Steel slag cutting method and steel slag cutting device

Abstract

To provide a scarfing method for a steel material that can stably scarf a surface of a steel material making scarfing depth shallow and uniform.SOLUTION: A scarfing method for a steel material comprises: a preheating step of spraying flammable gas and oxygen for preheating to a surface of the steel material to burn the surface so that a molten metal pool is formed on the surface of the steel material: and a scarfing step of spraying oxygen for scarfing to the surface of the steel material, and simultaneously conveying the steel material so as to scarf the surface of the steel material by heat of oxidation reaction of the oxygen for scarfing with iron. The scarfing method is configured to: jet front-side shield gas composed of flammable gas and oxygen to a front side in a progressing direction of scarfing at a fire point formed resulting from oxidation reaction of the oxygen for scarfing with the steel material; and simultaneously, jet rear-side shield gas composed of flammable gas to a rear side in the progressing direction of scarfing at the fire point, in the scarfing step. In the scarfing step, a flow velocity of the oxygen for scarfing that is sprayed to the surface of the steel material is set to a supersonic velocity.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for scalding a surface of a steel material, and to an apparatus for scalding a steel material. [Background technology]

[0002] For example, surface defects such as inclusions and surface flaws may occur on the surface of steel materials such as cast slabs produced by continuous casting. To remove such surface defects of steel materials, for example, scarifying devices (scarfer equipment) are used as disclosed in Patent Documents 1 to 4. These scarifying devices (scarfer equipment) locally heat and melt the surface of the slab (steel material) to remove surface defects. In the above-mentioned scarifying device (scarfer equipment), a scarfer unit is disposed so as to face the surface of the steel material.

[0003] In a scarifying device (scarfer equipment) configured in this manner, first, combustible gas and preheating oxygen are sprayed onto the surface of the steel material to burn the combustible gas, and the heat of combustion melts the surface of the steel material locally to form a basin (preheating step). Next, oxygen for slag cutting is supplied to the surface of the steel material while the steel material is being transported, and the basin described above is used as a heat source to cause an oxidation reaction between the oxygen for slag cutting and iron, and the heat from this oxidation reaction melts the surface of the steel material and removes surface defects (slag cutting step). The area where the oxygen for slag cutting is supplied and where the oxidation reaction with the iron of the steel material occurs is called the hot spot.

[0004] When steel is scalded using the scalding equipment described above, the scalding depth of the steel is roughly determined by the oxygen supply rate. To increase the scalding depth, the oxygen supply pressure must be increased or the steel feed speed must be slowed down to increase the amount of oxygen supplied per unit time. In order to improve the productivity of swarf cutting, it is common to increase the feed speed of the steel material, but as the feed speed increases, the swarf cutting depth gradually becomes shallower, resulting in localized areas that are not swarfed.

[0005] To address this issue, for example, Patent Documents 1 and 2 disclose a method of uniformizing the dry-cutting oxygen in the width direction by inserting an orifice or a flow straightening plate into the oxygen flow path. Furthermore, Patent Document 3 discloses a method of setting an angle between the ejection direction of the nozzle and the direction of the cutting. Furthermore, Patent Document 4 discloses a method of alternately switching the oxygen supply pressure between high and low pressures. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Utility Model Application Publication No. 03-070856 [Patent Document 2] Japanese Patent Application Publication No. 10-272561 [Patent Document 3] Japanese Patent Application Publication No. 07-214302 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-029911 Summary of the Invention [Problem to be solved by the invention]

[0007] Recently, in order to improve productivity and yield during cutting, it has become necessary to perform cutting shallowly and uniformly. However, if the feed rate of the steel material is increased to reduce the cutting depth to 2 mm or less, the oxygen supply becomes unstable, making it impossible to perform stable cutting, resulting in fluctuations in the cutting depth in the width direction and the formation of large irregularities on the surface of the steel material after cutting. This makes it difficult to reduce the cutting depth.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a steel cutting device and a steel cutting method that can stably cut the surface of steel and can cut the surface shallowly and uniformly. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a method for laser-cutting a steel material, which uses a steel material laser-cutting device having a preheating gas jetting section that jets out combustible gas and preheating oxygen, and a laser-cutting oxygen jetting section that jets out laser-cutting oxygen, and which laser-cuts the surface of the steel material, and includes a preheating step of spraying combustible gas and preheating oxygen from the preheating gas jetting section onto the surface of the steel material to combust and form a basin on the surface of the steel material, and a step of spraying laser-cutting oxygen from the laser-cutting oxygen jetting section onto the surface of the steel material to form a basin on the surface of the steel material. and a slag-cutting process in which the steel material is transported while being slag-cut by heat of oxidation reaction between the slag-cutting oxygen and iron, and the surface of the transported steel material is slag-cut by heat of oxidation reaction between the slag-cutting oxygen and iron, and in the slag-cutting process, a front shielding gas consisting of a combustible gas and oxygen is ejected to the front side of a hot spot formed by an oxidation reaction between the slag-cutting oxygen and the steel material in the slag-cutting advance direction, and a rear shielding gas consisting of a combustible gas is ejected to the rear side of the hot spot in the slag-cutting advance direction, and the slag-cutting oxygen ejection part is a slit nozzle, Slit Nozzle The outlet of the nozzle is provided with a contraction section, a throat section, and an expansion section, and the flow rate of the oxygen for use in the cutting process that is sprayed onto the surface of the steel material is made supersonic.

[0010] According to this method for laser-cutting steel, the flow velocity of the laser-cutting oxygen sprayed onto the surface of the steel is made supersonic in the laser-cutting step, which increases the momentum of the laser-cutting oxygen and reliably burns the rear shielding gas made of a flammable gas, improving shielding properties and preventing air from entering the hot spot. This allows high-purity oxygen to be supplied to the hot spot, enabling the surface of the steel to be laser-cut stably and achieving shallow and uniform laser-cutting.

[0011] Here, in the method for scarifying steel material of the present invention, the scarifying oxygen jetting portion is 、 Oxygen amount for cutting Q (Nm 3 It is preferable that the flow rate (Q / h / unit) satisfies Q≧309.5×h, where h (mm) is the interval between the throat portions of the slit nozzle. In this case, the amount of oxygen for cutting Q (Nm 3 / h / unit) is specified as described above, it is possible to make the flow rate of the slag-cutting oxygen sufficiently supersonic.

[0012] The apparatus for scalding steel according to the present invention has a preheating gas jetting section for jetting combustible gas and preheating oxygen, and a scalding oxygen jetting section for jetting scalding oxygen, and sprays the scalding gas and preheating oxygen onto the surface of the steel to form a basin on the surface of the steel, and scalding oxygen is sprayed toward this basin to scalculate the surface of the steel by heat of oxidation reaction between the scalding oxygen and iron, and the scalding oxygen jetting section is a slit nozzle, and the outlet portion of this slit nozzle Top and bottom of the long side The valve is characterized by having a contraction section, a throat section, and an expansion section.

[0013] According to this steel cutting method, the cutting oxygen jet is a slit nozzle, and the outlet of this slit nozzle is configured with a contraction section, a throat section, and an expansion section, so that the cutting oxygen compressed in the contraction section is accelerated as it expands in the expansion section, making it possible to make the flow rate of the cutting oxygen supersonic. As a result, high-purity oxygen is supplied to the hot point, allowing the surface of the steel to be stably cut, and making it possible to cut the steel to a shallow and uniform depth.

[0014] In the steel material laser cutting device of the present invention, the contraction section is preferably shaped so that the slit width narrows toward the outlet side at an inclination of 15° to 45°. In this case, the slag-cutting oxygen passing through the contracted portion can be sufficiently compressed, and can be sufficiently accelerated when expanding in the expanded portion.

[0015] In the steel material laser cutting device of the present invention, the expanding portion is preferably shaped so that the slit width increases toward the outlet side at an inclination of 3° to 7°. In this case, the passing slag cutting oxygen can be sufficiently expanded to accelerate it sufficiently. [Effects of the Invention]

[0016] As described above, according to the present invention, it is possible to provide a steel material rake-cutting device and a steel material rake-cutting method that can stably rake the surface of steel material and rake the surface to a shallow and uniform depth. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic explanatory diagram of a steel material laser cutting device according to an embodiment of the present invention, in which (a) shows a preheating step and (b) shows a laser cutting step. [Figure 2] FIG. 2 is an explanatory diagram of an oxygen jetting portion for slag-cutting of the steel slag-cutting device of FIG. 1. [Figure 3] FIG. 2 is an explanatory diagram of the shape of a Laval nozzle. [Figure 4] 4 is a graph showing the conditions under which the Laval nozzle shown in FIG. 3 reaches a supersonic region. [Figure 5] 1A and 1B are diagrams showing the results of a computational fluid dynamics analysis of the oxygen concentration distribution at the hot spot (plane perpendicular to the conveying direction X), where (a) is a conventional example (straight nozzle) and (b) is an example of the present invention (Laval nozzle). [Figure 6] 1 shows the uneven shape of the swarf-cut surface, where (a) is a conventional example (straight nozzle) and (b) is an example of the present invention (Laval nozzle). DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a method for rake-cutting steel material and an apparatus for rake-cutting steel material according to embodiments of the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiments.

[0019] As shown in Figure 1, a steel material scarifying apparatus 10 embodying the present invention has a scarfer unit 20 arranged to face the surface of the steel material 1, and a conveying table (not shown) for conveying the steel material 1. 1, the scarfer unit 20 is provided with a preheating gas ejection section 21 that ejects preheating oxygen 27 and combustible gas 28, and a fracturing-cutting oxygen ejection section 30 that ejects fracturing-cutting oxygen 37. The fracturing-cutting oxygen ejection section 30 is configured to eject a rear shielding gas 38 consisting of a combustible gas together with the fracturing-cutting oxygen 37. The steel material 1 is placed on a conveying table and is configured to be conveyed in the direction of arrow X in FIG. As shown in Figures 1(a) and 1(b), the jet of cutting oxygen 37 jetted from the cutting oxygen jetting section 30 is positioned so as to collide further forward in the conveying direction X of the steel material 1 than the jets of preheating oxygen 27 and combustible gas 28 jetted from the preheating gas jetting section 21.

[0020] Here, the shape of the oxygen jetting portion 30 for scalculating in the steel scalculating apparatus 10 of this embodiment will be described. 2, the oxygen jetting section 30 for thermal cutting is a slit nozzle extending in the width direction, and is provided with a contracting section 31 in which the slit width narrows toward the outlet side, a throat section 32 in which the slit width is constant, and an expanding section 33 in which the slit width widens toward the outlet side. In other words, the oxygen jetting section 30 for thermal cutting in this embodiment is a slit nozzle to which a Laval structure is applied.

[0021] In this embodiment, the contracted portion 31 has a shape in which the slit width narrows toward the outlet side at a gradient angle θ1. Here, the gradient angle θ1 of the contracted portion 31 is preferably within a range of 5° to 45°. The slope angle θ1 of the contracted portion 31 is more preferably 10° or more, and even more preferably 15° or more. On the other hand, the slope angle θ1 of the contracted portion 31 is more preferably 30° or less, and even more preferably 20° or less.

[0022] The expanded portion 33 has a shape in which the slit width increases toward the outlet side at an inclination angle θ2. Here, the inclination angle θ2 of the expanded portion 33 is preferably within a range of 1° to 7°. The gradient angle θ2 of the expanded portion 33 is more preferably 2° or more, and even more preferably 2.5° or more. On the other hand, the gradient angle θ2 of the expanded portion 33 is more preferably 5° or less, and even more preferably 3° or less.

[0023] Here, in the Laval nozzle constituting the oxygen jetting section 30 for surface cutting, as shown in Fig. 3, when a compressible fluid is jetted out, the fluid is compressed in the contracting section 31 and expands in the expanding section 33. At this time, the flow velocity of the passing fluid is accelerated. Nozzle inlet pressure P o and the pressure at the nozzle outlet P b Relative to P o / P b and the cross-sectional area of ​​the nozzle outlet A e and the cross-sectional area of ​​the throat A * Ratio to A e / A * The relationship is shown in Figure 4. As shown in Figure 4, by optimizing the nozzle shape, it is possible to make the fluid passing through supersonic. For example, P o / P b When the value is set to the range of 3.5 to 4.5, the cross-sectional area A of the nozzle outlet is set to 1 / 200 of the value of 3.5 to 4.5. e and the cross-sectional area of ​​the throat A * Ratio to A e / A * It is preferable to set it to 1.15.

[0024] Next, a method for laser cutting a steel material 1 using the laser cutting apparatus 10 for steel material according to this embodiment will be described. In the steel material laser cutting apparatus 10 configured as described above, first, as shown in Fig. 1(a), preheating oxygen 27 and combustible gas 28 are ejected from the preheating gas ejection portion 21 of the scarfer unit 20 toward the surface of the steel material 1, and the combustible gas 28 is burned. Then, a part of the surface of the steel material 1 is melted by the combustion heat of the combustible gas 28, and a basin portion 3 is formed (preheating step). The length of the well portion 3 formed on the surface of the steel material 1 along the conveying direction X is set to, for example, a range of about 20 mm to 30 mm.

[0025] Next, the oxygen for scalding 37 is jetted from the oxygen for scalding jetting portion 30 of the scarfer unit 20 toward the surface of the steel material 1, and the steel material 1 on which the basin portion 3 has been formed is transported in the transport direction X. At this time, preheating oxygen 27 and combustible gas 28 are ejected from the preheating gas ejection part 21 and used as front shielding gas. In addition, rear shielding gas 38, which is made of combustible gas, is ejected. The rear shielding gas 38 is burned by a part of the cutting oxygen 37. This prevents the intrusion of air into the vicinity of the fire point.

[0026] The jet of cutting oxygen 37 jetted from the cutting oxygen jetting section 30 passes through the pool 3 of the steel material 1 being transported, and this pool 3 serves as a heat source to cause an oxidation reaction between the cutting oxygen 37 and iron, and the heat of this oxidation reaction melts the surface of the steel material 1, thereby cutting the surface of the steel material 1 (cutting process). That is, the rear side of the basin 3 in the conveying direction X is scalded by the heat of oxidation reaction. Note that the region where scalding oxygen 37 is supplied and an oxidation reaction with iron in the steel material 1 occurs becomes a hot spot.

[0027] In the steel cutting device 10 of this embodiment, the cutting oxygen jetting section 30 has a Laval structure with a contraction section 31, a throat section 32, and an expansion section 33, so that the jetted cutting oxygen 37 becomes supersonic. In this embodiment, the amount of oxygen for cutting Q (Nm 3It is preferable that the air flow rate (Q / h / unit) is set so as to satisfy Q≧309.5×h, where h (mm) is the interval between throat portions 32 of oxygen ejection portion 30 for dry-cutting, which is a slit nozzle.

[0028] Here, Fig. 5 shows the results of computational fluid dynamics analysis of a conventional oxygen jetting unit for thermal cutting (straight nozzle) and the oxygen jetting unit for thermal cutting (Laval nozzle) of this embodiment. Fig. 5 shows the oxygen concentration distribution in the region (hot spot) where the oxidation reaction between the iron in the steel material 1 and the oxygen 37 jetted from the oxygen jetting unit for thermal cutting 30 of the scarfer unit 20 occurs, and the steel material 1 is transported from the top to the bottom of the figure. In a conventional oxygen jetting part (straight nozzle) for surface cutting, the oxygen concentration fluctuates in a wavy manner in the width direction, as shown in FIG. 5(a). In contrast, in the oxygen jetting part for surface cutting (Laval nozzle) of this embodiment, the oxygen concentration is uniform across the width, as shown in Fig. 5(b), which is presumably because the rear shielding gas 38 is sufficiently combusted and protected from the atmosphere.

[0029] Figure 6 shows the amount of oxygen used for cutting Q = 1750 Nm 3 The figures show the uneven shape of the slag-cutting surface when slag-cutting was performed at 1 / h / unit. In the conventional slag-cutting oxygen jetting part (straight nozzle) shown in (a), the slit spacing h = 6 mm, so the slag-cutting oxygen flow rate was in the subsonic range, with an average slag-cutting depth of 2.51 mm and a standard deviation of the unevenness of 0.34 mm. In contrast, in the slag-cutting oxygen jetting part (Laval nozzle) of this embodiment shown in (b), the throat spacing h = 5.5 mm, so the slag-cutting oxygen flow rate was supersonic, and the average slag-cutting depth remained almost unchanged at 2.46 mm, but the standard deviation of the unevenness was significantly smoothed to 0.21 mm.

[0030] According to the method for laser-cutting steel material of this embodiment configured as described above, the flow velocity of the laser-cutting oxygen 37 sprayed onto the surface of the steel material 1 in the laser-cutting process is made supersonic, which increases the momentum of the laser-cutting oxygen 37 and ensures that the rear shielding gas 38 made of a flammable gas is burned, improving shielding properties and preventing air from entering the hot spot. This allows high-purity oxygen to be supplied to the hot spot, enabling the surface of the steel material 1 to be laser-cut stably and to laser-cut to a shallow and uniform depth.

[0031] In this embodiment, the amount of oxygen for cutting Q (Nm 3 When the flow rate (Q / h / unit) is set so as to satisfy Q≧309.5×h with respect to the spacing h (mm) of the throat portions 32 of the oxygen jetting portions 30 for use in cut- ting, the flow velocity of the oxygen for use in cut- ting 37 can be made sufficiently supersonic, the surface of the steel material 1 can be stably cut, and the cutting depth can be made shallow and uniform.

[0032] According to the steel material laser-cutting device 10 of this embodiment, the laser-cutting oxygen jetting section 30 is a slit nozzle, and this slit nozzle has a Laval structure equipped with a contraction section 31, a throat section 32, and an expansion section 33. Therefore, the laser-cutting oxygen 37 compressed in the contraction section 31 is accelerated when it expands in the expansion section 33, and the flow velocity of the laser-cutting oxygen 37 can be made supersonic. Therefore, highly pure oxygen is supplied to the hot point, the surface of the steel material 1 can be stably laser-cut, and the laser-cutting depth can be made shallow and uniform.

[0033] In this embodiment, when the contraction section 31 is shaped so that the slit width narrows toward the outlet side at a gradient angle θ1 of 15° or more and 45° or less, the oxygen for welding 37 passing through the contraction section 31 can be sufficiently compressed, and the oxygen for welding 37 can be sufficiently accelerated when expanding in the expansion section 33. In addition, in this embodiment, when the expansion section 33 is shaped so that the slit width widens toward the exit side at a gradient angle θ2 of 3° or more and 7° or less, the passing cutting oxygen 37 can be sufficiently expanded and accelerated sufficiently.

[0034] The above describes the steel cutting device 10 and steel cutting method, which are embodiments of the present invention, but the present invention is not limited to this and can be modified as appropriate within the scope of the technical concept of the invention. In this embodiment, the apparatus for laser-cutting steel materials has been described as having the configuration shown in FIG. 1, but is not limited to this. As long as it has a preheating gas ejection section that ejects combustible gas and preheating oxygen, and a laser-cutting oxygen ejection section that ejects laser-cutting oxygen, and the laser-cutting oxygen ejected from the laser-cutting oxygen ejection section is supersonic, there are no particular limitations on the other structures. [Explanation of symbols]

[0035] 1 Steel material 3. Bathtub 10. Steel cutting equipment 20 Scarfer Unit 21 Preheating gas outlet 30 Oxygen jet for scouring 31 Contraction section 32 throat 33 Enlarged section

Claims

1. A method for laser-cutting a steel material, using a laser-cutting device for steel material having a preheating gas jetting section that jets combustible gas and preheating oxygen, and a laser-cutting oxygen jetting section that jets laser-cutting oxygen, comprising: a preheating step of blowing combustible gas and preheating oxygen from the preheating gas jetting portion onto the surface of the steel material to combust them and form a basin on the surface of the steel material; a slag-cutting step of spraying slag-cutting oxygen from the slag-cutting oxygen jetting portion onto a surface of the steel material while transporting the steel material, and slag-cutting the surface of the transported steel material by heat of oxidation reaction between the slag-cutting oxygen and iron; and In the thermal cutting process, a front shielding gas consisting of a combustible gas and oxygen is ejected to the front side of a hot spot formed by an oxidation reaction between the oxygen for thermal cutting and the steel material in the direction of thermal cutting progress, and a rear shielding gas consisting of a combustible gas is ejected to the rear side of the hot spot in the direction of thermal cutting progress, The cutting oxygen jetting portion is a slit nozzle, and an outlet portion of the slit nozzle is provided with a contraction portion, a throat portion, and an expansion portion, A method for laser cutting a steel material, characterized in that in the laser cutting step, the flow rate of the laser cutting oxygen sprayed onto the surface of the steel material is made supersonic.

2. The oxygen jetting portion for slag cutting has an oxygen amount Q (Nm ３ 2. The method for hot cutting steel material according to claim 1, wherein the distance Q ( / h / unit) satisfies Q≧309.5×h, where h (mm) is the distance between the throat portions of the slit nozzle.

3. A steel material slag-cutting device having a preheating gas jetting section that jets out combustible gas and preheating oxygen, and a slag-cutting oxygen jetting section that jets out slag-cutting oxygen, wherein the slag-cutting device sprays the slag-cutting oxygen and the preheating oxygen onto a surface of the steel material to form a basin on the surface of the steel material, and slag-cutting oxygen is sprayed toward the basin to slag-cut the surface of the steel material by heat of oxidation reaction between the slag-cutting oxygen and iron, The oxygen jetting section for use in laser cutting is a slit nozzle, and a contraction section, a throat section, and an expansion section are provided on the upper and lower long side surfaces of the outlet section of the slit nozzle.

4. 4. The steel material laser cutting device according to claim 3, wherein the contraction portion is shaped so that the slit width narrows toward the outlet side at an angle of 5° to 45°.

5. 5. The steel material laser cutting device according to claim 3 or 4, wherein the expanding portion is shaped so that the slit width increases toward the outlet side at an angle of 1° to 7°.

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