Steel cutting method and steel 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, scarfs a surface of the steel material using a scarfer unit that has a preheating-gas jetting part that jets flammable gas and oxygen for preheating and a scarfing-oxygen jetting part that jets oxygen for scarfing. The 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 jet rear-side shield gas composed of flammable gas to a rear side in the progressing direction of scarfing at the fire point, in a scarfing step. In the scarfing step, a gas quantity Q of the rear-side shield gas is set in accordance with an area S (mm2) of a gap between the scarfer unit and the steel material on a cross section orthogonal to an advancing direction of the steel material.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] For example, surface defects such as inclusions and surface scratches may occur on the surface of a steel material such as a slab produced by continuous casting. When removing such surface defects of steel materials, for example, scarifying devices (scarfer equipment) disclosed in Patent Documents 1 to 4 are used. 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 as described above, first, combustible gas and preheating oxygen are sprayed onto the surface of the steel material to combust the combustible gas, and the heat of combustion melts the surface of the steel material locally to form a pool portion (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 slag cutting oxygen and iron are oxidized using the above-mentioned basin as a heat source, 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 the above-mentioned cutting device is used to cut steel, the cutting depth of the steel is determined by the oxygen supply rate. To increase the cutting depth, the oxygen supply pressure is increased or the feed speed of the steel is 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. However, as the feed speed is increased, the swarf cutting depth gradually becomes shallower, resulting in localized unswarfed areas.

[0005] To address such problems, 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 straightening plate into the oxygen flow path. Moreover, Patent Document 3 discloses a method of setting an angle between the discharge direction of the nozzle and the direction of machining. Furthermore, Patent Document 4 discloses a method of alternately switching the supply oxygen 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] JP 2010-029911 A Summary of the Invention [Problem to be solved by the invention]

[0007] Recently, in order to improve the productivity of the cutting and the yield rate during the cutting, it is required to perform the cutting with a shallow and uniform depth. However, when the feed speed of the steel material is increased in an attempt 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 an apparatus for sintering steel material, and a method for sintering steel material, which are capable of stably sintering the surface of steel material and capable of sintering the surface of steel material to a shallow and uniform depth. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors conducted extensive research and obtained the following findings. Conventionally, in the above-mentioned thermal cutting process, a rear shield gas made of a combustible gas is ejected rearward of the hot spot in the direction of progress of the thermal cutting, thereby preventing the intrusion of air into the hot spot. If the ejected rear shielding gas is not discharged stably, the rear shielding gas may flow toward the hot point, making it difficult to stably supply oxygen for cutting to the hot point.

[0010] The present invention has been made based on the above-mentioned findings, and the method for thermal cutting of steel material according to the present invention is a method for thermal cutting of steel material, using a scarfer unit having a preheating gas jetting section which jets out combustible gas and preheating oxygen, and a thermal cutting oxygen jetting section which jets out oxygen for thermal cutting, to thermally cut the surface of the steel material, the method comprising the steps of: 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 portion on the surface of the steel material; and a laser cutting process in which the steel material is transported and the surface of the transported steel material is laser cut by heat of oxidation reaction between the laser cutting oxygen and iron. In the laser cutting process, a front shielding gas consisting of a combustible gas and oxygen is ejected on the front side of the laser cutting advance direction of a hot point formed by an oxidation reaction between the laser cutting oxygen and the steel material, and a rear shielding gas consisting of a combustible gas is ejected on the rear side of the hot point in the laser cutting advance direction. In the laser cutting process, a gap area S (mm 2 ) is S≧5.5×W with respect to the width W (mm) of the scarfer unit, the gas amount Q (Nm 3 / h / unit) is within the range of 0.09×W≦Q≦0.19×W with respect to the width W (mm) of the scarfer unit, and the gap area S (mm 2 ) is S < 5.5 × W with respect to the width W (mm) of the scarfer unit, the gas amount Q (Nm 3 / h / unit) and the gap area S (mm 2 ), the characteristic of this product is that it is within the range of (0.6×S / (5.5×W)+0.4)×0.09×W≦Q≦(0.6×S / (5.5×W)+0.4)×0.19×W.

[0011] According to the method for scarifying steel material having this configuration, in the scarifying step, the gap area S (mm 2 ) depending on the amount of rear shielding gas Q (Nm 3 / h / unit), the ejected rear shielding gas can be discharged to the rear side of the scarfer unit, preventing the rear shielding gas from entering the vicinity of the fire point, allowing a stable supply of oxygen for cutting to the fire point, enabling the surface of the steel to be stably cut, and enabling the cutting depth to be shallow and uniform.

[0012] In the method for scarifying a steel material according to the present invention, in the scarifying step, the gap area S (mm 2 It is preferable that S≧5.5×W, where W (mm) is the width of the scarfer unit. In this case, the ejected rear shield gas can be discharged to the rear side of the scarfer unit, so that the oxygen for scouring can be stably supplied to the hot point, the surface of the steel material can be scouring stably, and the scouring depth can be made shallow and uniform. In addition, the gas amount Q of the rear shield gas (Nm 3 Since the amount of gas Q (Nm m / h / unit) is 0.09×W or more with respect to the width W (mm) of the scarfer unit, it is possible to suppress the intrusion of air into the vicinity of the fire point. 3 Since the time required for the rear shielding gas to flow into the fire point is suppressed, the time required for the rear shielding gas to flow into the fire point is suppressed, and oxygen for laser cutting can be stably supplied to the fire point.

[0013] The present invention relates to an apparatus for laser-cutting steel, the apparatus comprising: a scarfer unit having a preheating gas ejection section which ejects combustible gas and preheating oxygen; and an oxygen ejection section which ejects oxygen for laser-cutting; the apparatus sprays the combustible gas and preheating oxygen onto a surface of the steel to form a pool of hot water on the surface of the steel; and sprays oxygen for laser-cutting toward the pool of hot water to laser-cut the surface of the steel by heat of oxidation reaction between the oxygen for laser-cutting and iron; A skid is disposed under the scarfer unit, and the height of the skid is set to 5.5 mm or more; The gap area S (mm 2 ) is such that S≧5.5×W, where W (mm) is the width of the scarfer unit.

[0014] According to the steel material scarifying apparatus having this configuration, the gap area S (mm 2 Since the distance S between the shielding gas and the ground is set to S≧5.5×W with respect to the width W (mm) of the scarfer unit, the ejected rear shield gas can be discharged to the rear side of the scarfer unit. This allows a stable supply of oxygen for cutting to the hot point, and the surface of the steel material can be stably cut, making it possible to perform shallow and uniform cutting.

[0015] Also, The height of the skid attached to the lower part of the scarfer unit is set to 5.5 mm or more, so even if the bottom surface of the skid is in contact with the surface of the steel material, the gap area S (mm 2 ) can be sufficiently secured, and S≧5.5×W can be satisfied, where W (mm) is the width of the scarfer unit, making it possible to exhaust the ejected rear shield gas to the rear side of the scarfer unit. Effect of the Invention

[0016] As described above, according to the present invention, it is possible to provide an apparatus for laser cutting steel material and a method for laser cutting steel material, which are capable of stably laser cutting the surface of steel material and capable of laser cutting to a shallow and uniform depth. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic explanatory diagram of a steel material laser cutting apparatus according to an embodiment of the present invention, in which (a) shows a preheating step and (b) shows a laser cutting step. [Diagram 2] FIG. 2 is an explanatory diagram of a scarfer unit of the steel material scarifying apparatus of FIG. 1. [Diagram 3] 1 is a graph showing the results of an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0019] As shown in FIG. 1, a steel material scarifying apparatus 10 according to an embodiment of 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 laser cutting oxygen ejection section 30 that ejects laser cutting oxygen 37. The laser cutting oxygen ejection section 30 is configured to eject a rear shielding gas 38 consisting of a combustible gas together with the laser 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 oxygen for melt cutting 37 jetted out from the oxygen jetting section 30 is positioned so as to collide forward in the conveying direction X of the steel material 1 relative to the jets of preheating oxygen 27 and combustible gas 28 jetted out from the preheating gas jetting section 21.

[0020] Here, in the steel material scarifying apparatus 10 of this embodiment, as shown in FIG. 2, a skid 41 is disposed below the scarfer unit 20, and it is preferable that the height of the skid 41 is 5.5 mm or more. In the steel material scarifying device 10 of this embodiment, when the steel material 1 is brought into contact with the bottom surface of the skid 41, the gap area S (mm 2 It is preferable that S≧5.5×W, where W (mm) is the width of the scarfer unit 20. In FIG. 2, two skids 41 are arranged, and the gap area S is S=S1+S2+S3.

[0021] Next, a method for laser cutting a steel material using the laser cutting apparatus 10 for a steel material according to this embodiment will be described. In the steel material melt-cutting apparatus 10 having the above-mentioned configuration, first, as shown in Fig. 1(a), preheating oxygen 27 and combustible gas 28 are ejected from the preheating gas ejection part 21 of the scarfer unit 20 toward the surface of the steel material 1, and the combustible gas 28 is combusted. Then, a part of the surface of the steel material 1 is melted by the combustion heat of the combustible gas 28 to form a basin part 3 (preheating process). 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, within a range of about 20 mm to 30 mm.

[0022] Next, oxygen for slag cutting 37 is ejected from the oxygen for slag cutting ejection portion 30 of the scarfer unit 20 toward the surface of the steel material 1, and the steel material 1 with the well portion 3 formed thereon 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 a front shielding gas. Also, rear shielding gas 38 made of combustible gas is ejected. The rear shielding gas 38 is burned by a part of the cutting oxygen 37. This prevents the air from entering the vicinity of the fire point.

[0023] The jet of oxygen for cutting 37 jetted out from the oxygen for cutting jetting section 30 passes through the pool 3 of the steel material 1 being transported, and causes an oxidation reaction between the oxygen for cutting 37 and the iron using the pool 3 as a heat source. The heat of this oxidation reaction melts the surface of the steel material 1, and the surface of the steel material 1 is laser-cut (laser-cutting process). That is, the rear side of the well 3 in the transport direction X is scalded by the heat of oxidation reaction. Note that the region where oxygen 37 for scalding is supplied and oxidation reaction with the iron of the steel material 1 occurs becomes a hot spot.

[0024] In this embodiment, the gas amount Q (Nm 3 / h / unit) is the gap area S (mm 2 ) is set according to the

[0025] The above-mentioned gap area S (mm 2 ) is S≧5.5×W with respect to the width W (mm) of the scarfer unit 20, the gas amount Q (Nm 3 / h / unit) is within the range of 0.09×W≦Q≦0.19×W, where W (mm) is the width of the scarfer unit 20. The above-mentioned gap area S (mm 2 ) with respect to the width W (mm) of the scarfer unit 20, when S < 5.5 × W, the gas amount Q (Nm 3 / h / unit) and the gap area S (mm 2 ) shall be in the range of (0.6×S / (5.5×W)+0.4)×0.09×W≦Q≦(0.6×S / (5.5×W)+0.4)×0.19×W.

[0026] According to the method for scarifying steel material of the present embodiment configured as described above, in the scarifying process, the gap area S (mm 2 ) depending on the gas amount Q (Nm 3 Since the gas supply rate (gas supply rate) is set at 1 / h / unit, the ejected rear shielding gas 38 can be discharged to the rear side of the scarfer unit 20, and the rear shielding gas 38 is prevented from entering the vicinity of the hot point. Therefore, the oxygen for cutting 37 can be stably supplied to the hot point, the surface of the steel material 1 can be stably cut, and the cutting depth can be made shallow and uniform.

[0027] In this embodiment, the gap area S (mm 2 When the distance S between the shielding gas 38 and the surface of the scarfer unit 20 is set to S≧5.5×W with respect to the width W (mm) of the scarfer unit 20, the ejected rear shielding gas 38 can be stably discharged to the rear side of the scarfer unit 20. Therefore, it is possible to stably supply oxygen for cutting to the fire point, stably cut the surface of the steel material, and make it possible to perform shallow and uniform cutting. In addition, the gas amount Q (Nm 3 Since the gas amount Q (Nm / h / unit) is 0.09×W or more with respect to the width W (mm) of the scarfer unit 20, it is possible to suppress the intrusion of air into the vicinity of the fire point. 3 Since the distance (hr / h / unit) between the scarfer unit 20 and the width W (mm) is 0.19×W or less, the ejected rear shielding gas 38 can be prevented from flowing toward the fire point, and the oxygen 37 for cutting can be stably supplied to the fire point.

[0028] According to the steel material scarifying device of this embodiment, the gap area S (mm 2) is set to S≧5.5×W with respect to the width W (mm) of the scarfer unit 20, so that the ejected rear shield gas 38 can be stably discharged to the rear side of the scarfer unit 20. Therefore, the oxygen for cutting 37 can be stably supplied to the hot point, the surface of the steel material 1 can be stably cut, and the cutting depth can be made shallow and uniform.

[0029] In this embodiment, when the height of the skid attached to the lower part of the scarfer unit 20 is set to 5.5 mm or more, even when the bottom surface of the skid is in contact with the surface of the steel material 1, the gap area S (mm 2 ) can be sufficiently secured, and S≧5.5×W can be satisfied, where W (mm) is the width of the scarfer unit 20, so that the ejected rear shielding gas 38 can be stably discharged to the rear side of the scarfer unit 20.

[0030] The above describes the steel material cutting apparatus 10 and the steel material cutting method, which are embodiments of the present invention, but the present invention is not limited to this and can be modified as appropriate without departing from the technical concept of the invention.

[0031] In this embodiment, a skid is provided below the scarfer unit, but the present invention is not limited to this. The scarfer unit may be provided at a distance from the surface of the steel material to perform scarifying without using a skid. Even in this case, the gap area S (mm 2 ) The amount of rear shielding gas Q can be adjusted according to the EXAMPLES

[0032] The results of experiments carried out to confirm the effects of the present invention will be described below.

[0033] In the steel material laser cutting apparatus described in this embodiment, the gap area S between the scarfer and the steel material and the amount of rear shielding gas Q were set as shown in Table 1, and the laser cutting state was confirmed. Cases where swarf cutting was performed stably and uniformly were rated as "good", and cases where swarf cutting was performed unevenly in the width direction (commonly known as "too much") or where swarf cutting was not performed at all were rated as "bad".

[0034] In addition, Figure 3 shows an image of the limit of rear shielding gas entrainment, as well as the limit of air entrainment to the fire point, when the gap area S between the scarfer and the steel material and the amount of rear shielding gas Q are varied. Air entrainment to the fire point tends to occur easily when the rear shielding gas amount Q is small or the gap area S between the scarfer and the steel material is large. On the other hand, shielding gas entrainment to the fire point tends to occur easily when the rear shielding gas amount Q is large or the gap area S between the scarfer and the steel material is small.

[0035] [Table 1]

[0036] When the gap area S between the scarfer and the steel is "0", the amount of rear shielding gas Q is 15 Nm 3 Stable cutting is possible only when the shielding gas volume Q is 10 Nm 3 If the flow rate is too low, below 30 Nm / h / unit, the air will be drawn in and the flow rate will be 30 Nm 3 If the discharge rate was higher than 1 / h / unit, shielding gas was introduced to reduce the oxygen concentration at the hot point, and the cutting condition was marked as "X."

[0037] On the other hand, when the gap area S between the scarfer and the steel material is "≧5.5×W", the amount of shielding gas Q is 30 to 45 Nm 3 / h / unit, stable cutting was possible, but the shielding gas volume Q was 15Nm 3 If the speed is too low, below 50 Nm / h / unit, air will be drawn in and the speed will be reduced to 50 Nm 3If the discharge rate was higher than 1 / h / unit, shielding gas was introduced to reduce the oxygen concentration at the hot point, and the cutting condition was marked as "X."

[0038] In addition, when the gap area S between the scarfer and the steel material is "0 to less than 5.5 × W", the range in which cutting is possible varies depending on the size of the gap area S. When the amount of shielding gas Q is too small, air is drawn in, and when it is too large, the shielding gas is drawn in, reducing the concentration of oxygen for cutting at the hot point, resulting in the cutting status being "×".

[0039] The above results are illustrated in Figure 3. As described above, it was confirmed that the present invention can provide an apparatus and a method for scalding steel that can stably scalculate the surface of steel and can scalculate the surface of steel to a shallow and uniform depth. [Explanation of symbols]

[0040] 1 Steel material 3. Bathtub 10. Steel cutting equipment 20 Scarfer Unit 21 Preheating gas outlet 30 Oxygen outlet for cutting

Claims

1. A method for scarifying a surface of a steel material by using a scarfer unit having a preheating gas ejection section that ejects a combustible gas and preheating oxygen, and a scarifying oxygen ejection section that ejects oxygen for scarifying, comprising: a preheating step in which combustible gas and preheating oxygen are blown from the preheating gas jetting part onto the surface of the steel material to combust and form a pool of hot water on the surface of the steel material; and a laser-cutting step in which laser-cutting oxygen is blown from the laser-cutting oxygen jetting part onto the surface of the steel material while the steel material is being transported, and the surface of the transported steel material is laser-cut by heat of oxidation reaction between the laser-cutting oxygen and iron, 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 point formed by an oxidation reaction between the oxygen for thermal cutting and the steel material in a thermal cutting proceeding direction, and a rear shielding gas consisting of a combustible gas is ejected to the rear side of the hot point in the thermal cutting proceeding direction, In the above-mentioned scarifying process, the gap area S (mm ２ ) is S≧5.5×W, where W (mm) is the width of the scarfer unit, the gas amount Q (Nm3 / h / unit) of the rear shielding gas is within the range of 0.09×W≦Q≦0.19×W, Gap area S (mm ２ When S<5.5×W is the width W (mm) of the scarfer unit, the gas amount Q (Nm ３ / h / unit) and the gap area S (mm ２ 4)×0.09×W≦Q≦(0.6×S / (5.5×W)+0.4)×0.19×W.

2. In the above-mentioned scarifying process, the gap area S (mm ２ 2. The method for scarifying steel material according to claim 1, characterized in that S≧5.5×W, where W (mm) is the width of the scarfer unit.

3. A scarfer unit having a preheating gas ejection section which ejects combustible gas and preheating oxygen, and a cutting oxygen ejection section which ejects cutting oxygen, the scarfer unit ejects the combustible gas and preheating oxygen onto a surface of a steel material to form a pool of hot water on the surface of the steel material, and the cutting oxygen is ejected toward the pool of hot water to cut the surface of the steel material by heat of oxidation reaction between the cutting oxygen and iron, A skid is disposed under the scarfer unit, and the height of the skid is set to 5.5 mm or more; The gap area S (mm ２ ) is S≧5.5×W, where W (mm) is the width of the scarfer unit.

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