coil C can be placed in a manner where its axial direction is parallel to the base plate of the dehydrogenation device 300a.

[0109] From the viewpoint of uniformly applying vibration to the entire surface of the steel sheet coil C, it is preferable to arrange multiple electromagnets 63 along the height and width directions of the inner wall of the dehydrogenation device 300a in a manner that surrounds the steel sheet coil C. Figure 5 (C) shows a diagram of an example of a dehydrogenation unit viewed from the side (b). Figure 5 As shown in (C), the electromagnets 63 can be arranged at uniform intervals along the height and width directions of side b. Additionally, Figure 5 (D) shows another example of the dehydrogenation unit viewed from the side (b). The electromagnet 63 only needs to apply vibration to the steel sheet coil C, for example... Figure 5 As shown in (D), it can be a rectangular tube shape with a rectangular cross-section. In addition, an electromagnet 63 can be placed in the hollow part divided by the steel plate coil C to add vibration from the inside of the steel plate coil C.

[0110] It should be noted that since diffusible hydrogen is released from the end face of the steel coil C, the efficiency of reducing the amount of diffusible hydrogen in the central part of the steel coil in the width direction is considered to be lower compared to the end of the steel coil C in the width direction. Therefore, it is preferable that the electromagnet 63 is specifically provided near the central part of the steel coil C in the width direction.

[0111] It should be noted that, as shown in the figure, a coil holding section 90 is appropriately provided within the dehydrogenation device 300a. The shape of the coil holding section 90 is not particularly limited; when the steel sheet coil C is placed with its winding axis parallel to the bottom plate of the dehydrogenation device 300a, as shown in the figure... Figure 5 As shown in (A), the coil holding part 90 can be a pair of rod-shaped members that clamp the steel sheet coil C from both sides to prevent the steel sheet coil C from rolling within the dehydrogenation device 300a. Figure 5 As shown in (A), the coil holding part 90 can be a pair of rod-shaped members having a concave arc-shaped upper surface that follows the arc drawn along the outermost periphery of the steel coil C. Additionally, although not shown, the steel coil C can be placed in a manner where its axial direction is parallel to the base plate of the dehydrogenation device 300a.

[0112] Figure 6 An example of a dehydrogenation apparatus is shown for reducing diffusible hydrogen in steel by applying vibration to steel sheet coil C via vibration attachment device 70. Figure 6 This diagram is obtained by observing the dehydrogenation unit 300a from the end face of steel sheet coil C. (See diagram below.) Figure 6As shown, the dehydrogenation apparatus 300a includes a receiving section 80 for accommodating a steel sheet coil C, and an oscillator 72 for additionally vibrating the steel sheet coil C housed in the receiving section 80. The oscillator 72 contacts the steel sheet coil C and adds vibration to it. It should be noted that, although not shown, each vibration adding device 70 incorporates a controller 71 and a vibration detector 73 into each oscillator 72, and the oscillator 72 adds vibration to the steel sheet coil C. In the dehydrogenation apparatus 300a that adds vibration through the vibration adding devices 70, as... Figure 6 As shown, the oscillator 72 is arranged along the surface of the steel sheet coil C in a manner that the oscillator 72 is in surface contact with the surface of the steel sheet coil C within the housing 80. The manner in which the oscillator 72 is arranged along the surface of the steel sheet coil C within the dehydrogenation device 300a is not particularly limited. For example, a bracket can be provided within the housing 80 to cover the surface of the steel sheet coil C, and the oscillator 72 can be fixed to the bracket at certain intervals.

[0113] From the viewpoint of uniformly applying vibration to the entire surface of the steel sheet coil C, it is preferable to arrange the vibrators 72 at certain intervals along the width direction of the steel sheet coil C. Alternatively, as... Figure 4 As shown in (B), it is preferable to use an oscillator 72 that extends along the width direction of the steel sheet coil C.

[0114] It should be noted that since diffusible hydrogen is released from the end face of the steel coil C, the efficiency of reducing the amount of diffusible hydrogen in the central part of the steel coil in the width direction is considered to be lower compared to the end of the steel coil C in the width direction. Therefore, it is preferable that the oscillator 72 is specifically disposed near the central part of the steel coil C in the width direction.

[0115] It should be noted that, as shown in the figure, a roll material holding section 90 is appropriately provided within the dehydrogenation device 300a. Since the details of the roll material holding section 90 have already been described above, they are omitted here.

[0116] (frequency of vibration)

[0117] From the viewpoint of promoting hydrogen diffusion, it is important that the vibration frequency of the steel coil C is 100 Hz or higher. If the frequency is lower than 100 Hz, the effect of removing hydrogen contained in the cold-rolled steel sheet S cannot be achieved. From this viewpoint, the frequency is preferably 500 Hz or higher, and more preferably 1000 Hz or higher. It should be noted that the steel coil C vibrates unintentionally. However, in these vibrations, the vibration frequency of the steel coil C is as high as about 20 Hz, in which case the effect of removing hydrogen contained in the steel coil C cannot be achieved. On the other hand, if the frequency is too high, sufficient time for the lattice spacing to expand within the steel sheet cannot be ensured, and the effect of hydrogen removal still cannot be achieved. From this viewpoint, it is important that the frequency is 100,000 Hz or lower, preferably 80,000 Hz or lower, and more preferably 50,000 Hz or lower. The vibration frequency of the steel coil C can be adjusted by... Figure 1 Vibration detector 64 shown Figure 4 Vibration detector 73, shown in Figure A, was used for measurement. Additionally, the frequency of vibration of the steel sheet coil C was determined at... Figure 1 In the case of the vibration auxiliary device 60 shown, the frequency can be adjusted by controlling the frequency of the DC pulse current or the frequency of the AC continuous current. Figure 4 In the case of the vibration auxiliary device 70 shown in A and B, the vibration frequency of the oscillator 72 can be adjusted by controlling the vibration frequency of the oscillator 72.

[0118] (Maximum amplitude of vibration)

[0119] When the maximum amplitude of the steel coil C is less than 10 nm, the lattice spacing on the steel plate surface does not expand sufficiently, resulting in insufficient promotion of hydrogen diffusion, and therefore the effect of removing hydrogen contained in the steel coil C cannot be achieved. Therefore, it is important that the maximum amplitude of the steel coil C is 10 nm or more, preferably 100 nm or more, and more preferably 500 nm or more. Furthermore, when the maximum amplitude of the steel coil C exceeds 500 μm, the strain on the steel plate surface increases, resulting in plastic deformation and hydrogen capture, and therefore the effect of removing hydrogen contained in the steel coil C cannot be achieved. From this perspective, it is important that the maximum amplitude of the steel coil C is 500 μm or less, preferably 400 μm or less, and more preferably 300 μm or less. It should be noted that the steel coil C vibrates itself during its passage, or vibrates, for example, by receiving gas from the gas wiping device 32. However, in these vibrations, the maximum amplitude of the steel coil C is at least 0.5 mm, and therefore the effect of removing hydrogen contained in the steel coil C cannot be achieved. The maximum amplitude of steel sheet coil C can be achieved through Figure 1 Vibration detector 64 shown Figure 4 Vibration detector 73, shown in Figure A, was used for measurement. Additionally, the maximum amplitude of the steel sheet coil C was measured... Figure 1In the case of the vibration auxiliary device 60 shown, the vibration can be adjusted by controlling the amount of current flowing through the electromagnet 63. Figure 4 In the case of the vibration attachment 70 shown in A and B, the amplitude of the vibration of the oscillator 72 can be adjusted by controlling the vibration amplitude.

[0120] (Vibration with added time)

[0121] There is no particular limitation on the duration of additional vibration applied to the steel sheet coil C. In this embodiment, since the vibration is applied to the steel sheet coil after hot rolling or cold rolling, unlike the case where vibration is applied while the steel strip is passing through the plate, the vibration can be applied without being limited by the irradiation time. It is presumed that the longer the duration of additional vibration, the more diffusible hydrogen can be reduced; therefore, the duration of additional vibration is preferably 1 minute or more. The duration of additional vibration is more preferably 30 minutes or more, and even more preferably 60 minutes or more. On the other hand, from the viewpoint of productivity, the duration of additional vibration is preferably 30,000 minutes or less, more preferably 10,000 minutes or less, and even more preferably 1,000 minutes or less. The duration of additional vibration can be controlled, for example, by using a control unit to control the drive time of the vibration application device 60.

[0122] [Heating device]

[0123] [[Maintenance temperature for steel sheet / coil]]

[0124] The dehydrogenation apparatus 300a may further include a heating section for simultaneously heating and vibrating the steel coil C. The temperature of the steel coil C during the vibration application process is not particularly limited. This is because, according to this embodiment, diffusible hydrogen in the steel can be reduced even without heating the steel coil C. However, since the hydrogen diffusion rate can be further increased by applying vibration while heating the steel coil C using the heating section, the amount of diffusible hydrogen in the steel can be further reduced. Therefore, the temperature of the steel coil C during the applied vibration is preferably 30°C or higher, more preferably 50°C or higher, and even more preferably 100°C or higher. The upper limit of the temperature of the steel coil C during the vibration application process is not particularly limited, but from the viewpoint of appropriately preventing changes in the microstructure of the steel coil C, as described later, it is preferably 300°C or lower, except in cases where vibration is applied during batch annealing. It should be noted that, in this embodiment, the temperature of the steel coil C during the applied vibration is based on the temperature at the radial half-position of the steel coil. The temperature at the radial half-point of the steel sheet coil can be measured by directly clamping a thermocouple at the radial half-point of the steel sheet coil and measuring the temperature of the steel strip present at the radial half-point. Heating methods for the steel sheet coil C include, for example, installing a heater on one side wall of the housing section, or, more generally, introducing high-temperature air generated externally into the housing section 80 and circulating it within the housing section.

[0125] The dehydrogenation apparatus 300a of this embodiment may further have a vibration damping portion on the outside of the dehydrogenation apparatus 300a to prevent the transmission of the aforementioned vibrations. The vibration damping portion may be, for example, a vibration damping material provided in a manner that surrounds the inner wall of the receiving portion 80.

[0126] According to this embodiment, the diffusible hydrogen content of the product coil C obtained after vibration application can be reduced to 0.5 ppm by mass or less. By reducing the diffusible hydrogen content of the product coil C to 0.5 ppm by mass or less, hydrogen embrittlement of the steel sheet can be prevented. The diffusible hydrogen content in the steel after vibration application is preferably 0.3 ppm by mass or less, and more preferably 0.2 ppm by mass or less.

[0127] The diffusive hydrogen content of product coil C was determined as follows. A test piece with a length of 30 mm and a width of 5 mm was taken from the radial halfway point of the product coil. When the steel sheet was hot-dip galvanized or alloyed hot-dip galvanized, the hot-dip galvanized layer or alloyed hot-dip galvanized layer on the test piece was removed by grinding or alkali treatment. Then, the amount of hydrogen released from the test piece was determined using Thermal Desorption Spectrometry (TDS). Specifically, the temperature was continuously increased from room temperature to 300°C at a rate of 200°C / h, then cooled to room temperature, and the cumulative amount of hydrogen released from room temperature to 210°C was measured as the diffusive hydrogen content of product coil C.

[0128] The following provides a more detailed explanation of application examples of this embodiment.

[0129] Hot-rolled steel plate

[0130] The dehydrogenation apparatus 300a and the steel plate manufacturing method of this embodiment can be used to manufacture hot-rolled steel plates.

[0131] The steel sheet manufacturing system of this application example is a steel sheet manufacturing system comprising a hot rolling mill for hot rolling steel billets to produce hot-rolled steel sheets, a hot rolling coiling mill for winding the hot-rolled steel sheets to obtain hot-rolled coils, and a dehydrogenation unit for forming the hot-rolled coils into the steel sheet coil C. The hot rolling mill performs hot rolling, consisting of roughing and finishing rolling, on steel billets having a known composition to produce hot-rolled steel sheets. The hot rolling coiling mill winds the hot-rolled steel sheets to form hot-rolled coils. The dehydrogenation unit 300a applies vibration to the hot-rolled coils as steel sheet coil C under the aforementioned conditions. This additional vibration reduces the amount of diffusible hydrogen in the steel, resulting in hot-rolled steel sheets with excellent resistance to hydrogen embrittlement. It should be noted that the obtained hot-rolled steel sheets can be further cold-rolled to produce cold-rolled steel sheets.

[0132] The steel plate manufacturing method of this application example includes a step of hot rolling a steel billet to produce a hot-rolled steel plate, and a step of winding the hot-rolled steel plate to obtain a hot-rolled coil, and then forming the hot-rolled coil into the steel plate coil. The manufacturing method of the hot-rolled coil before the additional vibration is not particularly limited; it is sufficient to hot-roll a steel billet having a known composition by roughing and finishing to produce a hot-rolled steel plate, and then wind the hot-rolled steel plate using a known method to produce a hot-rolled coil. By adding vibration to the hot-rolled coil under the above conditions, the amount of diffusible hydrogen in the steel can be reduced, resulting in a hot-rolled steel plate with excellent resistance to hydrogen embrittlement. It should be noted that the obtained hot-rolled steel plate can be further cold-rolled to produce a cold-rolled steel plate.

[0133] Cold-rolled steel sheet

[0134] The dehydrogenation device 300a and the steel plate manufacturing method of this embodiment can also be used to manufacture cold-rolled steel plates.

[0135] The steel sheet manufacturing system of this application example is a steel sheet manufacturing system comprising a cold rolling apparatus for cold rolling hot-rolled steel sheets to produce cold-rolled steel sheets, a cold-rolled steel sheet winding apparatus for winding the aforementioned cold-rolled steel sheets to obtain cold-rolled coils, and a dehydrogenation apparatus 300a for forming the aforementioned cold-rolled coils into the aforementioned steel sheet coil C. The cold rolling apparatus performs hot-rolled steel sheet annealing, or not, on a known hot-rolled steel sheet, and performs one cold rolling or two or more cold rolling operations with intermediate annealing on the hot-rolled steel sheet or the hot-rolled steel sheet after hot rolling, to produce a cold-rolled steel sheet with a final sheet thickness. The cold-rolled steel sheet winding apparatus winds the cold-rolled steel sheet according to a known method to produce a cold-rolled coil. The dehydrogenation apparatus 300a uses the cold-rolled coil as steel sheet coil C and applies vibration to the cold-rolled coil under the aforementioned conditions. Through this additional vibration, the amount of diffusible hydrogen in the steel can be reduced, resulting in a cold-rolled steel sheet with excellent resistance to hydrogen embrittlement. It should be noted that the steel sheet manufacturing system may further include a dehydrogenation device 300a capable of subjecting the hot-rolled coil obtained by winding the hot-rolled steel sheet to vibration under the aforementioned conditions. Next, the hot-rolled steel sheet is unwound from the vibrated hot-rolled coil and cold-rolled to produce a cold-rolled coil. This cold-rolled coil is then further vibrated using the dehydrogenation device 300a, thereby further reducing the amount of diffusible hydrogen in the steel and obtaining a steel sheet with particularly excellent resistance to hydrogen embrittlement.

[0136] The steel sheet manufacturing method of this application example includes a step of cold rolling a hot-rolled steel sheet to produce a cold-rolled steel sheet, and a step of winding the cold-rolled steel sheet to obtain a cold-rolled coil, and then forming the cold-rolled coil into the steel sheet coil. The manufacturing method of the cold-rolled coil before the additional vibration is not particularly limited. In one example, a hot-rolled steel sheet can be produced by hot rolling a steel billet with a known composition, consisting of rough rolling and finishing rolling. The hot-rolled steel sheet can be subjected to hot rolling annealing, or not, and then the hot-rolled steel sheet or the hot-rolled steel sheet after hot rolling annealing can be subjected to one cold rolling or two or more cold rollings with intermediate annealing to produce a cold-rolled steel sheet with a final sheet thickness. The cold-rolled steel sheet is then wound into a cold-rolled coil according to a known method. By applying vibration to the cold-rolled coil under the above conditions, the amount of diffusible hydrogen in the steel can be reduced, resulting in a cold-rolled steel sheet with excellent resistance to hydrogen embrittlement. It should be noted that, in addition to applying vibration to cold-rolled coils, hot-rolled steel sheets can also be wound into hot-rolled coils, and then vibrated under the aforementioned conditions. Next, a hot-rolled steel sheet is unwound from the vibrated hot-rolled coil and cold-rolled to produce a cold-rolled coil. Further vibration is then applied to this cold-rolled coil, thereby further reducing the amount of diffusible hydrogen in the steel and obtaining a steel sheet with particularly excellent resistance to hydrogen embrittlement.

[0137] In this embodiment, the type of hot-rolled or cold-rolled steel sheet subjected to the additional vibration is not particularly limited. The composition of the steel sheet is not particularly limited, but steel sheets with the following compositions can be exemplified as particularly preferred for this embodiment. First, the appropriate range of the composition of the steel sheet and the reasons for limiting it will be explained.

[0138] [Essential Ingredients]

[0139] C: 0.030%~0.800%

[0140] Carbon (C) is an essential element for improving strength. By consuming 0.030% or more of C, particularly suitable strength can be obtained. Furthermore, by consuming 0.800% or less of C, embrittlement of the material itself can be particularly effectively prevented. From this viewpoint, the C content is preferably 0.030% or more, more preferably 0.800% or less, more preferably 0.080% or more, and even more preferably 0.500% or less.

[0141] Si: 0.01%–3.00%,

[0142] Si is a solid solution strengthening element that transforms into a substitutional solid solution, significantly hardening the material and effectively increasing the strength of steel sheets. To achieve this strength increase through Si addition, the Si content is preferably 0.01% or more. On the other hand, from the viewpoint of preventing steel embrittlement and reduced ductility, as well as preventing red scale and other defects to obtain good surface properties, and thus achieving a good plating appearance and adhesion, the Si content is preferably 3.00% or less. Therefore, Si is preferably 0.01% or more, and more preferably 3.00% or less. Si is more preferably 0.10% or more, and even more preferably 2.50% or less.

[0143] Mn: 0.01%~10.00%

[0144] Mn strengthens the steel sheet by solid solution treatment, thereby increasing its strength. To achieve this effect, the Mn content is preferably 0.01% or more. On the other hand, by keeping the Mn content at 10.00% or less, Mn segregation can be appropriately prevented, thus preventing unevenness in the steel structure and further suppressing hydrogen embrittlement. Therefore, the Mn content is preferably 10.00% or less. More preferably, the Mn content is 0.5% or more, and even more preferably 8.00% or less.

[0145] P: 0.001%~0.100%

[0146] P is an element that provides solid solution strengthening and can be added according to the desired strength. To achieve this effect, it is preferable that the P content is 0.001% or more. On the other hand, by keeping the P content below 0.100%, excellent weldability can be obtained. Furthermore, by keeping the P content below 0.100%, a decrease in the alloying rate can be prevented when a galvanized coating is formed on the steel plate surface and then alloyed to form an alloyed galvanized coating, resulting in a galvanized coating of excellent quality. Therefore, the P content is preferably 0.001% or more, preferably 0.100% or less. The P content is more preferably 0.003% or more. Furthermore, the P content is more preferably 0.050% or less.

[0147] S: 0.0001%~0.0200%

[0148] By reducing the sulfur content, it is possible to appropriately prevent the embrittlement of steel during hot working and to appropriately prevent the formation of sulfides, thereby improving the local deformation capacity. Therefore, the sulfur content is preferably 0.0200% or less, more preferably 0.0100% or less, and even more preferably 0.0050% or less. There is no particular limitation on the lower limit of the sulfur content; however, due to limitations in production technology, the sulfur content is preferably 0.0001% or more, more preferably 0.0050% or less.

[0149] N: 0.0005%~0.0100%

[0150] Reducing the nitrogen content can improve the aging resistance of steel. Therefore, the nitrogen content is preferably 0.0100% or less, more preferably 0.0070% or less. There is no particular limitation on the lower limit of the nitrogen content, but due to limitations in production technology, the nitrogen content is preferably 0.0005% or more, more preferably 0.0010% or more.

[0151] Al: Below 2.000%

[0152] Al acts as a deoxidizer, effectively improving the cleanliness of steel, and is preferably added during the deoxidation process. To achieve the desired effect, the amount of Al added is preferably 0.001% or more. On the other hand, from the viewpoint of appropriately preventing steel sheet cracks during continuous casting, the amount of Al is preferably 2.000% or less. More preferably, the amount of Al is 0.010% or more. Furthermore, the amount of Al is more preferably 1.200% or less.

[0153] [Any ingredients]

[0154] The composition may further contain, by mass percent, at least one element selected from Ti: less than 0.200%, Nb: less than 0.200%, V: less than 0.500%, W: less than 0.500%, B: less than 0.0050%, Ni: less than 1.000%, Cr: less than 1.000%, Mo: less than 1.000%, Cu: less than 1.000%, Sn: less than 0.200%, Sb: less than 0.200%, Ta: less than 0.100%, Ca: less than 0.0050%, Mg: less than 0.0050%, Zr: less than 0.0050%, and REM: less than 0.0050%.

[0155] Ti: below 0.200%

[0156] Ti contributes to the increase of steel sheet strength through precipitation strengthening and fine-grain strengthening caused by the inhibition of ferrite grain growth. When adding Ti, it is preferable to add 0.005% or more. More preferably, the amount of Ti added is 0.010% or more. Furthermore, by keeping the Ti amount at 0.200% or less, the precipitation of carbonitriding compounds can be appropriately prevented, further improving formability. Therefore, when adding Ti, it is preferable to add 0.200% or less. More preferably, the Ti amount is 0.100% or less.

[0157] Nb: below 0.200%, V: below 0.500%, W: below 0.500%

[0158] Nb, V, and W are effective in precipitation strengthening of steel. When adding Nb, V, and W, it is preferable that each is 0.005% or more. More preferably, each is 0.010% or more. Furthermore, by keeping Nb at 0.200% or less and V and W at 0.500% or less, the precipitation of carbonitriding compounds can be appropriately prevented, similar to that of Ti, further improving formability. Therefore, when adding Nb, the amount added is preferably 0.200% or less, more preferably 0.100% or less. When adding V and W, the amounts added are preferably 0.500% or less, more preferably 0.300% or less.

[0159] B: Below 0.0050%

[0160] Boron (B) is effective in strengthening grain boundaries and increasing the strength of steel sheets. When adding B, the amount is preferably 0.0003% or more. Furthermore, to obtain better formability, the amount of B is preferably 0.0050% or less. Therefore, when adding B, the amount added is preferably 0.0050% or less, more preferably 0.0030% or less.

[0161] Ni: below 1.000%

[0162] Ni is an element that increases the strength of steel through solid solution strengthening. When adding Ni, it is preferable to add 0.005% or more. Furthermore, from the viewpoint of further improving ductility by reducing the area ratio of hard martensite, Ni is preferably 1.000% or less. Therefore, when adding Ni, the amount added is preferably 1.000% or less, more preferably 0.500% or less.

[0163] Cr: less than 1.000%, Mo: less than 1.000%

[0164] Cr and Mo can be added as needed because they balance strength and formability. When adding Cr and Mo, the preferred concentrations are Cr: 0.005% or more and Mo: 0.005% or more. Furthermore, from the viewpoint of further improving ductility by reducing the area ratio of hard martensite, the preferred concentrations are Cr: 1.000% or less and Mo: 1.000% or less. Alternatively, the preferred concentrations are Cr: 0.500% or less and Mo: 0.500% or less.

[0165] Cu: below 1.000%

[0166] Cu is an effective element for strengthening steel and can be added as needed. When adding Cu, it is preferable to add 0.005% or more. In addition, from the viewpoint of further improving ductility by reducing the area ratio of hard martensite, when adding Cu, it is preferable to add 1.000% or less, more preferably 0.200% or less.

[0167] Sn: less than 0.200%, Sb: less than 0.200%

[0168] Sn and Sb effectively ensure strength and material stability by being added as needed, as they suppress decarburization in a region of approximately tens of μm on the surface of the steel plate caused by nitriding and oxidation. When adding Sn and Sb, the amounts are preferably 0.002% or more, respectively. Furthermore, to obtain superior toughness, the contents of Sn and Sb are preferably 0.200% or less, more preferably 0.050% or less, respectively.

[0169] Ta: below 0.100%

[0170] Like Ti and Nb, Ta forms alloy carbides and alloy carbonitrides, which contributes to high strength. Furthermore, it is believed that by partially dissolving in Nb carbides and Nb carbonitrides, forming composite precipitates such as (Nb,Ta)(C,N), the coarsening of precipitates is significantly suppressed, thus stabilizing the contribution to strength made by precipitation strengthening. Therefore, the presence of Ta is preferred. Here, the amount of Ta added is preferably 0.001% or more. There is no particular upper limit to the amount of Ta, but from the viewpoint of cost reduction, the content of Ta added is preferably 0.100% or less, more preferably 0.050% or less.

[0171] Ca: less than 0.0050%, Mg: less than 0.0050%, Zr: less than 0.0050%, REM: less than 0.0050%

[0172] Ca, Mg, Zr, and REM are elements that help to shape sulfides into spherical shapes and are effective in improving the adverse effects of sulfides on moldability. When these elements are added, the amount is preferably 0.0005% or more for each. Furthermore, to appropriately prevent the increase of inclusions and other defects, and to more appropriately prevent surface and internal defects, the amount of Ca, Mg, Zr, and REM added is preferably 0.0050% or less, more preferably 0.0020% or less for each.

[0173] This embodiment is particularly preferred for high-strength steel sheets where hydrogen embrittlement is a problem. By applying vibration to the steel sheet coil C made of high-strength steel sheet using a dehydrogenation device 300a or by applying the manufacturing method of this steel sheet, the amount of diffusible hydrogen in the steel can be reduced, resulting in a high-strength steel sheet with excellent resistance to hydrogen embrittlement. For example, the steel sheet manufactured in this embodiment can be a high-strength steel sheet with a tensile strength of 590 MPa or more, more preferably 1180 MPa or more, and even more preferably 1470 MPa or more. It should be noted that the tensile strength of the steel sheet is measured according to JIS Z 2241 (2011). In high-strength steel sheets, delayed fracture due to hydrogen embrittlement is often a problem, but according to this embodiment, a high-strength steel sheet with excellent resistance to hydrogen embrittlement can be manufactured without compromising tensile strength.

[0174] Furthermore, according to the dehydrogenation apparatus and steel plate manufacturing method of this embodiment, it is also possible to manufacture stainless steel with excellent resistance to hydrogen embrittlement by subjecting known stainless steel to additional vibration. The composition of the steel plate when it is made of stainless steel and the reasons for this limitation will be explained below.

[0175] [Essential Ingredients]

[0176] C: 0.001%~0.400%

[0177] C is an essential element for achieving high strength in stainless steel. However, if the C content exceeds 0.400%, it combines with Cr during tempering in steelmaking and precipitates as carbides, which deteriorate the steel's corrosion resistance and toughness. On the other hand, if the C content is less than 0.001%, sufficient strength is not obtained, and if it exceeds 0.400%, the aforementioned deterioration becomes significant. Therefore, the C content is set between 0.001% and 0.400%. The C content is preferably 0.005% or more. Furthermore, the C content is preferably 0.350% or less.

[0178] Si: 0.01%~2.00%

[0179] Si is a useful element as a deoxidizer. This effect is achieved by having a Si content of 0.01% or more. However, if Si is present in excess, the Si dissolved in the steel reduces the workability of the steel. Therefore, the upper limit for Si content is 2.00%. The Si content is preferably 0.05% or more. Furthermore, the Si content is preferably 1.8% or less.

[0180] Mn: 0.01%~5.00%

[0181] Mn has the effect of increasing the strength of steel. These effects are obtained by containing 0.01% or more Mn. However, if the Mn content exceeds 5.00%, the workability of the steel decreases. Therefore, the upper limit for Mn content is 5.00%. The Mn content is preferably 0.05% or more. Furthermore, the Mn content is preferably 4.6% or less.

[0182] P: 0.001%~0.100%

[0183] Phosphorus (P) is an element that promotes grain boundary destruction caused by grain boundary segregation, so the lower the content, the better, with an upper limit of 0.100%. Preferably, the P content is 0.030% or less. More preferably, the P content is 0.020% or less. It should be noted that there is no particular limitation on the lower limit of the P content; from a production technology point of view, it is 0.001% or more.

[0184] S: 0.0001%~0.0200%

[0185] Sulfur (S) is an element that, as an inclusion in sulfide compounds such as MnS, reduces ductility and corrosion resistance, especially when its content exceeds 0.0200%. Therefore, the S content is preferably as low as possible, with an upper limit of 0.0200%. Preferably, the S content is 0.010% or less. More preferably, the S content is 0.005% or less. It should be noted that the lower limit of the S content is not particularly limited, but from a production technology point of view, it is 0.0001% or more.

[0186] Cr: 9.0%–28.0%

[0187] Cr is a fundamental element constituting stainless steel and is also crucial for its corrosion resistance. Considering corrosion resistance in harsh environments above 180°C, sufficient corrosion resistance is not achieved when the Cr content is less than 9%, while exceeding 28.0% results in saturation and presents economic challenges. Therefore, the Cr content is set between 9.0% and 28.0%. A Cr content of 10.0% or more is preferred. Furthermore, a Cr content of 25.0% or less is more desirable.

[0188] Ni: 0.01%~40.0%

[0189] Ni is an element that improves the corrosion resistance of stainless steel, but its effect is not fully realized when the content is less than 0.01%. On the other hand, excessive addition not only hardens the stainless steel and deteriorates its formability, but also easily leads to stress corrosion cracking. Therefore, the Ni content is set between 0.01% and 40.0%. The Ni content is preferably 0.1% or more. Furthermore, the Ni content is preferably 30.0% or less.

[0190] N: 0.0005%~0.500%

[0191] Nitrogen (N) is an element detrimental to improving the corrosion resistance of stainless steel and is also an austenite-forming element. If its content exceeds 0.5%, it will precipitate as nitrides during heat treatment, deteriorating the corrosion resistance and toughness of the stainless steel. Therefore, the upper limit of N content is 0.500%, preferably 0.20%.

[0192] Al: Below 3.000%,

[0193] Besides acting as a deoxidizing element, Al also inhibits the peeling of oxide scale. However, if the content exceeds 3.000%, it leads to a decrease in elongation and a deterioration in surface quality. Therefore, the upper limit of Al content is set at 3.000%. The lower limit of Al content is not particularly limited, but is preferably 0.001% or more. Al content is preferably 0.01% or more. Furthermore, Al content is preferably 2.5% or less.

[0194] [Any ingredients]

[0195] The composition of stainless steel may further contain, by mass percent, at least one element selected from Ti: less than 0.500%, Nb: less than 0.500%, V: less than 0.500%, W: less than 2.000%, B: less than 0.0050%, Mo: less than 2.000%, Cu: less than 3.000%, Sn: less than 0.500%, Sb: less than 0.200%, Ta: less than 0.100%, Ca: less than 0.0050%, Mg: less than 0.0050%, Zr: less than 0.0050%, and REM: less than 0.0050%.

[0196] Ti: below 0.500%

[0197] Ti is an element added to improve corrosion resistance, resistance to intergranular corrosion, and deep drawing ability by combining with C, N, and S. However, if the addition exceeds 0.500%, the stainless steel will harden and its toughness will deteriorate due to solid solution Ti. Therefore, the upper limit of Ti content is 0.500%. The lower limit of Ti content is not particularly limited, but is preferably 0.003% or more. More preferably, the Ti content is 0.005% or more. Furthermore, the Ti content is preferably 0.300% or less.

[0198] Nb: below 0.500%

[0199] Like Ti, Nb is added to improve corrosion resistance, resistance to intergranular corrosion, and deep drawing ability by combining with C, N, and S. Furthermore, it is added as needed because it not only improves workability and high-temperature strength but also promotes the suppression of crevice corrosion and repassivation. However, excessive addition can lead to hardening of stainless steel and deterioration of formability; therefore, the upper limit of Nb content is 0.500%. The lower limit of Nb content is not particularly limited, but is preferably 0.003% or more. More preferably, it is 0.005% or more. Additionally, the Nb content is preferably 0.300% or less.

[0200] V: Below 0.500%

[0201] V is added as needed to suppress crevice corrosion. However, excessive addition hardens the stainless steel and deteriorates its formability; therefore, the upper limit of the V content is 0.500%. The lower limit of the V content is not particularly limited, but is preferably 0.01% or more, and more preferably 0.03% or more. Furthermore, the V content is preferably 0.300% or less.

[0202] W: Below 2.000%

[0203] W is added as needed to improve corrosion resistance and high-temperature strength. However, adding more than 2.000% can harden the stainless steel, leading to decreased toughness and increased costs during sheet manufacturing; therefore, the upper limit for W content is 2.000%. The lower limit for W content is not particularly limited, but is preferably 0.050% or more. More preferably, it is 0.010% or more. Furthermore, the W content is preferably 1.500% or less.

[0204] B: Below 0.0050%

[0205] Bo (B) is an element that improves the secondary processing properties of products by segregating at grain boundaries. Besides suppressing longitudinal cracks during secondary processing of parts, it also prevents crack formation in winter, and is therefore added as needed. However, excessive addition leads to a decrease in processability and corrosion resistance. Therefore, the upper limit of the B content is 0.0050%. The lower limit of the B content is not particularly limited, but is preferably 0.0002% or more. More preferably, the B content is 0.0005% or more. Furthermore, the B content is preferably 0.0035% or less.

[0206] Mo: 2.000% or less

[0207] Mo is an element that improves corrosion resistance, and is particularly effective in suppressing crevice corrosion in the presence of interstitial structures. However, if the content exceeds 2.0%, formability deteriorates significantly; therefore, the upper limit for its content is 2.000%. The lower limit for Mo content is not particularly limited, but is preferably 0.005% or more. More preferably, the Mo content is 0.010% or more. Furthermore, the Mo content is preferably 1.500% or less.

[0208] Cu: below 3.000%

[0209] Like Ni and Mn, Cu is an austenite stabilizing element, effective in refining grains caused by phase transformation. Furthermore, it is added as needed to promote the suppression and re-passivation of interstitial corrosion. However, excessive addition, besides hardening, deteriorates toughness and formability; therefore, its content is limited to an upper limit of 3.000%. The lower limit of Cu content is not particularly limited, but is preferably 0.005% or more. More preferably, Cu content is 0.010% or more. Furthermore, Cu content is preferably 2.000% or less.

[0210] Sn: below 0.500%

[0211] Sn is added as needed to improve corrosion resistance and high-temperature strength. However, if the addition exceeds 0.500%, slab cracking may occur during steel sheet manufacturing; therefore, the upper limit of its content is 0.500% or less. The lower limit of Sn content is not particularly limited, but is preferably 0.002% or more. Sn content is more preferably 0.005% or more. Furthermore, Sn content is preferably 0.300% or less.

[0212] Sb: below 0.200%

[0213] Sb is an element that segregates at grain boundaries, thereby increasing high-temperature strength. However, if the content exceeds 0.200%, Sb segregation occurs, leading to cracking during welding; therefore, the upper limit for its content is 0.200%. The lower limit for Sb content is not particularly limited, but is preferably 0.002% or more. More preferably, the Sb content is 0.005% or more. Furthermore, the Sb content is preferably 0.100% or less.

[0214] Ta: below 0.100%

[0215] Ta (Ta) is added as needed because it helps improve toughness by combining with C and N. However, if the addition exceeds 0.100%, its effect saturates, leading to increased manufacturing costs; therefore, its content is capped at 0.100%. There is no particular limitation on the lower limit of Ta content, but it is preferably 0.002% or more. More preferably, the Ta content is 0.005% or more. Furthermore, the Ta content is preferably 0.080% or less.

[0216] Ca: below 0.0050%, Mg: below 0.0050%, Zr: below 0.0050%, REM (Rare Earth Metal): below 0.0050%

[0217] Ca, Mg, Zr, and REM are elements that effectively improve the spherical shape of sulfides and mitigate their adverse effects on moldability. When any one of these elements is added, the content of each element is preferably 0.0005% or more. However, excessive amounts of any of these elements can increase inclusions and sometimes cause surface and internal defects. Therefore, when any one of these elements is added, the content of each element is preferably 0.0050% or less. There is no particular limitation on the lower limit of the content of these elements, but the content of each element is preferably 0.0002% or more. More preferably, the content of each element is 0.0005% or more. Furthermore, the content of each element is preferably 0.0035% or less.

[0218] Annealing apparatus

[0219] Annealing process

[0220] Annealing can be performed on the aforementioned cold-rolled and hot-rolled steel sheets. That is, the steel sheet manufacturing system can be equipped with an annealing apparatus for annealing cold-rolled and hot-rolled steel sheets. There is no particular limitation on the timing of annealing; however, since hydrogen generally penetrates the steel during the annealing process, it is preferable to perform annealing before additional vibration in order to ultimately obtain a steel sheet with excellent resistance to hydrogen embrittlement. The annealing apparatus can be a batch annealing furnace or a continuous annealing apparatus.

[0221] [Batch annealing]

[0222] When using a batch annealing furnace for the annealing process, the steel sheet manufacturing system includes: a batch annealing furnace for batch annealing cold-rolled or hot-rolled coils to obtain annealed coils, and a dehydrogenation device 300a for forming the annealed coils into the steel sheet coils C. The batch annealing furnace anneales cold-rolled or hot-rolled coils in batches to produce annealed coils. It should be noted that batch annealing in this specification refers to heating and holding in the batch annealing furnace, excluding slow cooling after heating and holding. The annealed coils are cooled by furnace cooling or air cooling within the batch annealing furnace. The dehydrogenation device 300a applies vibration to the annealed coils as steel sheet coils C under the aforementioned conditions. The dehydrogenation device 300a can be installed separately from the batch annealing furnace, and the housing 80 and heating section of the dehydrogenation device 300a can also function as a batch annealing furnace. In other words, a vibration device 60 can be installed in a batch annealing furnace to add vibration to the steel sheet coil C contained in the furnace to form a finished coil, thus creating a dehydrogenation device 300a. When the receiving part 80 and the heating part of the dehydrogenation device 300a are both part of the batch annealing furnace, the vibration can be added after batch annealing and after the annealed coil has been cooled to room temperature, or the vibration can be added while the annealed coil is being cooled. As mentioned above, the higher the temperature of the steel sheet, the more effectively diffusible hydrogen can be reduced. Therefore, the vibration can be added after batch annealing and after the annealed coil has been cooled to room temperature. By adding vibration while the annealed coil is being cooled, the diffusible hydrogen in the steel can be reduced more effectively.

[0223] When using a batch annealing furnace for the annealing process, the steel sheet manufacturing method includes a step of batch annealing cold-rolled or hot-rolled coils obtained by winding cold-rolled or hot-rolled steel sheets to obtain annealed coils. These annealed coils are then used as the aforementioned steel sheet coils, and vibration is applied to them under the conditions described above. First, cold-rolled or hot-rolled steel sheets are wound using known methods to produce cold-rolled or hot-rolled coils. Next, the cold-rolled or hot-rolled coils are placed in a batch annealing furnace and batch annealed to produce annealed coils. The annealed coils are then cooled using furnace cooling or air cooling within the batch annealing furnace. Finally, vibration is applied to the annealed coils under the conditions described above. This vibration application to the annealed coils can be performed during the batch annealing process, i.e., while the cold-rolled or hot-rolled coils are being heated and held. Furthermore, the vibration can be applied after batch annealing, i.e., after the cold-rolled or hot-rolled coil has been heated and held. The vibration can be applied after batch annealing, once the annealed coil has been cooled to room temperature, or it can be applied while the annealed coil is being cooled. As mentioned above, the higher the temperature of the steel sheet, the more effectively diffusible hydrogen can be reduced; therefore, it is preferable to apply vibration to the annealed coil during or after batch annealing while it is being cooled. The vibration of the annealed coil can also be applied within the batch annealing furnace, or it can be applied after the annealed coil has been removed from the batch annealing furnace. It is preferable to apply vibration to the annealed coil within the batch annealing furnace. By applying vibration to the annealed coil within the batch annealing furnace, diffusible hydrogen in the steel can be effectively reduced.

[0224] Annealing based on a continuous annealing apparatus

[0225] Annealing can also be performed by passing cold-rolled or hot-rolled steel sheets through a continuous annealing line (CAL). When performing the annealing process using a continuous annealing line, the steel sheet manufacturing system includes: a pre-annealing uncoiling device for uncoiling cold-rolled or hot-rolled steel sheets from cold-rolled or hot-rolled coils; a continuous annealing furnace for continuously annealing the aforementioned cold-rolled or hot-rolled steel sheets to produce annealed steel sheets; an annealed steel sheet winding device for winding the annealed steel sheets to obtain annealed coils; and a dehydrogenation device 300a for producing the annealed coils into the aforementioned steel sheet coil C. The pre-annealing uncoiling device uncoils the cold-rolled or hot-rolled steel sheets from the cold-rolled or hot-rolled coils and supplies the cold-rolled or hot-rolled steel sheets to the CAL. The configuration of the CAL is not particularly limited; in one example, the CAL includes a continuous annealing furnace with a heating zone, a soaking zone, and a cooling zone arranged sequentially. The cooling zone can consist of multiple cooling zones. In this case, some cooling zones can be holding zones that maintain the cold-rolled steel strip within a certain temperature range during the cooling process, and reheating zones that reheat the steel sheet during the cooling process. Additionally, the upstream side of the heating zone in the through-plate direction can also be a preheating zone. The uncoiling device before annealing can be an uncoiler located upstream of the continuous annealing furnace in the CAL (Continuous Annealing Furnace). The annealed steel sheet winding device can be a tension winding machine located downstream of the continuous annealing furnace in the CAL. In CAL, (A) for cold-rolled or hot-rolled steel sheets unwound from cold-rolled or hot-rolled coils using an uncoiler, (B) the sheets are passed through a continuous annealing furnace containing the heating zone, soaking zone, and cooling zone from the upstream side of the passing direction, (B-1) the cold-rolled or hot-rolled steel sheets are annealed in the heating zone and soaking zone to produce annealed steel sheets, (B-2) the annealed steel sheets are cooled in the cooling zone for continuous annealing, (C) the annealed steel sheets discharged from the continuous annealing furnace are passed through again, and (D) the steel sheets are wound using a tension winding machine to produce annealed coils. The dehydrogenation unit 300a uses this annealed coil as steel sheet coil C and applies vibration to the annealed coil under the above conditions. By applying this vibration, the amount of diffusible hydrogen in the steel can be reduced, resulting in annealed steel sheets with excellent resistance to hydrogen embrittlement. It should be noted that there are no particular limitations on the cooling method and cooling rate of the steel plates in the cooling zone; any cooling method such as gas jet cooling, water mist cooling, or water cooling can be used.

[0226] When performing the annealing process using a continuous annealing apparatus, the method for manufacturing steel sheets includes the steps of unwinding cold-rolled steel sheets from cold-rolled coils, continuously annealing the cold-rolled steel sheets to produce annealed steel sheets, and winding the annealed steel sheets to obtain annealed coils, and then forming the annealed coils into the steel sheet coils. In CAL, (A) the steel sheet coil is unwound using an uncoiler, (B) the steel sheet is passed through an annealing furnace containing the heating zone, soaking zone, and cooling zone from the upstream side in the through-plate direction, (B-1) the steel sheet is annealed in the heating zone and soaking zone, (B-2) the steel sheet is cooled in the cooling zone for continuous annealing, (C) the steel sheet discharged from the annealing furnace is continuously passed through, and (D) the steel sheet is wound using a tension winding machine to produce annealed coils. By adding vibration to the annealed coils under the above conditions, cold-rolled or hot-rolled steel sheets with excellent resistance to hydrogen embrittlement can be obtained.

[0227] [[Glazed Steel Sheet]]

[0228] Furthermore, the dehydrogenation apparatus 300a of this embodiment can also be used to manufacture coated steel sheets. The steel sheet manufacturing system of this application example includes: a coating apparatus for forming a coating film on the surface of hot-rolled or cold-rolled steel sheets to produce coated steel sheets; a coated steel sheet winding apparatus for winding the coated steel sheets to obtain coated steel sheet coils; and a dehydrogenation apparatus 300a for forming the coated steel sheet coils into the aforementioned steel sheet coils C. The coating apparatus uses hot-rolled or cold-rolled steel sheets as base steel sheets and forms a coating film on their surface to obtain coated steel sheets. The coated steel sheet winding apparatus winds the coated steel sheets to form coated steel sheet coils. The dehydrogenation apparatus 300a applies vibration to the coated steel sheet coils as steel sheet coils C under the aforementioned conditions. This additional vibration reduces the amount of diffusible hydrogen in the steel, resulting in coated steel sheets with excellent resistance to hydrogen embrittlement.

[0229] Alternatively, hot-rolled steel sheet or cold-rolled steel sheet can be used as the base steel sheet, and a coating film can be formed on its surface to obtain a coated steel sheet. This coated steel sheet can then be used as a steel sheet coil for additional vibration. When applying additional vibration to the coated steel sheet coil, the steel sheet manufacturing method includes: a step of forming a coating film on the surface of a hot-rolled steel sheet or cold-rolled steel sheet to produce a coated steel sheet, and a step of winding the coated steel sheet to obtain a coated steel sheet coil, and then forming the coated steel sheet coil into the aforementioned steel sheet coil.

[0230] [A coating is formed using a continuous hot-dip galvanizing apparatus]

[0231] There is no particular limitation on the type of coating equipment; for example, it can be a hot-dip galvanizing equipment. In one example, a hot-dip galvanizing equipment can be a continuous hot-dip galvanizing line (CGL). The composition of a CGL is not particularly limited; in one example, a CGL includes: a continuous annealing furnace with a heating zone, a soaking zone, and a cooling zone arranged sequentially, and hot-dip galvanizing equipment located after the cooling zone. In CGL, (A) for cold-rolled or hot-rolled steel sheets unwound from cold-rolled or hot-rolled coils using an uncoiler, (B) the sheets are passed through a continuous annealing furnace located in the heating zone, soaking zone, and cooling zone from the upstream side of the through-plate direction, (B-1) the hot-rolled or cold-rolled steel sheets are annealed in the soaking zone in a reducing atmosphere containing hydrogen to produce annealed steel sheets, (B-2) the annealed steel sheets are cooled in the cooling zone for continuous annealing, (C) the annealed steel sheets discharged from the annealing furnace are continuously passed through, (C-1) the annealed steel sheets are immersed in a hot-dip galvanizing bath located downstream of the through-plate direction of the continuous annealing furnace to produce hot-dip galvanized steel sheets, and (D) the hot-dip galvanized steel sheets are wound using a tension winding machine to produce hot-dip galvanized steel sheet coils. The dehydrogenation unit 300a uses the hot-dip galvanized steel sheet coil as steel sheet coil C, and applies vibration to the hot-dip galvanized steel sheet coil under the conditions described above. By applying this vibration, the amount of diffusible hydrogen in the steel can be reduced, resulting in a hot-dip galvanized steel sheet with excellent resistance to hydrogen embrittlement.

[0232] There are no particular limitations on the method for forming a coating on the surface of hot-rolled or cold-rolled steel sheets, and the coating process may include a hot-dip galvanizing process. That is, hot-dip galvanized steel sheets can be produced by hot-dip galvanizing hot-rolled or cold-rolled steel sheets. In one example, a continuous hot-dip galvanizing line (CGL) can be used to perform hot-dip galvanizing on the steel sheet. In CGL, (A) a steel sheet coil is unwound using an uncoiler; (B) a hot-rolled or cold-rolled steel sheet is passed through an annealing furnace containing a heating zone, a soaking zone, and a cooling zone from the upstream side of the through-plate direction; (B-1) the hot-rolled or cold-rolled steel sheet is annealed in a reducing atmosphere containing hydrogen in the soaking zone to produce an annealed steel sheet; (B-2) the annealed steel sheet is cooled in the cooling zone for continuous annealing; (C) the annealed steel sheet discharged from the annealing furnace is passed through continuously; and (D) the annealed steel sheet is wound using a tension winding machine to produce an annealed coil. Furthermore, step (C) includes (C-1) immersing the annealed steel sheet in a hot-dip galvanizing bath located downstream of the through-plate direction of the annealing furnace to perform hot-dip galvanizing treatment on the annealed steel sheet. The wound annealed coil is a hot-dip galvanized steel sheet coil made of hot-dip galvanized steel sheet. By subjecting the hot-dip galvanized steel sheet coil to vibration under the aforementioned conditions, a hot-dip galvanized steel sheet with excellent resistance to hydrogen embrittlement can be obtained.

[0233] Furthermore, the coating apparatus may include a hot-dip galvanizing unit and a subsequent alloying furnace. In one example, after manufacturing a hot-dip galvanized steel sheet using CGL, following the aforementioned process (C-1), (C-2) the steel sheet is passed through an alloying furnace located downstream of the hot-dip galvanizing bath in the passing direction, where the hot-dip galvanizing is heated and alloyed. The alloyed hot-dip galvanized steel sheet, alloyed in the alloying furnace, is then wound into an alloyed hot-dip galvanized steel sheet coil. The dehydrogenation unit 300a uses this alloyed hot-dip galvanized steel sheet coil as steel sheet coil C, and applies additional vibration to the alloyed hot-dip galvanized steel sheet coil under the aforementioned conditions. Through this additional vibration, an alloyed hot-dip galvanized steel sheet with excellent resistance to hydrogen embrittlement can be obtained.

[0234] Furthermore, the coating process can include a hot-dip galvanizing process and a subsequent alloying process. That is, the hot-dip galvanized steel sheet can be further alloyed to produce an alloyed hot-dip galvanized steel sheet, and vibration is applied to this hot-dip galvanized steel sheet. In one example, after manufacturing a hot-dip galvanized steel sheet using CGL, following the above-mentioned process (C-1), (C-2) the steel sheet is passed through an alloying furnace located downstream of the hot-dip galvanizing bath in the passing direction, and the hot-dip galvanizing is heated and alloyed. The alloyed hot-dip galvanized steel sheet alloyed by passing through the alloying furnace is wound into an alloyed hot-dip galvanized steel sheet coil. By applying vibration to this alloyed hot-dip galvanized steel sheet coil under the above conditions, an alloyed hot-dip galvanized steel sheet with excellent resistance to hydrogen embrittlement can be obtained.

[0235] In addition to zinc plating, the plating apparatus can also form Al plating or Fe plating. Furthermore, the plating apparatus is not limited to hot-dip plating; it can also be an electroplating apparatus.

[0236] Furthermore, there is no particular limitation on the type of coating film formed on the surface of the steel plate subjected to additional vibration; it can be an Al coating film or an Fe coating film. The method for forming the coating film is not limited to a hot-dip galvanizing process; it can also be an electroplating process.

[0237] The steel plate manufacturing system may further include a temper rolling apparatus, which performs temper rolling on hot-rolled steel plates, cold-rolled steel plates, and coated steel plates with various coatings on their surfaces, as described above, for purposes such as shape correction and surface roughness adjustment. That is, in this steel plate manufacturing method, hot-rolled steel plates, cold-rolled steel plates, and coated steel plates with various coatings on their surfaces, as described above, can be temper rolled for purposes such as shape correction and surface roughness adjustment. The reduction rate of the temper rolling is preferably controlled to be 0.1% or more, and more preferably 2.0% or less. By making the reduction rate of the temper rolling 0.1% or more, the effects of shape correction and surface roughness adjustment can be obtained more appropriately, and the control of the reduction rate also becomes more suitable. Furthermore, by making the reduction rate of the temper rolling 2.0% or less, the productivity is improved. It should be noted that the quenching and tempering rolling apparatus can be a continuous (online) apparatus with CGL or CAL, or a discontinuous (offline) apparatus with CGL or CAL. The target reduction rate can be achieved through a single quenching and tempering rolling operation, or by performing quenching and tempering rolling in several stages. Furthermore, the steel sheet manufacturing system can further include a coating apparatus that applies various coating treatments, such as resin or grease coating, to the surfaces of the hot-rolled steel sheet, cold-rolled steel sheet, and coated steel sheet with various coatings as described above. That is, various coating treatments, such as resin or grease coating, can also be applied to the surfaces of the hot-rolled steel sheet, cold-rolled steel sheet, and coated steel sheet with various coatings as described above.

[0238] <Implementation Method 2>

[0239] The dehydrogenation apparatus of Embodiment 2 of the present invention includes: an unwinding device for unwinding steel strip from steel sheet coil, a pass-through device for passing the steel strip through a plate, a winding device for winding the steel strip, and a vibration amplification device for amplifying the steel strip in the pass-through device in such a way that the frequency of the steel strip vibration is 100 to 100,000 Hz and the maximum amplitude of the steel strip is 10 nm to 500 μm.

[0240] Furthermore, the steel plate manufacturing method of Embodiment 2 of the present invention includes: a step of unwinding a steel strip from a steel plate coil, a step of passing the steel strip through a plate, and a step of winding the steel strip to form an article coil. The plate-passing step includes the following vibration addition step: adding vibration to the steel strip in such a way that the vibration frequency of the steel strip is 100 to 100,000 Hz and the maximum amplitude of the steel strip is 10 nm to 500 μm.

[0241] Steel sheets that have been hot-rolled or cold-rolled and then annealed, or coated steel sheets that have been further coated, are wound into coils to form steel sheet coils. The quality of these steel sheet coils often differs from their original packaging quality, therefore, packaging quality is differentiated in a recoil line. A steel strip is unwound from the steel sheet coil using an unwinding device, and the unwound steel strip is rewound using a rewinding device, and is sheared and divided at a stage where a specified packaging quality is achieved. In this embodiment, vibration is applied to the steel strip unwound from the recoil line. According to this embodiment, since vibration is applied to the steel strip in the continuous plate, vibration can be applied uniformly along the entire length of the steel strip. It should be noted that the dehydrogenation device in this embodiment is a discontinuous (offline) device from the continuous annealing device or continuous hot-dip galvanizing device; the dehydrogenation device does not include equipment for annealing, coating, and hot-dip galvanizing the steel strip.

[0242] (Vibration attachment 60)

[0243] Vibration can be added using a vibration attachment device. In one example, the vibration attachment device can be configured similarly to the vibration attachment device 60 of Embodiment 1, in that the steel strip in the through plate vibrates due to an external force (attraction) applied to the steel strip in the through plate by the electromagnet 63. The configuration of the vibration attachment device 60 can be the same as in Embodiment 1, except that the object of the added vibration is the steel strip in the through plate instead of the steel sheet coil.

[0244] It should be noted that the electromagnet 63 only needs to be positioned opposite one surface of the steel strip in the through plate, but it can also be positioned opposite both the front and back surfaces. However, in this case, it is preferable to stagger the height positions so that the electromagnet 63 on one side is not at the same height position as the electromagnet 63 on the other side.

[0245] (Vibration attachment 70)

[0246] In another example, the vibration attachment device, similar to the vibration attachment device 70 of Embodiment 1 described above, can be configured such that the steel strip in the through plate vibrates due to an external force (gravity) applied to the steel strip in the through plate by an oscillator. For example... Figure 4 As shown in Figure A, the vibration attachment 70 can be configured to have an oscillator 72 that contacts the steel strip in the through plate, through which the steel strip S vibrates. The configuration of the vibration attachment 70 can be the same as in Embodiment 1, except that the object of the additional vibration is the steel strip in the through plate instead of the steel sheet coil.

[0247] [Dehydrogenation unit]

[0248] Figure 7 The diagram shows a view of the dehydrogenation apparatus 300b used in the steel sheet manufacturing method of this embodiment, with the width direction of the steel strip S in front of it. Figure 7This is a diagram illustrating an example of a dehydrogenation device for reducing diffusible hydrogen in steel by applying additional vibration to the steel strip S in the through plate via a vibration attachment 60. Figure 7 As shown, in this dehydrogenation unit 300b, a vibration auxiliary device 60 is configured during the passage process of the steel strip S unwound by the unwinding device. It should be noted that, although not shown, each vibration auxiliary device 60 incorporates an amplifier 62, a power supply 65, and a controller 61 to each electromagnet 63, and a vibration detector 64 is further incorporated into the controller 61, thereby applying additional vibration to the steel strip S by the electromagnet 63. Figure 7 As shown, the vibration attachment 60 can be provided only on one side of the steel strip S in the through plate, either the surface or the back side, or it can be provided on both sides of the steel strip S in the through plate to excite the steel strip S. By providing the vibration attachment 60 on both sides of the steel strip S in the through plate, the timing of vibration attachment can be controlled to more effectively reduce the amount of diffusible hydrogen in the steel. It should be noted that, although not shown, the dehydrogenation device 300b includes a through plate device for passing the steel strip S from the unwinding device toward the winding device. The through plate device includes, for example, a through plate roller for passing the steel strip S toward the winding device through the through plate.

[0249] Preferably, a plurality of electromagnets 63 are arranged along the width direction of the steel strip S at predetermined intervals from the surface of the steel strip S in the through plate. By applying additional vibration from each electromagnet 63 toward the surface of the steel strip S in the through plate, vibration can be uniformly applied to the surface in the width direction. By arranging a plurality of electromagnets 63 having a width direction of the steel strip along the through plate direction, the time for the surface of the steel strip S to be subjected to additional vibration can be sufficiently ensured.

[0250] There is no particular limitation on the method of holding the electromagnets 63 at certain intervals within the dehydrogenation unit 300b. For example, a box-shaped part can be provided in such a way that the steel strip S in the through plate is covered in the through plate path, and the electromagnets 63 can be fixed to the inner wall of the box-shaped part at certain intervals.

[0251] Figure 8 An example of a dehydrogenation device is shown in the figure, which reduces diffusible hydrogen in steel by applying additional vibration to the steel strip S in the through plate through a vibration attachment 70. Figure 8 In the diagram, the width direction of the steel strip S is indicated in front. For example... Figure 8 As shown, the dehydrogenation unit 300b is equipped with an oscillator 72 of a vibration auxiliary device 70 during the passage process of the steel strip S unwound by the unwinding device. It should be noted that, although not shown, each vibration auxiliary device 70 incorporates a controller 71 and a vibration detector 73 into each oscillator 72, and the oscillator 72 applies additional vibration to the steel strip S. Figure 8As shown, the oscillator 72 is configured to contact the steel strip S in the through plate. The vibration attachment 70 can be provided only on one side of the steel strip S in the through plate, either the surface or the back side, or it can be provided on both sides of the steel strip S in the through plate to excite the steel strip S. By providing the vibration attachment 70 on both sides of the steel strip S in the through plate, the timing of vibration attachment can be controlled to more effectively reduce the amount of diffusible hydrogen in the steel.

[0252] Preferably, multiple oscillators 72 are arranged along the width direction of the steel strip in such a way that the oscillators 72 are in contact with the surface of the steel strip S in the through plate. By applying additional vibration to the surface of the steel strip S in the through plate by each oscillator 72, vibration can be applied uniformly in the width direction of the surface. By arranging multiple oscillators 72 along the width direction of the steel strip along the through plate direction, the time for the surface of the steel strip S to be subjected to additional vibration can be sufficiently ensured.

[0253] There is no particular limitation on the method of holding the oscillator 72 at certain intervals within the dehydrogenation unit 300b. For example, a box-shaped part can be provided in such a way that the steel strip S in the through plate is covered in the through plate path, and the oscillator 72 can be fixed to the inner wall of the box-shaped part at certain intervals.

[0254] In this embodiment, the frequency and maximum amplitude of the vibration added to the steel strip in the through plate can be the same as in embodiment 1.

[0255] [Vibration Additional Time]

[0256] In the rewinding line, unlike continuous annealing or continuous hot-dip galvanizing equipment, it is not necessary to adjust the pass-through speed while considering the annealing time. Therefore, according to this embodiment, vibration can be applied to the steel strip without being constrained by the irradiation time. It is presumed that the longer the applied vibration time, the more diffusible hydrogen can be reduced; therefore, the applied vibration time is preferably 1 minute or more. The applied vibration time is more preferably 30 minutes or more, and even more preferably 60 minutes or more. On the other hand, from the viewpoint of productivity, the applied vibration time is preferably 30,000 minutes or less, more preferably 10,000 minutes or less, and even more preferably 1,000 minutes or less. The applied vibration time can be adjusted by the pass-through speed of the steel strip S and the position of the vibration application device (for example, the number of device groups consisting of multiple vibration application devices 60 along the pass-through direction in the width direction of the steel strip).

[0257] According to this embodiment, the diffusible hydrogen content of the product coil obtained after vibration application can be reduced to 0.5 ppm by mass or less. By reducing the diffusible hydrogen content of the product coil to 0.5 ppm by mass or less, hydrogen embrittlement can be prevented. The diffusible hydrogen content in the steel after vibration application is preferably 0.3 ppm by mass or less, more preferably 0.2 ppm by mass or less. The diffusible hydrogen content in the steel after vibration application can be measured in the same manner as in Embodiment 1.

[0258] [Heating device]

[0259] [[Steel strip holding temperature]]

[0260] In addition, such as Figure 7 , 8 As shown, the dehydrogenation apparatus 300b may further include a heating device 74 for simultaneously heating the steel strip S at a temperature below 300°C and applying vibration. The temperature of the steel strip S during the vibration application process is not particularly limited. This is because, according to this embodiment, even without heating the steel strip S, diffusible hydrogen in the steel can be reduced. However, by applying vibration to the steel strip S while heating it using a heating element, the hydrogen diffusion rate can be further increased, thus further reducing the amount of diffusible hydrogen in the steel. Therefore, the temperature of the steel strip S during the applied vibration is preferably 30°C or higher, more preferably 50°C or higher, and even more preferably 100°C or higher. The upper limit of the temperature of the steel strip S during the vibration application process is not particularly limited, but from the viewpoint of appropriately preventing changes in the microstructure of the steel strip S, it is preferably 300°C or lower. It should be noted that, in this embodiment, the temperature of the steel strip S during the applied vibration is based on the surface temperature of the steel strip S. The surface temperature of the steel strip can be measured using a general radiation thermometer. The manner in which the heating device 74 is provided is not particularly limited; for example, it can be provided as follows: Figure 7 , 8 A heating device 74 is shown installed in the through-plate path of the steel strip S. By installing the heating device 74 in the through-plate path of the steel strip S, the steel strip S can be heated evenly. When the heating device 74 is installed in the through-plate path of the steel strip S, as shown... Figure 7 , 8 As shown, it is preferable to provide a heating device 74 upstream of the vibration attachment device 60 in the through-plate path. By providing the heating device 74 upstream of the vibration attachment device 60 in the through-plate path, vibration can be applied to the sufficiently heated steel strip S. Alternatively, for example, the steel strip S can be heated and vibrated while being covered by the aforementioned box-shaped portion and a heater can be provided on the side wall of the box-shaped portion. Alternatively, the steel strip S can be heated and vibrated while being vibrated by introducing high-temperature air generated externally into the box-shaped portion and circulating it within the box-shaped portion. The heating method is not particularly limited and can be either combustion-type or electric-type. In one example, the heating device 74 can be an induction heating device.

[0261] The dehydrogenation apparatus 300b of this embodiment may further include a vibration damping section to prevent the aforementioned vibrations from being transmitted to the outside of the dehydrogenation apparatus 300b. The specific configuration of the vibration damping section is not particularly limited, and the vibration damping section may be, for example, a vibration damping material that covers the inner steel strip S and the electromagnet 63.

[0262] The following provides a more detailed explanation of application examples of this embodiment.

[0263] Hot-rolled steel plate

[0264] Similar to Embodiment 1, the dehydrogenation apparatus 300b and the steel plate manufacturing method of this embodiment can be used to manufacture hot-rolled steel plates.

[0265] The steel plate manufacturing system of this application example includes: a hot rolling apparatus for hot rolling steel billets to produce hot-rolled steel plates, a hot-rolled steel plate winding apparatus for winding the hot-rolled steel plates to obtain hot-rolled coils, and a dehydrogenation apparatus 300b for forming the hot-rolled coils into the steel plate coils. By unwinding the hot-rolled steel plate from the hot-rolled coils produced by a known hot rolling apparatus and subjecting it to a pass-through, and by applying additional vibration to the hot-rolled steel plate in the pass-through under the aforementioned conditions, the amount of diffusible hydrogen in the steel can be reduced, thereby obtaining a hot-rolled steel plate with excellent resistance to hydrogen embrittlement.

[0266] Similar to Embodiment 1, the steel plate manufacturing method of this embodiment can be used to manufacture hot-rolled steel plates. The steel plate manufacturing method of this application example includes: a step of hot-rolling a steel billet to produce a hot-rolled steel plate, and a step of winding the hot-rolled steel plate to obtain a hot-rolled coil, and then forming the hot-rolled coil into the steel plate coil. The manufacturing method of the hot-rolled coil before the additional vibration is not particularly limited; for example, it can be the manufacturing method exemplified in Embodiment 1. By unwinding the hot-rolled steel plate from the hot-rolled coil and passing it through a slab, and then subjecting the hot-rolled steel plate in the slab to additional vibration under the aforementioned conditions, the amount of diffusible hydrogen in the steel can be reduced, thereby obtaining a hot-rolled steel plate with excellent resistance to hydrogen embrittlement.

[0267] Cold-rolled steel sheet

[0268] The dehydrogenation device 300b and the steel plate manufacturing method of this embodiment can also be used to manufacture cold-rolled steel plates.

[0269] The steel sheet manufacturing system of this application example includes: a cold rolling apparatus for cold rolling hot-rolled steel sheets to produce cold-rolled steel sheets; a cold-rolled steel sheet winding apparatus for winding the cold-rolled steel sheets to obtain cold-rolled coils; and a dehydrogenation apparatus 300b for forming the cold-rolled coils into the steel sheet coil C. A known hot-rolled steel sheet is cold-rolled using a known cold rolling apparatus to obtain a cold-rolled steel sheet. The cold-rolled steel sheet winding apparatus winds the cold-rolled steel sheet to form a cold-rolled coil. The cold-rolled coil, as the steel sheet coil C, is unwound from the cold-rolled coil and passed through a plate. The cold-rolled steel sheet in the plate is subjected to additional vibration under the aforementioned conditions, thereby reducing the amount of diffusible hydrogen in the steel and obtaining a cold-rolled steel sheet with excellent resistance to hydrogen embrittlement.

[0270] The steel sheet manufacturing method of this application example includes: a step of cold-rolling a hot-rolled steel sheet to produce a cold-rolled steel sheet, and a step of winding the cold-rolled steel sheet to obtain a cold-rolled coil, and then forming the cold-rolled coil into the steel sheet coil. The manufacturing method of the cold-rolled coil before the additional vibration is not particularly limited; for example, it can be the manufacturing method exemplified in Embodiment 1. By unwinding the cold-rolled steel sheet from the cold-rolled coil and passing it through a slab, and then subjecting the cold-rolled steel sheet in the slab to additional vibration under the aforementioned conditions, the amount of diffusible hydrogen in the steel can be reduced, resulting in a cold-rolled steel sheet with excellent resistance to hydrogen embrittlement.

[0271] The composition of hot-rolled steel sheets and cold-rolled steel sheets subjected to additional vibration by the dehydrogenation device 300b is not limited. According to this embodiment, by subjecting high-strength steel sheets with tensile strength of 590 MPa or more, more preferably 1180 MPa or more, and even more preferably 1470 MPa or more to additional vibration by the dehydrogenation device 300b, the amount of diffusible hydrogen in the steel can be reduced, thereby obtaining high-strength steel sheets with excellent resistance to hydrogen embrittlement.

[0272] The composition of hot-rolled steel sheets and cold-rolled steel sheets can be, for example, the composition exemplified in Embodiment 1.

[0273] Annealing apparatus

[0274] Similar to Embodiment 1, the steel sheet manufacturing system may include an annealing apparatus for annealing cold-rolled and hot-rolled steel sheets. The timing of annealing is not particularly limited; however, since hydrogen typically penetrates the steel during the annealing process, it is preferable to anneal before additional vibration in order to ultimately obtain a steel sheet with excellent resistance to hydrogen embrittlement. The annealing apparatus may be a batch annealing furnace or a continuous annealing apparatus.

[0275] Annealing process

[0276] Annealing can be performed on cold-rolled steel sheets and hot-rolled steel sheets in the same manner as in Embodiment 1. There is no particular limitation on the timing of annealing, but it is preferable to perform annealing before the vibration-assisted additional process. The annealing process can be carried out using a batch annealing furnace or a continuous annealing apparatus.

[0277] [Batch annealing]

[0278] When using a batch annealing furnace for the annealing process, the steel sheet manufacturing system includes: a batch annealing furnace for batch annealing cold-rolled or hot-rolled coils to obtain annealed coils, and a dehydrogenation device 300b for forming the annealed coils into the aforementioned steel sheet coil C. The annealed coils are cooled using furnace cooling or air cooling within the batch annealing furnace. An uncoiling device uncoils the annealed steel sheet from the annealed coils and supplies it to a plate-passing device, which passes the annealed steel sheet through the plate. A vibration attachment device 60 applies vibration to the annealed steel sheet in the plate-passing device under the aforementioned conditions. This vibration reduces the amount of diffusible hydrogen in the steel, resulting in an annealed steel sheet with excellent resistance to hydrogen embrittlement.

[0279] When using a batch annealing furnace for the annealing process, the steel sheet manufacturing method includes: a process of winding cold-rolled steel sheet or hot-rolled steel sheet to form cold-rolled coil or hot-rolled coil; and a process of batch annealing the cold-rolled coil or hot-rolled coil to obtain annealed coil; and then forming the annealed coil into the aforementioned steel sheet coil. The annealed coil is cooled using furnace cooling or air cooling within the batch annealing furnace. Next, the annealed steel sheet is unwound from the annealed coil and passed through a plate. The annealed steel sheet in the plate is subjected to additional vibration under the aforementioned conditions, thereby reducing the amount of diffusible hydrogen in the steel and obtaining a hot-rolled steel sheet or cold-rolled steel sheet with excellent resistance to hydrogen embrittlement.

[0280] Annealing based on a continuous annealing apparatus

[0281] Annealing can also be performed by passing cold-rolled or hot-rolled steel sheets through a continuous annealing line (CAL). When using a continuous annealing line for the annealing process, the steel sheet manufacturing system includes: a pre-annealing uncoiling device for uncoiling cold-rolled or hot-rolled steel sheets from cold-rolled or hot-rolled coils; a continuous annealing furnace for continuously annealing the aforementioned cold-rolled or hot-rolled steel sheets to produce annealed steel sheets; an annealed steel sheet winding device for winding the annealed steel sheets to obtain annealed coils; and a dehydrogenation device 300b for producing the aforementioned annealed coils into the aforementioned steel sheet coil C. The configuration of the continuous annealing line is the same as in Embodiment 1. The uncoiling device of the dehydrogenation device 300b uncoils the annealed steel sheet from the annealed coil and supplies it to the passing device, which passes the annealed steel sheet through the plate. A vibration attachment device 60 applies vibration to the annealed steel sheet in the passing plate under the aforementioned conditions. By adding this vibration, the amount of diffusible hydrogen in the steel can be reduced, resulting in annealed steel sheets with excellent resistance to hydrogen embrittlement.

[0282] When performing the annealing process using a continuous annealing apparatus, the annealed coil before vibration can be manufactured in the same manner as in Embodiment 1. Annealed steel strip is unwound from this annealed coil, and the annealed steel sheet in the through plate is subjected to vibration under the conditions described above, thereby obtaining cold-rolled or hot-rolled steel sheets with excellent resistance to hydrogen embrittlement.

[0283] [[Glazed Steel Sheet]]

[0284] Similar to Embodiment 1, the manufacturing method of the dehydrogenation device 300b and the steel plate in this embodiment can also be used to manufacture coated steel plates.

[0285] The steel sheet manufacturing system of this application example includes: a plating apparatus for forming a coating film on the surface of hot-rolled or cold-rolled steel sheet to produce a coated steel sheet; a coated steel sheet winding apparatus for winding the coated steel sheet to obtain a coated steel sheet coil; and a dehydrogenation apparatus 300b for forming the coated steel sheet coil into the steel sheet coil C. The type of coating film that can be formed on the surface of hot-rolled or cold-rolled steel sheet is not particularly limited; in addition to zinc coating, Al coating or Fe coating may also be used. The method of forming the coating film is not limited to a hot-dip galvanizing process; an electroplating process may also be used.

[0286] In addition, the steel plate manufacturing method of this application example includes: a step of forming a coating film on the surface of a hot-rolled steel plate or a cold-rolled steel plate to produce a coated steel plate, and a step of winding the coated steel plate to obtain a coated steel plate coil, and making the coated steel plate coil into the steel plate coil.

[0287] [A coating is formed using a continuous hot-dip galvanizing apparatus]

[0288] The type of coating apparatus is not particularly limited; for example, it can be a hot-dip galvanizing apparatus. In one example, the hot-dip galvanizing apparatus can be a continuous hot-dip galvanizing line (CGL). The configuration of the CGL can be the same as in Embodiment 1. The unwinding device of the dehydrogenation apparatus 300b unwinds the hot-dip galvanized steel sheet from the hot-dip galvanized steel sheet coil manufactured by the CGL and supplies it to the plate-passing device, which passes the hot-dip galvanized steel sheet through the plate. The vibration-applying device 60 applies vibration to the annealed steel sheet in the plate-passing device under the conditions described above. By applying this vibration, the amount of diffusible hydrogen in the steel can be reduced, resulting in a hot-dip galvanized steel sheet with excellent resistance to hydrogen embrittlement.

[0289] Alternatively, hot-dip galvanizing can be applied to the steel sheet before the additional vibration to produce hot-dip galvanized steel sheet. In one example, a continuous hot-dip galvanizing line (CGL) can be used to perform hot-dip galvanizing on the steel strip. The CGL can be configured the same as in Embodiment 1. The hot-dip galvanized steel sheet coil before the additional vibration can be manufactured in the same manner as in Embodiment 1. This hot-dip galvanized steel sheet coil is unwound and passed through a slab; the hot-dip galvanized steel sheet in the slab is then subjected to additional vibration under the conditions described above, thereby obtaining a hot-dip galvanized steel sheet with excellent resistance to hydrogen embrittlement.

[0290] Furthermore, the plating apparatus may include a hot-dip galvanizing apparatus and a subsequent alloying furnace. That is, in the method for manufacturing this steel sheet, the plating process may include a hot-dip galvanizing step and a subsequent alloying step. As a plating apparatus having an alloying furnace, the CGL illustrated in Embodiment 1, which has an alloying furnace downstream of the hot-dip galvanizing bath in the through-plate direction, can be used. By unwinding the alloyed hot-dip galvanized steel sheet from the alloyed hot-dip galvanized steel sheet coil formed by the hot-dip galvanizing step and the subsequent alloying step, and subjecting the alloyed hot-dip galvanized steel sheet to additional vibration under the aforementioned conditions, an alloyed hot-dip galvanized steel sheet with excellent resistance to hydrogen embrittlement can be obtained.

[0291] Similar to Embodiment 1, the steel plate manufacturing system may further include a tempering rolling apparatus, which performs tempering rolling on the hot-rolled steel plate, cold-rolled steel plate, and coated steel plate with various coatings on the surface of the hot-rolled or cold-rolled steel plate obtained as described above for purposes such as shape correction and surface roughness adjustment. Additionally, the steel plate manufacturing system may further include a coating equipment, which applies various coating treatments, such as resin or grease coating, to the surface of the hot-rolled steel plate, cold-rolled steel plate, and coated steel plate with various coatings on the surface of the hot-rolled or cold-rolled steel plate obtained as described above.

[0292] That is, in the manufacturing method of this steel sheet, the hot-rolled steel sheet, cold-rolled steel sheet, and coated steel sheet with various coatings on the surface of the hot-rolled or cold-rolled steel sheet obtained as described above can be subjected to quenching and tempering rolling in the same manner as in Embodiment 1. Furthermore, various coating treatments such as resin or grease coating can be applied to the surface of the hot-rolled steel sheet, cold-rolled steel sheet, and coated steel sheet with various coatings on the surface of the hot-rolled or cold-rolled steel sheet obtained as described above.

[0293] Example

[0294] <Example 1>

[0295] Steel billets with the composition shown in Table 1, the remainder consisting of Fe and unavoidable impurities, are smelted in a converter and produced as billets using continuous casting. The resulting billets are hot-rolled, then cold-rolled, and further annealed to obtain cold-rolled steel sheets (CR). A portion of the cold-rolled steel sheets are further hot-dip galvanized to produce hot-dip galvanized steel sheets (GI). A portion of the hot-dip galvanized steel sheets are further alloyed to obtain alloyed hot-dip galvanized steel sheets (GA). CR, GI, and GA are all 1.4 mm thick and 1000 mm wide. A CAL (Cold-Dip Galvanized) furnace with heating, soaking, and cooling zones arranged sequentially is used. A CGL (Cold-Dip Galvanized) furnace with heating, soaking, and cooling zones arranged sequentially, and hot-dip galvanizing equipment located after the cooling zone, is used. A general batch annealing furnace is used as the batch annealing furnace.

[0296]

[0297] Apply additional vibration to the obtained CR, GI, GA steel sheet coils or to the steel strip unwound from the steel sheet coils. Figure 1 or Figure 4 The vibration attachment shown is used to apply vibration under the conditions of frequency, maximum amplitude, and irradiation time shown in Table 2. Table 2 shows case A for applying vibration to steel sheet coils and case B for applying vibration to unwound steel strips. When applying vibration to steel sheet coils, the following is used... Figure 5 (a), (c) and Figure 6 The dehydrogenation device shown. When applying additional vibration to the steel strip, use... Figure 3 , 4(a) shows the dehydrogenation apparatus. When applying vibration to a steel sheet coil (outer diameter: 1500 mm, inner diameter: 610 mm, width: 1000 mm), the dimensions of the housing are: height: 2500 mm, depth: 2000 mm, width: 2500 mm. When applying vibration using an electromagnet, the electromagnet is arranged on the inner wall of the housing in a manner that surrounds the steel sheet coil. When applying vibration using an oscillator, oscillators 72 are arranged at 10° intervals along the circumference of the steel sheet coil on its surface. When applying vibration to a steel strip in a through-plate, electromagnets or oscillators are arranged on both the surface and back sides of the steel strip in the through-plate. Six electromagnets are evenly arranged along the width direction of the steel strip, starting from the end of the steel strip in the width direction. It should be noted that room temperature in Table 2 refers to around 25°C. It should be noted that the maximum amplitude is adjusted by fixing the position of the vibration attachment (i.e., the distance between the vibration attachment and the steel strip S or the steel sheet coil C), and then adjusting the frequency and value of the current flowing through the electromagnet or the frequency and value of the DC pulse current flowing through the vibrator. Furthermore, the irradiation time is adjusted by adjusting the drive time of the vibration attachment when applying vibration to the steel sheet coil. When applying vibration to the unwound steel strip, the additional vibration time is adjusted by adjusting the speed of the steel strip passing through the conveyor belt.

[0298] For each steel plate subjected to vibration, the tensile properties, diffusible hydrogen content in the steel, tensile flange properties, and bending properties were evaluated using the methods described below, and the results are shown in Table 2.

[0299] Tensile tests were conducted according to JIS Z 2241 (2011). JIS No. 5 test pieces were taken from each vibrated steel plate with the tensile direction perpendicular to the rolling direction. Each test piece was used with a crosshead displacement velocity of 1.67 × 10⁻⁶. －1 Tensile tests were conducted under conditions of mm / s to determine TS (tensile strength).

[0300] Tensile flange properties were evaluated by a hole expansion test. The hole expansion test was conducted according to JIS Z 2256. A 100 mm × 100 mm sample was cut from the obtained steel sheet by shearing. In this sample, a hole with a diameter of 10 mm was punched with a clearance of 12.5%. Using a die with an inner diameter of 75 mm, a conical punch with a 60° apex angle was pressed into the hole to determine the hole diameter under the crack initiation limit, with the periphery of the hole suppressed by a blank holder force of 9 ton (88.26 kN). The limiting hole expansion rate λ (%) was calculated by the following equation (4), and the hole expansion property was evaluated based on the value of this limiting hole expansion rate.

[0301] Limiting porosity: λ(%) = {(D)} f -D0) / D0}×100····(4)

[0302] In the above formula, D f D0 is the initial pore diameter (mm) at which cracks occur. It is unrelated to the strength of the steel plate; when λ is above 20%, it is considered to have good tensile flange properties.

[0303] The bending test was conducted according to JIS Z 2248. A rectangular test piece with a width of 30 mm and a length of 100 mm was taken from the obtained steel sheet, with the axis of the bending test parallel to the rolling direction of the steel sheet. Then, a bending test was performed using the V-block method with a bending angle of 90° under a compressive load of 100 kN and a holding time of 5 seconds. It should be noted that in this invention, during the 90° V-bending test, the ridge at the bend apex was observed using a 40x microscope (RH-2000: manufactured by HIROX Corporation). The minimum bending radius (R) was defined as the bending radius at which no cracks exceeding 200 μm in length were visible. A bending test was considered successful if the value of R divided by the sheet thickness (t) (R / t) was 5.0 or less.

[0304] The diffusible hydrogen content in steel was determined using the method described above.

[0305] As shown in Table 2, in the example of the present invention, due to the additional vibration process, it is possible to manufacture a steel sheet with low hydrogen content and excellent tensile flange properties (λ) and bending properties (R / t), which are indicators of hydrogen embrittlement resistance. On the other hand, in the comparative example, either tensile flange properties (λ) or bending properties (R / t) are poor.

[0306]

[0307] In this invention, by applying vibration to the steel plate, it is possible to manufacture a steel plate with excellent resistance to hydrogen embrittlement.

[0308] Symbol Explanation

[0309] 60 Vibration Addition Device

[0310] 61 Controller

[0311] 62 Amplifier

[0312] 63 Electromagnets

[0313] 63A Magnet

[0314] 63A1 Magnetic Pole Face

[0315] 63B roll material

[0316] 64 Vibration Detector

[0317] 65 power supply

[0318] 70 Vibration Addition Device

[0319] 71 Controller

[0320] 72 Oscillators

[0321] 73 Vibration Detector

[0322] 74 Heating device

[0323] 80 Containment Department

[0324] 90 Roll Material Retention Section

[0325] 300a and 300b dehydrogenation units

[0326] S-shaped steel strip

[0327] C Steel plate coil

Claims

1. A dehydrogenation device, comprising: The containment section contains steel sheet coils formed by winding steel strips into rolls; and A vibration attachment device applies vibration to the steel sheet coil housed in the housing portion in such a manner that the frequency of the steel sheet coil vibration is 100 to 100,000 Hz and the maximum amplitude of the steel sheet coil is 10 nm to 500 μm. in, The vibration attachment is: (i) having an electromagnet and being configured such that the steel sheet coil vibrates by an external force applied to the steel sheet coil by the electromagnet, the electromagnet having magnetic pole faces that are separated from and opposite to the surface of the steel sheet coil; or, (ii) having an oscillator that contacts the steel sheet coil and being configured such that the steel sheet coil vibrates by the oscillator.

2. The dehydrogenation apparatus according to claim 1, wherein, It further includes a heating section for applying the vibration while heating the steel sheet coil.

3. The dehydrogenation apparatus according to claim 1 or 2, wherein, It further includes a vibration damping section to prevent the vibration from being transmitted to the outside of the dehydrogenation device.

4. A steel plate manufacturing system, comprising: A hot rolling mill is used to hot roll steel billets to produce hot-rolled steel plates. A hot-rolled steel sheet winding device for winding the hot-rolled steel sheet to obtain a hot-rolled coil; and The dehydrogenation apparatus according to any one of claims 1 to 3, wherein the hot-rolled coil is formed into the steel plate coil.

5. A steel plate manufacturing system, comprising: A cold rolling mill is used to cold roll hot-rolled steel sheets to produce cold-rolled steel sheets. A cold-rolled steel sheet winding device for winding the cold-rolled steel sheet to obtain a cold-rolled coil; and The dehydrogenation apparatus according to any one of claims 1 to 3, wherein the cold-rolled coil is formed into the steel sheet coil.

6. A steel plate manufacturing system, comprising: A batch annealing furnace is used to anneal cold-rolled or hot-rolled coils in batches to obtain annealed coils; and The dehydrogenation apparatus according to any one of claims 1 to 3, wherein the annealed coil is formed into the steel sheet coil.

7. A steel plate manufacturing system, comprising: An uncoiling device before annealing uncoils cold-rolled steel sheets or hot-rolled steel sheets from cold-rolled coils or hot-rolled coils, respectively. A continuous annealing furnace is used to continuously anneal the cold-rolled steel sheet or hot-rolled steel sheet to produce annealed steel sheet; An annealed steel sheet winding device for winding the annealed steel sheet to obtain an annealed coil; and The dehydrogenation apparatus according to any one of claims 1 to 3, wherein the annealed coil is formed into the steel sheet coil.

8. A steel plate manufacturing system, comprising: A coating apparatus is used to form a coating film on the surface of hot-rolled or cold-rolled steel sheets to produce coated steel sheets. A coated steel sheet winding device for winding the coated steel sheet to obtain a coated steel sheet coil; and The dehydrogenation apparatus according to any one of claims 1 to 3, wherein the coated steel sheet coil is formed into the steel sheet coil.

9. The steel plate manufacturing system according to claim 8, wherein, The plating device is a hot-dip galvanizing device.

10. The steel plate manufacturing system according to claim 8, wherein, The plating apparatus includes a hot-dip galvanizing apparatus and an alloying furnace thereafter.

11. The steel plate manufacturing system according to claim 8, wherein, The plating device is an electroplating device.

12. A method for manufacturing a steel plate, comprising the following vibration additional step: adding vibration to a steel plate coil in which a steel strip is wound into a coil, wherein the frequency of the steel plate coil is 100 to 100,000 Hz and the maximum amplitude of the steel plate coil is 10 nm to 500 μm, thereby producing a product coil. The vibration additional process is: (i) using an electromagnet to vibrate the steel sheet coil by means of an external force applied to the steel sheet coil by the electromagnet, the electromagnet having magnetic pole faces separated from and opposite to the surface of the steel sheet coil; or, (ii) using an oscillator in contact with the steel sheet coil to vibrate the steel sheet coil by means of the oscillator.

13. The method for manufacturing a steel plate according to claim 12, wherein, The process includes the steps of hot rolling a steel billet to produce a hot-rolled steel sheet, and the steps of winding the hot-rolled steel sheet to obtain a hot-rolled coil, and then forming the hot-rolled coil into the steel sheet coil.

14. The method for manufacturing a steel plate according to claim 12, wherein, The process includes a step of cold rolling a hot-rolled steel sheet to produce a cold-rolled steel sheet, and a step of winding the cold-rolled steel sheet to obtain a cold-rolled coil, and then forming the cold-rolled coil into the steel sheet coil.

15. The method for manufacturing a steel plate according to claim 12, wherein, The process includes a step of annealing cold-rolled or hot-rolled coils in batches to obtain annealed coils, and then processing the annealed coils into the steel sheet coils.

16. The method for manufacturing a steel plate according to claim 12, wherein, The process includes: unwinding cold-rolled steel sheets or hot-rolled steel sheets from cold-rolled coils or hot-rolled coils respectively; continuously annealing the cold-rolled steel sheets or hot-rolled steel sheets to obtain annealed steel sheets; and winding the annealed steel sheets to obtain annealed coils; and then forming the annealed coils into the steel sheet coils.

17. The method for manufacturing a steel plate according to claim 12, wherein, The process includes a coating process of forming a coating film on the surface of a hot-rolled steel sheet or a cold-rolled steel sheet to produce a coated steel sheet, and a process of winding the coated steel sheet to obtain a coated steel sheet coil; and then forming the coated steel sheet coil into the steel sheet coil.

18. The method for manufacturing a steel plate according to claim 17, wherein, The plating process includes a hot-dip galvanizing process.

19. The method for manufacturing a steel plate according to claim 17, wherein, The plating process includes a hot-dip galvanizing process and a subsequent alloying process.

20. The method for manufacturing a steel plate according to claim 17, wherein, The plating process includes an electroplating process.

21. The method for manufacturing the steel plate according to any one of claims 12 to 20, wherein, The product roll is made of high-strength steel plate with a tensile strength of 590 MPa or more.

22. The method for manufacturing the steel plate according to any one of claims 12 to 20, wherein, The product coil comprises a base steel plate having the following composition by mass%, wherein the composition contains, in % by mass, C: 0.030%–0.800%, Si: 0.01%–3.00%, Mn: 0.01%–10.00%, P: 0.001%–0.100%, S: 0.0001%–0.0200%, N: 0.0005%–0.0100%, and Al: less than 2.000%, with the remainder consisting of Fe and unavoidable impurities.

23. The method for manufacturing a steel plate according to claim 22, wherein, The composition, by mass%, further contains at least one element selected from Ti: less than 0.200%, Nb: less than 0.200%, V: less than 0.500%, W: less than 0.500%, B: less than 0.0050%, Ni: less than 1.000%, Cr: less than 1.000%, Mo: less than 1.000%, Cu: less than 1.000%, Sn: less than 0.200%, Sb: less than 0.200%, Ta: less than 0.100%, Ca: less than 0.0050%, Mg: less than 0.0050%, Zr: less than 0.0050%, and REM: less than 0.0050%.

24. The method for manufacturing the steel plate according to any one of claims 12 to 20, wherein, The product coil comprises a stainless steel sheet having the following composition by mass%, wherein the composition contains, in weight percent: C: 0.001%–0.400%, Si: 0.01%–2.00%, Mn: 0.01%–5.00%, P: 0.001%–0.100%, S: 0.0001%–0.0200%, Cr: 9.0%–28.0%, Ni: 0.01%–40.0%, N: 0.0005%–0.500%, and Al: less than 3.000%, with the remainder consisting of Fe and unavoidable impurities.

25. The method for manufacturing a steel plate according to claim 24, wherein, The composition, by mass%, further contains at least one element selected from Ti: less than 0.500%, Nb: less than 0.500%, V: less than 0.500%, W: less than 2.000%, B: less than 0.0050%, Mo: less than 2.000%, Cu: less than 3.000%, Sn: less than 0.500%, Sb: less than 0.200%, Ta: less than 0.100%, Ca: less than 0.0050%, Mg: less than 0.0050%, Zr: less than 0.0050%, and REM: less than 0.0050%.

26. The method for manufacturing a steel plate according to any one of claims 12 to 20, wherein, The product roll has a diffusible hydrogen content of less than 0.50 ppm by mass.

27. The method for manufacturing the steel plate according to any one of claims 12 to 20, wherein, The vibration-assisted process is performed by keeping the steel sheet coil below 300°C.

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