Surface scarfing device and surface scarfing method

Abstract

To provide a technique that can change thicknesses of scarfing a steel piece according to a purpose.SOLUTION: A surface scarfing device (10), which scarfs a surface of a steel material, comprises a laser emitting part (14a), a gas blowing part (16a), and a control part (20) that controls the laser emitting part and the gas blowing part. In a case where the surface of the steel material can be scarfed into a predetermined scarfing depth, by setting a flow rate of the gas and oxygen purity of the gas to predetermined values, when the surface of the steel material cannot be scarfed into a scarfing depth smaller than the predetermined scarfing depth only by changing at least either of output of laser by the laser emitting part and the flow rate of the gas, the control part controls the laser emitting part so that a laser beam is emitted to the steel material, and controls the gas blowing part so that gas having oxygen purity specified according to the scarfing depth smaller than the predetermined scarfing depth is blown to the surface in an area, so as to scarf the surface of the steel material into the predetermined scarfing depth.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a surface scrubbing apparatus and a surface scrubbing method. [Background technology]

[0002] Examples of steel materials that are subjected to laser cutting include billets that are rolled to be processed into products, such as slabs, billets, and blooms. During the manufacturing process of these billets, cracks may occur on the surface of the billets due to external forces, thermal strain, or the like. These cracks are defects, and it is desirable that the surface of the billets be free of defects in order to maintain the quality of the products manufactured from the billets.

[0003] Therefore, techniques for removing defects on the surface of a billet have been proposed. For example, Patent Document 1 discloses a technique for removing defects on the surface of a billet by a surface cutting process using a laser and oxygen gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-106376 Summary of the Invention [Problem to be solved by the invention]

[0005] The use of electric furnaces is being considered as a method for producing iron sources with the aim of decarbonizing. In this method, a large amount of scrap is fed into the furnace, and it is expected that the scrap will contain a large amount of copper (Cu), such as from motors. Cu is a so-called tramp element, and is an element that cannot be removed during the blowing process, and is contained as is in steel products such as billets.

[0006] When the Cu content in steel increases, a problem called red embrittlement occurs. Red embrittlement occurs when scale forms on the surface of steel in the high-temperature oxygen atmosphere of a heating furnace, causing Cu that was dissolved in the steel to be expelled from the scale and then to concentrate in a liquid state at the interface between the scale and the base metal. Specifically, the liquid Cu that has concentrated at the interface between the scale and the base metal infiltrates the grain boundaries of the base metal, causing microcracks on the surface of the base metal. These microcracks on the surface of the base metal become apparent during the subsequent hot rolling process, posing a quality problem.

[0007] Here, the microcracks caused by the Cu-enriched layer are dispersed over the entire surface of the steel material, and the width and depth of the microcracks in the thickness direction are small, making them difficult to detect. Therefore, it is necessary to dissolve and remove the entire surface (both surfaces) of the steel material.

[0008] At this time, there is a concern that the yield will decrease due to the entire steel material being melted down, so it is important to melt down as thinly as possible to the minimum necessary depth.

[0009] The technology disclosed in Patent Document 1 is a technology for removing defects such as cracks on the surface of a billet by means of a thermal cutting process, and has the problem that it is difficult to adjust the thickness of the thermal cutting to be thin when performing thermal cutting on steel material.

[0010] An object of one aspect of the present invention is to realize a technology for adjusting the thickness of the shavings to be thin in the shaving process of steel material. [Means for solving the problem]

[0011] In order to solve the above problems, a surface scalding device according to one aspect of the present invention is a surface scalding device for scalding the surface of a steel material, and includes a laser irradiation unit that irradiates the steel material with laser light, a gas blowing unit that blows a gas containing oxygen as a main component onto an area on the steel material that is irradiated with laser light by the laser irradiation unit, and a control unit that controls the laser irradiation unit and the gas blowing unit, and sets the output of the laser irradiated by the laser irradiation unit, the flow rate of the gas blown by the gas blowing unit, and the oxygen purity of the gas blown by the gas blowing unit to predetermined values. When the surface of the steel material can be cut to a predetermined cutting depth by changing the laser output of the laser irradiation unit and / or the flow rate of the gas, and when the surface of the steel material cannot be cut to a cutting depth smaller than the predetermined cutting depth by simply changing the laser output of the laser irradiation unit and / or the flow rate of the gas, the control unit controls the laser irradiation unit to irradiate the steel material with laser light, and controls the gas spraying unit to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than the predetermined cutting depth onto the area, thereby cutting the surface of the steel material to the predetermined cutting depth.

[0012] In order to solve the above-mentioned problems, a surface rake-cutting method according to one aspect of the present invention is a surface rake-cutting method for rake-cutting the surface of a steel material by a surface rake-cutting device, the method using a surface rake-cutting device including a laser irradiation unit that irradiates the steel material with laser light, a gas blowing unit that blows a gas containing oxygen as a main component onto an area irradiated with the laser light by the laser irradiation unit, and a control unit that controls the laser irradiation unit and the gas blowing unit, and When the surface of the steel material can be cut to a predetermined cutting depth by setting the predetermined value, and when the surface of the steel material cannot be cut to a cutting depth smaller than the predetermined cutting depth by simply changing at least one of the laser output of the laser irradiation unit and the gas flow rate, the method includes a laser irradiation step of controlling the laser irradiation unit using the control unit to irradiate the steel material with laser light, and a gas spraying step of controlling the gas spraying unit to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than the predetermined cutting depth onto the area. [Effects of the Invention]

[0013] According to one aspect of the present invention, the thickness of the cutting can be adjusted to be thin in the cutting treatment of steel material. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing a configuration example of a surface rake-cutting device according to an embodiment of the present invention; [Figure 2] 1 is a diagram showing a configuration example of a surface rake-cutting device according to an embodiment of the present invention; [Figure 3] FIG. 1 is a flowchart showing an example of the flow of a surface scarification method according to an embodiment of the present invention. [Figure 4] 10A to 10C are diagrams illustrating an example of the operation of the surface rake-cutting device according to an embodiment of the present invention. [Figure 5] 1 is a graph showing the relationship between oxygen purity and laser output and cutting depth according to an example of the present invention. [Figure 6]1 is an image of a steel product that has been spalled according to an embodiment of the present invention. [Figure 7] 1 is an image of a steel product that has been spalled according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Embodiment 1] Hereinafter, one embodiment of the present invention will be described in detail.

[0016] The surface cutting device 10 of this embodiment is, as an example, a device that adjusts the thickness of the cutting to be thinner by controlling the purity of the oxygen gas contained in the sprayed gas in a cutting process in which the surface of steel is cut by performing laser irradiation and gas spraying in parallel.

[0017] (Configuration of surface rake device 10) 1 is a diagram showing an example of the configuration of a surface scalding apparatus 10. The surface scalding apparatus 10 is an apparatus that scaldes the surface of a steel material 100. As shown in FIG. 1, the surface scalding apparatus 10 includes a laser irradiation unit 14a, a gas spraying unit 16a, and a control unit 20.

[0018] The steel material 100 may be, for example, a steel material to be rolled after being cooled after processing in a continuous casting machine or the like, and then reheated in a heating furnace and rolled. The steel material 100 may be in the form of a variety of shapes and sizes, such as a steel billet such as a slab, a billet, or a bloom, or a steel pipe or wire rod. The steel material 100 may be produced from scrap or the like, and may contain tramp elements such as Cu in its composition.

[0019] When using a steel material 100 manufactured from scrap or the like as a raw material, a Cu-enriched layer or a fine crack layer due to Cu infiltration may occur in a shallow region in the thickness direction of the steel material 100 in a heating furnace. Therefore, before rolling the steel material 100, it is preferable to set the cutting depth as small as possible to remove the Cu-enriched layer or the fine crack layer due to Cu infiltration.

[0020] (Transport unit 12) The surface scraping apparatus 10 may further include, for example, a transport section 12 .

[0021] The transport unit 12 transports the steel material 100. The transport unit 12 may also transport the steel material 100, for example, from a heating furnace to a rolling mill. Here, the steel material 100 may be heated in a heating furnace, have its surface scale removed using a known technique, and then be transported to the surface laser-cutting device 10. A known descaling device that removes surface scale may also be installed immediately before the surface laser-cutting device. In other words, laser-cutting can be performed immediately after the surface scale is removed using a known technique.

[0022] Each of the conveying units 12 may include, for example, conveying rollers and a driving device. For example, as shown in Fig. 1, the steel materials 100 are placed on the conveying rollers provided in the plurality of conveying units 12, and the steel materials 100 are conveyed by rotating the conveying rollers using a driving device. In Fig. 1, the conveying units 12 convey the steel materials 100 in a conveying direction D.

[0023] (Laser irradiation unit 14) The laser irradiation unit 14 irradiates the steel material 100 with laser light L. As shown in FIG. 1, a laser irradiation unit 14a, which is an example of the laser irradiation unit 14, is connected to a laser oscillator 142 via an optical fiber cable F. For example, the laser irradiation unit 14a may have a linear focusing optical head that focuses the laser light in a line. Furthermore, for example, the laser irradiation unit 14a may be arranged opposite the surface of the steel material 100 and configured to irradiate the surface of the steel material 100 with laser light L.

[0024] FIG. 2 is a diagram showing an example of the arrangement of the laser irradiation units 14a and the configuration regarding the laser light L. The multiple laser irradiation units 14a may be arranged side by side in the width direction of the steel material 100, as shown in FIG. 2, for example. Here, the multiple laser irradiation units 14a may be arranged, for example, so that the ends of the focused spots of adjacent laser irradiation units 14a overlap in the width direction of the steel material 100. In other words, the multiple laser irradiation units 14a may be arranged, for example, so that convex stripes that become residual cutting are not generated in the region 104 between the points irradiated with the laser light L by adjacent laser irradiation units 14a. Furthermore, the multiple laser irradiation units 14a may irradiate the laser light L over the entire length in the width direction of the steel material 100, for example.

[0025] For example, as shown in Fig. 2, while the steel material 100 is conveyed in the conveying direction D relative to a plurality of laser irradiation units 14a, the plurality of laser irradiation units 14a may irradiate the steel material 100 with laser light L over the entire width of the steel material 100, thereby irradiating the entire surface of the steel material 100 with laser light L. The laser-cutting completed portion 102 in Fig. 2 is a portion of the steel material 100 where laser cutting has been completed after irradiation with laser light L.

[0026] (Gas spraying section 16) The gas blowing unit 16 blows a gas containing oxygen as a main component onto an area on the steel material 100 that is irradiated with laser light L by the laser irradiation unit 14. Gas blowing unit 16a, which is an example of the gas blowing unit 16, is provided with a gas blowing port 162a. For example, the gas blowing unit 16a may blow gas onto the steel material 100 via the gas blowing port 162a. The proportion of oxygen contained in the gas blown by the gas blowing unit 16a will be described later with reference to FIG. 3. Specific examples of gas components other than oxygen (O2) contained in the gas blown by the gas blowing unit 16a include inert gases such as helium (He) or argon (Ar), carbon dioxide (CO2), and nitrogen (N2).

[0027] Here, the laser cutting process using the laser irradiation unit 14a and the gas blowing unit 16a will be described. The Fe on the surface of the steel material 100 reacts with the irradiation of laser light L by the laser irradiation unit 14a and the oxygen contained in the gas G by the gas blowing unit 16a, generating a molten pool of melted FeO. FeO has a lower melting point than Fe and is characterized by the generation of reaction heat as it is generated. The molten pool is blown away by the gas blowing unit 16a, causing the molten iron SC made of FeO that constituted the molten pool to move in the direction of progress of the cutting, thereby preheating the surface of the steel material 100. At this time, the surface of the steel material 100 is cut by continuing combustion of the steel material surface by oxygen in addition to the heat from the laser irradiation.

[0028] (Second laser irradiation unit 14b) The surface laser-cutting device 10 may further include, for example, a second laser irradiation unit 14b as the laser irradiation unit 14. The second laser irradiation unit 14b may irradiate the laser light L onto the surface on the back side of the steel material 100, for example.

[0029] Here, if the laser irradiation unit 14a and the second laser irradiation unit 14b are arranged to face each other, there is a possibility that the laser light of the other will enter and damage the optical head. In order to prevent damage to the optical heads of the laser irradiation unit 14a and the second laser irradiation unit 14b, the laser irradiation unit 14a and the second laser irradiation unit 14b may be arranged, for example, offset from each other in the conveyance direction of the steel material 100. As an example, the second laser irradiation unit 14b may be arranged further forward in the conveyance direction D of the steel material 100 than the laser irradiation unit 14a, as shown in FIG. 1 . Also, as another example, the laser irradiation unit 14a may be arranged further forward in the conveyance direction D of the steel material 100 than the second laser irradiation unit 14b.

[0030] Other configurations of the second laser irradiation unit 14b in this embodiment may be similar to, for example, the configuration of the above-mentioned laser irradiation unit 14a in which laser light L is irradiated onto the back surface of the steel material 100 instead of the front surface, so explanations will be omitted here.

[0031] (Second gas blowing section 16b) The surface laser-cutting apparatus 10 may further include, for example, a second gas blowing unit 16b as the gas blowing unit 16. The second gas blowing unit 16b may, for example, blow a gas containing oxygen as a main component onto the area irradiated with laser light L by the second laser irradiation unit 14b. The second gas blowing unit 16b includes, as an example, a second gas blowing port 162b. The configuration of the second gas blowing unit 16b and the second gas blowing port 162b in this embodiment may be the same as, for example, the configuration of the above-mentioned gas blowing unit 16a and gas blowing port 162a in which gas is blown onto the back surface of the steel material 100 instead of the front surface, and therefore a description thereof will be omitted here.

[0032] (First shielding portion 18a) The surface sintering device 10 may further include, for example, a first shielding portion 18a. The first shielding portion 18a may, for example, shield the laser light L irradiated from the laser irradiation portion 14a. Furthermore, the first shielding portion 18a may be disposed, for example, as shown in FIG. 1, so as to face the laser irradiation portion 14a across the steel material 100 transported by the transport portion 12. The second gas spraying portion 16b may also include, for example, the first shielding portion 18a. Here, the surface of the first shielding portion 18a may be made of a material that easily absorbs the laser. Furthermore, for example, the surface of the first shielding portion 18a may be coated with a black paint or the like to increase the laser absorption rate.

[0033] (Second shielding portion 18b) The surface sintering device 10 may further include, for example, a second shielding portion 18b. The second shielding portion 18b may, for example, shield the laser light L irradiated from the second laser irradiation portion 14b. The second shielding portion 18b may be disposed opposite the second laser irradiation portion 14b, for example, across the steel material 100 transported by the transport portion 12. The gas blowing portion 16a may also include, for example, the second shielding portion 18b. Here, the surface of the second shielding portion 18b may be made of a material that easily absorbs the laser. For example, the surface of the second shielding portion 18b may be coated with black paint or the like to increase the laser absorption rate.

[0034] (Control unit 20) Here, consider a case where the surface of the steel material 100 can be laser-cut to a predetermined cutting depth by setting the laser output of the laser irradiation unit 14, the flow rate of the gas sprayed by the gas spray unit 16, and the oxygen purity of the gas sprayed by the gas spray unit 16 to predetermined values. Furthermore, consider a case where the surface of the steel material 100 cannot be laser-cut to a cutting depth smaller than the predetermined cutting depth by simply changing at least one of the laser output of the laser irradiation unit 14 and the gas flow rate of the gas spray unit 16. In these cases, the control unit 20 controls the laser irradiation unit 14 to irradiate the steel material 100 with laser light. The control unit 20 also controls the gas spray unit 16 to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than the predetermined cutting depth onto the area irradiated with the laser light. That is, the control unit 20 can appropriately set the laser output, gas flow rate, and oxygen purity of the gas depending on the components of the steel material 100.

[0035] The control unit 20 appropriately sets the laser beam output, gas flow rate, and oxygen purity of the gas according to the composition of the steel material 100. To further reduce the depth of the laser cutting under those conditions, the control unit generally reduces the laser beam output or gas flow rate. Reducing the laser beam output to achieve a thinner cutting depth prevents the Fe on the surface of the steel material 100 from reacting, making cutting difficult. Reducing the gas flow rate to achieve a thinner cutting depth weakens the pressure pushing forward the molten iron SC, primarily composed of FeO in the molten state, making cutting difficult. In other words, a condition (a lower limit of the cutting depth obtained by reducing at least one of the laser beam output and the gas flow rate) is determined below which cutting to a depth smaller than the predetermined cutting depth becomes impossible. Therefore, by appropriately setting the laser beam output and gas flow rate within the specified range, the oxygen purity of the gas sprayed by the gas spray unit 16 can be adjusted to achieve cutting to a depth smaller than the predetermined cutting depth.

[0036] Note that when the laser output is reduced to achieve a welding depth smaller than the predetermined welding depth, the amount of heat supplied by the laser beam is small, and if the laser beam is interrupted, the amount of heat required to react with the Fe on the surface of the steel material 100 is immediately insufficient, making welding impossible. Therefore, to perform welding, it is necessary to continuously irradiate the laser beam. That is, it is preferable that the control unit 20 controls the laser irradiation unit 14 to continuously irradiate the laser beam once it has started irradiating the laser beam until the welding process is completed. In other words, it is preferable that the control unit controls the laser irradiation unit 14 to continuously irradiate the steel material 100 with the laser beam during welding.

[0037] The control unit 20 controls the transport unit 12, the laser irradiation unit 14a, the second laser irradiation unit 14b, the gas spraying unit 16a, and the second gas spraying unit 16b.

[0038] The control unit 20 is configured by an electronic circuit including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), etc. The control unit 20 may also include an electronic circuit such as a PLD (Programmable Logic Device) or an ASIC (Application Specific Integrated Circuit) instead of or in addition to the CPU.

[0039] (Surface cutting method S1 flow) The surface rake-cutting method S1 executed by the surface rake-cutting device 10 will be described with reference to FIGS.

[0040] 3 is a flow diagram showing an example of the flow of the surface laser cutting method S1. As shown in FIG. 3, the surface laser cutting method S1 includes (step) S10, (step) S12, (step) S14, and a stopping process (step) S16.

[0041] FIG. 4 is a diagram showing an example of operation of the surface scratching device 10 in the scratching process.

[0042] In step S10 of FIG. 3 , the control unit 20 sets the laser output power of the laser irradiated by the laser irradiating unit 14, the flow rate of the gas sprayed by the gas spraying unit 16, and the oxygen purity of the gas sprayed by the gas spraying unit 16 to predetermined values. A case where the surface of the steel material 100 can be laser-cut to a predetermined cutting depth by setting the settings in this manner will be described below. In this case, the control unit 20 detects a condition where the surface of the steel material 100 cannot be laser-cut to a cutting depth smaller than the predetermined cutting depth by simply changing at least one of the laser output power of the laser irradiating unit and the gas flow rate. As mentioned above, it is preferable to remove the Cu-enriched layer and the microcrack layer caused by Cu infiltration that occur in the heating furnace before rolling the steel billet. Because the Cu-enriched layer and the microcrack layer caused by Cu infiltration are known to occur in shallow regions in the thickness direction of the steel material 100, it is preferable to set the laser-cutting depth as small as possible. Generally, the laser light output power or the gas flow rate is controlled to be low. If the laser beam output is controlled to be low in order to achieve thin cutting, the Fe on the surface of the steel material 100 will not react, making cutting difficult. Furthermore, if the gas flow rate is reduced in order to achieve thin cutting, the pressure pushing the molten iron SC, primarily composed of FeO in the molten state, forward will weaken, making cutting difficult. In other words, a condition is determined under which cutting to a depth smaller than the predetermined cutting depth (the lower limit of the cutting depth obtained by reducing at least one of the laser beam output and the gas flow rate). Therefore, as will be described in detail later in step S14, by changing the oxygen purity of the gas sprayed by the gas spraying unit 16, cutting to a depth smaller than the predetermined cutting depth will be possible.

[0043] 3, the control unit 20 controls the laser irradiation unit 14 to irradiate the steel material 100 with laser light L. That is, the control unit 20 sets the output of the laser light irradiated from the laser irradiation unit 14 and starts irradiation by the laser irradiation unit 14. The output amount of the laser light may be the predetermined value set in S10.

[0044] In addition, when the laser output is controlled to be small in order to perform welding to a depth smaller than the predetermined welding depth, if the heat supplied from the laser beam is interrupted, the amount of heat required to react with the Fe on the surface of the steel material 100 will be insufficient, making welding impossible. Therefore, in order to perform welding, it is preferable to continue irradiating the laser beam continuously. That is, it is preferable that the control unit 20 controls the laser irradiation unit 14 to start irradiating the laser beam once, and continue irradiating the laser beam without interruption until the welding process is completed.

[0045] 3, the control unit 20 controls the gas spraying unit 16 to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than a predetermined cutting depth onto the area irradiated with the laser light. That is, the oxygen purity is set so that the cutting depth falls within a range in which the cutting depth cannot be further reduced even if at least one of the laser output and the gas flow rate is changed, and the gas spraying unit 16 starts spraying. The gas flow rate may be the predetermined value set in S10.

[0046] The order of S12 and S14 may be reversed.

[0047] As described above, by setting the laser beam output, gas flow rate, and oxygen purity of the gas and performing the laser cutting process, it is possible to perform laser cutting to a predetermined depth by controlling the purity of the oxygen gas, even if the depth is difficult to cut by simply controlling the laser beam output and gas flow rate. The timing to start laser cutting may be determined by the control unit 20, for example, before the front end of the steel material 100 being transported by the transport unit 12 reaches the range of the laser beam L emitted from the laser irradiation unit 14a. The control unit 20 may start the irradiation of the laser beam L from the laser irradiation unit 14a and the spraying of the gas G from the gas spray unit 16a, for example, in response to information regarding the position of the steel material 100 being transported by the transport unit 12 or a user operation. Information regarding the position of the steel material 100 may be determined, for example, using an optical sensor that detects the arrival of light from a light source and the blocking of light from the light source by an object. Information regarding the position of the steel material 100 may also be determined, for example, by calculating the travel distance of the steel material 100 based on the travel speed of the steel material 100 and the travel time from a predetermined position. Furthermore, the control unit 20 may start the irradiation of the laser light L from the laser irradiation unit 14a and the spraying of the gas G from the gas spraying unit 16a at the same time, or may start them at different times.

[0048] Furthermore, for example, in the preparation process, the control unit 20 may start the irradiation of laser light L from the second laser irradiation unit 14b and the spraying of gas G from the second gas spraying unit 16b before the front end of the steel material 100 being transported by the transporting unit 12 reaches the range of the laser light L irradiated from the second laser irradiation unit 14b.

[0049] As mentioned above, it is preferable to remove the Cu-enriched layer and the Cu-infiltration-induced microcrack layer that form in the heating furnace before rolling the steel slab. It is known that the Cu-enriched layer and the Cu-infiltration-induced microcrack layer form in a shallow region in the thickness direction of the steel material 100. Specifically, depending on the composition of the steel material 100, the Cu-enriched layer and the Cu-infiltration-induced microcrack layer form at a depth of approximately 0.2 mm to 2 mm. To improve yield, it is preferable to perform laser cutting only to the thickness where the Cu-enriched layer and the Cu-infiltration-induced microcrack layer form. However, as mentioned above, it is difficult to perform laser cutting only to the depth where the Cu-enriched layer and the Cu-infiltration-induced microcrack layer form simply by reducing the laser output or gas flow rate. In other words, the depth where the Cu-enriched layer and the Cu-infiltration-induced microcrack layer form corresponds to a case where the laser cutting depth is smaller than the lower limit of the laser cutting depth that can be achieved by reducing at least one of the laser output and the gas flow rate. Simply reducing the laser output or gas flow rate to remove the Cu-enriched layer or the microcracked layer due to Cu infiltration results in a large amount of non-Cu base steel being removed, resulting in poor yield. Therefore, the removal depth of the steel material 100 is preferably 0.2 mm or more and 2 mm or less. In other words, the removal depth smaller than the predetermined removal depth is preferably 0.2 mm or more and 2 mm or less. To remove the Cu-enriched layer or the microcracked layer due to Cu infiltration, the oxygen purity of the gas G is preferably in the range of 70% or more and 98% or less, as shown in FIG. 5.

[0050] (Surface-cutting treatment on the front and back surfaces of the steel material 100) 4 is a diagram showing an example of the operation of the surface laser-cutting device 10 for the laser-cutting process on both the front surface and the back surface of the steel material 100. In FIG. 4, gas G is sprayed from the gas spraying port 162a of the gas spraying unit 16a and the second gas spraying port 162b of the second gas spraying unit 16b. In FIG. 4, laser-cutting of the front surface and the back surface of the steel material 100 starts from the front end. Also in FIG. 4, laser-cutting of the steel material 100 has been completed up to the laser-cutting-completed portion 102.

[0051] The control unit 20 may, for example, perform a laser cutting process to cut the surface on the back side of the steel material 100 by irradiating the steel material 100 with laser light L using the second laser irradiation unit 14b and spraying gas G using the second gas spraying unit 16b. Furthermore, for example, the control unit 20 may continue irradiating the steel material 100 with laser light L using the second laser irradiation unit 14b during the laser cutting process.

[0052] Here, for example, when the steel material 100 includes a Cu-enriched layer on the surface side, which has a higher concentration of Cu components than the base material, it is preferable that the Cu-enriched layer be removed in the thermal cutting process performed by the control unit 20. The thickness of the steel material 100 that has been thermally cut may be, for example, the minimum thickness necessary to remove the Cu-enriched layer included in the surface of the steel material 100.

[0053] (Stop processing) In step S16 of FIG. 3 , the control unit 20 stops the irradiation of the laser light L from the laser irradiation unit 14a and the spraying of the gas G from the gas spraying unit 16a after the rear end of the steel material 100 being transported by the transport unit 12 passes through the range reached by the laser light L from the laser irradiation unit 14a. The control unit 20 may stop the irradiation of the laser light L from the laser irradiation unit 14a and the spraying of the gas G from the gas spraying unit 16a, for example, in response to information regarding the position of the steel material 100 being transported by the transport unit 12 or a user operation. The information regarding the position of the steel material 100 may be determined, for example, using an optical sensor that detects the arrival of light from a light source and the blocking of light from the light source by an object. Furthermore, the information regarding the position of the steel material 100 may be determined, for example, by calculating the travel distance of the steel material 100 with reference to the travel speed of the steel material 100 and the travel time from a predetermined position.

[0054] In addition, the control unit 20 may stop the irradiation of laser light L from the second laser irradiation unit 14b and the spraying of gas G from the second gas spraying unit 16b, for example, after the rear end of the steel material 100 being transported by the transporting unit 12 has passed through the range of the laser light L from the second laser irradiation unit 14b.

[0055] (Effects of the surface scraping device 10) As described above, the surface scalding device 10 is a surface scalding device that scalds the surface of steel material, and the surface scalding device 10 includes a laser irradiation unit that irradiates the steel material with laser light, a gas spraying unit that sprays a gas containing oxygen as a main component onto the area on the steel material that is irradiated with laser light by the laser irradiation unit, and a control unit that controls the laser irradiation unit and the gas spraying unit, and sets the output of the laser irradiated by the laser irradiation unit, the flow rate of the gas sprayed by the gas spraying unit, and the oxygen purity of the gas sprayed by the gas spraying unit to predetermined values. When the surface of the steel material can be laser-cut to a predetermined cutting depth by changing at least one of the laser output of the laser irradiation unit and the flow rate of the gas, if the surface of the steel material cannot be laser-cut to a depth smaller than the predetermined cutting depth by simply changing the laser output of the laser irradiation unit and / or the flow rate of the gas, the control unit controls the laser irradiation unit to irradiate the steel material with laser light, and controls the gas spraying unit to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than the predetermined cutting depth onto the area, thereby laser-cutting the surface of the steel material to the predetermined cutting depth. This makes it possible to adjust the thickness of the laser cutting to be thinner in the laser-cutting process of the steel material.

[0056] 〔summary〕 The surface scalding apparatus according to a first aspect of the present invention is a surface scalding apparatus for scalding the surface of a steel material, and the surface scalding apparatus 10 comprises a laser irradiation unit that irradiates the steel material with laser light, a gas blowing unit that blows a gas containing oxygen as a main component onto an area on the steel material that is irradiated with laser light by the laser irradiation unit, and a control unit that controls the laser irradiation unit and the gas blowing unit, and sets the output of the laser irradiated by the laser irradiation unit, the flow rate of the gas blown by the gas blowing unit, and the oxygen purity of the gas blown by the gas blowing unit to predetermined values. When the surface of the steel material can be laser-cut to a predetermined cutting depth by changing at least one of the laser output of the laser irradiation unit and the flow rate of the gas, if the surface of the steel material cannot be laser-cut to a depth smaller than the predetermined cutting depth by simply changing the laser output of the laser irradiation unit and / or the flow rate of the gas, the control unit controls the laser irradiation unit to irradiate the steel material with laser light, and controls the gas spraying unit to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than the predetermined cutting depth onto the area, thereby laser-cutting the surface of the steel material to the predetermined cutting depth. This makes it possible to adjust the thickness of the laser cutting to be thinner in the laser-cutting process of the steel material.

[0057] In the surface cutting device according to aspect 2 of the present invention, in aspect 1, the cutting depth smaller than the predetermined cutting depth is 0.2 mm or more and 2 mm or less. This allows the steel surface to be cut to an appropriate thickness.

[0058] A surface laser-cutting apparatus according to a third aspect of the present invention is the same as that of the first or second aspect, wherein the oxygen purity of the gas is in the range of 70% or more and 98% or less. This allows the steel surface to be laser-cut to an appropriate thickness.

[0059] A fourth aspect of the present invention relates to a surface laser-cutting apparatus according to any one of the first to third aspects, wherein the control unit controls the laser irradiation unit to continuously irradiate the steel material with laser light while performing the laser-cutting, thereby enabling the steel material surface to be continuously laser-cut.

[0060] A surface rake-cutting method according to a fifth aspect of the present invention is a surface rake-cutting method for rake-cutting the surface of a steel material by a surface rake-cutting device, the surface rake-cutting device using a surface grinding device comprising: a laser irradiation unit that irradiates the steel material with laser light; a gas blowing unit that blows a gas containing oxygen as a main component onto an area irradiated with laser light by the laser irradiation unit; and a control unit that controls the laser irradiation unit and the gas blowing unit, and When the surface of the steel material can be laser-cut to a predetermined cutting depth by setting the value of the laser output of the laser irradiation unit and the flow rate of the gas to a value other than the predetermined value, and when the surface of the steel material cannot be laser-cut to a cutting depth smaller than the predetermined cutting depth by simply changing at least one of the laser output of the laser irradiation unit and the flow rate of the gas, the method includes a laser irradiation step of controlling the laser irradiation unit using the control unit to irradiate the steel material with laser light, and a gas spraying step of controlling the gas spraying unit to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than the predetermined cutting depth onto the area. This makes it possible to adjust the thickness of the laser cutting to be thinner in the laser cutting process of the steel material.

[0061] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0062] An embodiment of the present invention will now be described.

[0063] Figure 5 shows the results of laser cutting a sample heated to 1000°C, which simulates a steel billet extracted from a heating furnace. That is, it shows the results of laser cutting a sample heated to 1000°C. Figure 5 is a graph showing the relationship between oxygen purity and laser output and laser cutting depth (thickness of the laser cut) when the sample is heated to 1000°C.

[0064] As shown in Figure 5, when the oxygen purity was 100%, the cutting depth was about 3 mm, similar to conventional gas cutting. In other words, when the oxygen purity was 100%, the cutting depth was thicker than the Cu-enriched layer, which is thought to be about 0.2 to 2 mm thick, and as a result, excess steel was cut away.

[0065] As is clear from Figure 5, regardless of the laser output, the cutting depth becomes linearly shallower as the oxygen purity decreases. However, when the oxygen purity is controlled to 98% or less, the cutting depth levels off at a cutting depth of less than 2.0 mm, which includes the Cu-enriched layer. It is also thought that this leveling off continues up to about 70%. Below 70%, combustion does not occur and cutting becomes impossible.

[0066] That is, by changing the oxygen purity in the range of 70% to 98%, it was possible to perform laser cutting to a shallow depth that could not be achieved by simply changing the laser beam output. Furthermore, because laser cutting became unstable at less than 80%, it is more preferable to change the oxygen purity in the range of 80% to 98% to perform laser cutting to a shallow depth.

[0067] 6 and 7 are top views of the steel material 100 that has been subjected to thermal cutting.

[0068] Figure 6 shows the results of slicing a sample at room temperature with an oxygen purity of 94% and a laser output of 5 kW. The slicing depth was 0.5 mm.

[0069] Figure 7 shows the results of experimentally cutting a test material using a narrow laser and a cylindrical oxygen gas spray nozzle on a sample at room temperature.

[0070] In Figure 7 (A), the laser output was set to 6 kW and 100% oxygen gas was sprayed at a flow rate of 150 L / min, resulting in a 1.9 mm lamination depth. In (B), the laser output was set to 6 kW and 94% oxygen gas was sprayed at a flow rate of 350 L / min, resulting in a 0.7 mm lamination depth. In (C), the laser output was set to 7 kW and 100% oxygen gas was sprayed at a flow rate of 100 L / min, resulting in a 0.7 mm lamination depth. Comparing (A) and (B), it can be seen that (B), which has a lower oxygen purity, has a smaller lamination depth. In other words, even with the same laser output, the lamination depth can be adjusted to a thinner depth by changing the oxygen purity. On the other hand, (C), which has the same lamination depth as (B), has a lower gas flow rate compared to (B). The lamination bottom surfaces of (A) and (B) are relatively flat, but (C) is somewhat uneven and less flat. When the gas flow rate is reduced, the pressure with which the gas pushes the molten iron SC, primarily composed of molten FeO, forward decreases, resulting in insufficient discharge of the slag-cut iron SC, which remains in place. This results in a rough bottom surface, as shown in (C). If rolling is performed with the rough surface, it will result in a quality defect on the steel plate surface. In other words, when adjusting the gas flow rate to perform slag-cutting and adjust the slag-cutting depth under conditions of laser power and oxygen purity that allow sufficient slag-cutting, poor surface flatness becomes a problem. Therefore, it is preferable to measure the gas flow rate in advance to determine the conditions that allow slag-cutting with excellent flatness.

[0071] From the viewpoint of removing the Cu-enriched layer, it is preferable to make the cutting depth relatively shallow, for example, between 0.2 mm and 2 mm. From this viewpoint, (a) it is considered to set the oxygen purity in the range of 70% to 98%. For example, even if the oxygen purity is set to 100% and the gas flow rate is reduced, the cutting depth can be made 1 mm or less. However, as shown in Figure 7(C), the flatness of the cut bottom surface cannot be said to be good.

[0072] Furthermore, within this range of oxygen purity, it is preferable to carry out the process under the following conditions: (b) the gas flow rate is made small to a certain extent, and (c) the laser output is such that cutting stops when laser irradiation is stopped.

[0073] If the gas flow rate is above a certain level, the cutting process continues due to the gas blowing even after the laser irradiation is stopped. In this case, the process is essentially the same as gas cutting, making it difficult to reduce the cutting depth. Furthermore, in this case, even if the laser irradiation is continued, favorable results cannot be obtained.

[0074] As described above, it is preferable to perform the thermal cutting under conditions (a), (b), and (c). Condition (b) may be determined based on whether the thermal cutting continues when the laser irradiation is stopped under condition (a) by spraying gas. In other words, if the thermal cutting does not continue when the laser irradiation is stopped under condition (a), it may be determined that condition (b) is met. The thermal cutting conditions in Figure 7(B) are an example that satisfy these conditions (a), (b), and (c).

[0075] The laser power can be used to adjust the cutting depth under conditions (a), (b), and (c).

[0076] In the above, an example has been described in which the depth of the thermal cutting is made shallower by changing the oxygen purity, but the depth of the thermal cutting may also be made thicker by changing the oxygen purity under certain conditions. [Explanation of symbols]

[0077] 10 Surface cutting equipment 12 Conveyor 14a Laser irradiation part 14b Second laser irradiation unit 16a Gas spraying section 16b Second gas spraying section 18a First shielding part 18b Second shielding part 20 Control Unit 142 Laser Oscillator 162a Gas nozzle 162b Second gas nozzle

Claims

1. A surface scraping device for scraping the surface of a steel material, a laser irradiation unit that irradiates the steel material with laser light; a gas blowing unit that blows a gas containing oxygen as a main component onto an area on the steel material that is irradiated with laser light by the laser irradiation unit; a control unit that controls the laser irradiation unit and the gas spraying unit; Equipped with When the surface of the steel material can be cut to a predetermined cutting depth by setting the output of the laser irradiated by the laser irradiation unit, the flow rate of the gas blown by the gas blowing unit, and the oxygen purity of the gas blown by the gas blowing unit to predetermined values, and when the surface of the steel material cannot be cut to a cutting depth smaller than the predetermined cutting depth by simply changing at least one of the output of the laser of the laser irradiation unit and the flow rate of the gas, The control unit Controlling the laser irradiation unit to irradiate the steel material with laser light; A surface cutting device that controls the gas spraying unit to spray gas having an oxygen purity specified corresponding to a cutting depth smaller than the predetermined cutting depth onto the area, thereby cutting the surface of the steel material to the predetermined cutting depth.

2. The surface cutting device according to claim 1 , wherein the cutting depth smaller than the predetermined cutting depth is 0.2 mm or more and 2 mm or less.

3. The surface scraping apparatus according to claim 2 , wherein the oxygen purity of the gas is in the range of 70% to 98%.

4. The surface rake device according to claim 1 , wherein the control unit controls the laser irradiation unit to continuously irradiate the steel material with laser light while the rake is being performed.

5. A surface cutting method for cutting the surface of a steel material by a surface cutting device, a laser irradiation unit that irradiates the steel material with laser light; a gas blowing unit that blows a gas containing oxygen as a main component onto an area irradiated with laser light by the laser irradiation unit; a control unit that controls the laser irradiation unit and the gas spraying unit; A surface grinding device including: When the surface of the steel material can be cut to a predetermined cutting depth by setting the output of the laser irradiated by the laser irradiation unit, the flow rate of the gas blown by the gas blowing unit, and the oxygen purity of the gas blown by the gas blowing unit to predetermined values, and when the surface of the steel material cannot be cut to a cutting depth smaller than the predetermined cutting depth by simply changing at least one of the output of the laser of the laser irradiation unit and the flow rate of the gas, Using the control unit, a laser irradiation step of controlling the laser irradiation unit and irradiating the steel material with laser light; A surface machining method comprising: a gas spraying step of controlling the gas spraying unit to spray gas having an oxygen purity defined corresponding to a machining depth smaller than the predetermined machining depth onto the region.

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