Method for reducing surface slight warping defect of IF steel

Abstract

The invention provides a method for reducing IF steel surface slight warping defects, and belongs to the field of steel preparation. The method comprises the following steps: obtaining a plate blank; in a heating atmosphere with a set excess air coefficient, the plate blank is heated under set heating parameters, so that the bonding force between grain boundaries on the surface of the plate blank is improved; all-pass descaling is adopted, rough rolling is conducted on the heated plate blank at the set rough rolling outlet temperature, so that generation of oxide scales on the surface layer of the plate blank is reduced, and an intermediate blank is obtained; a high-speed steel roller is adopted, the intermediate blank is subjected to finish rolling, rolling lubricating liquid is put in the finish rolling process, and a hot rolled plate is obtained; and the hot-rolled plate is subjected to laminar cooling and coiling, and the hot-rolled coil for the galvanized IF steel is obtained. And by controlling the heating temperature and atmosphere of the IF steel plate blank, the bonding force between surface grain boundaries can be improved. And meanwhile, through IF steel rolling process control, strip steel surface micro-area damage is reduced. Therefore, the slight warping defect on the surface of the hot-rolled raw plate is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of steel preparation, and in particular to a method for reducing micro-warping defects on the surface of IF steel. Background Art

[0002] IF steel has excellent deep drawing performance, no aging, high strength, good formability and work hardening, and excellent surface quality. Therefore, IF steel is widely used in the fields of automobiles, home appliances, etc. Especially in the automotive industry, IF steel is widely used in the manufacture of automobile bodies, covers and other parts due to its excellent deep drawing performance and high strength. In addition, IF steel is also used to manufacture ultra-deep drawing parts such as oil pans.

[0003] However, the black spot defects on the surface of IF steel after galvanizing have always been a problem that has plagued the industry. The existence of black spot defects will seriously affect the aesthetics of the product and reduce the market competitiveness of the product. Especially in the automotive industry, black spot defects on parts such as the body and covering parts will directly affect the appearance quality of the entire vehicle, leaving a bad impression on consumers. In the prior art, the surface quality of the raw materials has not been improved simply from the process optimization of the galvanizing process, and the defects have not been effectively controlled. Studies have shown that the factors affecting this type of defects are complex, and some of the defects are related to the inheritance of micro-warping of hot-rolled original plates. Therefore, how to reduce the micro-warping defects of hot-rolled original plates has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method for reducing micro-warping defects on the surface of IF steel to solve the following technical problem: how to reduce micro-warping defects on the surface of hot-rolled original plates.

[0005] The present application embodiment provides a method for reducing micro-warping defects on the surface of IF steel, the method comprising:

[0006] A slab with a set chemical composition is obtained;

[0007] In a heating atmosphere with a set excess air coefficient, the slab is heated under set heating parameters to improve the inter-grain boundary bonding force on the surface of the slab;

[0008] Full-pass descaling is adopted to perform rough rolling on the heated slab at a set rough rolling outlet temperature to reduce the formation of iron oxide scale on the surface of the slab, thereby obtaining an intermediate slab;

[0009] Using high-speed steel rollers to finish-roll the intermediate billet, and adding rolling lubricant during the finish-rolling process to reduce micro-area damage on the surface of the strip steel, thereby obtaining a hot-rolled plate; and

[0010] The hot-rolled sheet is laminar-cooled and coiled to obtain a hot-rolled coil for galvanized IF steel.

[0011] Optionally, the set air excess coefficient is greater than 1.0.

[0012] Optionally, the hydrogen sulfide content in the heated coal gas is less than 150 mg / m 3 .

[0013] Optionally, the set heating parameters include: the heating temperature of the soaking section is 1100°C to 1250°C, the temperature rise amplitude of the soaking section is <50°C, and the total time in the furnace is >120min.

[0014] Optionally, the rough rolling outlet temperature is set to 1000°C to 1150°C.

[0015] Optionally, the mass concentration of the rolling lubricant is 0.15% to 0.95%.

[0016] Optionally, the inlet temperature of the refining is 980°C to 1100°C, and the final rolling temperature of the refining is 900°C to 950°C.

[0017] Optionally, the laminar cooling adopts front-stage centralized cooling.

[0018] Optionally, the coiling temperature is 600°C to 750°C.

[0019] Optionally, the degradation rate of the galvanized IF steel due to surface micro-warping slag point defects is ≤0.02%.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The embodiment of the present application provides a method for reducing micro-warping defects on the surface of IF steel. First, by controlling the heating parameters and the heating atmosphere, the austenite grain size can be refined, the inter-grain boundary bonding force on the surface of the slab can be improved, and the enrichment of harmful elements at the grain boundary can be reduced, thereby enhancing the overall performance of the slab and reducing surface defects; secondly, by adopting the full-pass descaling technology, the iron oxide scale and impurities on the surface of the slab can be completely removed, and the generation and adhesion of the iron oxide scale in the subsequent rolling process can be reduced, which helps to keep the surface of the strip clean and flat, and reduce the generation of micro-warping defects; thirdly, by adopting the high-speed steel roller in the finishing rolling process, its high hardness and wear resistance can reduce the wear and deformation during the rolling process, improve the service life of the roller and the surface quality of the strip. At the same time, an appropriate amount of rolling lubricant is added to reduce the friction and wear during the rolling process, reduce the micro-area damage and scratches on the surface of the strip, and further reduce the incidence of micro-warping defects; finally, the temperature of the strip is quickly reduced by laminar cooling, the generation and growth of iron oxide scale is inhibited, and the thickness of the iron oxide scale layer of the hot-rolled coil is reduced. Thereby reducing the micro-warping defects on the surface of the hot-rolled original plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the description, are used to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A schematic flow chart of a method for reducing micro-warping defects on the surface of IF steel provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0027] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0029] Figure 1 A schematic flow chart of a method for reducing micro-warping defects on the surface of IF steel provided in an embodiment of the present application.

[0030] like Figure 1 As shown, the present application provides a method for reducing micro-warping defects on the surface of IF steel, the method comprising:

[0031] S1. Obtaining a slab with a set chemical composition;

[0032] In the embodiments of the present application, it is necessary to ensure that the chemical composition of the slab meets the requirements of IF steel, especially the content of interstitial atoms such as C and N should be low, and at the same time, appropriate amounts of elements such as Ti and Nb should be added to fix C and N atoms to avoid the formation of interstitial solid solutions.

[0033] S2, heating the slab under set heating parameters in a heating atmosphere with a set excess air coefficient to improve the inter-grain boundary bonding force on the surface of the slab;

[0034] By reasonable heating temperature and atmosphere control, the austenite grain size is refined, the inter-grain boundary bonding strength on the slab surface is improved, and the enrichment of harmful elements at the grain boundaries is reduced.

[0035] In some embodiments, the set heating parameters include: the heating temperature of the soaking section is 1100°C to 1250°C, the temperature rise amplitude of the soaking section is <50°C, and the total time in the furnace is >120min.

[0036] It should be noted that the temperature rise amplitude refers to the temperature increment required for the slab to rise from room temperature or preheating temperature to the heating temperature of the soaking section during the heating process. It reflects the speed of the heating process and the severity of the temperature change.

[0037] Limiting the heating temperature of the soaking section to 1100℃~1250℃ can ensure that the austenite grains inside the slab are fully homogenized and avoid excessive grain growth. By limiting the heating temperature and heating time, the surface temperature of the slab can be effectively prevented from being too high and the austenite grain size can be refined. Limiting the temperature rise in the soaking section to less than 50℃ can ensure the temperature uniformity of the slab during the heating process and avoid inconsistent grain growth caused by local overheating or uneven temperature. At the same time, uniform heating temperature helps to reduce stress concentration and defects inside the slab. Limiting the total time in the furnace to more than 120min can ensure that the elements inside the slab are fully diffused and homogenized, improving the uniformity of the organization. Exemplarily, the heating temperature of the hot section can be 1100°C, 1120°C, 1150°C, 1180°C, 1200°C, 1230°C, 1250°C, etc., the temperature rise amplitude of the soaking section can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, etc., and the total time in the furnace can be 125min, 130min, 135min, 140min, 145min, 150min, 160min, 170min, 180min, etc.

[0038] In some implementations, the set air excess coefficient is greater than 1.0.

[0039] It should be noted that the excess air coefficient is defined as the ratio of the actual amount of air used for combustion to the theoretical amount of air, usually represented by α. The calculation formula is: α = V / V0, where V is the actual amount of air and V0 is the theoretical amount of air. The theoretical amount of air refers to the minimum amount of air required for complete combustion of the fuel, while the actual amount of air is the amount of air actually supplied during the combustion process.

[0040] Limiting the air excess coefficient of the heating atmosphere in the heating furnace to > 1.0 can ensure the sufficiency of the combustion process and reduce harmful gases and impurities produced by incomplete combustion. At the same time, it can also promote the oxidation reaction on the surface of the slab and help remove impurities and oil stains on the surface. Exemplarily, the air excess coefficient of the heating atmosphere in the heating furnace can be 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, etc.

[0041] In some embodiments, the hydrogen sulfide content in the heated coal gas is less than 150 mg / m 3 .

[0042] Hydrogen sulfide is a harmful reducing gas. Excessive hydrogen sulfide will lead to the accumulation of harmful elements at the grain boundaries of the slab surface, reducing the bonding strength between the grain boundaries. Strictly controlling the hydrogen sulfide content in the coal gas can reduce its adverse effects on the slab surface and improve the oxidation resistance and corrosion resistance of the slab. For example, the hydrogen sulfide content in the heated coal gas can be 80 mg / m 3 , 90mg / m 3 , 100mg / m 3 , 110mg / m 3 , 130mg / m 3 , 140mg / m 3 , 150mg / m 3 wait.

[0043] S3, using full-pass descaling, rough rolling the heated slab at a set rough rolling outlet temperature to reduce the formation of iron oxide scale on the surface of the slab, and obtaining an intermediate slab;

[0044] Full-pass descaling can completely remove the iron oxide scale and impurities on the surface of the slab, reducing the generation and adhesion of iron oxide scale during subsequent rolling. A clean surface helps reduce friction and wear during rolling, and improves the service life of the rolls and the surface quality of the strip.

[0045] In some embodiments, the rough rolling outlet temperature is set to be 1000°C to 1150°C.

[0046] Rough rolling is carried out in the austenite region, and the rough rolling outlet temperature is limited to 1000-1150°C, which can ensure that the slab maintains sufficient plasticity and toughness during the rough rolling process and avoid the generation of cracks and fractures. At the same time, it helps to reduce the formation and adhesion of iron oxide scale and improve the efficiency and surface quality of subsequent finishing rolling. Exemplarily, the rough rolling outlet temperature can be 1000°C, 1020°C, 1050°C, 1080°C, 1100°C, 1120°C, 1150°C, etc.

[0047] S4, using high-speed steel rollers to perform finish rolling on the intermediate billet, and adding rolling lubricant during the finish rolling process to reduce micro-area damage on the surface of the strip steel, thereby obtaining a hot-rolled plate;

[0048] High-speed steel rolls have high hardness and wear resistance, which can reduce wear and deformation during rolling, improve the service life of the rolls and the surface quality of the strip. At the same time, high-speed steel rolls can also reduce the damage to the strip surface caused by shear stress during rolling, and reduce the incidence of micro-warping defects.

[0049] In some embodiments, the mass concentration of the rolling lubricant is 0.15% to 0.95%.

[0050] Rolling lubrication can reduce friction and wear during rolling, reduce friction heat between the rolls and the strip, and reduce rolling temperature. Appropriate rolling lubrication can also reduce micro-area damage and scratches on the surface of the strip, and improve the surface quality and finish of the strip. For example, the mass concentration of the rolling lubricant is 0.15%, 0.25%, 0.45%, 0.65%, 0.85%, 0.95%, etc.

[0051] In some embodiments, the inlet temperature of the refining is 980°C to 1100°C, and the final rolling temperature of the refining is 900°C to 950°C.

[0052] S5. laminar cooling and coiling the hot-rolled sheet to obtain a hot-rolled coil for galvanized IF steel.

[0053] Laminar cooling can quickly reduce the temperature of the strip, inhibit the formation and growth of iron oxide scale, and reduce the thickness of the hot-rolled coil iron oxide scale.

[0054] In some embodiments, the laminar cooling uses front-stage concentrated cooling.

[0055] The front-end concentrated cooling can ensure that the strip has uniform temperature distribution and lower surface temperature before coiling, which can reduce the thickness of the iron oxide layer of the hot-rolled coil. At the same time, it is beneficial to improve the coiling quality and reduce the defects in the coiling process.

[0056] In some embodiments, the coiling temperature is 600°C to 750°C.

[0057] The appropriate coiling temperature can ensure that the strip maintains sufficient plasticity and toughness during the coiling process, avoiding the occurrence of coiling cracks and fractures. At the same time, this temperature range also helps to reduce the residual stress and deformation inside the strip, and improve the dimensional stability and surface quality after coiling. For example, the coiling temperature can be 600°C, 620°C, 650°C, 680°C, 700°C, 720°C, 750°C, etc.

[0058] In some embodiments, the degradation rate of the galvanized IF steel due to surface micro-slag point defects is ≤0.02%.

[0059] The embodiment of the present application can improve the surface grain boundary bonding strength by controlling the heating temperature and atmosphere of the IF steel slab. At the same time, by controlling the IF steel rolling process, the micro-area damage on the surface of the strip steel is reduced. Thus, the surface quality of the hot-rolled substrate is significantly improved, and the occurrence of slag spots on the surface after galvanizing is reduced.

[0060] The advantages of a method for reducing micro-warping defects on the surface of IF steel provided in the embodiment of the present application are summarized as follows:

[0061] (1) Improving the surface quality of slabs: By precisely controlling the chemical composition of slabs, especially reducing the content of interstitial atoms such as C and N, and adding appropriate amounts of elements such as Ti and Nb, the formation of interstitial solid solutions is effectively avoided, thereby improving the initial quality of slabs. At the same time, reasonable heating temperature and atmosphere control (such as heating temperature in the soaking section, temperature increase range, furnace time, air excess coefficient and strict control of hydrogen sulfide content in coal gas) not only refines the austenite grain size, but also improves the inter-grain boundary bonding strength on the slab surface, while reducing the enrichment of harmful elements at the grain boundaries, further improving the surface quality of slabs.

[0062] (2) Reduce the generation of iron oxide scale: The full-pass descaling technology can completely remove the iron oxide scale and impurities on the surface of the slab, reducing the generation and adhesion of iron oxide scale during the subsequent rolling process, thereby improving the surface quality of the strip. At the same time, rough rolling is carried out in the austenite zone and the rough rolling outlet temperature is strictly controlled, which helps to reduce the generation and adhesion of iron oxide scale and provides better conditions for subsequent finishing rolling.

[0063] (3) Reduce micro-area damage on the strip surface: High-speed steel rolls are used in the finishing rolling process. Their high hardness and wear resistance reduce wear and deformation during the rolling process, and improve the service life of the rolls and the surface quality of the strip. At the same time, adding an appropriate amount of rolling lubricant reduces friction and wear during the rolling process, reduces micro-area damage and scratches on the strip surface, and further improves the surface quality and finish of the strip.

[0064] (4) Optimize the cooling and coiling process: Laminar cooling adopts the front-stage centralized cooling method to ensure that the strip has a uniform temperature distribution and a lower surface temperature before coiling, reduce the thickness of the hot rolled coil iron oxide layer, improve the coiling quality and reduce the generation of defects. At the same time, the appropriate coiling temperature ensures that the strip maintains sufficient plasticity and toughness during the coiling process, avoids the generation of coiling cracks and fractures, and reduces the residual stress and deformation inside the strip, improving the dimensional stability and surface quality after coiling.

[0065] (5) Significantly improve the quality of galvanized IF steel: Through the comprehensive implementation of the above measures, the surface quality of the hot-rolled base plate is significantly improved, thereby reducing the occurrence of surface slag spots after galvanizing, reducing the degradation rate of galvanized IF steel due to surface micro-warping and slag point defects, and improving the quality and market competitiveness of the galvanized outer plate.

[0066] In summary, this method effectively improves the problem of micro-warping on the surface of IF steel by precisely controlling each link in the production process, significantly improves the quality and market competitiveness of galvanized IF steel, and provides strong technical support for production optimization and product upgrading of steel enterprises.

[0067] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0068] Example 1

[0069] This embodiment uses the IF steel plate composition system for production. The composition of the typical steel is: C: 0.003%, Si: 0.004%, Mn: 0.12%, S: 0.009%, P: 0.08%, Ti: 0.035%, and the rest is iron and residue. The slab thickness is 237mm, the heating time of the heating furnace is 120 minutes, the steel tapping temperature is 1100℃, and the temperature rise range of the soaking section is 10℃; the air excess coefficient in the heating furnace atmosphere is 1.05, and the hydrogen sulfide content in the coal gas is 90mg / m 3 . Rough rolling adopts 3+3 mode, full-pass descaling, and the outlet temperature of rough rolling R2 is 980℃. Finishing rolling F1~F7 uses high-speed steel rollers, rolling lubrication, rolling lubrication concentration 0.5%, inlet temperature 980℃, final rolling temperature 930℃, and cooling water between F1~F5 stands; laminar cooling adopts front-end centralized cooling process, and coiling temperature 710℃. This production is 1,000 tons, and the final galvanized product has a degradation rate of 0.02% due to surface micro-warping slag point defects.

[0070] Example 2

[0071] This embodiment uses the IF steel plate composition system for production. The composition of the typical steel is: C: 0.003%, Si: 0.004%, Mn: 0.12%, S: 0.009%, P: 0.08%, Ti: 0.035%, and the rest is iron and residue. The slab thickness is 237mm, the heating time of the heating furnace is 200 minutes, the steel tapping temperature is 1220℃, and the temperature rise range of the soaking section is 35℃; the air excess coefficient in the heating furnace atmosphere is 1.10, and the hydrogen sulfide content in the coal gas is 120mg / m 3. Rough rolling adopts 3+3 mode, full-pass descaling, and the outlet temperature of rough rolling R2 is 1030℃. Finishing rolling F1~F7 uses high-speed steel rollers, rolling lubrication, rolling lubrication concentration is 0.5%, inlet temperature is 1030℃, final rolling temperature is 930℃, and cooling water is added between F1~F5 stands; laminar cooling adopts front-end centralized cooling process, and coiling temperature is 710℃. This production is 1,200 tons, and the final galvanized product has a degradation rate of 0% due to surface micro-warping slag point defects.

[0072] Example 3

[0073] This embodiment uses the IF steel plate composition system for production. The composition of the typical steel produced is: C: 0.003%, Si: 0.004%, Mn: 0.12%, S: 0.009%, P: 0.08%, Ti: 0.035%, and the rest is iron and residue. The slab thickness is 237mm, the heating time of the heating furnace is 250 minutes, the steel tapping temperature is 1250℃, and the temperature rise range of the soaking section is 45℃; the air excess coefficient in the heating furnace atmosphere is 1.20, and the hydrogen sulfide content in the coal gas is 140mg / m 3 . Rough rolling adopts 3+3 mode, full-pass descaling, and the outlet temperature of rough rolling R2 is 1100℃. Finishing rolling F1~F7 uses high-speed steel rollers, rolling lubrication, rolling lubrication concentration is 0.5%, inlet temperature is 1100℃, final rolling temperature is 930℃, and cooling water is added between F1~F5 stands; laminar cooling adopts front-end centralized cooling process, and coiling temperature is 710℃. This production is 1,500 tons, and the final galvanized product has a degradation rate of 0.01% due to surface micro-warping slag point defects.

[0074] Comparative Example 1

[0075] This comparative example uses the IF steel plate composition system for production. The composition of the typical steel is: C: 0.003%, Si: 0.004%, Mn: 0.12%, S: 0.009%, P: 0.08%, Ti: 0.035%, and the rest is iron and residue. The slab thickness is 237mm, the heating time of the heating furnace is 200 minutes, the steel tapping temperature is 1260℃, and the temperature rise range of the soaking section is 60℃; the air excess coefficient in the heating furnace atmosphere is 0.95, and the hydrogen sulfide content in the coal gas is 180mg / m3. The rough rolling adopts the 3+3 mode, 4 passes of descaling are used, and the outlet temperature of the rough rolling R2 is 1050℃. The finishing rolling F5~F7 uses infinite cold hard rollers, no rolling lubrication, the inlet temperature is 1050℃, the final rolling temperature is 930℃, and the cooling water between the F1~F5 stands is put in; the laminar cooling adopts the front-stage centralized cooling process, and the coiling temperature is 710℃. This production is 1,000 tons, and the final galvanized product has a degradation rate of 10% due to surface micro-warping and slag point defects.

[0076] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0077] In the embodiment of the present application, a production method for controlling micro-warping defects on the surface of IF steel is provided, which significantly improves the surface quality of the hot-rolled substrate, thereby reducing the occurrence of surface slag spots after galvanizing. The degradation rate of galvanized IF steel due to micro-warping slag spot defects on the surface is ≤0.02%.

[0078] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for reducing micro-warping defects on the surface of IF steel, the method comprising: A slab with a set chemical composition is obtained; In a heating atmosphere with a set excess air coefficient, the slab is heated under set heating parameters to improve the inter-grain boundary bonding force on the surface of the slab; Full-pass descaling is adopted to perform rough rolling on the heated slab at a set rough rolling outlet temperature to reduce the formation of iron oxide scale on the surface of the slab, thereby obtaining an intermediate slab; The intermediate billet is finish-rolled by high-speed steel rollers, and a rolling lubricant is added during the finish-rolling process to reduce micro-area damage on the surface of the strip steel, thereby obtaining a hot-rolled plate; as well as The hot-rolled sheet is laminar-cooled and coiled to obtain a hot-rolled coil for galvanized IF steel.

2. The method according to claim 1, characterized in that The set air excess coefficient is greater than 1.

0.

3. The method according to claim 1, characterized in that The hydrogen sulfide content in the heated coal gas is less than 150 mg / m 3 .

4. The method according to claim 1, characterized in that: The set heating parameters include: the heating temperature of the soaking section is 1100°C to 1250°C, the temperature rise amplitude of the soaking section is less than 50°C, and the total time in the furnace is greater than 120 minutes.

5. The method according to claim 1, characterized in that The rough rolling outlet temperature is set to 1000°C to 1150°C.

6. The method according to claim 1, characterized in that The mass concentration of the rolling lubricant is 0.15% to 0.95%.

7. The method according to claim 1, characterized in that The inlet temperature of the refining is 980°C to 1100°C, and the final rolling temperature of the refining is 900°C to 950°C.

8. The method according to claim 1, characterized in that The laminar cooling adopts front-stage centralized cooling.

9. The method according to claim 1, characterized in that: The coiling temperature is 600°C to 750°C.

10. The method according to claim 1, characterized in that The degradation rate of the galvanized IF steel due to surface micro-warping slag point defects is ≤0.02%.

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