Dehydrogenation device, steel plate manufacturing system, and steel plate manufacturing method

Abstract

The present invention provides a steel plate dehydrogenation device, a steel plate manufacturing system and a steel plate manufacturing method capable of manufacturing a steel plate having excellent hydrogen embrittlement resistance without changing the mechanical properties of the steel plate. A dehydrogenation device comprises: a storage portion for storing a steel plate coiled in a coil form by winding a steel strip; and an acoustic wave irradiation device for irradiating the steel plate coiled in the storage portion with acoustic waves to produce a product coil.

Description

Technical Field

[0001] The present invention relates to a dehydrogenation device and a steel plate manufacturing system for manufacturing a steel plate suitable for use as a component in industrial fields such as automobiles, home appliances, and building materials. In particular, the present invention relates to a dehydrogenation device and a steel plate manufacturing system for obtaining a steel plate having a small amount of intrinsic diffusible hydrogen in steel and excellent resistance to hydrogen embrittlement, and a steel plate manufacturing method. Background Art

[0002] As a concern specific to high-strength steel sheets, it is known that hydrogen intruding into the steel sheet may cause embrittlement of the steel sheet (hydrogen embrittlement). When a continuous annealing device and a continuous hot-dip galvanizing device are used to anneal the steel sheet, a H2-N2 mixed gas, which is often used as a reducing or non-oxidizing gas, is introduced into the annealing furnace. The hydrogen in the H2-N2 mixed gas will intrude into the steel due to annealing. In addition, in steel sheets for automobiles, hydrogen is generated due to corrosion reactions in the use environment of the automobile and intrudes into the steel. If the diffusible hydrogen intruding into the steel is not sufficiently reduced, hydrogen embrittlement of the steel sheet will be caused by the diffusible hydrogen, which may lead to delayed fracture.

[0003] In the past, various studies have been conducted on methods for reducing the amount of diffusible hydrogen in steel. For example, Patent Document 1 discloses a method for reducing the amount of hydrogen trapped in steel by performing an aging treatment after annealing and elongation rolling. In addition, as a method for reducing diffusible hydrogen, there is a known method of leaving the annealed steel sheet at room temperature for a long time to separate the diffusible hydrogen from the surface of the steel sheet. Patent Document 2 discloses a method for reducing the amount of diffusible hydrogen in steel by keeping the steel sheet annealed after cold rolling in a temperature range of 50°C to 300°C for 1800s to 3200s.

[0004] Prior art literature

[0005] Patent Literature

[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 are difficult to apply to other steel sheets because the structure changes can be caused by heating and holding after annealing. In addition, the method of leaving the steel sheet at room temperature requires leaving the steel sheet for a long time, so the productivity is low.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a steel plate dehydrogenation apparatus, a steel plate manufacturing system, and a steel plate manufacturing method capable of manufacturing a steel plate having excellent hydrogen embrittlement resistance without changing the mechanical properties of the steel plate.

[0010] The inventors of the present invention have repeatedly conducted in-depth research to achieve the above-mentioned problems, and found that as long as the steel plate is irradiated with sound waves under fixed conditions, the amount of diffusible hydrogen in the steel can be reduced and hydrogen embrittlement can be suppressed. It is speculated that this is due to the following mechanism: by irradiating the steel plate with sound waves, the steel plate is forced to vibrate microvibration and repeatedly bends and deforms the steel plate. As a result, the lattice spacing on the surface is expanded compared to the center of the thickness of the steel plate. When the lattice spacing is wide, the hydrogen in the steel plate diffuses toward the surface of the steel plate with low potential energy and detaches from the surface.

[0011] The present invention has been accomplished based on the above findings. That is, the gist of the present invention is as follows.

[0012] [1] A dehydrogenation device having:

[0013] The storage section stores the steel sheet coiled material wound into a coil, and

[0014] The sonic wave irradiation device irradiates the steel sheet coil accommodated in the accommodation portion with sonic waves to produce a product coil.

[0015] [2] The dehydrogenation device according to [1] above, wherein the intensity of the sound waves generated by the sound wave irradiation device and the position of the sound wave irradiation device are set so that the maximum sound pressure level on the surface of the steel sheet coil satisfies 30 dB or more.

[0016] [3] The dehydrogenation apparatus according to [1] or [2], further comprising a heating unit for irradiating the steel sheet coil with the sound wave while heating the steel sheet coil.

[0017] [4] A dehydrogenation device comprising:

[0018] Unwinding device for unwinding steel strip from steel plate coil,

[0019] A plate-passing device for passing the steel strip through the plate,

[0020] A coiling device for coiling the steel strip, and

[0021] A sonic wave irradiation device is provided for irradiating the steel strip in the plate passing device with sonic waves to produce a product coil.

[0022] [5] The dehydrogenation device according to [4] above, wherein the intensity of the sound waves generated by the sound wave irradiation device and the position of the sound wave irradiation device are set so that the maximum sound pressure level on the surface of the steel strip satisfies 30 dB or more.

[0023] [6] The dehydrogenation apparatus according to [4] or [5], further comprising a heating unit for irradiating the steel strip with the sound waves while heating the steel strip.

[0024] [7] The dehydrogenation device according to any one of [1] to [5], further comprising a sound absorbing portion for preventing the sound waves from leaking to the outside of the dehydrogenation device.

[0025] [8] A steel plate manufacturing system comprising:

[0026] Hot rolling equipment, which hot-rolls steel billets to produce hot-rolled steel sheets,

[0027] A hot-rolled steel sheet coiling device for coiling the hot-rolled steel sheet to obtain a hot-rolled coil, and

[0028] In the dehydrogenation apparatus described in any one of [1] to [7] above, the hot-rolled coil is formed into the steel plate coil.

[0029] [9] A steel plate manufacturing system comprising:

[0030] Cold rolling equipment, which cold rolls hot rolled steel sheets to produce cold rolled steel sheets,

[0031] A cold-rolled steel sheet coiling device, which coils the cold-rolled steel sheet to obtain a cold-rolled coil, and

[0032] In the dehydrogenation apparatus described in any one of [1] to [7] above, the cold-rolled coil is made into the steel plate coil.

[0033]

[10] A steel plate manufacturing system comprising:

[0034] A batch annealing furnace for performing batch annealing on cold rolled coils or hot rolled coils to obtain annealed coils, and

[0035] In the dehydrogenation apparatus described in any one of [1] to [7], the annealed coil is formed into the steel plate coil.

[0036]

[11] A steel plate manufacturing system comprising:

[0037] Unwinding device before annealing, unwinding cold-rolled steel sheet or hot-rolled steel sheet from cold-rolled coil or hot-rolled coil,

[0038] A continuous annealing furnace is used to continuously anneal the cold-rolled steel sheet or the hot-rolled steel sheet to produce an annealed steel sheet.

[0039] An annealed steel sheet coiling device is used to coil the annealed steel sheet to obtain an annealed coil, and

[0040] In the dehydrogenation apparatus described in any one of [1] to [7], the annealed coil is formed into the steel plate coil.

[0041]

[12] A steel plate manufacturing system comprising:

[0042] A plating device is used to form a plating film on the surface of a hot-rolled steel sheet or a cold-rolled steel sheet to produce a plated steel sheet,

[0043] A plated steel sheet coiling device for coiling the plated steel sheet to obtain a plated steel sheet coil, and

[0044] In the dehydrogenation apparatus described in any one of [1] to [7], the plated steel sheet coil is formed into the steel sheet coil.

[0045]

[13] The steel sheet manufacturing system according to

[12] above, wherein the coating device is a hot-dip galvanizing device.

[0046]

[14] The steel sheet manufacturing system according to

[12] above, wherein the coating device includes a hot-dip galvanizing device and a subsequent alloying furnace.

[0047]

[15] The steel plate manufacturing system according to the above-mentioned

[12] , wherein the above-mentioned plating device is an electroplating device.

[0048]

[16] A method for manufacturing a steel plate, comprising the following sonication step: irradiating a steel plate coil obtained by winding a steel strip into a coil with sonication in such a way that the sound pressure on the surface of the steel plate coil becomes 30 dB or more to produce a product coil.

[0049]

[17] The method for manufacturing a steel plate according to

[16] above, wherein the sonication step is performed while keeping the steel plate coil at 300° C. or less.

[0050]

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

[0051] The process of unwinding steel strip from steel plate coils,

[0052] A plate-passing process of passing the steel strip through a plate, and

[0053] The process of winding the steel strip to make a finished coil.

[0054] The steel strip passing step includes a sound wave irradiation step of irradiating the steel strip with sound waves so that the sound pressure level on the surface of the steel strip satisfies 30 dB or more.

[0055]

[19] The method for manufacturing a steel plate according to

[18] above, wherein the sonication step is performed while keeping the steel strip at 300° C. or less.

[0056]

[20] A method for manufacturing a steel plate according to any one of

[16] to

[19] above, comprising the steps of hot rolling a steel slab to form a hot-rolled steel plate and coiling the hot-rolled steel plate to obtain a hot-rolled coil, and further converting the hot-rolled coil into the steel plate coil.

[0057]

[21] A method for manufacturing a steel plate according to any one of

[16] to

[19] above, comprising the steps of cold rolling a hot-rolled steel plate to obtain a cold-rolled steel plate and coiling the cold-rolled steel plate to obtain a cold-rolled coil, and further converting the cold-rolled coil into the steel plate coil.

[0058]

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

[16] to

[19] , comprising the step of batch annealing a cold-rolled coil or a hot-rolled coil to obtain an annealed coil, and further converting the annealed coil into the steel plate coil.

[0059]

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

[16] to

[19] above, comprising 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, continuously annealing the cold-rolled steel plate or the hot-rolled steel plate to obtain an annealed steel plate, and coiling the annealed steel plate to obtain an annealed coil, and further making the annealed coil into the steel plate coil.

[0060]

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

[16] to

[19] above, comprising a plating step of forming a plating film on the surface of a hot-rolled steel plate or a cold-rolled steel plate to form a plated steel plate and a step of coiling the plated steel plate to obtain a plated steel plate coil, and further forming the plated steel plate coil into the steel plate coil.

[0061]

[25] The method for manufacturing a steel sheet according to

[24] above, wherein the plating step includes a hot-dip galvanizing step.

[0062]

[26] The method for manufacturing a steel sheet according to

[24] above, wherein the plating step includes a hot-dip galvanizing step and a subsequent alloying step.

[0063]

[27] The method for manufacturing a steel sheet according to

[24] above, wherein the plating step includes an electroplating step.

[0064]

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

[16] to

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

[0065]

[29] A method for manufacturing a steel plate according to any one of

[16] to

[28] above, wherein the product coil comprises a base steel plate having the following composition, wherein the composition comprises, in mass %, 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: 2.000% or less, with the remainder being Fe and unavoidable impurities.

[0066]

[30] The method for manufacturing a steel sheet according to the above-mentioned

[29] , wherein the above-mentioned component composition further contains, in terms of mass%, at least one element selected from the group consisting of 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%.

[0067]

[31] A method for manufacturing a steel plate according to any one of

[16] to

[28] above, wherein the product coil comprises a stainless steel plate having the following composition, wherein the composition comprises, in mass %, 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: 3.000% or less, with the remainder being Fe and unavoidable impurities.

[0068]

[32] The method for manufacturing a steel plate according to the above-mentioned

[31] , wherein the above-mentioned component composition further contains, in terms of mass%, at least one element selected from the group consisting of 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%.

[0069]

[33] The method for manufacturing a steel sheet according to any one of

[16] to

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

[0070] According to the present invention, a steel sheet having excellent hydrogen embrittlement resistance can be manufactured without changing the mechanical properties of the steel sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a diagram showing an example of the configuration of the sound wave irradiation device.

[0072] Figure 2 It is a schematic diagram for illustrating an example of the structure of the dehydrogenation device of embodiment 1, (a) is a three-dimensional diagram of the dehydrogenation device, (b) is a diagram obtained by observing the dehydrogenation device from the side a, (c) is an example of a diagram obtained by observing an example of the dehydrogenation device from the side b, and (d) is a diagram obtained by observing another example of the dehydrogenation device from the side b.

[0073] Figure 3 This is a diagram showing an example of the configuration of the dehydrogenation apparatus according to the second embodiment as viewed from the coiling axis direction of the steel sheet coil.

[0074] Figure 4 This is a diagram showing an example of the arrangement of the sonic wave irradiation device for the unwound steel sheet in the dehydrogenation apparatus according to the second embodiment. DETAILED DESCRIPTION

[0075] Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments. In this specification, the numerical range represented by "to" represents a range including the numerical values ​​recorded before and after "to" as the lower limit and upper limit. In this specification, "steel plate" is a general term including hot-rolled steel plates, cold-rolled steel plates, annealed steel plates obtained by further annealing them, and plated steel plates having a plated film formed on their surfaces. The shape of the "steel plate" is not limited, and includes any of a steel plate coil and a rolled steel strip.

[0076] The dehydrogenation device reduces the amount of diffusible hydrogen in the steel by irradiating the steel plate with sound waves. According to the dehydrogenation device, since the steel plate does not need to be heated, the amount of diffusible hydrogen in the steel can be reduced without worrying about changing the structural properties of the steel plate.

[0077] In addition, in the manufacturing method of the steel plate, the steel plate is irradiated with sound waves in such a manner that the sound pressure level on the surface of the steel plate satisfies 30 dB or more. According to the manufacturing method of the steel plate, since the steel plate does not need to be heated, the amount of diffusible hydrogen in the steel can be reduced without worrying about changing the structural properties of the steel plate.

[0078] Here, the reason why the hydrogen embrittlement resistance of the steel sheet can be improved by irradiating the steel sheet with sound waves is not clear, but the present inventors speculate as follows.

[0079] That is, the steel plate is forcibly excited by irradiating the steel plate with sound waves under specified conditions. Due to the bending deformation caused by the forced excitation, the lattice spacing of the steel plate repeatedly expands (stretches) and contracts (compresses) in the thickness direction of the plate. Since the diffusible hydrogen in the steel is induced to diffuse toward the tensile side with lower potential energy, the diffusion of the diffusible hydrogen is promoted along with the expansion and contraction of the lattice spacing, and a diffusion path of diffusible hydrogen connecting the inside and the surface of the steel plate is forced to be formed. The diffusible hydrogen that has been forced to form a diffusion path is not easy to escape further to the outside of the steel plate, which is more advantageous in terms of potential energy, through the surface at the moment when the lattice spacing near the surface of the steel plate expands. It is speculated that the sound waves irradiated on the steel plate under specified conditions in this way can fully and effectively reduce the diffusible hydrogen in the steel, so that the hydrogen embrittlement of the steel plate can be well and simply suppressed.

[0080] The following describes (1) a dehydrogenation apparatus and a method for manufacturing a steel sheet by irradiating a steel sheet coil with sound waves and (2) a dehydrogenation apparatus and a method for manufacturing a steel sheet by irradiating an unwound steel sheet with sound waves while unwinding and rewinding the steel sheet coil.

[0081] <Implementation method 1>

[0082] The dehydrogenation device of this embodiment is a dehydrogenation device having a storage section for storing a steel sheet coil C wound up from a steel strip, and a sonication irradiation device for irradiating the steel sheet coil C stored in the storage section with sonication to produce a product coil. In various processes of manufacturing steel sheets, steel strips are wound up into steel sheet coils.

[0083] In addition, the method for manufacturing a steel plate of the present embodiment includes a sonic wave irradiation step as follows: a steel plate coil obtained by winding a steel strip into a coil is irradiated with sonic waves in such a manner that the sound pressure level on the surface of the steel plate coil satisfies 30 dB or more to produce a product coil. In various steps of manufacturing a steel plate, a steel strip is wound into a steel plate coil.

[0084] In the dehydrogenation device and the method for manufacturing a steel plate of the present embodiment, by irradiating the steel plate coil with sound waves, the amount of diffusible hydrogen in the steel can be reduced, thereby obtaining a steel plate having excellent hydrogen embrittlement resistance. It is considered that, in particular, in the steel plate coil, bending deformation is applied to the steel strip, and the lattice spacing of the radially outer surface of the steel strip is expanded, so that it is easy to form a hydrogen diffusion path toward the radial outer side. In the present embodiment, by irradiating the steel plate coil with sound waves, the steel strip in the state of expanding the lattice spacing of the radially outer surface is further subjected to slight bending deformation, so that the diffusible hydrogen in the steel can be further reduced.

[0085] [[Sound wave irradiation device]]

[0086] For the irradiation of the sound waves, a general sound wave irradiation device can be used. Figure 1 An example of the structure of the sound wave irradiation device is shown in FIG. Figure 1 As shown in the figure, in one example, the sound wave irradiation device 60 includes a sound pressure controller 69, a sound wave generator 62, a vibration transducer 64, a horn 66 and a speaker 68. The sound wave generator 62 converts an electrical signal of a general frequency (e.g., 50 Hz, 60 Hz) into an electrical signal of a desired frequency and transmits it to the vibration transducer 64. It should be noted that, in general, the voltage is usually AC200-240V, and is amplified to nearly 1000V inside the sound wave generator 62. The electrical signal of the desired frequency transmitted by the sound wave generator 62 is converted into mechanical vibration energy by a piezoelectric element located inside the vibration transducer 64, and the mechanical vibration energy is transmitted to the horn. The horn 66 amplifies the amplitude of the vibration energy transmitted by the vibration transducer 64 (or converts it into an optimal amplitude) and transmits it to the speaker 68. The speaker 68 is a component for making the vibration energy transmitted from the horn 66 directional and propagating it in the air in the form of directional sound waves. In one example, from the viewpoint of irradiating highly directional sound waves toward the steel sheet coil, the horn 68 may be a cylindrical member. In addition, the sound pressure level on the surface of the steel sheet coil is detected by the noise meter 70 and input to the sound pressure controller 69. The sound pressure controller 69 compares the target value of the sound pressure on the surface of the steel sheet coil with the actual value of the sound pressure detected by the noise meter 70, adjusts the sound pressure level via the horn 66 so that the actual value coincides with the target value, and irradiates the sound waves from the horn 68.

[0087] [[Dehydrogenation unit]]

[0088] In the present method for manufacturing a steel sheet, the method for irradiating the steel sheet coil with sound waves is not particularly limited. As an example, from the viewpoint of irradiating the steel sheet coil with sound waves having high directivity, the horn 68 may be a cylindrical member. Figure 2 An example of a dehydrogenation apparatus for reducing diffusible hydrogen in steel by irradiating a steel sheet coil with sound waves is shown in FIG. Figure 2 (a) is a perspective view of the dehydrogenation device 300a. It should be noted that Figure 2 (a) shows only several rows of horns 68 closest to the front side when viewed from the side a of the dehydrogenation device 300a. Figure 2 (b) is a view of the dehydrogenation device 300a viewed from the side a. Figure 2 (a) and Figure 2 As shown in (b) of FIG. 1 , the dehydrogenation device 300a includes a storage section 80 for storing the steel sheet coil C, and includes a horn 68 for irradiating the steel sheet coil C stored in the storage section 80 with sound waves. The number and arrangement of the horns 68 are not particularly limited. Figure 2In the example of FIG. 1 , a plurality of horns 68 are arranged so as to surround the periphery of the steel sheet coil C. Figure 2 (a) to (d) are not shown in the figure, but each speaker 68 is sequentially connected with a horn 66, a vibration transducer 64, a sound wave generator 62 and a sound pressure controller 69, so that the sound waves are irradiated to the steel sheet coil C by the speaker 68. By arranging a plurality of speakers 68 in a manner surrounding the periphery of the steel sheet coil C, the sound waves can be uniformly irradiated to the steel sheet coil C. Figure 2 When the horn 68 is provided so as to surround the steel sheet coil C as shown in (a), the sound waves irradiated by the horn 68 cause the coil surface of the steel sheet coil C to vibrate. It is considered that in the steel sheet coil C vibrating on the coil surface, the vibration propagates toward the inner periphery of the coil using the air between the steel sheets in the steel sheet coil C as a medium, or the vibration propagates directly from the vibration of the outermost peripheral surface of the coil toward the inner periphery of the coil, and finally the vibration propagates to the innermost part of the coil. It should be noted that, as shown in the figure, the storage section 80 can accommodate a plurality of steel sheet coils C.

[0089] From the viewpoint of uniformly irradiating the entire surface of the steel sheet coil C with sound waves, it is preferred that a plurality of horns be arranged in the height direction and the width direction of the inner wall of the dehydrogenation device 300 a so as to surround the steel sheet coil C. Figure 2 (c) in FIG. 1 shows an example of a dehydrogenation device observed from the side b. Figure 2 As shown in (c) in FIG. 1 , the cylindrical horns 68 can be arranged at uniform intervals along the height direction and the width direction of the side b. Figure 2 (d) in FIG. 1 shows another example of a dehydrogenation device observed from the side b. The horn 68 can irradiate the steel sheet coil C with sound waves, for example, Figure 2 As shown in (d) in FIG. 1 , a square tube with a rectangular cross section may be used. In addition, a horn 68 may be placed in the hollow portion defined by the steel sheet coil C to irradiate the steel sheet coil C with sound waves from the inside.

[0090] It should be noted that since diffusible hydrogen is released from the end faces of the steel sheet coil C, it is considered that the efficiency of reducing the amount of diffusible hydrogen in the central portion in the steel sheet width direction is lower than that in the end portions in the steel sheet width direction of the steel sheet coil C. Therefore, it is preferred that the horn 68 is particularly provided near the central portion of the steel sheet coil C in the steel sheet width direction.

[0091] It should be noted that, as shown in the figure, a coil holding portion 90 is appropriately provided in the dehydrogenation device 300a. The form of the coil holding portion 90 is not particularly limited. When the steel plate coil C is placed in a manner such that the winding axis of the steel plate coil C is parallel to the bottom plate of the dehydrogenation device 300a, as shown in FIG. Figure 2 As shown in (a) of FIG. 1 , the coil holding portion 90 may be a pair of rod-shaped members that clamp the steel sheet coil C from both sides so as to allow the steel sheet coil C to roll in the dehydrogenation device 300a. Figure 2 As shown in (a) in the figure, the coil holding part 90 may be a pair of rod-shaped members having a concave upper surface along the arc described by the outermost periphery of the steel sheet coil C. In addition, although not shown, the steel sheet coil C may be placed in a manner such that the winding axis direction is parallel to the bottom plate of the dehydrogenation device 300a.

[0092] [[frequency]]

[0093] The frequency of the sound wave irradiated by the sound wave irradiation device 60 is not particularly limited and can be set according to the type of steel sheet coil C accommodated in the accommodation portion 80. From the viewpoint that the rigidity of the steel sheet does not hinder vibration and further promotes the diffusion of hydrogen, the frequency of the sound wave irradiated by the sound wave irradiation device 60 is preferably 10 Hz or more. It should be noted that "frequency" refers to the frequency (Hz) of the sound wave output side set in any sound wave irradiation device. The higher the frequency, the higher the directivity of the sound wave, so it is easier to control the position of the irradiated sound wave. Therefore, the frequency of the sound wave is more preferably 100 Hz or more, more preferably 500 Hz or more, and most preferably 1000 Hz or more, 3000 Hz or more, or 5000 Hz. It should be noted that the upper limit of the frequency of the sound wave is not particularly limited, preferably 100 kHz or less, more preferably 80 kHz or less, and more preferably 50 kHz or less. This is because: if the frequency of the sound wave is 100000 Hz or less, it is possible to properly prevent the attenuation of the sound wave vibration in the air and fully excite the steel plate. It should be noted that the frequency of the sound waves generated by the sound wave irradiation device 60 can be controlled by adjusting the frequency and waveform of the AC voltage signal sent from the sound wave generator to the vibration transducer.

[0094] [[Sound pressure level]]

[0095] In the method for manufacturing a steel plate of the present embodiment, it is one of the important components that the steel plate coil is irradiated with a sound wave having a sound pressure level of 30 dB or more on the surface of the steel plate coil. Therefore, in the dehydrogenation device 300a of the present embodiment, it is preferable to set the maximum sound pressure level on the surface of the steel plate coil C to meet the intensity of the sound wave generated by the sound wave irradiation device 60 and the position of the sound wave irradiation device 60 to meet 30 dB or more. It should be noted that the surface of the steel plate coil C refers to the surface of the steel plate located at the outermost periphery of the steel plate coil C. Even if the sound wave with a sound pressure level of less than 30 dB is irradiated, the vibration given to the steel plate by the irradiated sound wave is hindered by the rigidity of the steel plate itself, and the diffusion of hydrogen to the outside of the steel plate cannot be promoted, and the amount of diffusible hydrogen in the steel cannot be fully reduced. In addition, the maximum sound pressure level on the surface of the steel plate coil C of the irradiated sound wave is more preferably 60 dB or more, and further 80 dB or more. The higher the sound pressure level of the irradiated sound wave, the greater the vibration of the steel plate, and the more residual hydrogen is released from the steel, thereby improving the hydrogen embrittlement resistance. On the other hand, based on the performance of the generally available sound wave irradiation device 60, the intensity of the sound waves generated by the sound wave irradiation device and the position of the sound wave irradiation device can be set in such a way that the maximum sound pressure level on the surface of the steel sheet coil C is usually 150 dB or less. It should be noted that the "sound pressure level" can be measured by setting a sound pressure meter near the surface of the steel sheet coil and directly below the sound wave irradiation device 60. Alternatively, if the intensity I of the sound waves generated by the sound wave irradiation device 60 and the distance D between the sound wave irradiation device and the steel sheet coil are determined, the "sound pressure level on the surface of the steel sheet coil" can also be grasped in an offline manner. That is, the "sound pressure level on the surface of the steel sheet coil" can be grasped by setting a sound pressure meter at a position at a distance D from the offline sound wave irradiation device that generates the sound waves of intensity I in the main traveling direction of the sound waves.

[0096] [[Irradiation time]]

[0097] The time for irradiating the steel sheet coil C with sound waves is not particularly limited. In the present embodiment, since the steel sheet coil is irradiated with sound waves after hot rolling or cold rolling, unlike the case where the steel strip is irradiated with sound waves while being passed through the plate, the sound waves can be irradiated without being restricted by the irradiation time. It is speculated that the longer the time of irradiation with sound waves, the more diffusible hydrogen can be reduced, so the time of irradiation with sound waves is preferably more than 1 minute. The irradiation time of sound waves is more preferably more than 30 minutes, and more preferably more than 60 minutes. On the other hand, from the perspective of productivity, the irradiation time of sound waves is preferably less than 30,000 minutes, more preferably less than 10,000 minutes, and more preferably less than 1,000 minutes. The irradiation time of sound waves can be controlled, for example, by controlling the driving time of the sound wave irradiation device 60 using a control unit.

[0098] [[Heating device]]

[0099] [[Keeping temperature of steel coil]]

[0100] The dehydrogenation device 300a may further include a heating unit for irradiating the steel sheet coil C with sound waves while heating it. The temperature of the steel sheet coil C in the sound wave irradiation step is not particularly limited. This is because according to the present embodiment, the diffusible hydrogen in the steel can be reduced even if the steel sheet coil C is not heated and maintained. However, since the diffusion rate of hydrogen can be further increased by irradiating the steel sheet coil C with sound waves while heating it using the heating unit, the amount of diffusible hydrogen in the steel can be further reduced. Therefore, the temperature of the steel sheet coil C when irradiating the sound waves is preferably 30°C or more, more preferably 50°C or more, and further preferably 100°C or more. The upper limit of the temperature of the steel sheet coil C in the sound wave irradiation step is not particularly limited, but from the viewpoint of appropriately preventing the structural change of the steel sheet coil C, as described later, it is preferably 300°C or less, except when the sound wave irradiation is performed in batch annealing. It should be noted that in the present embodiment, the temperature of the steel sheet coil C when irradiating the sound waves is based on the temperature at the radial half position of the steel sheet coil. The temperature at the radial half position of the steel sheet coil can be measured by directly clamping a thermocouple at the radial half position of the steel sheet coil and measuring the temperature of the steel strip at the radial half position. The heating method of the steel sheet coil C can be, for example, a method of providing a heater on one side wall of the storage part, or a general method such as a method of sending high-temperature air generated outside into the storage part and circulating it in the storage part.

[0101] The dehydrogenation device 300a of the present embodiment may further include a sound absorbing portion outside the dehydrogenation device 300a for preventing the sound waves from leaking out. The sound absorbing portion may be, for example, a sound absorbing material provided so as to surround the inner wall of the housing portion 80 .

[0102] According to the present embodiment, the amount of diffusible hydrogen in the product coil C obtained after the sonication can be reduced to 0.5 mass ppm or less. By reducing the amount of diffusible hydrogen in the product coil C to 0.5 mass ppm or less, hydrogen embrittlement of the steel sheet can be prevented. The amount of diffusible hydrogen in the steel after the sonication is preferably 0.3 mass ppm or less, and more preferably 0.2 mass ppm or less.

[0103] The amount of diffusible hydrogen of the product coil C is measured as follows. A test piece with a length of 30 mm and a width of 5 mm is taken from the radial half position of the product coil. When the steel plate is a hot-dip galvanized steel plate or an alloyed hot-dip galvanized steel plate, the hot-dip galvanized layer or the alloyed hot-dip galvanized layer of the test piece is removed by grinding or alkali. Then, the amount of hydrogen released from the test piece is measured using the Thermal Desorption Spectrometry (TDS). Specifically, after continuous heating from room temperature to 300°C at a heating rate of 200°C / h, it is cooled to room temperature, and the cumulative amount of hydrogen released from the test piece from room temperature to 210°C is measured as the amount of diffusible hydrogen of the product coil C.

[0104] Hereinafter, application examples of the present embodiment will be described in more detail.

[0105] [[Hot-rolled steel sheet]]

[0106] The dehydrogenation apparatus 300a and the method for producing a steel sheet according to the present embodiment can be used to produce a hot-rolled steel sheet.

[0107] The steel plate manufacturing system of this application example is a steel plate manufacturing system having a hot rolling device for hot rolling a steel slab to obtain a hot rolled steel plate, a hot rolled steel plate coiling device for coiling the hot rolled steel plate to obtain a hot rolled coil, and a steel plate dehydrogenation device for converting the hot rolled coil into the steel plate coil C. The hot rolling device performs hot rolling consisting of rough rolling and finish rolling on a steel slab having a known component composition to obtain a hot rolled steel plate. The hot rolled steel plate coiling device coils the hot rolled steel plate to obtain a hot rolled coil. The dehydrogenation device 300a irradiates the hot rolled coil with sound waves under the above-mentioned conditions as the steel plate coil C. By irradiating the sound waves, the amount of diffusible hydrogen in the steel can be reduced to obtain a hot rolled steel plate with excellent hydrogen embrittlement resistance. It should be noted that the obtained hot rolled steel plate can be further cold rolled to obtain a cold rolled steel plate.

[0108] The method for manufacturing a steel plate of this application example includes a step of hot-rolling a steel billet to obtain a hot-rolled steel plate, and a step of coiling the hot-rolled steel plate to obtain a hot-rolled coil, wherein the hot-rolled coil is made into the steel plate coil. The method for manufacturing the hot-rolled coil before irradiation with sound waves is not particularly limited, as long as a steel billet having a known composition is subjected to hot rolling consisting of rough rolling and finish rolling to obtain a hot-rolled steel plate, and the hot-rolled steel plate is coiled using a known method to obtain a hot-rolled coil. By irradiating the hot-rolled coil with sound waves under the above conditions, the amount of diffusible hydrogen in the steel can be reduced to obtain a hot-rolled steel plate with excellent hydrogen embrittlement resistance. It should be noted that the obtained hot-rolled steel plate can be further cold-rolled to obtain a cold-rolled steel plate.

[0109] [[Cold rolled steel sheet]]

[0110] The dehydrogenation apparatus 300a and the method for manufacturing a steel sheet according to the present embodiment can also be used to manufacture a cold-rolled steel sheet.

[0111] The steel sheet manufacturing system of this application example is a steel sheet manufacturing system including a cold rolling device for cold rolling a hot-rolled steel sheet to obtain a cold-rolled steel sheet, a cold-rolled steel sheet coiling device for coiling the cold-rolled steel sheet to obtain a cold-rolled coil, and a dehydrogenation device 300a for converting the cold-rolled coil into the steel sheet coil C. The cold rolling device performs or does not perform hot-rolled sheet annealing on a known hot-rolled steel sheet, and performs one cold rolling or two or more cold rollings with intermediate annealing on the hot-rolled steel sheet after hot rolling or the hot-rolled steel sheet after hot-rolled sheet annealing to obtain a cold-rolled steel sheet having a final sheet thickness. The cold-rolled steel sheet coiling device coils the cold-rolled steel sheet according to a known method to obtain a cold-rolled coil. The dehydrogenation device 300a uses the cold-rolled coil as the steel sheet coil C, and irradiates the cold-rolled coil with sound waves under the above-mentioned conditions. By irradiating the sound waves, the amount of diffusible hydrogen in the steel can be reduced to obtain a cold-rolled steel sheet having excellent hydrogen embrittlement resistance. It should be noted that the steel plate manufacturing system may further include a dehydrogenation device 300a capable of irradiating a hot-rolled coil obtained by coiling a hot-rolled steel plate after hot rolling under the above-mentioned conditions with sound waves. Then, the hot-rolled steel plate is unwound from the hot-rolled coil irradiated with sound waves and cold-rolled to obtain a cold-rolled coil, and the cold-rolled coil is further irradiated with sound waves by the dehydrogenation device 300a, thereby further reducing the amount of diffusible hydrogen in the steel and obtaining a steel plate having particularly excellent hydrogen embrittlement resistance.

[0112] The manufacturing method of the steel plate of this application example includes the steps of cold rolling a hot-rolled steel plate to form a cold-rolled steel plate, and the step of coiling the cold-rolled steel plate to obtain a cold-rolled coil, and the cold-rolled coil is made into the steel plate coil. The manufacturing method of the cold-rolled coil before irradiation with sound waves is not particularly limited. In one example, a steel billet having a known composition can be subjected to hot rolling consisting of rough rolling and finish rolling to form a hot-rolled steel plate, and the hot-rolled steel plate can be subjected to or not subjected to hot-rolled plate annealing, and the hot-rolled steel plate after hot rolling or the hot-rolled steel plate after hot-rolled plate annealing is subjected to one cold rolling or two or more cold rollings with intermediate annealing to form a cold-rolled steel plate with a final plate thickness. The cold-rolled steel plate after cold rolling is coiled according to a known method to form a cold-rolled coil. The cold-rolled coil is irradiated with sound waves under the above conditions, thereby reducing the amount of diffusible hydrogen in the steel and obtaining a cold-rolled steel plate with excellent hydrogen embrittlement resistance. It should be noted that, in addition to irradiating the cold-rolled coil with sonic waves, the hot-rolled steel sheet after hot rolling may be coiled to form a hot-rolled coil, and the hot-rolled coil may also be irradiated with sonic waves under the above-mentioned conditions. Then, the hot-rolled steel sheet is unwound from the hot-rolled coil irradiated with sonic waves, cold-rolled to form a cold-rolled coil, and the cold-rolled coil is further irradiated with sonic waves, thereby further reducing the amount of diffusible hydrogen in the steel and obtaining a steel sheet having particularly excellent hydrogen embrittlement resistance.

[0113] In the present embodiment, the type of hot-rolled steel sheet or cold-rolled steel sheet irradiated with the sound wave is not particularly limited. The component composition of the steel sheet is not particularly limited. As a steel sheet to which the embodiment can be particularly preferably applied, a steel sheet having the following component composition can be exemplified. First, the appropriate range of the component composition of the steel sheet and the reason for its limitation are described.

[0114] [Required Ingredients]

[0115] C: 0.030%~0.800%

[0116] C is an element necessary for improving strength. By making the C content 0.030% or more, particularly appropriate strength can be obtained. In addition, by making the C content 0.800% or less, embrittlement of the material itself can be particularly appropriately prevented. From such a viewpoint, the C content is preferably 0.030% or more, preferably 0.800% or less. The C content is more preferably 0.080% or more. In addition, the C content is more preferably 0.500% or less.

[0117] Si: 0.01% to 3.00%,

[0118] Si is a solid solution strengthening element that becomes a substitutional solid solution and greatly hardens the material, and is effective in increasing the strength of the steel plate. In order to obtain the effect of increasing strength by adding Si, the amount of Si is preferably 0.01% or more. On the other hand, from the perspective of preventing the embrittlement of steel and the reduction of ductility, and preventing red scales, etc., to obtain good surface properties, and then obtain good plating appearance and plating adhesion, the amount of Si is preferably 3.00% or less. Therefore, Si is preferably 0.01% or more, preferably 3.00% or less. Si is more preferably 0.10% or more, and more preferably 2.50% or less.

[0119] Mn: 0.01%~10.00%

[0120] Mn increases the strength of the steel plate by solid solution strengthening. In order to obtain this effect, the Mn content is preferably 0.01% or more. On the other hand, by making the Mn content 10.00% or less, Mn segregation can be appropriately prevented, uneven steel structure can be prevented, and hydrogen embrittlement can be further suppressed. Therefore, the Mn content is preferably 10.00% or less. The Mn content is more preferably 0.5% or more, and more preferably 8.00% or less.

[0121] P: 0.001%~0.100%

[0122] P is an element that has a solid solution strengthening effect and can be added according to the desired strength. In order to obtain such an effect, it is preferred that the P amount is 0.001% or more. On the other hand, by making the P amount less than 0.100%, excellent weldability can be obtained. In addition, by making the P amount less than 0.100%, it is possible to prevent the reduction of the alloying rate when a galvanized film is formed on the surface of the steel sheet and the galvanized film is alloyed to form an alloyed galvanized film, thereby forming a galvanized film of excellent quality. Therefore, the P amount is preferably 0.001% or more, preferably 0.100% or less. The P amount is more preferably 0.003% or more. In addition, the P amount is more preferably 0.050% or less.

[0123] S: 0.0001%~0.0200%

[0124] By reducing the amount of S, it is possible to appropriately prevent the embrittlement of steel during hot working, and appropriately prevent the generation of sulfides to improve local deformability. Therefore, the amount of S is preferably 0.0200% or less, more preferably 0.0100% or less, and further preferably 0.0050% or less. The lower limit of the amount of S is not particularly limited, but due to production technology constraints, the amount of S is preferably 0.0001% or more, and more preferably 0.0050% or less.

[0125] N: 0.0005%~0.0100%

[0126] By reducing the amount of N, the aging resistance of steel can be improved. Therefore, the amount of N is preferably 0.0100% or less, and more preferably 0.0070% or less. The lower limit of the amount of N is not particularly limited, but due to production technology constraints, the amount of N is preferably 0.0005% or more, and more preferably 0.0010% or more.

[0127] Al: 2.000% or less

[0128] Al is an element that acts as a deoxidizer and is effective for the cleanliness of steel, and is preferably added in the deoxidation process. In order to obtain the addition effect, the amount of Al is preferably 0.001% or more when added. On the other hand, from the viewpoint of appropriately preventing the occurrence of cracks in the steel sheet during continuous casting, the amount of Al is preferably 2.000% or less. The amount of Al is more preferably 0.010% or more. In addition, the amount of Al is more preferably 1.200% or less.

[0129] [Optional Ingredients]

[0130] The component composition may further contain, in terms of mass %, at least one element selected from the group consisting of 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%.

[0131] Ti: 0.200% or less

[0132] Ti contributes to the strength of the steel sheet by precipitation strengthening of the steel and fine grain strengthening due to the suppression of the growth of ferrite grains. When Ti is added, it is preferably 0.005% or more. When Ti is added, the amount of Ti is more preferably 0.010% or more. In addition, by making the amount of Ti 0.200% or less, the precipitation of carbonitrides can be appropriately prevented, and the formability can be further improved. Therefore, when adding Ti, it is preferably added in an amount of 0.200% or less. The amount of Ti is more preferably 0.100% or less.

[0133] Nb: 0.200% or less, V: 0.500% or less, W: 0.500% or less

[0134] Nb, V, and W are effective for precipitation strengthening of steel. When Nb, V, and W are added, it is preferably 0.005% or more, respectively. When Nb, V, and W are added, it is more preferably 0.010% or more, respectively. In addition, by making Nb less than 0.200% and V and W less than 0.500%, the precipitation amount of carbonitrides can be appropriately prevented in the same way as Ti, and the formability can be further improved. Therefore, when Nb is added, its addition amount is preferably 0.200% or less, and more preferably 0.100% or less. When V and W are added, their addition amounts are preferably 0.500% or less, respectively, and more preferably 0.300% or less, respectively.

[0135] B: 0.0050% or less

[0136] B is effective for strengthening the grain boundaries and increasing the strength of the steel sheet. When B is added, it is preferably 0.0003% or more. In addition, in order to obtain more ideal formability, B is preferably 0.0050% or less. Therefore, when B is added, its addition amount is preferably 0.0050% or less, and more preferably 0.0030% or less.

[0137] Ni: 1.000% or less

[0138] Ni is an element that increases the strength of steel by solid solution strengthening. When Ni is added, it is preferably 0.005% or more. In addition, from the viewpoint of reducing the area ratio of hard martensite and further improving ductility, Ni is preferably 1.000% or less. Therefore, when Ni is added, its addition amount is preferably 1.000% or less, and more preferably 0.500% or less.

[0139] Cr: 1.000% or less, Mo: 1.000% or less

[0140] Cr and Mo can be added as needed because they have the effect of improving the balance between strength and formability. When Cr and Mo are added, preferably Cr: 0.005% or more and Mo: 0.005% or more. In addition, from the viewpoint of reducing the area ratio of hard martensite and further improving ductility, Cr and Mo are preferably Cr: 1.000% or less and Mo: 1.000% or less, respectively. Cr and Mo are preferably Cr: 0.500% or less and Mo: 0.500% or less, respectively.

[0141] Cu: 1.000% or less

[0142] Cu is an element effective for strengthening steel and can be added as needed. When Cu is added, it is preferably 0.005% or more. In addition, from the viewpoint of reducing the area ratio of hard martensite and further improving ductility, when Cu is added, its amount is preferably 1.000% or less, and more preferably 0.200% or less.

[0143] Sn: 0.200% or less, Sb: 0.200% or less

[0144] Sn and Sb inhibit decarburization of the surface layer of the steel sheet in a region of several tens of μm caused by nitridation and oxidation of the steel sheet surface, so adding them as needed is effective for ensuring strength and material stability. When Sn and Sb are added, each is preferably 0.002% or more. In addition, in order to obtain better toughness, when Sn and Sb are added, their contents are preferably 0.200% or less, and more preferably 0.050% or less.

[0145] Ta: 0.100% or less

[0146] Ta, like Ti and Nb, generates alloy carbides and alloy carbonitrides, which contribute to high strength. In addition, it is believed that by partially dissolving in Nb carbides and Nb carbonitrides, composite precipitates such as (Nb, Ta) (C, N) are generated, which significantly inhibits the coarsening of precipitates and has the effect of stabilizing the contribution to strength through precipitation strengthening. Therefore, it is preferred to contain Ta. Here, when Ta is added, it is preferably 0.001% or more. The upper limit of the amount of Ta is not particularly limited. From the perspective of reducing costs, when Ta is added, its content is preferably less than 0.100%, and more preferably less than 0.050%.

[0147] Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.0050% or less, REM: 0.0050% or less

[0148] Ca, Mg, Zr and REM are elements that make the shape of sulfides spheroidal and are effective for improving the adverse effects of sulfides on formability. When these elements are added, each is preferably 0.0005% or more. In addition, when Ca, Mg, Zr and REM are added in order to appropriately prevent the increase of inclusions and more appropriately prevent surface and internal defects, the addition amount is preferably 0.0050% or less, more preferably 0.0020% or less.

[0149] This embodiment can also be particularly preferably used for high-strength steel plates where hydrogen embrittlement is a problem. By irradiating the steel plate coil C composed of high-strength steel plates with sound waves using a dehydrogenation device 300a or applying the manufacturing method of the steel plate, the amount of diffusible hydrogen in the steel can be reduced to obtain a high-strength steel plate with excellent hydrogen embrittlement resistance. For example, the steel plate manufactured in this embodiment can be a high-strength steel plate with a tensile strength of 590MPa or more, more preferably 1180MPa or more, and further preferably 1470MPa or more. It should be noted that the tensile strength of the steel plate is measured in accordance with JIS Z 2241 (2011). In high-strength steel plates, delayed fracture caused by hydrogen embrittlement often becomes a problem. According to this embodiment, a high-strength steel plate with excellent hydrogen embrittlement resistance can be manufactured without compromising the tensile strength.

[0150] In addition, according to the dehydrogenation apparatus and the method for producing a steel plate of the present embodiment, it is also possible to produce stainless steel having excellent hydrogen embrittlement resistance by irradiating known stainless steel with sound waves.

[0151] [Required Ingredients]

[0152] C: 0.001%~0.400%

[0153] C is an indispensable element for obtaining high strength in stainless steel. Among them, if the C content exceeds 0.400%, it combines with Cr during tempering in steel manufacturing and precipitates in the form of carbides, and the carbides deteriorate the corrosion resistance and toughness of the steel. On the other hand, when the C content is less than 0.001%, sufficient strength cannot be obtained, and if it exceeds 0.400%, the above-mentioned deterioration becomes obvious. Therefore, the C content is set to 0.001% to 0.400%. The C content is preferably 0.005% or more. In addition, the C content is preferably 0.350% or less.

[0154] Si: 0.01%~2.00%

[0155] Si is an element useful as a deoxidizer. This effect is obtained by making the Si content 0.01% or more. However, if Si is contained excessively, the Si dissolved in the steel reduces the workability of the steel. Therefore, the upper limit of the Si content is 2.00%. The Si content is preferably 0.05% or more. In addition, the Si content is preferably 1.8% or less.

[0156] Mn: 0.01%~5.00%

[0157] Mn has the effect of increasing the strength of steel. These effects are obtained by containing 0.01% or more of Mn. Among them, if the Mn content exceeds 5.00%, the workability of the steel decreases. Therefore, the upper limit of the Mn content is 5.00%. The Mn content is preferably 0.05% or more. In addition, the Mn content is preferably 4.6% or less.

[0158] P: 0.001%~0.100%

[0159] P is an element that promotes grain boundary destruction caused by grain boundary segregation, so the lower the better, and the upper limit is 0.100%. The P content is preferably 0.030% or less. The P content is further preferably 0.020% or less. It should be noted that the lower limit of the P content is not particularly limited, but is 0.001% or more from the perspective of production technology.

[0160] S: 0.0001%~0.0200%

[0161] S is an element that exists as sulfide inclusions such as MnS to reduce ductility, corrosion resistance, etc., and their adverse effects are particularly evident when the content exceeds 0.0200%. Therefore, the S content is preferably as low as possible, and the upper limit of the S content is 0.0200%. The S content is preferably 0.010% or less. It is further preferred that 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 is 0.0001% or more from the perspective of production technology.

[0162] Cr: 9.0%~28.0%

[0163] Cr is a basic element constituting stainless steel and an important element showing corrosion resistance. Considering the corrosion resistance in a severe environment above 180°C, when the Cr content is less than 9%, sufficient corrosion resistance cannot be obtained. On the other hand, if it exceeds 28.0%, the effect is saturated, and there are problems in terms of economic efficiency. Therefore, the Cr content is set to 9.0% to 28.0%. The Cr content is preferably 10.0% or more. In addition, the Cr content is preferably 25.0% or less.

[0164] Ni: 0.01%~40.0%

[0165] Ni is an element that improves the corrosion resistance of stainless steel, but when it is less than 0.01%, its effect cannot be fully exerted. On the other hand, excessive addition not only hardens the stainless steel and deteriorates the formability, but also easily causes stress corrosion cracking. Therefore, the Ni content is set to 0.01% to 40.0%. The Ni content is preferably 0.1% or more. In addition, the Ni content is preferably 30.0% or less.

[0166] N: 0.0005%~0.500%

[0167] N is an element harmful to improving the corrosion resistance of stainless steel and is also an austenite-forming element. If it contains more than 0.5%, it will become a nitride and precipitate during heat treatment, and the corrosion resistance and toughness of the stainless steel will deteriorate. Therefore, the upper limit of the N content is set to 0.500%, preferably 0.20%.

[0168] Al: 3.000% or less,

[0169] In addition to being added as a deoxidizing element, Al also has the effect of inhibiting the peeling of oxide scale. However, if added in excess of 3.000%, it will lead to a decrease in elongation and deterioration of surface quality. Therefore, the upper limit of the Al content is set to 3.000%. The lower limit of the Al content is not particularly limited, but is preferably 0.001% or more. The Al content is more preferably 0.01% or more. In addition, the Al content is preferably 2.5% or less.

[0170] [Optional Ingredients]

[0171] The component composition of the stainless steel may further contain, in mass %, at least one element selected from the group consisting of 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%.

[0172] Ti: 0.500% or less

[0173] Ti is an element added to improve corrosion resistance, intergranular corrosion resistance, and deep drawability by combining with C, N, and S. Among them, if more than 0.500% is added, the stainless steel will be hardened due to solid solution Ti, and the toughness will deteriorate. Therefore, the upper limit of the Ti content is set to 0.500%. The lower limit of the Ti content is not particularly limited, but is preferably 0.003% or more. The Ti content is more preferably 0.005% or more. In addition, the Ti content is preferably 0.300% or less.

[0174] Nb: 0.500% or less

[0175] Nb is an element added to improve corrosion resistance, intergranular corrosion resistance, and deep drawability in combination with C, N, and S, as is Ti. In addition, since it promotes the suppression of crevice corrosion and repassivation in addition to the improvement of processability and high-temperature strength, it is added as needed. Among them, since excessive addition will lead to the hardening of stainless steel and deterioration of formability, the upper limit of the Nb content is set to 0.500%. The lower limit of the Nb content is not particularly limited, but is preferably 0.003% or more. The Nb content is more preferably 0.005% or more. In addition, the Nb content is preferably 0.300% or less.

[0176] V: 0.500% or less

[0177] V is added as needed to suppress crevice corrosion. However, excessive addition hardens the stainless steel and deteriorates the formability, so 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 the V content is more preferably 0.03% or more. In addition, the V content is preferably 0.300% or less.

[0178] W: 2.000% or less

[0179] W is added as needed to improve corrosion resistance and high temperature strength. However, adding more than 2.000% will harden the stainless steel, resulting in deterioration of toughness and increased cost during steel plate manufacturing, so the upper limit of the W content is set to 2.000%. The lower limit of the W content is not particularly limited, but is preferably 0.050% or more. The W content is more preferably 0.010% or more. In addition, the W content is preferably 1.500% or less.

[0180] B: 0.0050% or less

[0181] B is an element that improves the secondary processability of the product by segregating at the grain boundary. In addition to suppressing longitudinal cracks when the parts are subjected to secondary processing, it also prevents cracks from occurring in winter, so it is added as needed. Among them, excessive addition will lead to reduced processability and corrosion resistance. Therefore, the upper limit of the B content is set to 0.0050%. The lower limit of the B content is not particularly limited, and is preferably 0.0002% or more. The B content is more preferably 0.0005% or more. In addition, the B content is preferably 0.0035% or less.

[0182] Mo: 2.000% or less

[0183] Mo is an element that improves corrosion resistance, and is particularly an element that suppresses crevice corrosion in the case of a crevice structure. However, if it exceeds 2.0%, the formability is significantly deteriorated, so the upper limit of its content is 2.000%. The lower limit of the Mo content is not particularly limited, but is preferably 0.005% or more. The Mo content is more preferably 0.010% or more. In addition, the Mo content is preferably 1.500% or less.

[0184] Cu: 3.000% or less

[0185] Cu is an austenite stabilizing element like Ni and Mn, and is effective for grain refinement caused by phase transformation. In addition, in order to promote the suppression of crevice corrosion and repassivation, it is added as needed. Among them, excessive addition not only hardens, but also deteriorates toughness and formability, so the upper limit of its content is 3.000%. The lower limit of the Cu content is not particularly limited, but is preferably 0.005% or more. The Cu content is more preferably 0.010% or more. In addition, the Cu content is preferably 2.000% or less.

[0186] Sn: 0.500% or less

[0187] Sn is added as needed to improve corrosion resistance and high temperature strength. If Sn is added in excess of 0.500%, slab cracks may occur during steel plate manufacturing, so the upper limit of the content is set to 0.500% or less. The lower limit of the Sn content is not particularly limited, but is preferably 0.002% or more. The Sn content is more preferably 0.005% or more. In addition, the Sn content is preferably 0.300% or less.

[0188] Sb: 0.200% or less

[0189] Sb is an element that segregates at grain boundaries and plays a role in improving high temperature strength. If it exceeds 0.200%, Sb segregation occurs, causing cracks during welding, so the upper limit of its content is 0.200%. The lower limit of the Sb content is not particularly limited, but is preferably 0.002% or more. The Sb content is more preferably 0.005% or more. In addition, the Sb content is preferably 0.100% or less.

[0190] Ta: 0.100% or less

[0191] Ta is added as needed because it helps improve toughness by combining with C and N. However, if it is added in excess of 0.100%, the effect is saturated, which leads to an increase in manufacturing costs, so the upper limit of its content is 0.100%. The lower limit of the Ta content is not particularly limited, but is preferably 0.002% or more. The Ta content is more preferably 0.005% or more. In addition, the Ta content is preferably 0.080% or less.

[0192] Ca: 0.0050% or less, Mg: 0.0050% or less, Zr: 0.0050% or less, REM (Rare Earth Metal): 0.0050% or less

[0193] Ca, Mg, Zr and REM are elements that make the shape of sulfides spheroidal and are effective in improving the adverse effects of sulfides on formability. When any of them is added, the content of each element is preferably 0.0005% or more. Among them, when the content is excessive, inclusions and the like increase, and surface and internal defects sometimes occur. Therefore, when any of them is added, the content of each element is 0.0050% or less. The lower limit of the content of these elements is not particularly limited, and the content of each element is preferably 0.0002% or more. The content of each element is more preferably 0.0005% or more. In addition, the content of each element is preferably 0.0035% or less.

[0194] [[Annealing device]]

[0195] Annealing process

[0196] Annealing can be performed on the cold-rolled steel sheet and the hot-rolled steel sheet. That is, the manufacturing system of the steel sheet can have an annealing device for annealing the cold-rolled steel sheet and the hot-rolled steel sheet. The timing of annealing is not particularly limited. Since hydrogen generally invades the steel during the annealing process, in order to finally obtain a steel sheet with excellent hydrogen embrittlement resistance, annealing is preferably performed before irradiation with sound waves. The annealing device can be a batch annealing furnace or a continuous annealing device.

[0197] [Batch annealing]

[0198] When a batch annealing furnace is used for the annealing process, the steel plate manufacturing system includes: a batch annealing furnace for batch annealing a cold-rolled coil or a hot-rolled coil to obtain an annealed coil, and a dehydrogenation device 300a for making the above-mentioned annealed coil into the above-mentioned steel plate coil C. The batch annealing furnace performs batch annealing on the cold-rolled coil or the hot-rolled coil to make an annealed coil. It should be noted that batch annealing in this specification refers to heating and holding in a batch annealing furnace, and does not include slow cooling after heating and holding. The annealed annealed coil is cooled by furnace cooling or air cooling in the batch annealing furnace. The dehydrogenation device 300a uses the annealed coil as the steel plate coil C and irradiates the steel plate coil C with sound waves under the above-mentioned conditions. The dehydrogenation device 300a can be set separately from the batch annealing furnace, and the storage part 80 and the heating part of the dehydrogenation device 300a can also serve as a batch annealing furnace. In other words, a sonic wave irradiation device 60 for irradiating the steel sheet coil C contained in the furnace with sonic waves to form a product coil can be provided in the batch annealing furnace to form a dehydrogenation device 300a. When the storage section 80 and the heating section of the dehydrogenation device 300a are both batch annealing furnaces, the sonic wave irradiation can be performed after the batch annealing and after the annealing coil is cooled to room temperature, or the sonic wave irradiation can be performed while the annealing coil is cooled. As described above, the higher the temperature of the steel sheet, the more effectively the diffusible hydrogen can be reduced. Therefore, the sonic wave irradiation can be performed after the batch annealing and after the annealing coil is cooled to room temperature. The diffusible hydrogen in the steel can be more effectively reduced by irradiating the sonic wave while the annealing coil is cooled.

[0199] When a batch annealing furnace is used for the annealing process, the method for manufacturing a steel plate includes a step of batch annealing a cold-rolled coil or a hot-rolled coil obtained by coiling a cold-rolled steel plate or a hot-rolled steel plate to obtain an annealed coil, and the annealed coil is used as the above-mentioned steel plate coil, and the annealed coil is irradiated with sound waves under the above-mentioned conditions. First, the cold-rolled steel plate or the hot-rolled steel plate is coiled by a known method to form a cold-rolled coil or a hot-rolled coil. Next, the cold-rolled coil or the hot-rolled coil is placed in a batch annealing furnace, and batch annealing is performed in the batch annealing furnace to form an annealed coil. The annealed coil after annealing is cooled by furnace cooling or air cooling in the batch annealing furnace. Next, the annealed coil is irradiated with sound waves under the above-mentioned conditions. The irradiation of the annealed coil with sound waves can be performed as long as it is carried out during the batch annealing, that is, during the heating and maintenance of the cold-rolled coil or the hot-rolled coil. In addition, the irradiation of sound waves can be performed after batch annealing, that is, after the cold-rolled coil or the hot-rolled coil is heated and maintained. The irradiation of sound waves can be performed after the batch annealing, after the annealed coil is cooled to room temperature, or while the annealed coil is cooled. As described above, the higher the temperature of the steel plate, the more effectively the diffusible hydrogen can be reduced. Therefore, it is preferred to irradiate the annealed coil with sound waves while cooling the annealed coil during or after the batch annealing. The irradiation of the annealed coil with sound waves can also be performed in a batch annealing furnace, or the annealed coil can be taken out of the batch annealing furnace. It is preferred to irradiate the annealed coil with sound waves in a batch annealing furnace. By irradiating the annealed coil with sound waves in a batch annealing furnace, the diffusible hydrogen in the steel can be effectively reduced.

[0200] [Annealing using a continuous annealing device]

[0201] Annealing can also be performed by passing the cold-rolled steel sheet or the hot-rolled steel sheet through a continuous annealing device (Continuous Annealing Line: CAL). When the annealing process is performed using a continuous annealing device, the steel sheet manufacturing system has: a pre-annealing unwinding device for unwinding the cold-rolled steel sheet or the hot-rolled steel sheet from a cold-rolled coil or a hot-rolled coil, a continuous annealing furnace for continuously annealing the cold-rolled steel sheet or the hot-rolled steel sheet to form an annealed steel sheet, an annealing steel sheet coiling device for coiling the annealed steel sheet to obtain an annealed coil, and a dehydrogenation device 300a for making the annealed coil into the steel sheet coil C. The pre-annealing unwinding device unwinds the cold-rolled steel sheet or the hot-rolled steel sheet from the cold-rolled coil or the hot-rolled coil, and supplies the cold-rolled steel sheet or the hot-rolled steel sheet to the CAL. The structure of the CAL is not particularly limited. In one example, the CAL has a continuous annealing furnace in which a heating zone, a soaking zone, and a cooling zone are sequentially arranged. The cooling belt may be composed of a plurality of cooling belts, in which case, a portion of the cooling belt may be a holding belt for keeping the cold-rolled steel strip in a certain temperature range during the cooling process, or a reheating belt for reheating the steel plate during the cooling process. In addition, the upstream side of the heating belt in the plate passing direction may also be a preheating belt. The unwinding device before annealing may be an uncoiler arranged upstream of the continuous annealing furnace of CAL. The annealed steel plate coiling device may be a tension coiler arranged downstream of the continuous annealing furnace of CAL. In CAL, (A) a cold-rolled steel sheet or hot-rolled steel sheet unwound from a cold-rolled coil or hot-rolled coil by an unwinder, (B) the sheet is passed through a continuous annealing furnace where a heating zone, a soaking zone and a cooling zone are located from the upstream side in the sheet passing direction, (B-1) the cold-rolled steel sheet or hot-rolled steel sheet is annealed in the heating zone and the soaking zone to form an annealed steel sheet, (B-2) the annealed steel sheet is cooled in the cooling zone to perform continuous annealing, (C) the annealed steel sheet discharged from the continuous annealing furnace is continuously passed through, and (D) the steel sheet is coiled by a tension coiler to form an annealed coil. The dehydrogenation device 300a uses the annealed coil as a steel sheet coil C and irradiates the annealed coil with sound waves under the above conditions. By irradiating with the sound waves, the amount of diffusible hydrogen in the steel can be reduced to obtain an annealed steel sheet with excellent hydrogen embrittlement resistance. In addition, the cooling method and cooling rate of the steel plate in the cooling zone are not particularly limited, and any cooling such as air jet cooling, water mist cooling, and water cooling may be used.

[0202] When the annealing process is performed using a continuous annealing device, the method for manufacturing a steel sheet includes the steps of unwinding a cold-rolled steel sheet from a cold-rolled coil, continuously annealing the cold-rolled steel sheet to obtain an annealed steel sheet, and coiling the annealed steel sheet to obtain an annealed coil, wherein the annealed coil is made into the steel sheet coil. In CAL, (A) the steel sheet coil is unwinded using an unwinder, (B) the steel sheet is passed through an annealing furnace where a heating zone, a soaking zone, and a cooling zone are located from the upstream side of the passing direction, (B-1) the steel sheet is annealed in the heating zone and the soaking zone, (B-2) the steel sheet is cooled in the cooling zone and continuously annealed, (C) the steel sheet discharged from the annealing furnace is continuously passed through, and (D) the steel sheet is coiled using a tension coiler to obtain an annealed coil. By irradiating the annealed coil with sound waves under the above conditions, a cold-rolled steel sheet or a hot-rolled steel sheet having excellent hydrogen embrittlement resistance can be obtained.

[0203] [[Coated steel sheet]]

[0204] In addition, the dehydrogenation device 300a of the present embodiment can also be used to manufacture plated steel sheets. The steel sheet manufacturing system of this application example includes: a plating device for forming a plating film on the surface of a hot-rolled steel sheet or a cold-rolled steel sheet to form a plated steel sheet, a plated steel sheet coiling device for coiling the plated steel sheet to obtain a plated steel sheet coil, and a dehydrogenation device 300a for making the plated steel sheet coil C from the plated steel sheet coil. The plating device uses a hot-rolled steel sheet or a cold-rolled steel sheet as a base steel sheet and forms a plating film on the surface to obtain a plated steel sheet. The plated steel sheet coiling device coils the plated steel sheet to form a plated steel sheet coil. The dehydrogenation device 300a uses the plated steel sheet coil as a steel sheet coil C and irradiates the plated steel sheet coil with sound waves under the above-mentioned conditions. By irradiating the sound waves, the amount of diffusible hydrogen in the steel can be reduced to obtain a plated steel sheet with excellent hydrogen embrittlement resistance.

[0205] In addition, a hot-rolled steel sheet or a cold-rolled steel sheet can be used as a base steel sheet, and a plated film can be formed on the surface to obtain a plated steel sheet, and the plated steel sheet can be used as a steel sheet coil irradiated with sound waves. When the plated steel sheet coil is irradiated with sound waves, the method for manufacturing the steel sheet includes: a step of forming a plated film on the surface of the hot-rolled steel sheet or the cold-rolled steel sheet to obtain a plated steel sheet, and a step of coiling the plated steel sheet to obtain a plated steel sheet coil, and the plated steel sheet coil is made into the steel sheet coil.

[0206] [Formation of the coating using a continuous hot-dip galvanizing device]

[0207] The type of the coating device is not particularly limited, and may be, for example, a hot-dip galvanizing device. In one example, the hot-dip galvanizing device may be a continuous hot-dip galvanizing line (CGL). The structure of the CGL is not particularly limited, and in one example, the CGL comprises: a continuous annealing furnace having a heating zone, a soaking zone, and a cooling zone arranged in sequence, and a hot-dip galvanizing device arranged after the cooling zone. In CGL, (A) a cold-rolled steel sheet or a hot-rolled steel sheet unwound from a cold-rolled coil or a hot-rolled coil by an uncoiler, (B) the sheet is passed through a continuous annealing furnace in which a heating zone, a soaking zone and a cooling zone are located from the upstream side in the sheet passing direction, (B-1) the hot-rolled steel sheet or the cold-rolled steel sheet is annealed in a reducing atmosphere containing hydrogen in the soaking zone to obtain an annealed steel sheet, (B-2) the annealed steel sheet is cooled in the cooling zone to perform continuous annealing, (C) the annealed steel sheet discharged from the annealing furnace is continuously passed through, (C-1) the annealed steel sheet is immersed in a hot-dip galvanizing bath located downstream in the sheet passing direction of the continuous annealing furnace, and the annealed steel sheet is hot-dip galvanized to obtain a hot-dip galvanized steel sheet, and (D) the hot-dip galvanized steel sheet is coiled by a tension coiler to obtain a hot-dip galvanized steel sheet coil. The dehydrogenation device 300a irradiates the hot-dip galvanized steel sheet coil with sound waves under the above conditions as the steel sheet coil C. The irradiation with sound waves can reduce the amount of diffusible hydrogen in the steel and obtain a hot-dip galvanized steel sheet with excellent hydrogen embrittlement resistance.

[0208] The method for forming a coating film on the surface of a hot-rolled steel sheet or a cold-rolled steel sheet is not particularly limited, and the plating process may include a hot-dip galvanizing process. That is, the hot-dip galvanizing process may be performed on the hot-rolled steel sheet or the cold-rolled steel sheet to obtain a hot-dip galvanized steel sheet. In one example, a continuous hot-dip galvanizing line (CGL) may be used to perform hot-dip galvanizing on the steel sheet. In CGL, (A) a steel sheet coil is unwound by an unwinder, (B) a hot-rolled steel sheet or a cold-rolled steel sheet is passed through an annealing furnace in which a heating zone, a soaking zone and a cooling zone are located from the upstream side in the passing direction of the steel sheet, (B-1) the hot-rolled steel sheet or the cold-rolled steel sheet is annealed in a reducing atmosphere containing hydrogen in the soaking zone to obtain an annealed steel sheet, (B-2) the annealed steel sheet is cooled in the cooling zone to perform continuous annealing, (C) the annealed steel sheet discharged from the annealing furnace is continuously passed through, (D) the annealed steel sheet is coiled by a tension coiler to obtain an annealed coil, and step (C) includes (C-1) the step of immersing the annealed steel sheet in a hot-dip galvanizing bath located downstream in the passing direction of the annealing furnace to perform hot-dip galvanizing on the annealed steel sheet. The coiled annealed coil is a hot-dip galvanized steel sheet coil composed of a hot-dip galvanized steel sheet. By irradiating the hot-dip galvanized steel sheet coil with sonic waves under the above-mentioned conditions, a hot-dip galvanized steel sheet with excellent hydrogen embrittlement resistance can be obtained.

[0209] In addition, the coating device may include a hot-dip galvanizing device and a subsequent alloying furnace. In one example, after a hot-dip galvanized steel sheet is manufactured using CGL, following the above-mentioned step (C-1), (C-2) passes the steel sheet through an alloying furnace located downstream in the direction of passing the steel sheet through the hot-dip galvanizing bath, and heats and alloys the hot-dip galvanizing. The alloyed hot-dip galvanized steel sheet alloyed by passing the steel sheet through the alloying furnace is coiled to form an alloyed hot-dip galvanized steel sheet coil. The dehydrogenation device 300a uses the alloyed hot-dip galvanized steel sheet coil as the steel sheet coil C, and irradiates the alloyed hot-dip galvanized steel sheet coil with sound waves under the above-mentioned conditions. By irradiating the sound waves, an alloyed hot-dip galvanized steel sheet with excellent hydrogen embrittlement resistance can be obtained.

[0210] In addition, the plating process may include a hot-dip galvanizing process and a subsequent alloying process. That is, the hot-dip galvanized steel sheet may be further alloyed to form an alloyed hot-dip galvanized steel sheet, and the hot-dip galvanized steel sheet may be irradiated with sound waves. In one example, after the hot-dip galvanized steel sheet is manufactured using CGL, following the above-mentioned process (C-1), (C-2) passes the steel sheet through an alloying furnace located downstream in the direction of passing the hot-dip galvanizing bath, and heats and alloys the hot-dip galvanizing. The alloyed hot-dip galvanized steel sheet alloyed by passing the steel sheet through the alloying furnace is coiled to form an alloyed hot-dip galvanized steel sheet coil. By irradiating the alloyed hot-dip galvanized steel sheet coil with sound waves under the above-mentioned conditions, an alloyed hot-dip galvanized steel sheet with excellent hydrogen embrittlement resistance can be obtained.

[0211] In addition, the plating device may form an Al plating film or an Fe plating film in addition to the zinc plating film. In addition, the plating device is not limited to a hot dip plating device, and may be an electroplating device.

[0212] The type of the plated film formed on the surface of the steel sheet irradiated with the sound wave is not particularly limited, and may be an Al plated film or an Fe plated film. The method of forming the plated film is not limited to the hot dip plating process, and may be an electroplating process.

[0213] The manufacturing system of the steel plate may further include a temper rolling device, which performs temper rolling on the hot-rolled steel plate, cold-rolled steel plate, and plated steel plate having various plating films on the surface of the hot-rolled steel plate or cold-rolled steel plate obtained as described above for the purpose of shape correction and surface roughness adjustment. That is, in the manufacturing method of the steel plate, the hot-rolled steel plate, cold-rolled steel plate, and plated steel plate having various plating films on the surface of the hot-rolled steel plate or cold-rolled steel plate obtained as described above can be temper rolled for the purpose of shape correction and surface roughness adjustment. The reduction rate of the temper rolling is preferably controlled to be 0.1% or more, and is preferably controlled to be 2.0% or less. By making the reduction rate of the temper rolling 0.1% or more, the effect of shape correction and the effect of adjusting the surface roughness can be more appropriately obtained, and the control of the reduction rate is also more appropriate. In addition, by making the reduction rate of the temper rolling 2.0% or less, the productivity is better. It should be noted that the temper rolling device can be a device that is continuous with CGL or CAL (online) or a device that is discontinuous with CGL or CAL (offline). The temper rolling with a target reduction ratio can be performed at one time or the target reduction ratio can be achieved by performing the temper rolling in several times. In addition, the steel plate manufacturing system can further include a coating device, and the coating treatment is applied to the surface of the hot-rolled steel plate, the cold-rolled steel plate, and the plated steel plate having various plating films on the surface of the hot-rolled steel plate or the cold-rolled steel plate obtained as described above, and various coating treatments such as resin or grease coating are applied to the surface of the plated steel plate having various plating films on the surface of the hot-rolled steel plate or the cold-rolled steel plate obtained as described above. That is, various coating treatments such as resin or grease coating are applied to the surface of the hot-rolled steel plate, the cold-rolled steel plate, and the plated steel plate having various plating films on the surface of the hot-rolled steel plate or the cold-rolled steel plate obtained as described above.

[0214] <Implementation method 2>

[0215] The dehydrogenation device of embodiment 2 of the present invention comprises: an unwinding device for unwinding a steel strip from a steel plate coil, a plate passing device for passing the steel strip through a plate, a coiling device for winding the steel strip, and a sound wave irradiation device for irradiating the steel strip in the plate passing device with sound waves to produce a product coil.

[0216] In addition, the manufacturing method of the steel plate of embodiment 2 of the present invention includes: a process of unwinding a steel strip from a steel plate coil, a plate passing process of passing the above-mentioned steel strip through a plate, and a process of winding the above-mentioned steel strip to make a product coil, and the above-mentioned plate passing process includes a sound wave irradiation process as follows: irradiating the above-mentioned steel strip with sound waves in a manner that the sound pressure on the surface of the above-mentioned steel strip is greater than 30dB.

[0217] The steel sheet that is annealed after hot rolling or cold rolling, or the plated steel sheet that is further formed with a coating film is wound into a coil to form a steel sheet coil. The quality of the steel sheet coil is often different from the packaging quality at the time of shipment, so the packaging quality is divided in the rewinding line. The steel strip is unwound from the steel sheet coil by an unwinding device, and the unwound steel strip is rewound again by a rewinding device, and is sheared and divided at the stage of reaching the specified packaging quality. In this embodiment, the steel strip unwound by the rewinding line is irradiated with sound waves. According to this embodiment, since the steel strip in the plate is irradiated with sound waves, the sound waves can be evenly irradiated over the entire length of the steel strip. It should be noted that the dehydrogenation device of this embodiment is a discontinuous device (offline) with the continuous annealing device or the continuous hot-dip galvanizing device, and the dehydrogenation device does not include equipment for annealing, plating and hot-dip galvanizing the steel strip.

[0218] [[Dehydrogenation unit]]

[0219] Figure 3 3 shows a view of the dehydrogenation device 300b used in the method for manufacturing a steel plate according to the present embodiment, viewed in front of the steel strip S in the width direction. Figure 3 As shown in FIG. 1 , in the present dehydrogenation device 300b, a sound wave irradiation device 60 is arranged during the steel strip S unwound by the unwinding device. It should be noted that, although not shown in the figure, in each sound wave irradiation device 60, a horn 68, a horn 66, a vibration transducer 64, a sound wave generator 62 and a sound pressure controller 69 are connected in sequence, and the horn 68 irradiates the steel strip S with sound waves. Figure 3 As shown, the sonic wave irradiation device 60 may be provided only on one side of the surface and the back side of the steel strip S in the plate, or may be provided on both sides of the surface and the back side of the steel strip S in the plate to excite the steel strip S. By providing the sonic wave irradiation device 60 on both sides of the surface and the back side of the steel strip S in the plate, the timing of sonic wave irradiation can be controlled to more effectively reduce the amount of diffusible hydrogen in the steel. It should be noted that, although not shown in the figure, the dehydrogenation device 300b is provided with a plate-passing device for passing the steel strip S from the unwinding device toward the winding device. The plate-passing device includes, for example, a plate-passing roller for passing the steel strip S toward the winding device.

[0220] A plurality of horns 68 are provided at predetermined intervals from the surface of the steel strip S in the through plate and along the width direction of the steel strip. By irradiating the surface of the steel strip S in the through plate with sound waves from each horn 68, the sound waves can be uniformly irradiated in the width direction of the surface. The main traveling direction of the sound waves can be, for example, 45° or more, 60° or more, or 90° or more relative to the surface of the steel strip S. In addition, by arranging a plurality of horns 68 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 exposed to the sound waves can be sufficiently ensured.

[0221] use Figure 4(a) and (b) in FIG. 1 illustrate an example of the configuration of the speaker 68. Figure 4 (a) and (b) are top views showing the arrangement of the horn 68 relative to the unwound steel strip S in the dehydrogenation device 300b of this embodiment. Figure 4 As shown in (a) of FIG. 1 , a plurality of horns 68 can be arranged at uniform intervals along the width direction of the steel strip S and the direction of the steel strip passing through the plate. The configuration of the horns 68 is not particularly limited as long as the steel strip S passing through the plate can be uniformly irradiated with sound waves, such as Figure 4 As shown in (b) in FIG. 1 , a plurality of square cylindrical horns 68 having a rectangular cross section can be provided along the plate passing direction. It should be noted that the method for holding the horns 68 at a certain interval in the dehydrogenation device 300b is not particularly limited. For example, a box-shaped portion 72 can be provided in a manner covering the steel strip S in the plate passing path, and the horns 68 can be fixed to the inner wall of the box-shaped portion 72 at a certain interval.

[0222] The structure of the sound wave irradiation device 60 may be the same as that of the first embodiment. The frequency of the sound wave may also be the same as that of the first embodiment.

[0223] [[Sound pressure level]]

[0224] The sound pressure level is not the sound pressure level of the surface of the steel sheet coil, but the sound pressure level of the surface of the steel strip, which is measured by installing a sound pressure meter near the surface of the steel strip in the plate and directly below the sound wave irradiation device 60, or the intensity I of the sound wave generated by the sound wave irradiation device 60 and the distance D between the sound wave irradiation device and the steel strip can be determined to grasp the "sound pressure level of the surface of the steel strip" in an offline manner. Other than this, the adjustment is performed in the same manner as in Embodiment 1. In this embodiment, it is preferred to irradiate the sound wave at a uniform sound pressure level in the width direction of the steel sheet, and it is preferred to adjust the sound pressure level in such a manner that the minimum value of the sound pressure level at the inner side of 5 mm from the end face in the width direction of the steel sheet satisfies 30 dB or more.

[0225] [[Irradiation time]]

[0226] In the rewinding line, unlike the continuous annealing device or the continuous hot-dip galvanizing device, there is no need to adjust the plate passing speed by taking into account the annealing time. Therefore, according to the present embodiment, the steel strip can be irradiated with sound waves without being restricted by the irradiation time. It is speculated that the longer the time of irradiation with sound waves, the more diffusible hydrogen can be reduced, so the time of irradiation with sound waves is preferably more than 1 minute. The irradiation time of sound waves is more preferably more than 30 minutes, and more preferably more than 60 minutes. On the other hand, from the perspective of productivity, the irradiation time of sound waves is preferably less than 30,000 minutes, more preferably less than 10,000 minutes, and more preferably less than 1,000 minutes. The irradiation time of sound waves can be adjusted by the plate passing speed of the steel strip S and the position of the sound wave irradiation device (for example, the number of devices along the plate passing direction of the device group composed of a plurality of sound wave irradiation devices 60 along the width direction of the steel plate).

[0227] According to this embodiment, the amount of diffusible hydrogen in the product coil obtained after the sonic wave irradiation can be reduced to 0.5 mass ppm or less. By reducing the amount of diffusible hydrogen in the product coil to 0.5 mass ppm or less, hydrogen embrittlement can be prevented. The amount of diffusible hydrogen in the steel after the sonic wave irradiation is preferably 0.3 mass ppm or less, and more preferably 0.2 mass ppm or less. The amount of diffusible hydrogen in the steel after the sonic wave irradiation can be measured in the same manner as in Embodiment 1.

[0228] [[Heating device]]

[0229] [[Steel belt holding temperature]]

[0230] In addition, if Figure 3 As shown, the dehydrogenation device 300b may further have a heating device 71 for heating the steel strip S at a temperature below 300°C while irradiating it with sound waves. The temperature of the steel strip S in the sound wave irradiation process is not particularly limited. This is because according to the present embodiment, even if the steel strip S is not heated and maintained, the diffusible hydrogen in the steel can be reduced. However, by using a heating section to heat the steel strip S while irradiating it with sound waves, the diffusion rate of hydrogen can be further increased, and thus the amount of diffusible hydrogen in the steel can be further reduced. Therefore, the temperature of the steel strip S when irradiated with sound waves is preferably above 30°C, more preferably above 50°C, and further preferably above 100°C. The upper limit of the temperature of the steel strip S in the sound wave irradiation process is not particularly limited, and is preferably below 300°C from the viewpoint of appropriately preventing changes in the structure of the steel strip S. It should be noted that in the present embodiment, the temperature of the steel strip S when irradiated with sound waves is based on the temperature of the surface 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 71 is provided is not particularly limited, and for example, it can be as follows Figure 3As shown in the figure, a heating device 71 is arranged in the plate-passing path of the steel strip S. By arranging the heating device 71 in the plate-passing path of the steel strip S, the steel strip S can be uniformly heated. When the heating device 71 is arranged in the plate-passing path of the steel strip S, Figure 3 As shown, it is preferred to provide a heating device 71 on the upstream side of the acoustic wave irradiation device 60 in the plate-through path. By providing the heating device 71 on the upstream side of the acoustic wave irradiation device 60 in the plate-through path, the sufficiently heated steel strip S can be irradiated with acoustic waves. In addition, for example, the steel plate in the plate-through path can be covered with the above-mentioned box-shaped portion 72 and a heater can be provided on the side wall of the box-shaped portion 72 to heat and maintain the steel strip S while irradiating it with acoustic waves. In addition, it is also possible to heat and maintain the steel strip S while irradiating it with acoustic waves by sending high-temperature air generated externally into the box-shaped portion 72 and circulating it in the box-shaped portion 72. The heating method is not particularly limited and can be any of combustion and electrical methods. In one example, the heating device 71 can be an induction heating device.

[0231] The dehydrogenation device 300b of this embodiment may further include a sound absorbing part for preventing the sound waves from leaking to the outside of the dehydrogenation device 300b. The specific structure of the sound absorbing part is not particularly limited, and for example, the steel strip S and the horn 68 are preferably covered with the sound absorbing part.

[0232] Hereinafter, application examples of the present embodiment will be described in more detail.

[0233] [[Hot-rolled steel sheet]]

[0234] Similar to the first embodiment, the dehydrogenation apparatus 300 b and the method for producing a steel sheet according to the present embodiment can be used for producing a hot-rolled steel sheet.

[0235] The steel plate manufacturing system of this application example comprises: a hot rolling device for hot rolling a steel slab to obtain a hot rolled steel plate, a hot rolled steel plate coiling device for coiling the hot rolled steel plate to obtain a hot rolled coil, and a dehydrogenation device 300b for the hot rolled coil to obtain the steel plate coil. By unwinding a hot rolled steel plate from a hot rolled coil manufactured by a known hot rolling device and passing the hot rolled steel plate through the hot rolled coil, and irradiating the hot rolled steel plate in the passed steel plate with sound waves under the above conditions, the amount of diffusible hydrogen in the steel can be reduced to obtain a hot rolled steel plate with excellent hydrogen embrittlement resistance.

[0236] As in the first embodiment, the method for manufacturing a steel plate of the present embodiment can be used to manufacture a hot-rolled steel plate. The method for manufacturing a steel plate of the present application example includes: a step of hot-rolling a steel billet to form a hot-rolled steel plate, and a step of coiling the hot-rolled steel plate to obtain a hot-rolled coil, wherein the hot-rolled coil is made into the steel plate coil. The method for manufacturing the hot-rolled coil before irradiating with the sound wave is not particularly limited, and for example, it may be the method exemplified in the first embodiment. By unwinding the hot-rolled steel plate from the hot-rolled coil, passing the plate, and irradiating the hot-rolled steel plate in the passed plate with the sound wave under the above-mentioned conditions, the amount of diffusible hydrogen in the steel can be reduced to obtain a hot-rolled steel plate with excellent hydrogen embrittlement resistance.

[0237] [[Cold rolled steel sheet]]

[0238] The dehydrogenation apparatus 300 b and the method for manufacturing a steel sheet according to the present embodiment can also be used to manufacture a cold-rolled steel sheet.

[0239] The steel plate manufacturing system of this application example comprises: a cold rolling device for cold-rolling a hot-rolled steel plate to obtain a cold-rolled steel plate, a cold-rolled steel plate coiling device for coiling the cold-rolled steel plate to obtain a cold-rolled coil, and a dehydrogenation device 300b for converting the cold-rolled coil into the steel plate coil C. A cold-rolled steel plate is obtained by cold-rolling a known hot-rolled steel plate using a known cold rolling device. The cold-rolled steel plate coiling device coils the cold-rolled steel plate to obtain a cold-rolled coil. By using the cold-rolled coil as the steel plate coil C, unwinding the cold-rolled steel plate from the cold-rolled coil to pass the plate, and irradiating the cold-rolled steel plate in the passed plate with sound waves under the above-mentioned conditions, the amount of diffusible hydrogen in the steel can be reduced to obtain a cold-rolled steel plate with excellent hydrogen embrittlement resistance.

[0240] The method for manufacturing a steel plate of this application example includes: a step of cold-rolling a hot-rolled steel plate to obtain a cold-rolled steel plate, and a step of coiling the cold-rolled steel plate to obtain a cold-rolled coil, wherein the cold-rolled coil is made into the steel plate coil. The method for manufacturing the cold-rolled coil before irradiating with sound waves is not particularly limited, and for example, it may be the manufacturing method illustrated in Embodiment 1. By unwinding a cold-rolled steel plate from the cold-rolled coil and passing the plate, and irradiating the cold-rolled steel plate in the passed plate with sound waves under the above-mentioned conditions, the amount of diffusible hydrogen in the steel can be reduced to obtain a cold-rolled steel plate with excellent hydrogen embrittlement resistance.

[0241] There is no limitation on the composition of the hot-rolled steel sheet and the cold-rolled steel sheet to which the sound waves are irradiated by the dehydrogenation device 300b. According to the present embodiment, by irradiating the high-strength steel sheet having a tensile strength of 590 MPa or more, more preferably 1180 MPa or more, and further preferably 1470 MPa or more with the sound waves by the dehydrogenation device 300b, the amount of diffusible hydrogen in the steel can be reduced, thereby obtaining a high-strength steel sheet with excellent hydrogen embrittlement resistance.

[0242] The chemical compositions of the hot-rolled steel sheet and the cold-rolled steel sheet may be the chemical compositions exemplified in the first embodiment, for example.

[0243] [[Annealing device]]

[0244] As in the first embodiment, the steel plate manufacturing system may include an annealing device for annealing cold-rolled steel plates and hot-rolled steel plates. The timing of annealing is not particularly limited. Since hydrogen generally invades the steel during the annealing process, it is preferred to perform annealing before irradiating the sound wave in order to finally obtain a steel plate having excellent hydrogen embrittlement resistance. The annealing device may be a batch annealing furnace or a continuous annealing device.

[0245] Annealing process

[0246] Annealing can be performed on the cold-rolled steel sheet and the hot-rolled steel sheet in the same manner as in Embodiment 1. The timing of annealing is not particularly limited, and annealing is preferably performed before the sonication step. The annealing step can be performed using a batch annealing furnace or a continuous annealing device.

[0247] [Batch annealing]

[0248] When the annealing process is performed using a batch annealing furnace, the steel plate manufacturing system includes: a batch annealing furnace for batch annealing a cold-rolled coil or a hot-rolled coil to obtain an annealed coil, and a dehydrogenation device 300b for converting the annealed coil into the steel plate coil C. The annealed coil after annealing is cooled by furnace cooling or air cooling in the batch annealing furnace. The unwinding device unwinds the annealed steel plate from the annealing coil and supplies it to the plate passing device, and the plate passing device passes the annealed steel plate. The acoustic wave irradiation device 60 irradiates the annealed steel plate in the plate passing with acoustic waves under the above conditions. By irradiating the acoustic waves, the amount of diffusible hydrogen in the steel can be reduced to obtain an annealed steel plate with excellent hydrogen embrittlement resistance.

[0249] When a batch annealing furnace is used for the annealing process, the method for manufacturing a steel plate includes: a process of coiling a cold-rolled steel plate or a hot-rolled steel plate to form a cold-rolled coil or a hot-rolled coil, and a process of batch annealing the cold-rolled coil or the hot-rolled coil to obtain an annealed coil, and the annealed coil is made into the above-mentioned steel plate coil. The annealed coil after annealing is cooled by furnace cooling or air cooling in a batch annealing furnace. Next, the annealed steel plate is unwound from the annealing coil to pass the plate, and the annealed steel plate in the passed plate is irradiated with sound waves under the above-mentioned conditions, so that the amount of diffusible hydrogen in the steel can be reduced to obtain a hot-rolled steel plate or a cold-rolled steel plate with excellent hydrogen embrittlement resistance.

[0250] [Annealing using a continuous annealing device]

[0251] Annealing can also be performed by passing the cold-rolled steel sheet or the hot-rolled steel sheet through a continuous annealing device (Continuous Annealing Line: CAL). When the annealing process is performed using a continuous annealing device, the steel sheet manufacturing system includes: a pre-annealing unwinding device for unwinding the cold-rolled steel sheet or the hot-rolled steel sheet from a cold-rolled coil or a hot-rolled coil, a continuous annealing furnace for continuously annealing the cold-rolled steel sheet or the hot-rolled steel sheet to form an annealed steel sheet, an annealing steel sheet coiling device for coiling the annealed steel sheet to obtain an annealed coil, and a dehydrogenation device 300b for making the annealed coil into the steel sheet coil C. The structure of the continuous annealing device is the same as that of Embodiment 1. The unwinding device of the dehydrogenation device 300b unwinds the annealing steel sheet from the annealing coil and supplies it to the plate passing device, and the plate passing device passes the annealed steel sheet. The acoustic wave irradiation device 60 irradiates the annealed steel sheet in the plate passing with acoustic waves under the above-mentioned conditions. By irradiating the sound waves, the amount of diffusible hydrogen in the steel can be reduced, thereby obtaining an annealed steel sheet having excellent hydrogen embrittlement resistance.

[0252] When the annealing process is performed using a continuous annealing device, the annealed coil before the sonic wave irradiation can be manufactured in the same manner as in Embodiment 1. By unwinding an annealed steel strip from the annealed coil and irradiating the annealed steel sheet in the through sheet with sonic waves under the above conditions, a cold-rolled steel sheet or a hot-rolled steel sheet having excellent hydrogen embrittlement resistance can be obtained.

[0253] [[Coated steel sheet]]

[0254] Similar to the first embodiment, the dehydrogenation apparatus 300 b and the method for producing a steel sheet according to the present embodiment can also be used to produce a plated steel sheet.

[0255] The steel sheet manufacturing system of this application example comprises: a plating device for forming a plating film on the surface of a hot-rolled steel sheet or a cold-rolled steel sheet to produce a plated steel sheet, a plated steel sheet coiling device for coiling the plated steel sheet to obtain a plated steel sheet coil, and a dehydrogenation device 300b for converting the plated steel sheet coil into the steel sheet coil C. The type of plating film that can be formed on the surface of the hot-rolled steel sheet or the cold-rolled steel sheet is not particularly limited, and in addition to the galvanized film, it can also be an Al-plated film or an Fe-plated film. The method of forming the plating film is not limited to the hot-dip plating process, and it can also be an electroplating process.

[0256] In addition, the method for manufacturing the steel plate of this application example includes: a step of forming a plating film on the surface of a hot-rolled steel plate or a cold-rolled steel plate to make a plated steel plate, and a step of winding the plated steel plate to obtain a plated steel plate coil, and making the plated steel plate coil into the steel plate coil.

[0257] [Formation of the coating using a continuous hot-dip galvanizing device]

[0258] The type of the coating device is not particularly limited, and for example, it may be a hot-dip galvanizing device. In one example, the hot-dip galvanizing device may be a continuous hot-dip galvanizing line (CGL). The structure of the CGL may be the same as that of Embodiment 1. The unwinding device of the dehydrogenation device 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 acoustic wave irradiation device 60 irradiates the annealed steel sheet in the plate passing with acoustic waves under the above-mentioned conditions. By irradiating with the acoustic waves, the amount of diffusible hydrogen in the steel can be reduced to obtain a hot-dip galvanized steel sheet with excellent hydrogen embrittlement resistance.

[0259] The steel sheet before being irradiated with the sound waves may also be subjected to hot-dip galvanizing treatment to obtain a hot-dip galvanized steel sheet. In one example, a continuous hot-dip galvanizing line (CGL) may be used to perform hot-dip galvanizing treatment on the steel strip. The structure of the CGL may be the same as that of the first embodiment. The hot-dip galvanized steel sheet coil before being irradiated with the sound waves may be manufactured in the same manner as that of the first embodiment. The hot-dip galvanized steel sheet coil may be obtained by unwinding the hot-dip galvanized steel sheet and passing the sheet through, and irradiating the hot-dip galvanized steel sheet in the passed sheet with the sound waves under the above-mentioned conditions to obtain a hot-dip galvanized steel sheet with excellent hydrogen embrittlement resistance.

[0260] In addition, the plating device may include a hot-dip galvanizing device and a subsequent alloying furnace. That is, in the manufacturing method of the steel sheet, the plating treatment may include a hot-dip galvanizing step and a subsequent alloying step. As a plating device having an alloying furnace, the CGL having an alloying furnace downstream of the hot-dip galvanizing bath in the sheet passing direction as exemplified in Embodiment 1 may be used. By unwinding an alloyed hot-dip galvanized steel sheet from an alloyed hot-dip galvanized steel sheet coil formed by the hot-dip galvanizing step and the subsequent alloying step, and irradiating the alloyed hot-dip galvanized steel sheet with sound waves under the above-mentioned conditions, an alloyed hot-dip galvanized steel sheet having excellent hydrogen embrittlement resistance can be obtained.

[0261] Similar to the first embodiment, the steel sheet manufacturing system may further include a temper rolling device, which performs temper rolling on the hot-rolled steel sheet, the cold-rolled steel sheet, and the plated steel sheet having various plating films on the surface of the hot-rolled steel sheet or the cold-rolled steel sheet obtained as described above for the purpose of shape correction and surface roughness adjustment. In addition, the steel sheet manufacturing system may further include a coating device, which performs various coating treatments such as resin or grease coating on the surface of the hot-rolled steel sheet, the cold-rolled steel sheet, and the plated steel sheet having various plating films on the surface of the hot-rolled steel sheet or the cold-rolled steel sheet obtained as described above.

[0262] That is, in the manufacturing method of the steel sheet, the hot-rolled steel sheet, the cold-rolled steel sheet, and the plated steel sheet having various plating films on the surface of the hot-rolled steel sheet or the cold-rolled steel sheet obtained as described above can be subjected to temper rolling in the same manner as in Embodiment 1. In addition, various coating treatments such as resin or grease coating can be applied to the surface of the hot-rolled steel sheet, the cold-rolled steel sheet, and the plated steel sheet having various plating films on the surface of the hot-rolled steel sheet or the cold-rolled steel sheet obtained as described above.

[0263] Example

[0264] <Example 1>

[0265] Steel having a composition containing C: 0.09% to 0.37%, Si: 2.00% or less, Mn: 0.50% to 3.60%, P: 0.001% to 0.100%, S: 0.0200% or less, Al: 0.010% to 1.000%, N: 0.0100% or less, and the remainder consisting of Fe and inevitable impurities is melted in a converter and made into a slab by a continuous casting method. The obtained slab is hot-rolled and cold-rolled to obtain a cold-rolled coil. As shown in Table 1, at some levels, a cold-rolled annealed steel sheet (CR) steel sheet coil is manufactured by CAL or batch annealing, at other levels, a hot-dip galvanized steel sheet (GI) steel sheet coil is manufactured by CGL, and at the remaining levels, an alloyed hot-dip galvanized steel sheet (GA) steel sheet coil is manufactured by CGL. CR, GI, and GA all had a plate thickness of 1.4 mm and a width of 1000 mm. As the CAL, a CAL having a heating zone, a soaking zone, and a cooling zone arranged in sequence was used. As the CGL, a CGL having a continuous annealing furnace having a heating zone, a soaking zone, and a cooling zone arranged in sequence, and a hot-dip galvanizing device installed after the cooling zone was used. As the batch annealing furnace, a general batch annealing furnace was used.

[0266] The obtained CR, GI, or GA steel sheet coil or the steel strip unwound from the steel sheet coil is irradiated with sound waves. Figure 1 The general sound wave irradiation device shown in FIG. 1 irradiates sound waves under the conditions of sound pressure level, frequency and irradiation time shown in Table 1. In Table 1, the case of irradiating the steel sheet coil with sound waves is shown as A, and the case of irradiating the unwinding steel strip with sound waves is shown as B. When irradiating the steel sheet coil with sound waves, use Figure 2 The dehydrogenation device shown in (a) and (c) is used when irradiating the steel strip with sound waves. Figure 3 , 4The dehydrogenation device shown in (a) in FIG. 1 . It should be noted that as the horn, a cylindrical horn is used. When the steel plate coil (outer diameter: 1500mm, inner diameter: 610mm, width: 1000mm) is irradiated with sound waves, the size of the receiving section is 2500mm in height direction, 2000mm in depth direction, and 2500mm in width direction, and the horn is arranged on the inner wall of the receiving section in a manner to surround the steel plate coil. When the steel strip in the through plate is irradiated with sound waves, horns are arranged on both the surface and back sides of the steel strip in the through plate. Six horns are evenly arranged along the width direction of the steel strip from the end in the width direction of the steel strip along the width direction of the steel strip. The cylindrical height direction of the horn is arranged parallel to the plate thickness direction of the steel strip in a manner that the main travel direction of the sound wave is perpendicular to the surface of the steel strip. It should be noted that the room temperature in Table 1 refers to around 25°C. It should be noted that the sound pressure level is adjusted by adjusting the intensity of the sound waves generated by the sound wave irradiation device after the position of the sound wave irradiation device (i.e., the distance between the sound wave irradiation device 60 and the steel strip S) is fixed. In addition, the irradiation time is adjusted by adjusting the driving time of the sound wave irradiation device when irradiating the steel plate coil with sound waves. When irradiating the unwinding steel strip with sound waves, the irradiation time of the sound waves is adjusted by adjusting the passing speed of the steel strip. When irradiating the unwinding steel strip with sound waves, the minimum value of the sound pressure level relative to the inner side of 5 mm from the end face in the width direction of the steel plate is 30 dB or more.

[0267] The tensile properties, the amount of diffusible hydrogen in the steel, the stretch flange formability, and the bendability of each steel plate before and after the sonication were evaluated by the methods described below. The results are shown in Table 1.

[0268] The tensile test was conducted in accordance with JIS Z 2241 (2011). A JIS No. 5 test piece was taken from each steel plate after sonication, with the tensile direction being perpendicular to the rolling direction of the steel plate. Each test piece was used at a crosshead displacement speed of 1.67×10 -1 The tensile test was carried out under the condition of 1000 mm / s to measure TS (tensile strength).

[0269] The tensile flangeability is evaluated by a hole expansion test. The hole expansion test is performed in accordance with JIS Z 2256. A sample of 100 mm × 100 mm is taken from the obtained steel plate by shearing. In this sample, a hole with a diameter of 10 mm is punched out with a gap of 12.5%. Using a die with an inner diameter of 75 mm, a conical punch with a top angle of 60° is pressed into the hole while the periphery of the hole is suppressed by a clamping force of 9 ton (88.26 kN) to determine the hole diameter at the limit of crack generation. The limiting hole expansion ratio: λ (%) is calculated by the following formula (4), and the hole expandability is evaluated based on the value of the limiting hole expansion ratio.

[0270] Limit hole expansion ratio: λ(%)={(D f-D0) / D0}×100····(4)

[0271] In the above formula, D f is the hole diameter (mm) when cracks occur, and D0 is the initial hole diameter (mm). Regardless of the strength of the steel sheet, when the value of λ is 20% or more, the stretch flangeability is judged to be good.

[0272] The bending test is carried out in accordance with JIS Z 2248. A rectangular test piece with a width of 30 mm and a length of 100 mm is taken from the obtained steel plate in a manner such that the direction parallel to the rolling direction of the steel plate is the axial direction of the bending test. Thereafter, a bending test is carried out using a V-block method at a bending angle of 90° under the conditions of a pressing load of 100 kN and a pressurization holding time of 5 seconds. It should be noted that in the present invention, a 90° V bending test is carried out, and the ridgeline portion of the bending vertex is observed using a 40x microscope (RH-2000: manufactured by HIROX Co., Ltd.), and the bending radius when no cracks with a crack length of more than 200 μm are observed is taken as the minimum bending radius (R). When the value (R / t) obtained by dividing R by the plate thickness (t) is less than 5.0, it is judged that the bending test is good.

[0273] The amount of diffusible hydrogen in steel is measured according to the above method.

[0274]

[0275] As shown in Table 1, in the examples of the present invention, since the sonication step is performed, it is possible to manufacture a steel sheet having a low amount of hydrogen and excellent stretch flange formability (λ) and bendability (R / t) as indices of hydrogen embrittlement resistance. On the other hand, in the comparative examples, either the stretch flange formability (λ) or the bendability (R / t) is poor.

[0276] <Example 2>

[0277] The steel billet having the composition shown in Table 1 and the remainder consisting of Fe and inevitable impurities was melted in a converter and made into a steel billet by continuous casting. The obtained steel billet was hot-rolled, cold-rolled, and further annealed to obtain a cold-rolled steel sheet (CR). A portion of the cold-rolled steel sheet was further hot-dip galvanized to obtain a hot-dip galvanized steel sheet (GI). A portion of the hot-dip galvanized steel sheet was further alloyed to obtain an alloyed hot-dip galvanized steel sheet (GA). CR, GI, and GA all had a plate thickness of 1.4 mm and a width of 1000 mm.

[0278] The obtained CR, GI, and GA are wound into a coil to form a steel sheet coil. The steel sheet coil or the steel strip unwound from the steel sheet coil is irradiated with sound waves. The sound waves of the frequencies shown in Table 2 are used as the sound pressure levels shown in Table 2 measured on the surface of the steel sheet, and the temperature at the radial half position of the steel sheet coil or the surface temperature of the steel strip is maintained at the temperature shown in Table 2 while irradiating for the time shown in Table 2. As a sound wave irradiation device, a Figure 1 The general irradiation device shown in FIG. It should be noted that a cylindrical horn is used as the horn. When irradiating the steel plate coil with sound waves, a Figure 2 When the unwinding steel strip is irradiated with sound waves, the product coil is obtained by using the dehydrogenation device shown in (a) to (c) in FIG. Figure 3 and Figure 4 In the dehydrogenation device shown in (a), the steel strip after sound wave irradiation is coiled to form a product coil. When the steel plate coil (outer diameter: 1500mm, inner diameter: 610mm, width: 1000mm) is irradiated with sound waves, the size of the receiving section is 2500mm in height direction, 2000mm in depth direction, and 2500mm in width direction, and the horn is arranged on the inner wall of the receiving section in a manner to surround the steel plate coil. When the unwinding steel strip is irradiated with sound waves, the horns are arranged on both the surface and back sides of the steel strip in the through plate. Six horns are evenly arranged along the width direction of the steel strip from the end of the steel strip in the width direction of the steel strip. The cylindrical height direction of the horn is arranged parallel to the plate thickness direction of the steel strip in a manner that the main traveling direction of the sound wave is perpendicular to the surface of the steel strip. It should be noted that the sound pressure level is adjusted by adjusting the intensity of the sound waves generated from the sound wave irradiation device after the position of the sound wave irradiation device (i.e., the distance between the sound wave irradiation device 60 and the cold-rolled steel plate S) is fixed. In addition, the irradiation time is adjusted by adjusting the driving time of the sonic wave irradiation device when the steel sheet coil is irradiated with sonic waves. The irradiation time of sonic waves is adjusted by adjusting the plate passing speed of the steel strip when the unwinding steel strip is irradiated with sonic waves. When the unwinding steel strip is irradiated with sonic waves, the minimum value of the sound pressure level relative to the inner side of 5mm from the end face in the width direction of the steel plate is 30dB or more. The tensile properties and hydrogen embrittlement resistance properties of each steel plate before and after the sonic wave irradiation are evaluated according to the method described below, and the results are shown in Table 2.

[0279] Using a JIS No. 5 test piece cut from the radial half position of the product coil in such a way that the tensile direction is at right angles to the rolling direction of the steel plate, a tensile test is carried out in accordance with JIS Z 2241 (2011), and the EL' (total elongation) after sonication irradiation is measured. It should be noted that EL' is measured within 72 hours after the end of annealing. The TS (tensile strength) and EL when the hydrogen content in the steel is 0 mass ppm are measured in the following manner, that is, by placing the sample obtained from the product coil as described above in the atmosphere for a long time for more than 10 weeks to reduce the hydrogen in the steel inside, and then confirming that the hydrogen content in the steel is 0 mass ppm by the above-mentioned TDS, and then conducting a tensile test. In addition, using a JIS No. 5 test piece taken from the steel plate coil before sonication irradiation, a tensile test is carried out in accordance with JIS Z 2241 (2011), and the EL" before sonication irradiation is measured.

[0280] The hydrogen embrittlement resistance was evaluated as follows based on the tensile test: When the value obtained by dividing the EL' of the steel sheet after sonication by the EL of the same steel sheet when the hydrogen content in the steel was 0 mass ppm was 0.7 or more, the hydrogen embrittlement resistance was determined to be good.

[0281] In addition, the amount of diffusible hydrogen in the steel before and after the sonication was measured by the TDS. When measuring the amount of diffusible hydrogen in the steel before the sonication, a test piece was obtained from the steel sheet coil as described above instead of the product coil, and the diffusible hydrogen amount was measured.

[0282]

[0283]

[0284] In the examples of the present invention, since the steel sheet is irradiated with ultrasonic waves, a steel sheet having excellent hydrogen embrittlement resistance can be manufactured.

[0285] Explanation of symbols

[0286] 60 Sound wave irradiation device

[0287] 62 Sound wave generator

[0288] 64 Vibration transducer

[0289] 66 horn

[0290] 68 Speaker

[0291] 69 Sound pressure controller

[0292] 70 Noise Meter

[0293] 71 Heating device

[0294] 72 Box

[0295] 80 Containment Division

[0296] 90 Coil holding unit

[0297] 300a, 300b Dehydrogenation unit

[0298] S steel belt

[0299] C Steel Coil

Claims

1. A dehydrogenation device comprising: a receiving section for receiving a steel plate coil obtained by winding the steel strip into a coil; and The sonic wave irradiation device generates and propagates sonic waves in the air to irradiate the steel sheet coil accommodated in the accommodation portion, thereby reducing the amount of diffusible hydrogen in the steel sheet coil to produce a product coil. The sonic wave irradiation device is arranged at a distance from the surface of the steel sheet coil. in, The intensity of the sound waves generated by the sound wave irradiation device and the position of the sound wave irradiation device are set so that the maximum sound pressure level on the surface of the steel plate coil satisfies 30 dB or more.

2. The dehydrogenation device according to claim 1, wherein: The invention further comprises a heating unit for irradiating the sound wave while heating the steel sheet coil.

3. A dehydrogenation device comprising: An unwinding device unwinds the steel strip from the steel plate coil; A plate-passing device for passing the steel strip through the plate; A coiling device for coiling the steel strip; as well as an acoustic wave irradiation device, in the plate-passing device, the steel strip in the plate-passing device is irradiated by generating and propagating acoustic waves in the air, thereby reducing the amount of diffusible hydrogen in the steel strip to form a product coil, and the acoustic wave irradiation device is arranged at a distance from the surface of the steel strip, The intensity of the sound waves generated by the sound wave irradiation device and the position of the sound wave irradiation device are set so that the maximum sound pressure level on the surface of the steel strip meets 30 dB or more.

4. The dehydrogenation device according to claim 3, wherein: The invention further includes a heating unit for irradiating the sound wave while heating the steel strip.

5. The dehydrogenation device according to any one of claims 1 to 4, wherein: A sound absorbing portion is further provided to prevent the sound waves from leaking to the outside of the dehydrogenation device.

6. A steel plate manufacturing system, comprising: A hot rolling device for hot rolling a steel slab into a hot rolled steel sheet; a hot-rolled steel plate coiling device for coiling the hot-rolled steel plate to obtain a hot-rolled coil; and The dehydrogenation device according to any one of claims 1 to 5, wherein the hot rolled coil is made into the steel plate coil.

7. A steel plate manufacturing system comprising: A cold rolling device for cold rolling a hot rolled steel sheet to produce a cold rolled steel sheet; a cold-rolled steel sheet coiling device for coiling the cold-rolled steel sheet to obtain a cold-rolled coil; and The dehydrogenation device according to any one of claims 1 to 5, wherein the cold rolled coil is made into the steel plate coil.

8. A steel plate manufacturing system, comprising: A batch annealing furnace for performing batch annealing on cold-rolled coils or hot-rolled coils to obtain annealed coils; and The dehydrogenation apparatus according to any one of claims 1 to 5, wherein the annealed coil is made into the steel plate coil.

9. A steel plate manufacturing system, comprising: Unwinding device before annealing, unwinding cold-rolled steel sheet or hot-rolled steel sheet from cold-rolled coil or hot-rolled coil; A continuous annealing furnace, for continuously annealing the cold-rolled steel sheet or the hot-rolled steel sheet to produce an annealed steel sheet; An annealed steel plate coiling device is used to coil the annealed steel plate to obtain an annealed coil; as well as The dehydrogenation apparatus according to any one of claims 1 to 5, wherein the annealed coil is made into the steel plate coil.

10. A steel plate manufacturing system, comprising: A plating device for forming a plating film on the surface of a hot-rolled steel sheet or a cold-rolled steel sheet to produce a plated steel sheet; a coated steel sheet coiling device for coiling the coated steel sheet to obtain a coated steel sheet coil; and The dehydrogenation device according to any one of claims 1 to 5, wherein the plated steel sheet coil is made into the steel sheet coil.

11. The steel plate manufacturing system according to claim 10, wherein: The coating device is a hot-dip galvanizing device.

12. The steel plate manufacturing system according to claim 10, wherein: The coating device comprises a hot-dip galvanizing device and a subsequent alloying furnace.

13. The steel plate manufacturing system according to claim 10, wherein: The plating device is an electroplating device.

14. A method for manufacturing a steel plate, comprising the following sonic irradiation step: a steel plate coil obtained by winding a steel strip into a coil is irradiated with sonic waves generated and propagated in the air from a sonic irradiation device disposed at a distance from the surface in such a manner that the sound pressure on the surface of the steel plate coil is 30 dB or more, thereby reducing the amount of diffusible hydrogen in the steel strip to produce a finished coil.

15. The method for manufacturing a steel plate according to claim 14, wherein: The sonication step is performed while keeping the steel sheet coil at 300° C. or less.

16. A method for manufacturing a steel plate, comprising the following steps: The process of unwinding steel strip from steel plate coils, The steel strip is subjected to a plate-passing process, and The process of rolling up the steel strip to form a product coil; Furthermore, the plate passing step includes the following sound wave irradiation step: the steel strip is irradiated with sound waves generated and propagated in the air from a sound wave irradiation device arranged at a distance from the surface in such a manner that the sound pressure level on the surface of the steel strip satisfies 30 dB or more, thereby reducing the amount of diffusible hydrogen in the steel strip.

17. The method for manufacturing a steel plate according to claim 16, wherein: The sonication step is performed while keeping the steel strip at 300° C. or less.

18. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The method comprises the steps of hot-rolling a steel slab to obtain a hot-rolled steel sheet, and coiling the hot-rolled steel sheet to obtain a hot-rolled coil, wherein the hot-rolled coil is further converted into the steel sheet coil.

19. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The method comprises the steps of cold-rolling a hot-rolled steel sheet to obtain a cold-rolled steel sheet, and coiling the cold-rolled steel sheet to obtain a cold-rolled coil, and further converting the cold-rolled coil into the steel sheet coil.

20. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The method comprises the step of performing batch annealing on a cold-rolled coil or a hot-rolled coil to obtain an annealed coil, and further converting the annealed coil into the steel sheet coil.

21. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The method comprises: unwinding a cold-rolled steel sheet or a hot-rolled steel sheet from a cold-rolled coil or a hot-rolled coil, continuously annealing the cold-rolled steel sheet or the hot-rolled steel sheet to obtain an annealed steel sheet, and coiling the annealed steel sheet to obtain an annealed coil; and further making the annealed coil into the steel sheet coil.

22. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The invention comprises a plating step of forming a plating film on the surface of a hot-rolled steel sheet or a cold-rolled steel sheet to obtain a plated steel sheet and a step of winding the plated steel sheet to obtain a plated steel sheet coil; and further the plated steel sheet coil is made into the steel sheet coil.

23. The method for manufacturing a steel plate according to claim 22, wherein: The plating step includes a hot-dip galvanizing step.

24. The method for manufacturing a steel plate according to claim 22, wherein: The plating step includes a hot-dip galvanizing step and a subsequent alloying step.

25. The method for manufacturing a steel plate according to claim 22, wherein: The plating process includes an electroplating process.

26. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The product coil is composed of a high-strength steel plate having a tensile strength of 590 MPa or more.

27. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The product coil comprises a base steel plate having the following composition, which comprises, by mass%, 0.030% to 0.800% C, 0.01% to 3.00% Si, 0.01% to 10.00% Mn, 0.001% to 0.100% P, 0.0001% to 0.0200% S, 0.0005% to 0.0100% N and less than 2.000% Al, with the remainder being Fe and unavoidable impurities.

28. The method for manufacturing a steel plate according to claim 27, wherein: The component composition further contains, in mass%, at least one element selected from the group consisting of 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.

29. The method for producing a steel plate according to any one of claims 14 to 17, wherein: The product coil comprises a stainless steel plate having the following composition, wherein the composition, in mass %, comprises 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: 3.000% or less, and the remainder is composed of Fe and unavoidable impurities.

30. The method for manufacturing a steel plate according to claim 29, wherein: The component composition further contains, in mass %, at least one element selected from the group consisting of 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.

31. The method for manufacturing a steel plate according to any one of claims 14 to 17, wherein: The product coil has a diffusible hydrogen content of 0.50 mass ppm or less.

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