Hot Rolling Equipment and Hot Rolling Method

Description

/ 37 Hot Rolling Equipment and Hot Rolling Method - Technical Field

[001] The present description refers to a hot rolling machine and a hot rolling method. FUNDAMENTALS OF THE TECHNIQUE

[002] International Publication No. 2008 / 146891 describes a method for trimming the surface layer portion of a hot plate, in which part or all of the surface layer portion of a steel material (e.g., a plate), after being continuously melted, is cut to a depth of 1 mm or more from the surface of the steel material using a milling-type surface layer cutting apparatus configured by an electric rotary cutting tool with numerous cutting blades.

[003] In addition, JP-A document no. H6-198304 describes a hot rolling method in which the surface layer of a steel material (e.g., a plate) after being continuously melted is removed by a scarifying apparatus or a grinding apparatus and then the steel material is hot rolled. SUMMARY Technical Problem

[004] In recent years, sources of iron other than iron ores have been used to reduce carbon dioxide emissions in the steelmaking process. For example, increasing the rate of use of scrap iron as a source of iron is being considered.

[005] However, when scrap iron is used as a source of iron, surface defects caused by the copper (Cu) included in the scrap iron can occur during the steelmaking process. For example, in the hot rolling process, hot brittleness cracks can occur due to the concentration of Cu in the surface layer of the steel material. Petition 870250092353, dated 09 / 10 / 2025, page 6 / 79 / 37 reducing the surface quality of the steel material. For this reason, it is difficult to increase the utilization rate of scrap iron, including Cu as a source of iron, hindering the achievement of an environmentally friendly steel manufacturing process.

[006] In the technique described in International Publication No. 2008 / 146891, the surface layer of the steel material after its continuous casting is removed by a surface layer cutting device of the milling type, therefore, there is room for improvement in order to inhibit cracking due to lack of heat.

[007] On the other hand, in the technique described in JP-A No. H6-198304, the continuously melted steel material is heated by a heating furnace and subsequently the surface layer of the steel material is removed by a scarifying apparatus or a grinding apparatus. Therefore, a Cu-rich layer that formed on the surface layer of the steel when the steel was heated in the heating furnace is removed by the scarifying apparatus or similar. Consequently, hot brittle cracking on the surface of the steel material is inhibited.

[008] However, the technique described in JP-A No. H6-198304 does not consider the effect that the removal of the surface layer of the steel material by the scarifying apparatus or similar has on the subsequent rolling of the steel material, and there is room for improvement in terms of the rolling quality of the steel material.

[009] Thus, an objective of the present description is to provide a hot rolling method and hot rolling equipment that can inhibit hot brittleness cracking in a steel material and inhibit a reduction in the rolling quality of a steel material. Solution to the Problem

[0010] The hot rolling equipment pertaining to a first aspect is hot rolling equipment for rolling the Petition 870250092353, dated 09 / 10 / 2025, p. 7 / 79 / 37 hot a steel material containing Cu, the hot rolling equipment including: a heating furnace that heats the steel material to a predetermined temperature after melting; a rolling apparatus that rolls the steel material that has been heated in the heating furnace; a removal apparatus that is provided downstream of the heating furnace and upstream of the rolling apparatus in a direction of conveying the steel material and that removes, from the steel material that has been heated in the heating furnace, a target region including a Cu-rich layer that is present on one side of the surface of the steel material and in which a concentration of Cu components is greater than a concentration of Cu components in a base material of the steel material;and a post-removal descaling apparatus that is provided downstream of the removal apparatus and upstream of the rolling apparatus in the direction of transport of the steel material and that descales the steel material using cooling water.

[0011] Hot rolling equipment pertaining to a second aspect is hot rolling equipment pertaining to the first aspect, in which the post-removal descaling apparatus cools the steel material so that the temperature on a surface of the steel material becomes less than 1100°C.

[0012] Hot rolling equipment pertaining to a third aspect is hot rolling equipment pertaining to the first or second aspect, wherein the hot rolling equipment includes a width reduction apparatus which is provided downstream of the heating furnace and upstream of the stripping apparatus in the direction of conveying the steel material and which reduces the steel material in a direction of width of the steel material.

[0013] Hot rolling equipment belonging to a fourth aspect is hot rolling equipment belonging to any one Petition 870250092353, dated 09 / 10 / 2025, p. 8 / 79 / 37 from the first aspect to the third aspect, in which the hot rolling equipment includes a pre-removal descaling apparatus that is provided downstream of the heating furnace and upstream of the removal apparatus in the direction of transport of the steel material and that descales the steel material using cooling water.

[0014] Hot rolling equipment belonging to a fifth aspect is hot rolling equipment belonging to any of the first to fourth aspects, wherein the rolling apparatus is a rough rolling apparatus that rolls rough steel material or a finishing rolling apparatus that rolls finished steel material.

[0015] Hot rolling equipment belonging to a sixth aspect is hot rolling equipment belonging to any of the first to fifth aspects, wherein the target region is a region of 2 mm or less of a steel material surface in a steel material thickness direction.

[0016] Hot rolling equipment belonging to a seventh aspect is hot rolling equipment belonging to any of the second to sixth aspects, wherein the stripping apparatus removes the target region of the steel material by means of scarification or removes the target region of the steel material by means of mechanical stripping.

[0017] Hot rolling equipment belonging to an eighth aspect is hot rolling equipment belonging to any of the first to seventh aspects, in which the heating furnace is supplied separately with a production line of a casting machine that melts the steel material.

[0018] Hot rolling equipment belonging to a ninth aspect is hot rolling equipment belonging to any of the first to seventh aspects, in which the heating furnace is provided. Petition 870250092353, dated 09 / 10 / 2025, page 9 / 79 / 37 in a production line of a casting machine that melts steel material.

[0019] A hot rolling method pertaining to a tenth aspect is a hot rolling method for hot rolling a Cu-containing steel material, the hot rolling method including: a heating process that heats the steel material to a predetermined temperature after casting; a stripping process that performs a treatment on the steel material that was heated in the heating process, the treatment removing a target region including a Cu-rich layer that is present on one side of the surface of the steel material and in which a concentration of Cu components is greater than a concentration of Cu components in a base material of the steel material; a post-scaling process that descales the steel material using cooling water after the stripping process; and a rolling process that rolls the steel material after the post-scaling process.

[0020] A hot rolling method belonging to an eleventh aspect is the hot rolling method belonging to the tenth aspect, in which, in the post-removal descaling process, the steel material is cooled so that a temperature on a surface of the steel material becomes less than 1100°C.

[0021] A hot rolling method belonging to a twelfth aspect is a hot rolling method belonging to the tenth or eleventh aspect, further including a width reduction process that reduces the steel material in a width direction of the steel material after the heating process and before the stripping process.

[0022] A hot rolling method belonging to a thirteenth aspect is a hot rolling method belonging to any of the tenth to twelfth aspects, including a process Petition 870250092353, dated 09 / 10 / 2025, p. 10 / 79 / 37, concerning pre-removal descaling that descales steel material using cooling water after the heating process and before the removal process.

[0023] A hot rolling method belonging to a fourteenth aspect is a hot rolling method belonging to any of the tenth to thirteenth aspects, in which, in the rolling process, rough rolling or finishing rolling is carried out on the steel material.

[0024] A hot rolling method belonging to a fifteenth aspect is a hot rolling method belonging to any of the tenth to fourteenth aspects, wherein the target region is a region of 2 mm or less of a steel material surface in a steel material thickness direction.

[0025] A hot rolling method belonging to a sixteenth aspect is a hot rolling method belonging to any of the tenth to fifteenth aspects, in which, in the stripping process, the target region is removed from the steel material by scarifying or the target region is removed from the steel material by mechanical stripping.

[0026] A hot rolling method belonging to a seventeenth aspect is a hot rolling method belonging to any of the tenth to sixteenth aspects, in which the steel material contains Cu at 0.15% by mass or more. Advantageous Effects of the Invention

[0027] As described above, according to the present description, a hot rolling method and a hot rolling equipment are provided that can inhibit hot brittleness cracking in a steel material and inhibit a reduction in the rolling quality of a steel material. BRIEF DESCRIPTION OF THE DRAWINGS Petition 870250092353, dated 09 / 10 / 2025, p. 11 / 79 / 37

[0028] Figure 1 is a schematic diagram showing an example of the schematic configuration of hot rolling equipment belonging to a first embodiment of the description.

[0029] Figure 2 is a schematic diagram showing an example of the thermal history of a steel material in hot rolling equipment belonging to the first embodiment of the description.

[0030] Figure 3 is a cross-sectional diagram showing a steel material being scarified by a scarifying device belonging to the first embodiment of the description.

[0031] Figure 4 is a schematic diagram showing an example of the schematic configuration of the scarifying device belonging to the first embodiment of the description.

[0032] Figure 5 is a schematic diagram showing an example of the schematic configuration of a target region belonging to the first modality of the description.

[0033] Figure 6 is a flowchart showing an example of a hot rolling process belonging to the first embodiment of the description.

[0034] Figure 7 is a schematic diagram showing an example of the schematic configuration of a hot rolling mill belonging to a first example modification.

[0035] Figure 8 is a schematic diagram showing an example of the thermal history of a steel material in hot rolling equipment belonging to the first example modification.

[0036] Figure 9 is a schematic diagram showing an example of the schematic configuration of the hot rolling equipment belonging to the second example modification.

[0037] Figure 10 is a schematic diagram showing an example of the schematic configuration of hot rolling equipment. Petition 870250092353, dated 09 / 10 / 2025, page 12 / 79 / 37 belonging to a second type of description.

[0038] Figure 11 is a schematic diagram showing an example of the schematic configuration of a cutting apparatus belonging to the second embodiment of the description.

[0039] Figure 12 is a schematic diagram showing an example of the schematic configuration of hot rolling equipment belonging to a third embodiment of the description.

[0040] Figure 13 is a schematic diagram showing an example of the thermal history of a steel material in hot rolling equipment belonging to the third embodiment of the description.

[0041] Figure 14 is a schematic diagram showing an example of the schematic configuration of a hot rolling mill belonging to a third example modification.

[0042] Figure 15 is a schematic diagram showing an example of the thermal history of a steel material in hot rolling equipment belonging to the third example modification.

[0043] Figure 16 is a graph showing the relationship between the percentage of the number of Cu-rich areas and the depth of the scarfing belonging to the Examples in the description. DETAILED DESCRIPTION

[0044] The preferred embodiments of the description will be described in detail below with reference to the attached drawings. It should be noted that redundant description will be omitted when assigning identical reference signs to constituent elements that have substantially identical functional configurations in the specification and drawings. Furthermore, unless otherwise specified, each constituent element is not limited to one and may be plural. <Primeira Modalidade>

[0045] First, the schematic configuration of the equipment Petition 870250092353, dated 09 / 10 / 2025, p. 13 / 79 / 37 hot rolling mill 10 belonging to a first embodiment of the description will be described with reference to figure 1. Figure 1 is a diagram showing the schematic configuration of the hot rolling mill 10 equipment.

[0046] As shown in Figure 1 as an example, the hot rolling equipment 10 is equipment for hot rolling a steel material 1. The hot rolling equipment 10 is, for example, provided separately from a production line of a continuous casting machine 11 that continuously melts the steel material 1. The hot rolling equipment 10 includes a heating furnace 20, a scarifying apparatus 30, a width reduction apparatus 23, a descaling apparatus 40, a rough rolling apparatus 50 and a finishing rolling apparatus 60. It should be noted that the steel material 1 is not limited to being melted continuously and can also be melted individually.

[0047] Heating furnace 20 heats steel material 1 (e.g., a plate 1A) to a predetermined temperature. This material is obtained by cutting steel material 1 discharged from the continuous casting machine 11 to a predetermined length. The “predetermined temperature” here is, for example, 1100°C or higher. Plate 1A is heated by heating furnace 20 while being conveyed by conveyor rollers 22. Although plate 1A is mentioned as an example of steel material 1 here, it is only an example, and steel material 1 could also be a billet.

[0048] Steel material 1 is a steel material containing Cu and is, for example, a steel material containing Cu at 0.15% by weight (% by mass) or more and particularly containing Cu at 0.25% by weight or more. It should be noted that the Cu content here means the average Cu content in the base material of steel material 1 described below or the average Cu content in the molten steel that becomes steel material 1. Furthermore, the Cu content in Petition 870250092353, dated 09 / 10 / 2025, page 14 / 79 / 37 steel material 1 is, for example, 5.6% by weight or less.

[0049] The scarifying apparatus 30 removes the surface layer of plate 1A by scarifying plate 1A discharged from the heating furnace 20. Details about the scarifying apparatus 30 will be described later. The scarifying apparatus 30 is located downstream of the heating furnace 20 in the direction of transport of plate 1A. Furthermore, the scarifying apparatus 30 is located upstream of the width reduction apparatus 23 and the descaling apparatus 40 in the direction of transport of plate 1A. More specifically, the scarifying apparatus 30 is located downstream of the heating furnace 20 and upstream of the width reduction apparatus 23 in the direction of transport of plate 1A. The width reduction device 23 is a device that adjusts the width of plate 1A by reducing (pressing), in the direction of the width of plate 1A, the plate 1A that has been heated in the heating oven 20.The width reduction device 23 has a pair of vertical rollers 24 arranged on both sides of the width direction of plate 1A. The pair of vertical rollers 24 is arranged along the thickness direction of plate 1A. The pair of vertical rollers 24 reduces (presses) the surfaces (side edge faces) of plate 1A on both sides in the width direction towards the center of the width direction of plate 1A, thus adjusting the width of plate 1A. It should be noted that in this descriptive report, “removal” is a concept that is not limited to complete removal and also includes cases where there is insufficient removal within a generally acceptable range in the technical field to which the description pertains and to an extent that does not contradict the spirit of the description. It should be noted that the scarifying device 30 is an example of a removal device.

[0050] The descaling device 40 removes the scale (i.e., an oxide film) formed on the surfaces of plate 1A on both sides in the thickness direction and on the surfaces (end faces) Petition 870250092353, dated 09 / 10 / 2025, page 15 / 79 / 37 lateral) of plate 1A on both sides in the width direction before rough rolling by the rough rolling apparatus 50. The descaling apparatus 40 removes the scale from the surfaces of plate 1A by spraying a fluid (e.g., cooling water) from a nozzle 42 onto the surfaces of plate 1A. In addition, the descaling apparatus 40 cools plate 1A by spraying the fluid from the nozzle 42 onto plate 1A. Because of this, scale formation is inhibited. The descaling apparatus 40 sprays cooling water W, which is supplied, for example, from a cooling water tank (not shown in the drawings) and pressurized to a predetermined hydraulic pressure using a pump (not shown in the drawings), from the nozzle 42 on the plate 1A.The scale on plate 1A is removed by descaling apparatus 40, and the temperature on the surfaces of plate 1A is cooled to less than 1100°C by heat removal using cooling water W. Here, the temperature on the surfaces of plate 1A (e.g., the surfaces in the width direction of plate 1A) after scale removal by descaling apparatus 40 is measured by an infrared thermometer. It should be noted that descaling apparatus 40 is an example of a post-removal descaling apparatus.

[0051] The rough rolling mill 50 rolls (hot rolls) plate 1A to thin plate 1A to a predetermined thickness. Specifically, the rough rolling mill 50 reduces plate 1A, which has been reduced in the width direction by the width reduction machine 23 (the vertical rolls 24), from the top and bottom directions to form a rough bar 1B. In the example shown in Figure 1, the rough rolling mill 50 includes four rolling mills 51, 52, 53, 54. Each of the rolling mills 51 to 54 has a plurality of rolls that interleave plate 1A from both sides in the thickness direction. The rough rolling mill 50 uses the rolling mills 51 to 54 to continuously roll plate 1A. In the rough rolling mill 50, plate 1A is thinned to a thickness Petition 870250092353, dated 09 / 10 / 2025, p. 16 / 79 / 37 of approximately 25 to 50 mm, for example, and formed on the raw bar 1B. It should be noted that, although an example in which the raw rolling mill 50 includes the four rolling mills 51 to 54 is described here, this is only an example, and the raw rolling mill 50 may include two rolling mills, for example. In this case, in the raw rolling mill 50, reciprocating rolling is carried out between the two rolling mills. It should be noted that the raw rolling mill 50 is an example of a rolling mill.

[0052] The finishing rolling mill 60 also hot finish rolls the raw bar 1B to a predetermined thickness. Specifically, the finishing rolling mill 60 hot finish rolls the raw bar 1B, which has been reheated by a raw bar heating apparatus 62, to a thickness of about a few mm (e.g., 1 to 2 mm). The finishing rolling mill 60 has a plurality of finishing roll groups 64 in 6 to 7 rolling stands. Each finishing roll group 64 has a plurality of rolling rolls arranged in a vertically straight line. The finishing rolling mill 60 gradually reduces the raw bar 1B by passing the raw bar 1B through openings in the various finishing roll groups 64.A steel strip 1C, obtained as a result of the finishing rolling of the raw bar 1B to a thickness predetermined by the finishing rolling apparatus 60, is fed to a cooling apparatus 70. It should be noted that, although an example in which the finishing rolling apparatus 60 has 6 to 7 rolling cages of finishing roll groups 64 is described here, this is only an example, and the finishing rolling apparatus 60 may, for example, have five rolling cages of finishing roll groups 64. It should be noted that the finishing rolling apparatus 60 is an example of a rolling apparatus. Petition 870250092353, dated 09 / 10 / 2025, page 17 / 79 / 37

[0053] Cooling apparatus 70 cools finished steel strip 1C with cooling water W. Cooling apparatus 70 is, for example, a tube laminar nozzle type cooling apparatus. 1C cooled by cooling apparatus 70 is wound into a coil by a coiling apparatus 80 and transported as a hot-rolled coil 1D from the hot rolling equipment 10 to the next process.

[0054] Figure 2 shows an example of the thermal history of steel material 1 in a series of continuous casting, hot rolling, and cold rolling processes. As shown in Figure 2, at the beginning of continuous casting, the temperature of steel material 1 is about 1500°C, which is why scale forms on the surface of steel material 1. This occurs because when steel material 1 reaches 1100°C or more, a 2Fe+O2 = 2FeO reaction proceeds mainly on the surface of steel material 1, so that iron oxide (i.e., FeO) is formed on the surface of steel material 1 and becomes scale. In this temperature range, if the base material of steel material 1 includes a relatively large amount of Cu (for example, if the average concentration of Cu components in the base material is 0.15% by weight (% by mass) or more), the iron oxide formed on the surface of steel material 1 also includes Cu.Since the Cu in iron oxide is present in a liquid phase state without being oxidized, it infiltrates the surface layer of the base metal piece of steel material 1 from the iron oxide. The Cu that infiltrated the surface layer of the base metal piece of steel material 1 from the iron oxide deposits and concentrates mainly at the grain boundaries in the surface layer. In this way, a region (hereinafter referred to as the "Cu-rich layer") in which the concentration of Cu components is greater than the average concentration of Cu components in the base material of steel material 1 is formed in the surface layer (surface side) of the base metal piece of steel material 1 (i.e., a phenomenon of... Petition 870250092353, dated 09 / 10 / 2025, page 18 / 79 / 37 (concentration of Cu).

[0055] It should be noted that the “Cu-rich layer” means a region where the concentration of Cu components is greater than the average concentration of Cu components in the base material of the steel material in the base metal part of the steel material that is not oxidized when the fouling associated with oxidation is formed on the surface of the steel material. In other words, “Cu-rich layer” means a region of the boundary between the fouling formed on the surface of the steel material and the base metal part of the steel material, that is, from the surface of the base metal part of the steel material that is not oxidized, towards the center of the thickness direction of the steel material until the Cu components concentrated at the grain boundaries are no longer observed.The “region where Cu components concentrated at grain boundaries are not observed” here means a region where the concentration of Cu components present at the grain boundaries is equal to or less than the average concentration of the steel material + 1%. Furthermore, “base material of the steel material” means the steel material excluding the Cu-rich layer.

[0056] When Cu is present in a liquid phase state (e.g., at 1100°C or more) at the grain boundaries, the ductility of the grain boundaries decreases. For this reason, when a Cu-rich layer is formed on steel material 1, steel material 1 exhibits hot brittleness, and hot brittle cracks occur on the surface of steel material 1. Cracks that occur on the surface of steel material 1 need to be removed because they become a quality defect. Particularly in high-quality steel materials and automotive steel sheets, where importance is given to surface quality, surface cracks in steel material 1 need to be removed.

[0057] In conventionally known surface cutting methods, surface layer defects, such as iron oxide that Petition 870250092353, dated 09 / 10 / 2025, page 19 / 79 / 37, states that inclusions and casting dust that became incorporated into the surface layer of plate 1A during casting, or air bubble marks in the surface layer of plate 1A, are removed by a grinder or similar. This removal of surface layer defects is carried out before the heating process (i.e., heating by heating furnace 20) in the hot rolling process. That is, the surface layer defects are removed from plate 1A before the hot rolling process. However, in the heating process in the hot rolling process, plate 1A is reheated to 1100°C or more (e.g., about 1400°C), so that the fouling forms again on the surface of plate 1A. As a result, the phenomenon of Cu concentration occurs again on plate 1A, and hot brittleness cracks also occur again.

[0058] Thus, as a result of extensive research, the present inventors arrived at the idea of ​​removing the Cu-rich layer on the surface of plate 1A after plate 1A has been heated by heating furnace 20 in the hot rolling process. That is, in the thermal history of steel material 1 shown in Figure 2, once steel material 1 cools to 1000°C or lower in the rough rolling process after exiting heating furnace 20, its temperature does not rise again to 1100°C or higher. That is, no fouling forms on steel material 1 in processes after the heating process in which steel material 1 is heated by heating furnace 20. Consequently, in processes subsequent to the heating process in which steel material 1 is heated by heating furnace 20, the phenomenon of Cu concentration does not occur and neither do hot brittle cracks occur in steel material 1.

[0059] Thus, in the hot rolling equipment 10 belonging to this embodiment, the surface layer of the plate 1A is removed by the scarifying apparatus 30 located downstream of the heating furnace 20 in the direction Petition 870250092353, dated 09 / 10 / 2025, p. 20 / 79 / 37, regarding the transport of plate 1A. As shown in Figure 3 as an example, the scarifying apparatus 30 has two scarifying units 31 that oppose the surfaces of the steel material 1 on both sides (upper and lower sides) in the thickness direction and two scarifying units 31 that oppose the surfaces (lateral end faces) of the steel material 1 on both sides (left and right sides) in the width direction. It should be noted that the four scarifying units 31 have the same configuration. For this reason, the scarifying unit 31 that opposes the surface of the steel material 1 on one side (the upper side) in the thickness direction will be described below.

[0060] As shown in Figure 4, the scarifying apparatus 30 has a scarifying unit 31 arranged so as to oppose the surface of the steel material 1. The scarifying unit 31 includes a preheating gas blasting unit 34 and a scarifying oxygen blasting unit 36. The preheating gas blasting unit 34 ejects preheating oxygen 32 and a fuel gas 33. The scarifying oxygen blasting unit 36 ​​ejects scarifying oxygen 37. It should be noted that a shielding gas 38, comprising a fuel gas, is ejected along with the scarifying oxygen 37 from the lower portion of the scarifying oxygen blasting unit 36. The steel material 1 is configured to be conveyed in the direction of arrow Y in Figure 4.

[0061] It should be noted that, as shown in figure 4, the jet stream of scarifying oxygen 37, ejected from the scarifying oxygen blasting unit 36, is ejected further forward in the Y transport direction of the steel material 1 than the jet streams of preheating oxygen 32 and fuel gas 33, ejected from the preheating gas blasting unit 34.

[0062] In the scarifying apparatus 30, first, as shown Petition 870250092353, dated 09 / 10 / 2025, page 21 / 79 / 37 on the left side of figure 4, a preheating process is performed. In the preheating process, preheating oxygen 32 and fuel gas 33 are ejected from the preheating gas blasting unit 34 of the scarifying unit 31 towards the surface of the steel material 1, causing the fuel gas 33 to burn. Then, a piece of the surface of the steel material 1 is melted by the heat of the burning fuel gas 33, forming a reservoir 1E.

[0063] It should be noted that the length, along the transport direction Y, of the reservoir 1E formed on the surface of the steel material 1 is in the range of about 20 mm to 30 mm, for example.

[0064] Next, as shown on the right side of Figure 4, a scarifying process is performed. In the scarifying process, scarifying oxygen 37 is ejected from the scarifying oxygen blasting unit 36 ​​of the scarifying unit 31 towards the surface of the steel material 1, and the steel material 1 in which the reservoir 1E was formed is transported in the transport direction Y. At this time, the shielding gas 38 is ejected along with the scarifying oxygen 37 from the scarifying oxygen blasting unit 36, and the scarifying oxygen 37 is shielded by the shielding gas 38. It should be noted that the scarifying process is an example of a removal process.

[0065] Next, the jet stream of scarifying oxygen 37, expelled from the scarifying oxygen blasting unit 36, passes through reservoir 1E into the transported steel material 1, and an oxidation reaction occurs between the scarifying oxygen 37 and the iron, with reservoir 1E acting as a heat source. The heat from the oxidation reaction melts the surface of the steel material 1 and scarifies the surface of the steel material 1. That is, the surface of the steel material 1 is scarified by the heat of the oxidation reaction at the rear of reservoir 1E in the Y transport direction. In this way, the surface layer of plate 1A, after being heated in Petition 870250092353, dated 09 / 10 / 2025, page 22 / 79 / 37 heating furnace 20, is scarified by scarifying apparatus 30.

[0066] As shown in Figure 5 as an example, the scarifying apparatus 30 removes a target region T, which is a region including a Cu-rich layer R. Here, the target region T is a strip extending a predetermined distance from the surface of plate 1A (i.e., the surface of scale S) in a thickness direction t of plate 1A. The predetermined distance is, for example, greater than 0 mm and equal to or less than 3 mm (0 < distance < 3 mm), preferably greater than 0 mm and equal to or less than 1 mm (0 < distance < 1 mm), more preferably greater than 0 mm and equal to or less than 2 mm (0 < distance < 2 mm), and even more preferably greater than 1 mm and equal to or less than 2 mm (1 < distance < 2 mm).

[0067] The thickness of plate 1A is approximately 250 mm, for example. Thus, by removing a region of 1 mm or less from the surface of plate 1A as the target region T in the direction of plate 1A thickness t, the reduction in plate 1A thickness is attenuated, so that the yield of plate 1A can be improved. Furthermore, by removing a region of 2 mm or less from the surface of plate 1A as the target region T in the direction of plate 1A thickness t, the yield of plate 1A can be improved and the CuR-rich layer can be removed more reliably.

[0068] It should be noted that figure 5 shows an example where the surface of steel material 1 is scarred on one side in the thickness direction.

[0069] Because the target region T, including the Cu-rich R layer, is scarred (removed) from the steel material 1, the Cu-rich R1 areas present at the GB grain boundaries are removed. As a result, hot brittle cracking on the surface of plate 1A is inhibited.

[0070] Next, a hot rolling method belonging to the present embodiment will be described with reference to Figure 6. Figure 6 is a Petition 870250092353, dated 09 / 10 / 2025, p. 23 / 79 / 37 flowchart to describe a part of a manufacturing process for a hot-rolled steel sheet belonging to the present embodiment. As shown in Figure 6, first, in the heating process of step ST10, the plate 1A after being continuously melted is heated to a predetermined temperature (e.g., about 1300 °C) by the heating furnace 20. After the execution of the heating process of step ST10, the manufacturing process proceeds to step ST12.

[0071] In the scarifying (removal) process of step ST12, the surface layer of plate 1A that was heated in step ST10 is scarified by the scarifying apparatus 30, whereby the target region T, including the Cu-rich layer, is removed from plate 1A. After the execution of the scarifying process of step ST12, the manufacturing process moves on to step ST14.

[0072] It should be noted that if the average concentration of Cu components in the base material of steel material 1 is less than 0.15% by weight, a Cu-rich layer is less likely to form on steel material 1 (plate 1A), therefore the surface layer of steel material 1 (plate 1A) does not need to be scarified by scarifying apparatus 30. That is, if the average concentration of Cu components in the base material of steel material 1 is less than 0.15% by weight, the scarifying process (removal process) of step ST12 does not need to be performed.

[0073] In the descaling process of step ST14, descaling using cooling water W is performed by descaling apparatus 40 on plate 1A from which the target region T was removed in step ST12. Due to the descaling performed, the surface temperature of plate 1A drops to less than 1100°C, for example. After the execution of the descaling process of step ST14, the manufacturing process moves on to step ST16.

[0074] It should be noted that in the present modality, a process of Petition 870250092353, dated 09 / 10 / 2025, page 24 / 79 / 37 width reduction is performed after step ST12 (the scarifying process) and before step ST14 (the descaling process). In the width reduction process, plate 1A, which was scarified in step ST12, is reduced in width by the width reduction device 23, through which the width of plate 1A is adjusted.

[0075] In the rough rolling process of step ST16, plate 1A, which was descaled in step ST14, is rough rolled by rough rolling machine 50. Therefore, plate 1A is formed from raw bar 1B having a predetermined thickness. After the execution of the rough rolling process of step ST16, the manufacturing process moves on to step ST18.

[0076] In the finishing rolling process of stage ST18, the raw bar 1B obtained in stage ST16 is finished rolled by the finishing rolling mill 60. Therefore, the raw bar 1B is formed into a steel strip 1C with a predetermined thickness. After the execution of the finishing rolling process of stage ST18, the manufacturing process moves on to stage ST20.

[0077] In the coiling process of step ST20, the steel strip 1C that was finished in step ST18 is coiled by the coiling device 80 and thus formed into the hot-rolled coil 1D. After the execution of the coiling process of step ST20, a part of the manufacturing process of the hot-rolled steel sheet related to this embodiment is completed.

[0078] As described above, in the hot rolling equipment 10 belonging to the first embodiment, the target region T including the Cu-rich layer formed in the steel material 1 is removed after heating by the heating furnace 20. When the steel material 1 is heated to the predetermined temperature (e.g., 1300°C) in the heating furnace 20, the Cu in liquid phase state concentrates at the boundaries Petition 870250092353, dated 09 / 10 / 2025, page 25 / 79 / 37 of the GB grains near the surface (surface layer) of steel material 1. The area (surface layer) of steel material 1 where Cu is concentrated has low ductility compared to the base metal piece of steel material 1. For this reason, the occurrence of a Cu-rich layer becomes one of the causes of hot brittleness cracking. In the present embodiment, in steel material 1, after being heated by heating furnace 20, the target region T, including the Cu-rich layer, is removed from steel material 1. Consequently, according to the present embodiment, the occurrence of hot brittleness cracking in steel material 1 is inhibited.

[0079] It is conceivable, for example, to remove the Cu-rich layer from the steel material 1 beforehand after its continuous casting. However, in this case, a Cu-rich layer reforms in the steel material 1 because the steel material 1 is heated to a predetermined temperature in the heating furnace 20. For this reason, it is difficult to inhibit hot brittleness cracking in the steel material 1. According to the present embodiment, the target region T including the Cu-rich layer is removed from the steel material 1 after heating by the heating furnace 20. Then, in processes that follow heating by the heating furnace 20 after continuous casting in the hot rolling process, the steel material 1 is not heated to a temperature equal to or higher than the temperature at which a Cu-rich layer is formed (e.g., 1100°C), so the reformation of a Cu-rich layer is inhibited. As a result, the occurrence of hot brittleness cracking in the steel material 1 is inhibited.

[0080] It should be noted that even if steel material 1 is heated to 1100°C or more in the rough rolling process or in the finishing rolling process, the fouling that causes a Cu-rich layer will not form on the surface of steel material 1 because the heating of steel material 1 associated with rolling is of short duration.

[0081] In addition, in hot rolling equipment 10 Petition 870250092353, dated 09 / 10 / 2025, page 26 / 79 / 37, pertaining to the first embodiment, after the target region T is removed from the steel material 1 by the scarifying apparatus 30, the descaling of the steel material 1 is carried out by the descaling apparatus 40. During descaling, cooling water W is sprayed onto the surface of the steel material 1, thus removing the scale S formed on the surface. Due to this descaling, the scale S is removed from the surface of the steel material 1 and the temperature on the surface of the steel material 1 is reduced. Due to the reduction in temperature on the surface of the steel material 1, the reformation of a Cu-rich layer is further inhibited. Consequently, according to the present embodiment, the occurrence of hot brittleness cracking in the steel material 1 is inhibited.

[0082] Furthermore, in the hot rolling equipment 10 belonging to the first embodiment, the temperature on the surface of the steel material 1 is cooled to less than 1100°C by the descaling apparatus 40. Due to the reduction in temperature on the surface of the steel material 1, the reformation of a Cu-rich layer is further inhibited. Consequently, according to the present embodiment, the occurrence of hot brittleness cracking in the steel material 1 is inhibited.

[0083] Furthermore, in the hot rolling equipment 10 belonging to the first embodiment, the steel material 1 is roughly rolled by the rough rolling apparatus 50 after descaling of the steel material 1 by the descaling apparatus 40. The temperature on the surface of the steel material 1 is reduced by the rough rolling, which further inhibits the reformation of a Cu-rich layer. Consequently, according to the present embodiment, the occurrence of hot brittleness cracking in the steel material 1 is inhibited.

[0084] Furthermore, in the hot rolling equipment 10 belonging to the first embodiment, a region of 2 mm or less of the surface of the steel material 1 in the direction of the thickness t of the steel material 1 Petition 870250092353, dated 09 / 10 / 2025, page 27 / 79 / 37, is removed by scarifying apparatus 30. The Cu-rich layer is formed mainly in a region of 2 mm or less from the surface of steel material 1 in the direction of thickness t of steel material 1. For this reason, removing a region of 2 mm or less from the surface of steel material 1 in the direction of thickness t of steel material 1 contributes to the removal of the Cu-rich layer. Consequently, according to the present embodiment, the occurrence of hot brittleness cracking in steel material 1 is inhibited.

[0085] Furthermore, in the hot rolling equipment 10 belonging to the first embodiment, the steel material 1 is scarified by the scarifying apparatus 30, whereby the target region T, including the Cu-rich layer, is removed from the steel material 1. Removing the target region T by scarifying results in high productivity compared to removing the target region T by cutting. Consequently, according to the present embodiment, the productivity of the steel material 1 can be improved.

[0086] Furthermore, the hot rolling equipment 10 belonging to the first embodiment is provided separately from the continuous casting machine 11 production line. Therefore, depending on the production capacities of the continuous casting machine 11 and the hot rolling equipment 10, for example, it becomes possible to hot roll steel materials 1 with one hot rolling equipment line 10 that were continuously cast by two continuous casting machines 11. Moreover, for example, even if the hot rolling equipment 10 is stopped, the continuous casting of the steel material 1 can be continued without stopping the continuous casting machine 11. Furthermore, as the thickness (plate thickness) of the steel material 1 becomes thicker, the percentage of removal of the Cu-rich layer relative to the steel material 1 can be relatively reduced. Petition 870250092353, dated 09 / 10 / 2025, page 28 / 79 / 37 (First Example Modification)

[0087] In the first embodiment, an example was described in which a descaling process is not carried out before and after (immediately before and immediately after) the scarfing process (removal process), but the description is not limited to this example. In a first example modification, a pre-removal descaling process is carried out before the scarfing process (removal process) and a post-removal descaling process is carried out after the scarfing process (removal process).

[0088] As shown in Figure 7 as an example, a pre-removal descaling apparatus 40A is provided downstream of the heating furnace 20 and upstream of the scarifying apparatus 30 in the direction of transport of the steel material 1. The basic configuration of the pre-removal descaling apparatus 40A is the same as that of the descaling apparatus 40.

[0089] The pre-removal descaling apparatus 40A removes scale and similar substances adhered to the surface of the steel material 1 before (immediately before) the surface of the steel material 1 is scarified by the scarifying device 30. That is, in the first example modification, the pre-removal descaling process is carried out after the heating process and before the scarifying process.

[0090] Here, if there are incrustations or similar substances adhering to the surface of the steel material 1 when the surface of the steel material 1 is scarified by the scarifying apparatus 30, the combustion reaction between the sprayed scarifying oxygen 37 from the scarifying apparatus 30 (see figure 4) and the steel material 1 can be prevented and the scarifying of the steel material 1 can be interrupted. Particularly by stopping the depth at which the steel material 1 is scarified by the scarifying apparatus 30 by about 1 mm to 2 mm, it is likely that the scarifying of the steel material 1 by the apparatus Petition 870250092353, dated 09 / 10 / 2025, p. 29 / 79 / 37 regarding scarification 30 to be interrupted.

[0091] In contrast, in the first example modification, as described above, the scale adhering to the surface of the steel material 1 is removed by the pre-removal descaling apparatus 40A before the steel material 1 is scarified by the scarifying apparatus 30. Because of this, the combustion reaction between the sprayed scarifying oxygen 37 from the scarifying apparatus 30 (see figure 4) and the steel material 1 tends to become stable. Consequently, an interruption or something similar in the scarifying of the steel material 1 by the scarifying apparatus 30 can be inhibited.

[0092] Furthermore, the pre-removal descaling apparatus 40A removes the scale adhered to the surface of the steel material 1 by spraying cooling water W onto the surface of the steel material 1. At this point, the surface of the steel material 1 is cooled by the cooling water W, so that a Cu-rich layer is further inhibited from reforming on the steel material 1. Moreover, in the first example modification, the surface of the steel material 1 is cooled to less than 1100°C by the pre-removal descaling apparatus 40A. Consequently, a Cu-rich layer is further inhibited from reforming on the steel material 1.

[0093] In addition, the post-removal descaling apparatus 40B is provided downstream of the scarifying apparatus 30 and upstream of the width reduction apparatus 23 in the direction of transport of the steel material 1. The basic configuration of the post-removal descaling apparatus 40B is the same as that of the descaling apparatus 40.

[0094] The post-removal descaling apparatus 40B removes scale and similar substances formed on the surface of the steel material 1 after the steel material 1 has been scarified by the scarifying device 30. That is, in the first example modification, the post-removal descaling process is carried out after the scarifying process and before the process of Petition 870250092353, dated 09 / 10 / 2025, page 30 / 79 / 37 width reduction.

[0095] In this way, as the post-removal descaling apparatus 40B removes scale and similar substances formed on the surface of the steel material 1, the quality of the width adjustment of the steel material 1 by the width reduction apparatus 23 can be improved.

[0096] Furthermore, when the scarifying apparatus 30 scarifies the steel material 1, the temperature on the surface of the steel material 1 increases (e.g., about 50°C). In contrast, the post-removal descaling apparatus 40B removes the scale adhered to the surface of the steel material 1 by spraying cooling water W onto the surface of the steel material 1. At this point, the surface of the steel material 1 is cooled by the cooling water W, so that a Cu-rich layer is further inhibited from reforming on the steel material 1. Moreover, in the first example modification, the surface of the steel material 1 is cooled to less than 1100°C by the post-removal descaling apparatus 40B. Consequently, a Cu-rich layer is further inhibited from reforming in steel material 1. Consequently, the occurrence of hot brittle cracking in steel material 1 is inhibited.

[0097] Figure 8 shows an example of the thermal history of steel material 1 in a series of continuous casting, hot rolling, and cold rolling processes in the first example modification. As shown in Figure 8, at the beginning of continuous casting, the temperature of steel material 1 is about 1500°C. For this reason, scale forms on the surface of steel material 1. On the other hand, steel material 1 cools to 1000°C or lower during the rough rolling process after exiting the heating furnace 20, and from then on, its temperature does not rise to 1100°C or higher. Consequently, in the first example modification, the same effects as those of the first embodiment can be obtained. Petition 870250092353, dated 09 / 10 / 2025, page 31 / 79 / 37

[0098] It should be noted that in the first example modification, a pre-removal descaling process is performed before the scarfing process (removal process) and a post-removal descaling process is performed after the scarfing process (removal process). However, at least one of the pre-removal and post-removal descaling processes may be omitted. (Second Example Modification)

[0099] In the first embodiment, an example was described in which the scarifying process (removal process) is carried out before the width reduction process, but the description is not limited to this example. In a second example modification, the scarifying process (removal process) is carried out after the width reduction process and before the rough rolling process. Furthermore, in the second example modification, a pre-removal descaling process is carried out after the width reduction process and before the scarifying process, and a post-removal descaling process is carried out after the scarifying process and before the rough rolling process.

[00100] As shown in Figure 9 as an example, a scarifying device 30 is provided downstream of the width reduction device 23 and upstream of the rough rolling device 50 in the direction of transport of the steel material 1. In addition, a pre-removal descaling device 40A is provided downstream of the width reduction device 23 and upstream of the scarifying device 30 in the direction of transport of the steel material 1. Furthermore, the post-removal descaling device 40B is provided downstream of the scarifying device 30 and upstream of the rough rolling device 50 in the direction of transport of the steel material 1.

[00101] The scarifying apparatus 30 scarifies the surface of the steel material 1 that has been reduced in the width direction by the width reduction apparatus 23. That is, in the second example modification, the process of Petition 870250092353, dated 09 / 10 / 2025, page 32 / 79 / 37 scarfing is performed after the width reduction process and before the rough rolling process.

[00102] Here, when steel material 1 is reduced in the width direction by the width reduction apparatus 23, hot brittle cracks may occur due to a Cu-rich layer on the surfaces (lateral end faces) of steel material 1 on both sides in the width direction, for example. In contrast, in the second example modification, after steel material 1 is reduced in the width direction by the width reduction apparatus 23, the surfaces of steel material 1 on both sides in the thickness direction and the surfaces (lateral end faces) of steel material 1 on both sides in the width direction are scarred by the scarifying apparatus 30. Because of this, it is possible to remove hot brittle cracks formed on the surfaces (lateral end faces) of steel material 1 on both sides in the width direction. Consequently, quality defects on the surface of steel material 1 can be inhibited.

[00103] Furthermore, in the second example modification, the pre-removal descaling process is carried out before the scarifying process, and the post-removal descaling process is carried out after the scarifying process. Consequently, in the second example modification, the same effects as those of the first example modification can be obtained. <Segunda Modalidade>

[00104] In the first embodiment, an example was described in which the target region T, including the Cu-rich layer, is removed from the steel material 1 by the scarifying apparatus 30, but the description is not limited to this example. In a second embodiment, the target region T is removed from the steel material 1 by a cutting apparatus 90 instead of the scarifying apparatus 30. It should be noted that the cutting apparatus 90 is an example of Petition 870250092353, dated 09 / 10 / 2025, page 33 / 79 / 37 a removal device.

[00105] As shown in Figure 10 as an example, the hot rolling equipment 10 includes the 90 cutting apparatus instead of the 30 scarifying apparatus. The 90 cutting apparatus removes the workpiece from the surface of plate 1A by cutting the plate 1A discharged from the heating furnace 20. Details about the 90 cutting apparatus will be described later. The 90 cutting apparatus is located downstream of the heating furnace 20 in the direction of transport of plate 1A. Furthermore, the 90 cutting apparatus is located upstream of the width reduction apparatus 23 and the descaling apparatus 40 in the direction of transport of plate 1A. More specifically, the 90 cutting apparatus is located downstream of the heating furnace 20 and upstream of the width reduction apparatus 23 (the vertical rolls 24) in the direction of transport of plate 1A.

[00106] As shown in Figure 11 as an example, the cutting apparatus 90 includes a rotary cutting tool 92. The rotary cutting tool 92 has a holder 94 and numerous cutting blades 96 fixed to the outer peripheral edge portion of the holder 94. The rotary cutting tool 92 receives energy from a power source (not shown in the drawings) and rotates. Furthermore, the rotary cutting blades 96 come into contact with the surface of the steel material 1, thus cutting the surface of the steel material 1. In this way, the surface of the steel material 1 is cut by the cutting apparatus 90, removing the target region T on the surface of the steel material 1 after it has been heated in the heating furnace 20.

[00107] It should be noted that, although an example in which the cutting apparatus 90 has a rotary cutting tool 92 is described here, the description is not limited to this example. For example, a surface of the steel material 1 can be cut by a plurality of rotary cutting tools 92. Furthermore, the cutting apparatus 90 may include the rotary cutting tools 92 in positions opposite to the surfaces of Petition 870250092353, dated 09 / 10 / 2025, page 34 / 79 / 37 steel material 1 on both sides in the thickness direction and to the surfaces (lateral end faces) of steel material 1 on both sides in the width direction.

[00108] As described above, in the hot rolling equipment 10 belonging to the second embodiment, the target region T including the Cu-rich layer is removed from the steel material 1 by the cutting apparatus 90. Mechanical removal, such as cutting, is less likely to cause deterioration in the surface texture of the steel material 1 (e.g., surface roughness) compared to removal by scarifying. Consequently, according to the present embodiment, deterioration in the surface texture of the steel material 1 in the hot rolling process can be inhibited.

[00109] It should be noted that, although in the second embodiment an example was described in which the steel material 1 is cut by the cutting apparatus 90, the description is not limited to this example. The removal apparatus is not limited to the cutting apparatus 90 and may, for example, use a mechanical removal method, such as grinding using a grinding wheel apparatus. <Terceira Modalidade>

[00110] In the first embodiment, an example was described in which the heating furnace 20 is provided separately from the production line of the continuous casting machine 11 that continuously melts the steel material 1, but the description is not limited to this example. In a third embodiment, a heating furnace 102 is provided in a production line of a continuous casting machine that continuously melts the steel material 1.

[00111] As shown in Figure 12 as an example, the continuous casting machine 11 continuously casts a plate 1A that is thinner (e.g., 50 mm to 100 mm) than in the continuous casting machine 11 in the first embodiment. The hot rolling equipment 100 is provided in the production line of the continuous casting machine 11. That is, the line of Petition 870250092353, dated 09 / 10 / 2025, p. 35 / 79 / 37 production of hot rolling equipment 100 is continuous with the production line of the continuous casting machine 11. Hot rolling equipment 100 includes a heating furnace 102, a pre-removal descaling apparatus 40A, a scarifying apparatus 30, a post-removal descaling apparatus 40B, a rough rolling apparatus 50, a rough bar heating furnace 104 and a finishing rolling apparatus 60. It should be noted that the hot rolling equipment 100 of the third embodiment does not include the width reduction apparatus 23 of the first embodiment (see figure 1). Furthermore, the rough rolling apparatus 50 of the third embodiment has, as an example, two rolling mills 51, 52.

[00112] Heating furnace 102 is, for example, a table heating furnace. Furthermore, heating furnace 102 is provided upstream of the raw rolling apparatus 50 in the direction of conveying the steel material 1. Heating furnace 102 heats the steel material 1 (for example, plate 1A) to a predetermined temperature (1100 °C or higher), which is obtained by cutting the steel material 1 discharged from the continuous casting machine 11 to a predetermined length.

[00113] The raw bar heating furnace 104 is, for example, a table heating furnace. Furthermore, the raw bar heating furnace 104 is provided downstream of the rough rolling mill 50 and upstream of the finishing rolling mill 60 in the direction of conveying the steel material 1. The raw bar heating furnace 104 heats the steel material 1, which has been roughly rolled by the rough rolling mill 50, to a predetermined temperature (less than 1100°C).

[00114] Figure 13 shows an example of the thermal history of steel material 1 in a series of continuous casting, hot rolling, and cold rolling processes in the third mode. As shown in Figure 13, at the beginning of continuous casting, the temperature of steel material 1 is Petition 870250092353, dated 09 / 10 / 2025, page 36 / 79 / 37 approximately 1500°C. For this reason, incrustations form on the surface of steel material 1. On the other hand, steel material 1 cools to 1000°C or lower during the rough rolling process after exiting the heating furnace 102 and, from then on, its temperature does not rise to 1100°C or higher. Consequently, in the third embodiment, the same effects as those of the first embodiment can be obtained.

[00115] Furthermore, in the third embodiment, the hot rolling equipment 100 is supplied in the production line of the continuous casting machine 11. Because of this, there is less heat loss between the continuous casting machine 11 and the hot rolling equipment 100, which can improve energy efficiency. In addition, since the steel material 1 is thin and the rolling load on the hot rolling equipment 100 is lower, the hot rolling equipment 100 can be reduced. (Third Example Modification)

[00116] Although in the third embodiment an example was described in which the hot rolling equipment 100 includes the rough rolling apparatus 50, the present description is not limited to this example. For example, in a third example modification, the hot rolling equipment 110 does not include the rough rolling apparatus 50.

[00117] As shown in Figure 14 as an example, the hot rolling equipment 110 includes a heating furnace 102, a pre-removal descaling apparatus 40A, a scarifying apparatus 30, a post-removal descaling apparatus 40B, a raw bar heating apparatus 62 and a finishing rolling apparatus 60, but does not include the raw rolling apparatus 50.

[00118] Thus, when the plate 1A that is continuously cast by the continuous casting machine 11 is thin, the rough rolling apparatus 50 can be omitted. Furthermore, although in the third example modification the hot rolling equipment 110 includes the apparatus of Petition 870250092353, dated 09 / 10 / 2025, p. 37 / 79 / 37 raw bar heating 62, the hot rolling equipment 110 does not need to include the raw bar heating apparatus 62.

[00119] Figure 15 shows an example of the thermal history of steel material 1 in a series of continuous casting, hot rolling, and cold rolling processes in the third example modification. As shown in Figure 15, at the beginning of continuous casting, the temperature of steel material 1 is about 1500°C. For this reason, scale forms on the surface of steel material 1. On the other hand, steel material 1 cools to 1000°C or lower during the rough rolling process after exiting the heating furnace 102, and from then on, its temperature does not rise to 1100°C or higher. Consequently, in the third example modification, the same effects as those of the first embodiment can be obtained. EXAMPLES

[00120] To evaluate the performance of the hot rolling equipment 10 and the hot rolling method described, an evaluation was conducted of the relationship between the scarification depth of the steel material 1 and the number of Cu-rich areas in the steel material 1.

[00121] Specifically, as in Example 1, the components of steel material 1 were adjusted to C: 0.0027% by weight, Si: 0.039% by weight, Mn: 0.2% by weight, P: 0.02% by weight, S: 0.011% by weight, Cu: 0.45% by weight, and Fe for the remainder. In Example 1, three steel materials 1 adjusted in this way were heated for 120 minutes in the heating furnace 20 of the hot rolling equipment 10 to raise the temperature of each steel material 1 to 1250°C. Then, the surfaces of the three steel materials 1 were scarified to different scarification depths. Furthermore, the surface of each steel material 1 was descaled, and subsequently, each steel material 1 had its temperature reduced to approximately 1000°C, corresponding to the temperature at the beginning of rolling in Petition 870250092353, dated 09 / 10 / 2025, page 38 / 79 / 37 gross, and then it was tempered.

[00122] The components of the steel materials 1 in Example 2 were the same as those of the steel materials 1 in Example 1, except that the Cu component was defined as 0.98% by weight. In Example 2, four steel materials 1 adjusted in this way were heated, scarified, descaled, and cooled in the same manner as in Example 1. It should be noted that the seven steel materials 1 from Example 1 and Example 2 exhibited different scarification depths. Each steel material 1 from Example 1 and Example 2 manufactured in this manner was cut. Then, the cut faces near the surfaces of the steel materials 1 were observed, and the number of grain boundaries where the Cu concentration was observed outside the grain boundaries reaching the surface of the steel materials 1 was measured in a 1 cm strip in the sheet passage direction (transport direction) or in the width direction of the steel material 1.

[00123] Figure 16 shows the results of measuring the number of Cu-rich areas in each of the steel materials 1 from Example 1 and Example 2. It should be noted that the vertical geometric axis in Figure 16 (the percentage of the number of Cu-rich areas) indicates the percentage of the measurement results for each steel material 1 relative to a maximum value (100%) of the measurement results (the number of Cu-rich areas) for each steel material 1. As shown in Figure 16 as an example, in Example 1, the percentage of the number of Cu-rich areas in each steel material 1 was significantly reduced after scarifying each steel material 1. For example, in Example 1, the percentage of the number of Cu-rich areas in each steel material 1 was 70 to 90% before scarifying each steel material 1 (before scarifying), but decreased to 30% or less after scarifying each steel material 1 to a scarification depth of approximately 1 mm (after scarification).

[00124] In Example 2, as in Example 1, the percentage of Petition 870250092353, dated 09 / 10 / 2025, page 39 / 79 / 37 number of areas rich in Cu decreased after each steel material 1 was scarified. For example, in the case of steel material 1 that was scarfed to a scarfing depth of approximately 3 mm, the percentage of Cu-rich areas was approximately 70% before scarfing of steel material 1, but decreased to 0% after scarfing of steel material 1. Furthermore, in the case of the two steel materials 1 that were scarfed to a scarfing depth of approximately 1.5 mm, the percentage of Cu-rich areas in each steel material 1 was approximately 100% or 35% before scarfing of each steel material 1, but decreased to 0% after scarfing of each steel material 1.Furthermore, in the case of steel material 1, which was scarified to a scarification depth of approximately 0.75 mm, the percentage of Cu-rich areas in steel material 1 was approximately 35% before scarifying, but decreased to approximately 25% after scarifying. By scarifying steel materials 1 in this manner, it was confirmed that the Cu-rich areas were reduced.

[00125] Although preferred embodiments of the description have been described in detail above with reference to the accompanying drawings, the present description is not limited to those embodiments. It will be evident that a variety of example alterations or example applications within the category of technical thinking set forth in the claims may occur to one skilled in the art to whom the description pertains, and it will be understood that these also naturally belong to the technical scope of the description.

[00126] In addition, the description of Japanese Patent Application No. 2023-054364 filed on March 29, 2023 is incorporated herein by reference in its entirety.

[00127] All documents, patent applications and technical standards mentioned in this descriptive report are incorporated herein by reference to the same extent as if each individual document, patent application or technical standard were specifically and individually indicated to be. Petition 870250092353, dated 09 / 10 / 2025, page 40 / 79 / 37 incorporated by reference.

[00128] In addition to the above modalities, the following addenda are also described. (Addendum 1)

[00129] A hot rolling method for hot rolling a copper (Cu)-containing steel material, the hot rolling method comprising: A heating process that heats the steel material to a predetermined temperature after continuous casting; and a stripping process that performs a treatment on the steel material that was heated in the heating process, the treatment removing a target region including a Cu-rich layer that is present on one side of the surface of the steel material and in which a concentration of Cu components is higher than in a base material. (Addendum 2)

[00130] The hot rolling method of appendix 1, further comprising a descaling process that descales the steel material using cooling water after the descaling process. (Addendum 3)

[00131] The hot rolling method of appendix 2, in which, during the descaling process, the temperature on the surface of the steel material is cooled to 1100°C or less. (Addendum 4)

[00132] The hot rolling method of appendix 2 or appendix 3, further comprising a rough rolling process which performs rough rolling on the steel material, wherein the rough rolling process is carried out after the descaling process. (Addendum 5)

[00133] The hot rolling method according to anyone Petition 870250092353, dated 09 / 10 / 2025, page 41 / 79 / 37 of addendum 1 to addendum 4, in which the target region is a region of 2 mm or less of the surface of the steel material in a direction of thickness of the steel material. (Addendum 6)

[00134] The hot rolling method of any of the addenda 1 to addendum 5, in which, in the removal process, the target region is removed by scarification. (Addendum 7)

[00135] The hot rolling method of any of the addenda 1 to addendum 5, in which, in the removal process, the target region is removed by mechanical removal. Petition 870250092353, dated 09 / 10 / 2025, p. 42 / 79

Claims

1 / 4 CLAIMS 1. Hot rolling equipment for hot rolling of a copper (Cu) containing steel material, the hot rolling equipment characterized by the outfit comprising: a heating furnace that heats the steel material to a predetermined temperature after melting; a rolling apparatus that rolls the steel material that has been heated in the heating furnace; a removal apparatus that is provided downstream of the heating furnace and upstream of the rolling apparatus in a direction of conveying the steel material and that removes, from the steel material that has been heated in the heating furnace, a target region including a Cu-rich layer that is present on one side of the surface of the steel material and in which a concentration of Cu components is greater than a concentration of Cu components in a base material of the steel material;and a post-removal descaling apparatus that is provided downstream of the removal apparatus and upstream of the rolling apparatus in the direction of transport of the steel material and that descales the steel material using cooling water.

2. Hot rolling equipment according to claim 1, characterized in that the post-removal descaling apparatus cools the steel material so that the temperature on a surface of the steel material becomes less than 1100°C.

3. Hot rolling equipment according to claim 1 or 2, characterized in that the hot rolling equipment includes a width reduction apparatus which is provided downstream of the heating furnace and upstream of the stripping apparatus in the direction of transport of the steel material and which reduces the steel material in a width direction of the steel material. Petition 870250086589, dated 09 / 25 / 2025, p. 49 / 107 2 / 4 4. Hot rolling equipment according to any one of claims 1 to 3, characterized in that the hot rolling equipment includes a pre-descaler apparatus that is provided downstream of the heating furnace and upstream of the descaler apparatus in the direction of transport of the steel material and that descales the steel material using cooling water.

5. Hot rolling equipment according to any one of claims 1 to 4, characterized in that the rolling apparatus is either a rough rolling apparatus that rolls rough steel material or a finishing rolling apparatus that rolls finished steel material.

6. Hot rolling equipment according to any one of claims 1 to 5, characterized in that the target region is a region of 2 mm or less of a steel material surface in a steel material thickness direction.

7. Hot rolling equipment according to any one of claims 1 to 6, characterized in that the stripping apparatus removes the target region of the steel material by means of scarification or removes the target region of the steel material by means of mechanical stripping.

8. Hot rolling equipment according to any one of claims 1 to 7, characterized in that the heating furnace is provided separately from a production line of a casting machine that melts the steel material.

9. Hot rolling equipment according to any one of claims 1 to 7, characterized in that the heating furnace is provided in a production line of a casting machine that melts the steel material.

10. Hot rolling method for hot rolling of a copper (Cu)-containing steel material, characterized in that it comprises: a heating process that heats the steel material to a predetermined temperature after casting; a stripping process that performs a treatment on the steel material that was heated in the heating process, the treatment removing a target region including a Cu-rich layer that is present on one side of the surface of the steel material and in which a concentration of Cu components is greater than a concentration of Cu components in a base material of the steel material; a post-scaling process that descales the steel material using cooling water after the stripping process; and a rolling process that rolls the steel material after the post-scaling process.

11. Hot rolling method according to claim 10, characterized in that, in the post-removal descaling process, the steel material is cooled so that a temperature on a surface of the steel material becomes less than 1100°C.

12. Hot rolling method according to claim 10 or 11, characterized in that it further comprises a width reduction process that reduces the steel material in a width direction of the steel material after the heating process and before the stripping process.

13. Hot rolling method according to any one of claims 10 to 12, characterized in that it further comprises a pre-removal descaling process that descales the steel material using cooling water after the heating process and before the removal process.

14. Hot rolling method according to any Petition 870250086589, dated 09 / 25 / 2025, page 51 / 107 4 / 4 one of claims 10 to 13, characterized in that, in the rolling process, rough rolling or finishing rolling is carried out on the steel material.

15. Hot rolling method according to any one of claims 10 to 14, characterized in that the target region is a region of 2 mm or less of a steel material surface in a thickness direction of the steel material.

16. Hot rolling method according to any one of claims 10 to 15, characterized in that, in the stripping process, the target region is removed from the steel material by means of scarification and the target region is removed from the steel material by means of mechanical stripping.

17. Hot rolling method according to any one of claims 10 to 16, characterized in that the steel material contains Cu at 0.15% by mass or more. Petition 870250086589, dated 09 / 25 / 2025, p. 52 / 107

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