Steel plate with clean surface and manufacturing process thereof

Abstract

The invention relates to the technical field of metallurgical steel rolling, and provides a clean-surface steel plate and a manufacturing process thereof, the clean-surface steel plate comprises the following components by weight percentage: 0.15%-0.17% of C, less than or equal to 0.05% of Si, 1.28%-1.33% of Mn, 0.012%-0.020% of Ti, and the balance Fe and inevitable impurities. Through the technical scheme, the problems of poor surface quality and low mechanical strength of the steel plate in the related technology are solved.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical steel rolling, and in particular to a clean surface steel plate and a manufacturing process thereof. Background Art

[0002] Steel plates are widely used in industries such as bridges, construction, automobile manufacturing, precision machining and engineering machinery manufacturing. These fields require steel plates to have extremely high surface quality and high mechanical strength. However, in the manufacturing process of steel plates, due to the objective existence of air oxidation, the surface of hot-rolled steel plates will contact the air during the heating and rolling processes. Under high temperature conditions, the oxygen in the air will continue to react with the iron atoms and silicon atoms in the steel plates to form an uneven oxide surface. The rolling process is unevenly pressed, or the high-pressure water is not completely removed. The primary and secondary iron oxide scales on the steel plates are unevenly retained on the surface of the steel plates, resulting in uneven reflection of the steel plates, or uneven spots, poor visual observation, and inconsistent touch with fingers. If the cleanliness, surface quality and mechanical strength of the steel surface are low, then the welding quality, coating and surface treatment effects will deteriorate, corrosion resistance will decrease, and service life will decrease in engineering machinery manufacturing. Therefore, more and more engineering machinery manufacturers have put forward higher requirements for the surface quality, surface cleanliness and mechanical strength of steel plates. Summary of the invention

[0003] The present invention provides a clean surface steel plate and a manufacturing process thereof, which solves the problems of poor surface quality and low mechanical strength of the steel plate in the related art.

[0004] The technical solution of the present invention is as follows: The invention provides a clean surface steel plate, which is composed of the following components in weight percentage: C 0.15%-0.17%, Si≤0.05%, Mn 1.28%-1.33%, Ti 0.012%-0.020%, and the balance is Fe and inevitable impurities.

[0005] As a further technical solution, the clean surface steel plate is composed of the following components in weight percentage: C 0.15%, Si 0.03%, Mn 1.33%, Ti 0.014%, and the balance is Fe and unavoidable impurities.

[0006] In the present invention, by further limiting the composition of each component in the steel plate, the surface quality and mechanical strength of the steel plate can be further improved.

[0007] The present invention also proposes a manufacturing process for a clean surface steel plate, the manufacturing process comprising the following steps: S1. preparing raw materials according to the components, smelting to obtain smelted molten steel, deoxidizing and refining to obtain refined molten steel, and continuously casting to obtain slabs; S2. After the slab is heated, rough rolled and finish rolled, a steel plate is obtained.

[0008] As a further technical solution, the refining is to perform LF refining and RH refining in sequence.

[0009] As a further technical solution, the deoxidizer used for deoxidation in S1 is an aluminum block.

[0010] As a further technical solution, after the aluminum block is added into the smelted molten steel, the aluminum content in the smelted molten steel is 0.023% to 0.033%.

[0011] As a further technical solution, the heating temperature in S1 is 1040-1100°C.

[0012] As a further technical solution, the heating time in S1 is 2.5 to 4.5 hours.

[0013] The formation process of iron oxide scale is also a diffusion process of oxygen and iron. Oxygen diffuses from the surface to the inside of the iron, while iron diffuses to the outside. When the concentration of oxygen in the outer layer is high and the concentration of iron is low, high-valent oxides of iron are generated; when the concentration of iron in the inner layer is high and the concentration of oxygen is low, low-valent oxides of oxygen are generated, so the structure of the iron oxide scale is layered. The traditional slab heating temperature is higher than 1230°C, at least 1190°C, which will seriously oxidize the surface of the slab in the heating furnace, thicken the iron oxide scale on the surface of the slab, and cause serious metal burnout, which is not economical. The present invention adopts a heating temperature of 1040~1100°C, which can reduce the severity of oxidation in the furnace, improve the surface quality and mechanical strength of the steel plate, and at the same time improve the metal yield, reduce costs and increase efficiency.

[0014] The present invention controls the silicon content in the steel plate to overcome the generation and adhesion of Fe2SiO4, and cooperates with low-temperature heating to reduce excessive oxidation, thereby further improving the surface quality and mechanical properties of the steel plate.

[0015] As a further technical solution, the starting rolling temperature of the rough rolling in S2 is 1010~1080℃.

[0016] As a further technical solution, the final rolling temperature of the rough rolling in S2 is 930-970°C.

[0017] As a further technical solution, the starting temperature of the finishing rolling in S2 is 890-920°C.

[0018] As a further technical solution, the final rolling temperature of the finishing rolling in S2 is 770-810°C.

[0019] As a further technical solution, the rough rolling is performed for a total of 7 times.

[0020] As a further technical solution, the number of passes of the finish rolling is 6 times in total.

[0021] As a further technical solution, the equipment used for the rough rolling and the finish rolling are both four-roll reversible rolling mills.

[0022] As a further technical solution, during the rough rolling, descaling is performed in the first pass, the fifth pass and the seventh pass.

[0023] As a further technical solution, during the finish rolling, descaling is performed in the first pass, the third pass and the sixth pass.

[0024] As a further technical solution, the high-pressure water pressure used for descaling is 22~25MPa.

[0025] In the present invention, during the four-roll rough rolling and four-roll finishing rolling stages, high-pressure water of more than 22 MPa is sprayed in reasonable distribution passes, and the final rolling temperature of the finishing rolling is reduced to below 810°C, so that the secondary iron oxide scale of the steel plate is uniform and firmly bonded to the substrate.

[0026] In the present invention, the descaling process adopts 22-25 MPa high-pressure water, which not only provides the prerequisite for improving the surface quality, but also saves energy consumption, improves quality and saves costs.

[0027] As a further technical solution, the thickness of the steel plate is 6~40mm.

[0028] Through the preparation method of the clean surface steel plate of the present invention, coupled with strengthening the maintenance and management of the equipment, it is ensured that the roller body and the straightening roller body are clean, each roller is a perfect circle with a smooth surface, and scratches on the upper and lower surfaces of the steel plate and foreign matter are prevented from being pressed in; and protective covers are provided on the lifting and transporting slings, so as to improve and protect the surface quality of the steel plate throughout the whole process, and ensure that the high surface quality of the steel plate is always maintained from the preparation to the delivery to the consumer.

[0029] The working principle and beneficial effects of the present invention are: In the present invention, by limiting the four components of C, Si, Mn and Ti in the steel plate, the reaction rate of iron and oxygen can be slowed down, the amount of iron oxide scale generated can be reduced, the problem of roughness and unevenness on the surface can be reduced, the appearance can be improved, the quality of steel can be improved, and a steel plate with extremely high surface quality can be obtained. The limit of Si≤0.05% can make the pores in the iron oxide scale smaller and more evenly distributed, so that cracks can be more easily extended to the base metal along the pores, the iron oxide scale can be more effectively peeled off during descaling, the color of the iron scale tends to be more blue-gray, the surface will be cleaner, and the mechanical properties of the steel plate are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0031] Figure 1 This is a product picture of the steel plate in Example 1 of the present invention; Figure 2 This is a product image of a steel plate in Example 2 of the present invention; Figure 3 This is a product picture of the steel plate in Example 3 of the present invention; Figure 4 This is a product picture of the steel plate in Comparative Example 1 of the present invention; Figure 5 This is a product picture of the steel plate in Comparative Example 2 of the present invention; Figure 6 This is a product picture of the steel plate in Comparative Example 3 of the present invention; Figure 7 This is a product picture of the steel plate in Comparative Example 4 of the present invention; Figure 8 This is a product picture of the steel plate in Comparative Example 5 of the present invention; Fig. 9 This is a product picture of the steel plate in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments 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.

[0033] In the following examples and comparative examples: Silicon manganese alloy: Si 18wt%, Mn 16wt%, the rest is Fe; Aluminum block: 99wt%.

[0034] Example 1 The clean surface steel plate is composed of the following components in mass percentage: C 0.16%, Si 0.04%, Mn 1.28%, Ti0.012%, and the balance is Fe and unavoidable impurities; The method for preparing a clean surface steel plate comprises the following steps: S1. Prepare raw materials according to the composition, smelt to obtain molten steel, add aluminum blocks for deoxidation, and then perform LF refining and RH refining to obtain refined molten steel, and continuously cast to obtain slabs; wherein after the aluminum blocks are added to the molten steel, the aluminum content in the molten steel is 0.028%; S2. The slab is kept at 1068°C for 3.5 hours, rough rolled, finish rolled, and cooled to obtain a steel plate with a thickness of 40 mm.

[0035] Among them, the starting rolling temperature of rough rolling is 1036℃, and the final rolling temperature is 965℃; the starting rolling temperature of finishing rolling is 918℃, and the final rolling temperature is 807℃; the equipment used for rough rolling and finishing rolling is a four-roll reversible rolling mill; There are 7 rough rolling passes, among which 23MPa water pressure is used for descaling in the first, fifth and seventh passes; there are 6 finishing rolling passes, among which 23MPa water pressure is used for descaling in the first, third and sixth passes.

[0036] Steel plate tensile test results: Yield strength (Rel): 443MPa, tensile strength (Rm): 539MPa, elongation after fracture (A): 21%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 215J; Steel plate visual inspection results: The visual inspection is qualified, the surface of the steel plate has a thin iron oxide scale, and the visual reflection is as clean as a mirror. Figure 1 shown.

[0037] Example 2 The clean surface steel plate is composed of the following components in mass percentage: C 0.17%, Si 0.05%, Mn 1.28%, Ti0.015%, and the balance is Fe and unavoidable impurities; The method for preparing a clean surface steel plate comprises the following steps: S1. Prepare raw materials according to the composition, smelt to obtain molten steel, add aluminum blocks for deoxidation, and then perform LF refining and RH refining to obtain refined molten steel, and continuously cast to obtain slabs; wherein after the aluminum blocks are added to the molten steel, the aluminum content in the molten steel is 0.029%; S2. The slab is kept at 1057°C for 3.8 hours, rough rolled, finish rolled, and cooled to obtain a steel plate with a thickness of 6 mm.

[0038] Among them, the starting rolling temperature of rough rolling is 1022℃, and the final rolling temperature is 959℃; the starting rolling temperature of finishing rolling is 919℃, and the final rolling temperature is 787℃; the equipment used for rough rolling and finishing rolling is a four-roll reversible rolling mill; There are 7 rough rolling passes, among which 23MPa water pressure is used for descaling in the first, fifth and seventh passes; there are 6 finishing rolling passes, among which 23MPa water pressure is used for descaling in the first, third and sixth passes.

[0039] Steel plate tensile test results: Yield strength (Rel): 399MPa, tensile strength (Rm): 517MPa, elongation after fracture (A): 22%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 79J.

[0040] Steel plate visual inspection results: The visual inspection is qualified, the surface of the steel plate has a thin iron oxide scale, and the visual reflection is as clean as a mirror. Figure 2 shown.

[0041] Example 3 The clean surface steel plate is composed of the following components in mass percentage: C 0.15%, Si 0.03%, Mn 1.33%, Ti0.014%, and the balance is Fe and unavoidable impurities; The method for preparing a clean surface steel plate comprises the following steps: S1. Prepare raw materials according to the components, smelt to obtain molten steel, add aluminum blocks for deoxidation, and then perform LF refining and RH refining to obtain refined molten steel, and continuously cast to obtain slabs; wherein after the aluminum blocks are added to the molten steel, the aluminum content in the molten steel is 0.031%; S2. The slab is kept at 1061°C for 3.6 hours, rough rolled, finish rolled, and cooled to obtain a steel plate with a thickness of 25 mm.

[0042] Among them, the starting rolling temperature of rough rolling is 1031℃, and the final rolling temperature is 958℃; the starting rolling temperature of finishing rolling is 912℃, and the final rolling temperature is 802℃; the equipment used for rough rolling and finishing rolling is a four-roll reversible rolling mill; There are 7 rough rolling passes, among which the first, fifth and seventh passes are descaled with a water pressure of 22.5MPa; there are 6 finishing rolling passes, among which the first, third and sixth passes are descaled with a water pressure of 22.5MPa.

[0043] Steel plate tensile test results: Yield strength (Rel): 421MPa, tensile strength (Rm): 523MPa, elongation after fracture (A): 22%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 213J.

[0044] Steel plate visual inspection results: The visual inspection is qualified, the steel plate surface is lightly oxidized, uniformly, bluish in color, thin, and visually reflective like a mirror. Figure 3 shown.

[0045] Comparative Example 1 Compared with Example 1, the only difference of this comparative example is that the aluminum block is replaced with an equal amount of ferrosilicon manganese alloy.

[0046] Steel plate tensile test results: Yield strength (Rel): 382MPa, tensile strength (Rm): 510MPa, elongation after fracture (A): 24%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 47J.

[0047] Steel plate visual inspection results: The surface quality is average. The steel plate surface is not reflective and has uneven iron oxide spots. The test results are as follows: Figure 4 shown.

[0048] Comparative Example 2 Compared with Example 1, the only difference of this comparative example is that 1068° C. in step S2 is replaced by 1227° C.

[0049] Steel plate tensile test results: Yield strength (Rel): 390MPa, tensile strength (Rm): 513MPa, elongation after fracture (A): 23%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 43J.

[0050] Steel plate visual inspection results: The surface quality is average. The steel plate surface is not reflective and has uneven iron oxide spots. The test results are as follows: Figure 5 shown.

[0051] Comparative Example 3 Compared with Example 1, the difference of this comparative example is that the temperature of the rough rolling in this comparative example is 1175°C.

[0052] Steel plate tensile test results: Yield strength (Rel): 363MPa, tensile strength (Rm): 497MPa, elongation after fracture (A): 23%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 86J.

[0053] Steel plate visual inspection results: The surface quality is average. The steel plate surface is not reflective and has uneven iron oxide spots. The test results are as follows: Figure 6 shown.

[0054] Comparative Example 4 Compared with Example 1, the difference of this comparative example is that the temperature of the rough rolling in this comparative example is 1067°C.

[0055] Steel plate tensile test results: Yield strength (Rel): 367MPa, tensile strength (Rm): 503MPa, elongation after fracture (A): 24%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 113J.

[0056] Steel plate visual inspection results: The surface quality is average. The steel plate surface is not reflective and has uneven iron oxide spots. The test results are as follows: Figure 7 shown.

[0057] Comparative Example 5 Compared with Example 1, the only difference of this comparative example is that Si is 0.36%.

[0058] Steel plate tensile test results: Yield strength (Rel): 375MPa, tensile strength (Rm): 522MPa, elongation after fracture (A): 23%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 91J.

[0059] Steel plate visual inspection results: The surface quality is average. The steel plate surface is not reflective and has uneven iron oxide spots. The test results are as follows: Figure 8 shown.

[0060] Comparative Example 6 Compared with Example 1, the only difference of this comparative example is that 1068° C. in step S2 is replaced by 1227° C., and Si is 0.36%.

[0061] Steel plate tensile test results: Yield strength (Rel): 367MPa, tensile strength (Rm): 498MPa, elongation after fracture (A): 22%, bending b=2a, d=3a, 180º good, impact energy at room temperature: 39J.

[0062] Steel plate visual inspection results: The surface quality is average. The steel plate surface is not reflective and has uneven iron oxide spots. The test results are as follows: Fig. 9 shown.

[0063] Analysis of the measurement results of the steel plates in Examples 1 to 3 and Comparative Examples 1 to 6: In the present invention, the yield strength, tensile strength, bending performance, toughness and surface quality of the steel plates in Examples 1 to 3 are better than those in Comparative Examples 1 to 6, indicating that the yield strength, tensile strength, bending performance, toughness and surface quality of the steel plates can be improved by limiting the content of components in the steel plates and limiting the manufacturing process in the present invention.

[0064] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A clean surface steel plate, characterized in that: It is composed of the following components in weight percentage: C 0.15%~0.17%, Si≤0.05%, Mn 1.28%~1.33%, Ti 0.012%~0.020%, and the balance is Fe and inevitable impurities.

2. The clean surface steel plate according to claim 1, characterized in that: The clean surface steel plate is composed of the following components in weight percentage: C 0.15%, Si 0.03%, Mn 1.33%, Ti 0.014%, and the balance is Fe and inevitable impurities.

3. A process for manufacturing a clean surface steel plate according to any one of claims 1 to 2, characterized in that: The manufacturing process comprises the following steps: S1. preparing raw materials according to the components, smelting to obtain smelted molten steel, deoxidizing and refining to obtain refined molten steel, and continuously casting to obtain slabs; S2. After the slab is heated, rough rolled and finish rolled, a steel plate is obtained.

4. According to the manufacturing process of a clean surface steel plate according to claim 3, the deoxidizer used for deoxidation in S1 is an aluminum block.

5. The manufacturing process of a clean surface steel plate according to claim 3, characterized in that: The heating temperature in S2 is 1040-1100°C.

6. The manufacturing process of a clean surface steel plate according to claim 3, characterized in that: The starting rolling temperature of the rough rolling in S2 is 1010-1080°C.

7. The manufacturing process of a clean surface steel plate according to claim 3, characterized in that: The final rolling temperature of the rough rolling in S2 is 930-970°C.

8. The manufacturing process of a clean surface steel plate according to claim 3, characterized in that: The start rolling temperature of the finishing rolling in S2 is 890-920°C.

9. The manufacturing process of a clean surface steel plate according to claim 3, characterized in that: The final rolling temperature of the finishing rolling in S2 is 770-810°C.

10. The manufacturing process of a clean surface steel plate according to claim 3, characterized in that: The thickness of the steel plate is 6-40 mm.

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