A method for improving edge pit defects of thin strip steel

Abstract

The present invention belongs to the technical field of thin strip continuous casting, and relates to a method for improving edge pit defects of thin strip steel. The method of the present invention improves the solidification rate of molten steel in the edge area during thin strip continuous casting, and increases the strength and thickness of the cast strip in the edge area by controlling the edge roughness of the crystallization roller. At the same time, by real-time adjustment of the hot rolling bending roll force and the rolling force, the hot rolling reduction in the edge area is increased, the difference in reduction between the edge area and the center area is reduced, the surface quality of the strip in the edge area is improved, and the surface pit defects in the edge area are solved. The method of the present invention improves the surface quality of the edge of the thin strip steel by controlling the edge roughness of the crystallization roller, the hot rolling force and the bending roll force, solves the problem of strip cutting loss caused by edge pit defects, and improves the overall yield rate of hot-rolled thin strip steel.

Description

Technical Field

[0001] The invention belongs to the technical field of thin strip continuous casting, relates to edge quality control technology of thin strip steel produced by thin strip continuous casting, and more specifically to a method for improving edge pit defects of thin strip steel. Background Art

[0002] The thin strip continuous casting process is to pass the molten steel through the distribution system and enter a pair of crystallization rollers rotating in opposite directions. The thin strip steel is then discharged as the crystallization rollers rotate. Subsequently, the thin strip steel is hot-rolled into ultra-thin strip steel products through one or two passes. Due to the small number of rolling passes, there is a difference between the edge rolling and the center area rolling of the thin strip steel. The edge quality of the hot-rolled thin strip steel is poor and there are many surface pit defects. Therefore, when selling, trimming is required, resulting in a large loss of raw materials and a low yield rate.

[0003] In the prior art, the control of the surface quality of thin strip steel is carried out during the hot rolling and annealing process of thick slabs, and the control of the edge surface quality is rarely involved. Patent document 201811190436.6 discloses a method for improving the surface quality of strip steel, in which a group of high-pressure compressed air is used to blow the surface of the thick slab, and the oxide scale of the hot-rolled strip steel crushed by high-pressure water is secondary cleaned and swept to avoid pressing the slag into the surface of the strip steel during processing, thereby improving the surface quality of the steel. Patent document 202110865912.5 provides a process method for improving the surface quality of medium-carbon manganese-boron steel, which improves the surface quality of the continuous casting billet by adjusting the superheat of the molten steel, enhancing the cooling intensity of the crystallizer, and weakening the cooling of the secondary cooling zone, while matching a suitable heating system to improve the surface quality of the medium-carbon manganese-boron steel. Patent document 201910211400.X discloses a method for improving the surface quality of P-containing high-strength IF steel continuously annealed plates. By controlling the slab heating temperature, finishing rolling inlet temperature, continuous annealing temperature, soaking temperature, etc., the defects of pitting on the surface of the hot-rolled plate and needle points on the surface of the continuously annealed plate during the preparation of the P-containing high-strength IF steel continuously annealed plate are solved to improve the surface quality of the product.

[0004] However, the above-mentioned prior art cannot solve the surface quality defects of the thin strip steel directly discharged from the crystallization roller by the thin strip continuous casting of molten steel after hot rolling, nor does it involve the control of the surface quality of the edge of the thin strip steel. Therefore, how to solve the pit defect on the edge of the thin strip steel produced by the thin strip continuous casting and hot rolling in one or two passes is still a problem that needs to be solved. Summary of the invention

[0005] The object of the present invention is to provide a method for improving the edge pit defect of thin strip steel. The method of the present invention improves the edge pit defect of thin strip steel and improves the edge quality of thin strip steel by controlling the edge roughness of the crystallization roll and adjusting the rolling force and bending roll force of hot rolling in real time and quickly according to the pit defect situation.

[0006] The purpose of the present invention is specifically achieved through the following technical solutions:

[0007] According to one aspect of the present invention, a method for improving edge pit defects of thin strip steel is proposed, the method comprising the following steps:

[0008] 1) Molten steel with qualified composition is obtained by steelmaking in an electric furnace or a converter, and is led out into a cast strip through a pair of crystallization rollers rotating in opposite directions, wherein the edge area in the width direction of the cast strip:

[0009] The roughness R1 of the crystallization roller in the edge L1 is controlled to be less than 2 μm, where the value of L1 is within 60 mm from the edge of the casting strip.

[0010] The roughness R2 of the crystallization roller in the edge L1-L2 is controlled to be 2-4.5 μm, wherein the value of L2 is within 300 mm from the edge of the casting strip;

[0011] 2) subjecting the cast strip obtained in step 1) to one hot rolling process to be rolled into a hot-rolled thin strip steel with a thickness of less than 1.8 mm, and measuring the width of the edge pit area of ​​the hot-rolled thin strip steel as A;

[0012] 3) Real-time monitoring of the bending roll force F of one hot rolling pass w0 , and adjust the bending roll force in real time according to the following relationship, and control the bending roll force within the range of -3 to 2MN:

[0013] F w =(1+βA)F w0 ,

[0014] Among them, F w is the adjusted bending roll force value, β is the bending roll force adjustment parameter, where the value range of β is -0.01~0.2;

[0015] 4) Real-time monitoring of the rolling force F0 of one hot rolling pass, and real-time adjustment of the rolling force according to the following relationship, and control the rolling force within the range of 10 to 25 MN:

[0016] F=(1+αA)F0,

[0017] Wherein, F is the adjusted rolling force value, α is the rolling force adjustment parameter, and the value range of α is 0.005~0.1;

[0018] 5) In the hot rolling process, the hot rolling reduction R in the center area C of the thin strip steel is c and the hot rolling reduction R in the edge E region e Take control:

[0019] The hot rolling reduction R cand hot rolling reduction R e The difference D r =R c -R e It is controlled to be no higher than 8%, wherein the value of the central area C is between 20 and 300 mm, and the value of the edge area E is between 0 and 100 mm.

[0020] According to the method for improving edge pit defects of thin strip steel of the present invention, preferably, in step 1), the molten steel is low carbon steel, high carbon steel, low alloy steel, high alloy steel or high silicon steel.

[0021] According to the method for improving edge pit defects of thin strip steel of the present invention, preferably, the method further comprises: the value of L1 of edge roughness control is within 50 mm from the edge of the cast strip.

[0022] According to the method for improving edge pit defects of thin strip steel of the present invention, preferably, the method further comprises: the value of L2 of edge roughness control is within 200 mm of the edge of the cast strip.

[0023] According to the method for improving edge pit defects of thin strip steel of the present invention, preferably, the method further comprises: the bending roll force is controlled within a range of -3 to 1MN.

[0024] According to the method for improving edge pit defects of thin strip steel of the present invention, preferably, the method further comprises: the rolling force is controlled within 18 to 25 MN.

[0025] According to the method for improving the edge pit defect of thin strip steel of the present invention, preferably, the method further comprises: reducing the hot rolling reduction amount R c and hot rolling reduction R e The difference D r =R c -R e Controlled to be no higher than 6%.

[0026] According to the method for improving the edge pit defect of thin strip steel of the present invention, preferably, the method further comprises: reducing the hot rolling reduction amount R c and hot rolling reduction R e The difference D r =R c -R e Controlled to no more than 5%.

[0027] According to the method for improving the edge pit defect of thin strip steel of the present invention, preferably, the value of the central area C is between 40 and 200 mm.

[0028] According to the method for improving the edge pit defect of thin strip steel of the present invention, preferably, the value of the edge area E is between 0 and 80 mm.

[0029] Beneficial technical effects

[0030] Compared with the prior art, the technical concept and corresponding technical solution of the present invention can at least achieve the following beneficial technical effects:

[0031] The technical solution of the present invention fully considers the edge pit defects of thin strip steel in the production process, controls the edge strength and thickness of thin strip steel in the continuous casting process for the first time, and controls the edge reduction amount in the hot rolling process of the continuously cast thin strip steel.

[0032] The technical solution of the present invention proposes to increase the solidification rate of molten steel during continuous casting in the edge area by controlling the roughness of the edge of the crystallization roller, increase the strength and thickness of the cast strip in the edge area, and at the same time, increase the hot rolling reduction in the edge area by quickly adjusting the hot rolling bending roll force and the rolling force, reduce the difference in reduction with the center area, improve the surface quality of the strip in the edge area, solve the surface pit defects in the edge area, and improve the edge quality of thin strip steel.

[0033] In summary, the technical solution of the present invention effectively solves the problem of strip edge loss caused by edge pits, and improves the yield rate of hot-rolled thin strip steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments are briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0035] Figure 1 It is a schematic diagram of the edge pit defect of thin strip steel in the prior art.

[0036] Figure 2 This is the edge surface of the steel strip after adjustment according to the method of Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one of ordinary skill in the art to which the present invention belongs.

[0039] The following are embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments that can be obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] After steelmaking in an electric furnace or converter, the molten steel with qualified composition is obtained, and then it is continuously cast into thin strip steel through a pair of crystallization rollers rotating in opposite directions. The roughness of the crystallization roller within the range of 45mm on the edge is 1.5μm, and the roughness within the range of 100-200mm on the edge is 3.1μm.

[0042] The continuously cast thin strip steel is rolled into a thin strip steel with a thickness of 0.7 mm through one hot rolling process. The bending roll force is 1.5 MN, the rolling force is 21 MN, the hot rolling reduction within 210 mm of the center of the strip steel is 25%, and the width of the thin strip steel bottom line thickness measurement pit area is 15 mm.

[0043] The bending roll force adjustment parameter is -0.1, and according to the bending roll force adjustment method F w =(1+βA)F w0 , quickly adjust the bending roll force to -0.7MN. When the bending roll force is adjusted to a positive value, that is, positive bending, it means that the bending roll force is opposite to the rolling pressure direction; correspondingly, when the bending roll force is adjusted to a negative value, that is, negative bending, it means that the bending roll force is adjusted in the direction of rolling pressure.

[0044] The rolling force adjustment parameter is 0.01, and according to the rolling force adjustment method F = (1 + αA) F0, the rolling force is quickly adjusted to 24MN, the reduction within 60mm of the edge is controlled to be 21%, and the difference between the reduction at the edge and the reduction in the center area is 4%. Figure 2 As shown, the produced hot-rolled thin strip steel has no pit defects on the edge and the edge surface is smooth.

[0045] Example 2

[0046] The molten steel with qualified composition is obtained by electric furnace or converter steelmaking, and then continuously cast into thin strip steel by a pair of crystallization rollers rotating in opposite directions. The roughness of the crystallization roller within the range of 20mm on the edge is 0.3μm, and the roughness within the range of 20-80mm on the edge is 1.7μm.

[0047] The continuously cast thin strip steel is rolled into a thin strip steel with a thickness of 1.6 mm through one hot rolling process. The bending roll force is 1.1 MN, the rolling force is 12 MN, the hot rolling reduction within 260 mm of the center of the strip steel is 50%, and the width of the thin strip steel bottom line thickness measurement pit area is 37 mm.

[0048] The bending roll force adjustment parameter is -0.08, and according to the bending roll force adjustment method F w =(1+βA)F w0 , quickly adjust the bending roll force to -2.2MN. When the bending roll force is adjusted to a positive value, that is, positive bending, it means that the bending roll force is opposite to the rolling pressure direction; correspondingly, when the bending roll force is adjusted to a negative value, that is, negative bending, it means that the bending roll force is adjusted in the direction of rolling pressure.

[0049] The rolling force adjustment parameter is 0.02, and according to the rolling force adjustment method F=(1+αA)F0, the rolling force is quickly adjusted to 21MN, the reduction within 50mm of the edge is controlled to be 47%, and the difference between the reduction at the edge and the reduction in the center area is 3%. The hot-rolled thin strip steel produced has no pit defects on the edge and the edge surface is smooth.

[0050] Example 3

[0051] The molten steel with qualified composition is obtained by electric furnace or converter steelmaking, and then continuously cast into thin strip steel by a pair of crystallization rollers rotating in opposite directions. The roughness of the crystallization roller within the range of 32mm on the edge is 1.9μm, and the roughness within the range of 32-130mm on the edge is 4.3μm.

[0052] The continuously cast thin strip steel is rolled into a thin strip steel with a thickness of 1.1 mm through one hot rolling process. The bending roll force is 0.7 MN, the rolling force is 15 MN, the hot rolling reduction within 280 mm of the center of the strip steel is 46%, and the width of the thin strip steel bottom line thickness measurement pit area is 8 mm.

[0053] The bending roll force adjustment parameter is -0.11, and according to the bending roll force adjustment method F w =(1+βA)F w0 , quickly adjust the bending roll force to 0.1MN. Among them, when the bending roll force is adjusted to a positive value, that is, positive bending, it means that the bending roll force is opposite to the rolling pressure direction; correspondingly, when the bending roll force is adjusted to a negative value, that is, negative bending, it means that the bending roll force is adjusted in the direction of rolling pressure.

[0054] The rolling force adjustment parameter is 0.03, and according to the rolling force adjustment method F=(1+αA)F0, the rolling force is quickly adjusted to 19MN, the reduction within 30mm of the edge is controlled to be 45%, and the difference between the reduction at the edge and the reduction in the center area is 1%. The hot-rolled thin strip steel produced has no pit defects on the edge and the edge surface is smooth.

[0055] The above description is only a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the edge pit defect of thin strip steel, characterized in that: The method comprises the following steps: 1) Molten steel with qualified composition is obtained by steelmaking in an electric furnace or a converter, and is led out into a cast strip through a pair of crystallization rollers rotating in opposite directions, wherein the edge area in the width direction of the cast strip: The roughness R1 of the crystallization roller in the edge L1 is controlled to be less than 2 μm, where L1 is the vertical distance from the edge of the crystallization roller, and the value of L1 is ≤60 mm. The roughness R2 of the crystallization roller in the edge L1-L2 is controlled to be 2-4.5 μm, where L2 is the vertical distance from the edge of the crystallization roller, and the value of L2 is ≤300 mm; 2) subjecting the cast strip obtained in step 1) to one hot rolling process to be rolled into a hot-rolled thin strip steel with a thickness of less than 1.8 mm, and measuring the width of the edge pit area of ​​the hot-rolled thin strip steel as A; 3) Real-time monitoring of the bending roll force F of one hot rolling pass w0 , and adjust the bending roll force in real time according to the following relationship, and control the bending roll force within the range of -3 to 2MN: F w =(1+βA)F w0 , Among them, F w is the adjusted bending roll force value, β is the bending roll force adjustment parameter, where the value range of β is -0.01~0.2; 4) Real-time monitoring of the rolling force F0 of one hot rolling pass, and real-time adjustment of the rolling force according to the following relationship, and control the rolling force within the range of 10 to 25 MN: F=(1+αA)F0, Wherein, F is the adjusted rolling force value, α is the rolling force adjustment parameter, and the value range of α is 0.005~0.1; 5) In the hot rolling process, the hot rolling reduction R in the center area C of the thin strip steel is c and the hot rolling reduction R in the edge E region e Take control: The hot rolling reduction R c and hot rolling reduction R e The difference D r =R c -R e It is controlled to be no higher than 8%, wherein the central area C is a symmetrical area between 20 and 300 mm away from the center point of the thin strip width, and the edge area E is an area between 0 and 100 mm away from the edge of the thin strip.

2. The method for improving the edge pit defect of thin strip steel according to claim 1, characterized in that: In step 1), the molten steel is low carbon steel, high carbon steel, low alloy steel, high alloy steel or high silicon steel.

3. The method for improving the edge pit defect of thin strip steel according to claim 1, characterized in that: The method further comprises: The value of L1 for edge roughness control is ≤50mm.

4. The method for improving the edge pit defect of thin strip steel according to claim 1, characterized in that: The method further comprises: The value of L2 for edge roughness control is ≤200mm.

5. The method for improving the edge pit defect of thin strip steel according to claim 1, characterized in that: The method further comprises: The bending roll force is controlled within -3 to 1MN.

6. The method for improving the edge pit defect of thin strip steel according to claim 1, characterized in that: The method further comprises: The rolling force is controlled within 18 to 25 MN.

7. The method for improving the edge pit defect of thin strip steel according to claim 1, characterized in that: The method further comprises: The hot rolling reduction R c and hot rolling reduction R e The difference D r =R c -R e Controlled to be no higher than 6%.

8. The method for improving the edge pit defect of thin strip steel according to claim 7, characterized in that: The method further comprises: The hot rolling reduction R c and hot rolling reduction R e The difference D r =R c -R e Controlled to no more than 5%.

9. The method for improving the edge pit defect of thin strip steel according to any one of claims 1 to 8, characterized in that: The central area C is a symmetrical area between 40 and 200 mm from the center point of the width of the thin strip.

10. The method for improving the edge pit defect of thin strip steel according to any one of claims 1 to 8, characterized in that: The edge area E is the area between 0 and 80 mm from the edge of the thin strip.

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