A method for reducing roller marks on steel plate surface

Abstract

This invention discloses a method for reducing roller marks on steel plate surfaces. By designing the appropriate chemical composition of the steel plate, controlling heating process parameters, descaling methods, roller surface hardness, and straightening methods for steel plates of varying strengths, as well as inspecting and maintaining the straightening roller surfaces and configuring appropriate side spraying, roller marks can be effectively eliminated. This method significantly improves the surface quality of steel plates, reducing the amount of additional grinding, scrapping, and downgrading required due to roller marks by 91.2% compared to pre-implementation levels. This is a highly effective method.

Description

Technical Field

[0001] The invention relates to the technical field of steel rolling, and in particular to a method for reducing roller marks on the surface of a steel plate. Background Art

[0002] During the production of wide and thick plates, the slab is first rolled through a rolling mill, and the rolled steel plate is then straightened by a straightening machine. If there are pits or foreign matter on the rollers or straightening rollers, periodic roller marks will be generated on the surface of the steel plate during the rolling or straightening process. These roller marks may appear on either the upper or lower surface of the steel plate. In addition, if there are pits or protrusions on the conveyor rollers, roller marks will also be generated on the surface of the steel plate when the steel plate passes through. This is especially true for the rollers before and after the straightening machine. Due to the high pressure on the rollers during straightening, roller marks are easily generated if there are defects on the roller surface. Roller marks on the surface of the steel plate are generally distributed periodically and continuously. If the roller marks are shallow, they can usually be repaired by grinding or shot blasting, but this will increase manufacturing costs and extend the manufacturing cycle. If the roller marks are deep and the thickness of the defect is below the lower limit of the standard requirement, the steel plate will have to be downgraded or scrapped, resulting in significant losses.

[0003] Patent publication number CN103506382A, "A Production Method for Improving the Surface Quality of Thick Ship Plates," provides a method for controlling iron oxide scale on steel plates. This method effectively controls the intrusion of iron oxide scale onto steel plates, eliminating pitting defects. However, this method only controls pitting and the intrusion of iron oxide scale, and does not address solutions for roller marks on steel plate surfaces.

[0004] Patent publication number CN113369312A, "A Process for Controlling Pits in 25-40mm Q235 Steel," provides a method for controlling surface pitting in medium-thick Q235 steel. This method effectively controls pitting in 25-40mm thick Q235 steel. However, this method is limited to controlling pitting and does not address solutions for roller marks on the steel plate surface.

[0005] Patent publication number CN102319734A, "A Method for Effectively Controlling Small Pits on the Surface of Medium and Thick Plates," provides a method for controlling pitting on steel plate surfaces. While this method effectively reduces pitting on steel plate surfaces, it only addresses pitting control and does not address solutions for roller marks on steel plate surfaces. Summary of the Invention

[0006] The purpose of the present invention is to provide a method that is simple to operate, can effectively reduce roller marks on the surface of steel plates, improve the surface quality of steel plates, and meet the quality requirements of subsequent processed products.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for reducing roller marks on the surface of a steel plate, comprising:

[0009] (1) The Si content of the steel plate does not exceed 0.25%;

[0010] (2) When the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is controlled between 0.8% and 2.2%. After the slab is removed from the furnace, the conveying speed of the slab on the roller is 2.5 m / s.

[0011] (3) After the slab is discharged from the furnace, it is descaled by the initial descaling machine. The descaling pressure is not less than 20 MPa, and the roller speed of the descaling machine is 0.8 m / s.

[0012] (4) For the first five passes of steel plate rolling, descaling is performed in each pass, and the descaling method for the first two passes is simultaneous descaling in the forward and reverse directions; for the sixth and subsequent passes, descaling is performed in the odd-numbered passes, and the descaling method is forward descaling;

[0013] (5) The hardness of the surface of the 6 conveyor rollers before and after the straightening machine is more than 10HB higher than the hardness of the straightening roller surface;

[0014] (6) After producing steel with a yield strength greater than or equal to 550 MPa, check the six rollers before and after the grinding and straightening machine to ensure that the roller surface quality is good;

[0015] (7) When straightening steel plates with a yield strength greater than or equal to 460 MPa, the bite speed of the steel plate during straightening is 0.6 m / s, and the straightening roller gap of the steel plate head 1 m is 0.2 mm to 0.6 mm larger than that of the other parts of the steel plate;

[0016] (8) Check the surface of the straightening roller every two hours. If there is iron oxide on the roller surface, stop and grind it immediately.

[0017] (9) At the entrance of the straightening machine, a side spray is set, the side spray water is always open, the side spray water pressure is 1.2MPa, and the water volume is 18m 3 / h.

[0018] Furthermore, the Si content of the steel plate is 0.25%; when the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is 0.8%; after the slab is taken out of the furnace, the conveying speed of the slab on the roller is 2.5m / s; after the slab is taken out of the furnace, it is descaled by the initial descaling machine, the descaling pressure is 20MPa, and the roller speed of the descaling machine is 0.8m / s; the steel plate is descaled in each of the first five passes of rolling, and the descaling method of the first two passes is simultaneous descaling in forward and reverse directions; the descaling of the odd-numbered passes and subsequent passes is positive descaling; the hardness of the surface of the 6 conveyor rollers before and after the straightening machine is greater than that of the straightening roller surface. The hardness is as high as 10HB. After producing steel with a yield strength greater than or equal to 550MPa, check and grind the six rollers in front and behind the straightening machine to ensure that the roller surface quality is good. When straightening steel plates with a yield strength of 460MPa, the bite speed of the steel plate during straightening is 0.6m / s, and the straightening roller gap of 1m at the head of the steel plate is 0.2mm larger than that of other parts of the steel plate. Check the roller surface status of the straightening roller every two hours. If there is iron oxide on the roller surface, stop and grind it immediately. At the entrance of the straightening machine, set a side spray, the side spray water is always on, the side spray water pressure is 1.2MPa, and the water volume is 18m 3 / h; Check the surface of the steel plate, the surface quality is good and there are no roller marks.

[0019] Furthermore, the Si content of the steel plate is 0.21%; when the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is 2.2%; after the slab is taken out of the furnace, the conveying speed of the slab on the roller is 2.5m / s; after the slab is taken out of the furnace, it is descaled by the initial descaling machine, the descaling pressure is 20.5MPa, and the roller speed of the descaling machine is 0.8m / s; the steel plate is descaled in each of the first five passes of rolling, and the descaling method of the first two passes is simultaneous descaling in forward and reverse directions; the descaling of the odd-numbered passes and subsequent passes is positive descaling; the hardness of the surface of the 6 conveyor rollers before and after the straightening machine is greater than that of the straightening roller surface. The hardness is as high as 12.2HB. After producing steel with a yield strength greater than or equal to 550MPa, check and grind the six rollers in front and behind the straightening machine to ensure that the roller surface quality is good. When straightening a steel plate with a yield strength of 472MPa, the bite speed of the steel plate during straightening is 0.6m / s, and the straightening roller gap of 1m at the head of the steel plate is 0.6mm larger than that of the other parts of the steel plate. Check the roller surface status every two hours. If there is iron oxide on the roller surface, stop and grind it immediately. At the entrance of the straightening machine, set a side spray, the side spray water is always on, the side spray water pressure is 1.2MPa, and the water volume is 18m 3 / h; Check the surface of the steel plate, the surface quality is good and there are no roller marks.

[0020] Furthermore, the Si content of the steel plate is 0.22%; when the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is 1.3%; after the slab is taken out of the furnace, the conveying speed of the slab on the roller is 2.5m / s; after the slab is taken out of the furnace, it is descaled by the initial descaling machine, the descaling pressure is 20.3MPa, and the roller speed of the descaling machine is 0.8m / s; the steel plate is descaled in each of the first five passes of rolling, and the descaling method for the first two passes is simultaneous descaling in forward and reverse directions; the descaling method for the sixth and subsequent passes is odd-numbered passes, and the descaling method is forward descaling; the surface hardness of the six conveyor rollers before and after the straightening machine is 11.4HB higher than the hardness of the straightening roller surface; After producing steel with a yield strength greater than or equal to 550MPa, check and grind the six rollers before and after the straightening machine to ensure that the surface quality of the rollers is good; when straightening steel plates with a yield strength of 480MPa, the bite speed of the steel plates during straightening is 0.6m / s, and the straightening roller gap of 1m at the head of the steel plate is 0.4mm larger than that of other parts of the steel plate; check the status of the straightening roller surface every two hours. If there is iron oxide on the roller surface, stop and grind it immediately; at the entrance of the straightening machine, set a side spray, the side spray water is always on, the side spray water pressure is 1.2MPa, and the water volume is 18m3 / h; check the surface of the steel plate, the surface quality is good, and there are no roller marks.

[0021] Roller marks on the surface of steel plates affect their surface quality, so they require careful attention from composition design to production processes and equipment maintenance. The steel plates are designed with a low silicon content, primarily to facilitate the removal of the oxide scale formed during slab heating during descaling. Using low residual oxygen during slab heating can reduce the generation of oxide scale during the heating process. The descaling machine utilizes high descaling pressure and low descaling roller speeds during descaling, effectively removing the oxide scale generated during slab heating and preventing residual oxide scale from scratching the rolls during rolling, which could result in roller marks on the finished steel plate. The surface hardness of each of the six rollers before and after the leveler is higher than that of the straightening rollers, and the 1m roll gap at the head of the straightening roller is larger than that of the rest of the steel plate. This is primarily to prevent the head of the steel plate from scratching the roller surface during straightening, which could result in roller marks on the lower surface of the steel plate. At the entrance of the straightening machine, a side spray is set up to blow away the powdered iron oxide scale on the surface of the steel plate to prevent the straightening roller from sticking to the iron oxide scale, which will cause roller marks on the straightened steel plate.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The method provided by the present invention is simple to operate, requires no additional equipment, and can be easily implemented on-site. It effectively eliminates roller marks on steel plate surfaces during production. Steel plates produced using this method exhibit significantly improved surface quality, with the amount of additional grinding, scrapping, and downgrading due to roller marks reduced by 91.2% compared to pre-implementation levels. This is a significant improvement. DETAILED DESCRIPTION

[0024] Example 1

[0025] The Si content of the steel plate is 0.25%. When the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is 0.8%. After the slab is removed from the furnace, the conveying speed of the slab on the roller is 2.5m / s. After the slab is removed from the furnace, it is descaled by the initial descaling machine with a descaling pressure of 20MPa and a roller speed of 0.8m / s. The steel plate is descaled in each of the first five passes of rolling, and the descaling method for the first two passes is simultaneous descaling in the forward and reverse directions; for the sixth and subsequent passes, the odd-numbered passes are descaled in the forward direction. The surface hardness of the six conveyor rollers before and after the straightening machine is 10HB higher than that of the straightening roller surface. After producing steel grades with a yield strength greater than or equal to 550MPa, the six rollers before and after the straightening machine are inspected and polished to ensure good roller surface quality. When straightening a steel plate with a yield strength of 460MPa, the bite speed of the steel plate during straightening is 0.6m / s, and the straightening roller gap of the steel plate head 1m is 0.2mm larger than the other parts of the steel plate. Check the roller surface of the straightening roller every two hours. If there is iron oxide on the roller surface, stop and grind it immediately. At the entrance of the straightening machine, set a side spray, the side spray water is always on, the side spray water pressure is 1.2MPa, and the water volume is 18mm 3 / h. Check the surface of the steel plate, which is of good quality and has no roller marks.

[0026] Example 2

[0027] The Si content of the steel plate is 0.21%. When the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is 2.2%. After the slab is removed from the furnace, the conveying speed of the slab on the roller is 2.5m / s. After the slab is removed from the furnace, it is descaled by the initial descaling machine with a descaling pressure of 20.5MPa and a roller speed of 0.8m / s. The steel plate is descaled in each of the first five passes of rolling, and the descaling method for the first two passes is simultaneous descaling in the forward and reverse directions. For the sixth and subsequent passes, the odd-numbered passes are descaled in the forward direction. The surface hardness of the six conveyor rollers before and after the straightening machine is 12.2HB higher than that of the straightening roller surface. After producing steel grades with a yield strength greater than or equal to 550MPa, the six rollers before and after the straightening machine are inspected and polished to ensure good roller surface quality. When straightening a steel plate with a yield strength of 472MPa, the bite speed of the steel plate during straightening is 0.6m / s, and the straightening roller gap of the steel plate head 1m is 0.6mm larger than the other parts of the steel plate. Check the roller surface of the straightening roller every two hours. If there is iron oxide on the roller surface, stop and grind it immediately. At the entrance of the straightening machine, set a side spray, the side spray water is always on, the side spray water pressure is 1.2MPa, and the water volume is 18mm 3 / h. Check the surface of the steel plate, which is of good quality and has no roller marks.

[0028] Example 3

[0029] The Si content of the steel plate is 0.22%. When the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is 1.3%. After the slab is removed from the furnace, the conveying speed of the slab on the roller is 2.5m / s. After the slab is removed from the furnace, it is descaled by the initial descaling machine with a descaling pressure of 20.3MPa and a roller speed of 0.8m / s. The steel plate is descaled in each of the first five passes of rolling, and the descaling method for the first two passes is simultaneous descaling in the forward and reverse directions. For the sixth and subsequent passes, the odd-numbered passes are descaled in the forward direction. The surface hardness of the six conveyor rollers before and after the straightening machine is 11.4HB higher than that of the straightening roller surface. After producing steel grades with a yield strength greater than or equal to 550MPa, the six rollers before and after the straightening machine are inspected and polished to ensure good roller surface quality. When straightening a steel plate with a yield strength of 480MPa, the bite speed of the steel plate during straightening is 0.6m / s, and the straightening roller gap of the steel plate head 1m is 0.4mm larger than the other parts of the steel plate. Check the roller surface of the straightening roller every two hours. If there is iron oxide on the roller surface, stop and grind it immediately. At the entrance of the straightening machine, set a side spray, the side spray water is always on, the side spray water pressure is 1.2MPa, and the water volume is 18mm 3 / h. Check the surface of the steel plate, which is of good quality and has no roller marks.

[0030] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for reducing roller marks on the surface of a steel plate, characterized in that: include: (1) The Si content of the steel plate does not exceed 0.25%; (2) When the slab is heated, the residual oxygen content of the exhaust gas from the heating furnace is controlled between 0.8% and 2.2%. After the slab is discharged from the furnace, the conveying speed of the slab on the roller is 2.5 m / s. (3) After the slab comes out of the furnace, it is descaled by the initial descaling machine. The descaling pressure is not less than 20 MPa, and the roller speed of the descaling machine is 0.8 m / s; (4) For the first five passes of steel plate rolling, descaling is performed in each pass, and the descaling method for the first two passes is simultaneous descaling in the forward and reverse directions; for the sixth and subsequent passes, descaling is performed in the odd-numbered passes, and the descaling method is forward descaling; (5) The hardness of the surface of the 6 conveyor rollers before and after the straightening machine is more than 10HB higher than the hardness of the straightening roller surface; (6) After producing steel with a yield strength greater than or equal to 550 MPa, check the six rollers before and after the grinding and straightening machine to ensure that the surface quality of the rollers is good; (7) When straightening steel plates with a yield strength greater than or equal to 460 MPa, the bite speed of the steel plate during straightening is 0.6 m / s, and the straightening roller gap of the steel plate head 1 m is 0.2 mm to 0.6 mm larger than that of other parts of the steel plate; (8) Check the surface of the straightening roller every two hours. If there is iron oxide on the roller surface, stop and grind it immediately. (9) At the entrance of the straightening machine, a side spray is set, the side spray water is always open, the side spray water pressure is 1.2MPa, and the water volume is 18m 3 / h.

2. The method for reducing roller marks on the surface of a steel plate according to claim 1, wherein: The Si content of the steel plate is 0.25%. When the slab is heated, the residual oxygen content in the exhaust gas from the heating furnace is 0.8%. After leaving the furnace, the slab is descaled in an initial descaling machine at a pressure of 20 MPa. The surface hardness of the six conveyor rollers before and after the straightening machine is 10 HB higher than that of the straightening rollers. When straightening a steel plate with a yield strength of 460 MPa, the gap between the straightening rollers at the top of the plate is 0.2 mm larger than that of the rest of the plate. Check the surface of the steel plate, the surface quality is good and there are no roller marks.

3. The method for reducing roller marks on the surface of a steel plate according to claim 1, characterized in that: The Si content of the steel plate is 0.21%; when the slab is heated, the residual oxygen content of the heating furnace exhaust gas is 2.2%; after the slab is taken out of the furnace, it is descaled by the initial descaling machine with a descaling pressure of 20.5MPa; the hardness of the surface of the 6 conveyor rollers before and after the straightening machine is 12.2HB higher than the hardness of the straightening roller surface; when straightening steel plates with a yield strength of 472MPa, the straightening roller gap of 1m at the head of the steel plate is 0.6mm larger than that of other parts of the steel plate; the surface of the steel plate was inspected and the surface quality was good with no roller marks.

4. The method for reducing roller marks on the surface of a steel plate according to claim 1, wherein: The Si content of the steel plate is 0.22%. During slab heating, the residual oxygen content in the exhaust gas from the heating furnace is 1.3%. After leaving the furnace, the slab is descaled in an initial descaling machine at a pressure of 20.3 MPa. The surface hardness of the six conveyor rollers before and after the leveler is 11.4 HB higher than that of the straightening rollers. When straightening a steel plate with a yield strength of 480 MPa, the gap between the straightening rollers at the top of the plate is 0.4 mm larger than that of the rest of the plate. Check the surface of the steel plate, the surface quality is good and there are no roller marks.