Cold-rolled steel strip and method for producing the same

Abstract

The present application discloses a cold-rolled strip steel and a production method thereof. The production method comprises the following steps: smelting of molten steel, continuous casting, hot rolling, pickling, cold rolling, continuous annealing, skin pass and oiling treatment. The molten steel comprises C: 0.01-0.04%, Si: ≤0.08%, Mn: 0.10-0.40%, P: ≤0.015%, S: ≤0.015%, and the rest is Fe and impurities. The surface roughness of the fifth rack roller is 1.2-2.0 μm during cold rolling. The surface roughness of the skin pass roller is 2.5-3.5 μm, the RPc peak count value is 70-100, and the blowing unit adopts hot air drying except the last row of nozzles, and the hot air temperature is 80-120 ℃. The oiling treatment adopts double knife beams arranged in front and back, the knife slit of one of the knife beams gradually widens from the transmission end to the operation end, and the knife slit of the other knife beam gradually narrows from the transmission end to the operation end.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel material preparation, and particularly relates to a cold-rolled strip steel and a production method thereof. BACKGROUND

[0002] Cold-rolled strip steel is widely used in household appliances, automobile manufacturing, construction industry, mechanical industry, precision instruments, office supplies, pressure vessels, power systems, food packaging and other industries due to its good surface finish, thin specification, good formability and other characteristics. However, the surface of the cold-rolled strip steel needs to be treated, such as internal and external coating, in many product applications. A commonly used surface treatment method is silane treatment.

[0003] Silane treatment is a process of treating the surface of metal materials with organosilane as the main raw material. Compared with traditional phosphating, silane treatment has the advantages of no harmful heavy metal ions, no phosphorus, short treatment time, no need for heating, no sediment generated during the treatment process, and simple control. However, silane treatment is prone to water washing spots on the surface of the cold-rolled strip steel, which affects the water washing effect and cannot meet the application requirements of downstream customers. Therefore, the production method of the cold-rolled strip steel needs to be improved to eliminate the water washing spots on the surface of the strip steel after subsequent silane treatment. SUMMARY

[0004] The present application aims to provide a cold-rolled strip steel and a production method thereof to solve the problem of water washing spots on the surface of the cold-rolled strip steel after subsequent silane treatment.

[0005] To achieve the above-mentioned application purpose, an embodiment of the present application provides a production method of a cold-rolled strip steel, which comprises sequentially performed molten steel smelting, continuous casting, hot rolling, pickling, cold rolling, continuous annealing, flattening and oiling treatment processes.

[0006] The chemical composition of the molten steel obtained by the molten steel smelting process includes, in terms of mass percentage: C: 0.01-0.04%, Si≤0.08%, Mn: 0.10-0.40%, P≤0.015%, S≤0.015%, and the rest is Fe and unavoidable impurities.

[0007] The cold rolling process adopts a five-stand cold rolling mill to cold roll the hot-rolled plate into a cold-rolled strip steel, wherein the surface roughness of the rollers of the fifth stand is 1.2-2.0 μm.

[0008] In the flattening process, after flattening is performed on the flattening machine, drying is performed on the blowing unit. The surface roughness of the flattening rollers of the flattening machine is 2.5-3.5 μm, and the RPc peak count value of the flattening rollers is 70-100. The blowing unit has 4-6 rows of nozzles. The last row of nozzles uses normal temperature compressed air for drying, and the remaining rows of nozzles use hot air for drying. The temperature of the hot air is 80-120°C.

[0009] In the oiling treatment process, the oiling machine adopts double knife beams arranged in front and back to perform oiling, the knife slit of one of the knife beams gradually widens from the transmission end to the operation end, and the knife slit of the other of the knife beams gradually narrows from the transmission end to the operation end.

[0010] As a further improvement of the embodiment of the present application, in the oiling treatment process, the absolute value of the difference between the width of the knife slit of each of the knife beams at the transmission end and at the operation end is 0.02-0.06 mm.

[0011] As a further improvement of the embodiment of the present application, in the oiling treatment process, if the knife slit at the transmission end is narrower than the knife slit at the operation end, the width of the knife slit at the transmission end is 0.04-0.06 mm, and the width of the knife slit at the operation end is 0.06-0.12 mm.

[0012] If the knife slit at the transmission end is wider than the knife slit at the operation end, the width of the knife slit at the transmission end is 0.06-0.12 mm, and the width of the knife slit at the operation end is 0.04-0.06 mm.

[0013] As a further improvement of the embodiment of the present application, in the oiling treatment process, the single-side oiling amount of the cold-rolled strip steel is 300-800 mg / m 2 .

[0014] As a further improvement of the embodiment of the present application, if the service stroke of the smoothing roller is ≤50 km, the soaking temperature of the continuous annealing process is controlled to be 780-820℃, and the reduction of the smoothing process is controlled to be 0.8-1.2%.

[0015] If the service stroke of the smoothing roller is >50 km, the soaking temperature of the continuous annealing process is controlled to be 820-840℃, and the reduction of the smoothing process is controlled to be 1.2-1.5%.

[0016] As a further improvement of the embodiment of the present application, if the soaking temperature of the continuous annealing process is 780-800℃, the reduction of the smoothing process is controlled to be 0.8-1.0%.

[0017] If the soaking temperature of the continuous annealing process is 800-820℃, the reduction of the smoothing process is controlled to be 1.0-1.2%.

[0018] As a further improvement of the embodiment of the present application, the thickness of the continuous casting billet obtained in the continuous casting process is 180-220 mm, and the continuous casting speed is 1.0-1.5 m / min.

[0019] As a further improvement of the embodiment of the present application, in the hot rolling process, after the continuous casting billet obtained from the continuous casting process is heated in a heating furnace, rough rolling, finish rolling, laminar cooling and coiling are sequentially performed to obtain a hot-rolled coil with a thickness of 2-6 mm, wherein the discharge temperature of the continuous casting billet in the heating furnace is ≥1200℃, the finish rolling temperature is 840-900℃, and the coiling temperature is 660-720℃.

[0020] As a further improvement of the embodiment of the present application, in the cold rolling process, the hot-rolled coil after pickling is cold-rolled into a cold-rolled strip with a thickness of 0.5-1.5 mm, wherein the cold-rolling reduction rate is 75-85%.

[0021] To achieve the above-mentioned purposes, the embodiment of the present application further provides a cold-rolled strip prepared by the production method of the cold-rolled strip as described above.

[0022] Compared with the prior art, the production method of the cold-rolled strip of the present application and the cold-rolled strip prepared by the production method have the following beneficial effects: through chemical composition scheme design and process design of each process, the finally prepared cold-rolled strip has excellent mechanical properties, the yield strength is 185-230 MPa, the tensile strength is 290-370 MPa, and the elongation is ≥37%, and the occurrence of water spot after silane treatment of the finally prepared cold-rolled strip is avoided, which can meet the application requirements of the downstream customers on the surface quality of the cold-rolled strip and the apparent beautification after silane treatment. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The apparent photo of the cold-rolled strip prepared in Example 1 of the present application after silane treatment;

[0024] Figure 2 The apparent photo of the cold-rolled strip prepared in Example 2 of the present application after silane treatment;

[0025] Figure 3 The apparent photo of the cold-rolled strip prepared in the comparative example of the present application after silane treatment. DETAILED DESCRIPTION

[0026] The technical solutions of the present application are further described below in combination with specific embodiments, but the scope of protection is not limited to the description.

[0027] The present application provides a production method of a cold-rolled strip and a cold-rolled strip prepared by the production method. The production method of the cold-rolled strip comprises sequentially performed molten steel smelting, continuous casting, hot rolling, pickling, cold rolling, continuous annealing, flattening and oiling treatment processes. Each process is described below.

[0028] (1) Molten steel smelting process

[0029] The molten iron is smelted into molten steel, and the chemical composition of the obtained molten steel includes, in mass percentage: C: 0.01-0.04%, Si≤0.08%, Mn: 0.10-0.40%, P≤0.015%, S≤0.015%, and the balance of Fe and inevitable impurities.

[0030] C is an important element for improving the strength of steel, but too high C content will reduce the plasticity of the steel and affect the forming performance of the steel, and too low C content will increase the process energy consumption cost and is not conducive to environmental protection requirements. In order to make the product have good performance matching, the C content in the present application is controlled at 0.01-0.04%.

[0031] Si is a ferrite forming element, which can improve the strength of the solid solution in the steel and has a significant effect on improving the tensile strength of the steel. For steel with good flexibility, the increase of Si content is not conducive to the improvement of the forming performance, and too high Si content will deteriorate the welding performance of the steel. In the present application, the Si content is ≤0.08%.

[0032] Mn is one of the important solid solution strengthening elements in steel and is also an austenite stabilizing element, which can expand the austenite region in the iron-carbon phase diagram, promote the medium temperature structure transformation of the steel, and obtain a microstructure mainly composed of acicular structure. This kind of structure has good uniformity, excellent weather resistance, high strength and toughness. However, too high Mn content will not only reduce the elongation and damage the toughness of the steel, but also reduce the corrosion resistance and welding performance of the steel, and increase the manufacturing cost. Therefore, in the present application, the Mn content is controlled at 0.1-0.4%.

[0033] Specifically, the molten steel smelting process includes sequentially performed molten iron pre-desulfurization, converter smelting, and refining steps.

[0034] It can be understood that the chemical composition of the molten steel obtained by the molten steel smelting process and the chemical composition of the continuous casting billet obtained by the continuous casting process are consistent with the chemical composition of the cold-rolled strip steel finally obtained by the production method.

[0035] (2) Continuous casting process

[0036] The molten steel obtained by the molten steel smelting process is used to produce a continuous casting billet with a thickness of 180-220 mm by using a continuous casting machine. The continuous casting speed is 1.0-1.5 m / min.

[0037] (3) Hot rolling process

[0038] After the continuous casting billet obtained by the continuous casting process is heated in a heating furnace, rough rolling, finish rolling, laminar cooling and coiling are sequentially performed to obtain a hot-rolled coil with a thickness of 2-6 mm.

[0039] The continuous casting billet has an out-furnace temperature of greater than or equal to 1200 DEG C in the heating furnace, the finish-rolling temperature of the finish rolling is 840-900 DEG C, and the coiling temperature is 660-720 DEG C.

[0040] By designing the chemical composition scheme and controlling the temperature at each stage in the hot rolling process, the microstructure of the hot-rolled plate can be stabilized, the rolling difficulty in the subsequent cold rolling process can be reduced, and the foundation for the excellent mechanical properties of the finally prepared cold-rolled steel strip is laid.

[0041] (4) Pickling process

[0042] The hot-rolled plate after hot rolling is pickled.

[0043] (5) Cold rolling process

[0044] The hot-rolled plate after pickling is rolled into a cold-rolled steel strip by using a five-stand cold rolling mill, wherein the surface roughness of the roller of the fifth stand is 1.2-2.0 μm, so that the occurrence of water washing spots of the finally prepared cold-rolled steel strip after silane treatment can be reduced.

[0045] Specifically, the roller surface of the fifth stand is roughened, so that the surface becomes rough and the surface roughness is controlled to be 1.2-2.1 μm, which is beneficial to improve the RPc peak count value of the surface of the cold-rolled steel strip; the roller surfaces of the remaining stands are not roughened.

[0046] Preferably, the thickness of the cold-rolled steel strip is 0.5-1.5 mm, wherein the cold rolling reduction rate is 75-85%.

[0047] (6) Continuous annealing process

[0048] The steel strip obtained by cold rolling is annealed by using a continuous annealing furnace.

[0049] Preferably, the soaking temperature of the continuous annealing process is 780-840 DEG C.

[0050] (7) Skin pass process

[0051] After skin pass rolling in a skin pass mill, drying is carried out in a blowing unit, wherein the surface roughness of the skin pass roller of the skin pass mill is 2.5-3.5 μm, the RPc peak count value of the skin pass roller is 70-100, the blowing unit has 4-6 rows of nozzles, the last row of nozzles uses normal temperature compressed air for drying, and the remaining rows of nozzles use hot air for drying, and the hot air temperature is 80-120 DEG C.

[0052] By controlling the surface roughness and RPc peak count value of the skin pass roll, the surface of the skin pass roll can have fine and dense peak-shaped protrusions, so that the occurrence of water washing spots on the final prepared cold-rolled strip after silane treatment can be greatly reduced. By setting different drying methods and drying temperatures for different rows of nozzles of the blowing unit, the occurrence of water washing spots on the final prepared cold-rolled strip after silane treatment due to surface oxidation and rust can be avoided.

[0053] Preferably, if the service distance of the skin pass roll is ≤50km, the soaking temperature of the continuous annealing process is controlled to be 780-820℃, and the reduction of the skin pass process is controlled to be 0.8-1.2%;

[0054] If the service distance of the skin pass roll is >50km, the soaking temperature of the continuous annealing process is controlled to be 820-840℃, and the reduction of the skin pass process is controlled to be 1.2-1.5%.

[0055] The service distance of the skin pass roll refers to the total length of the strip that has been leveled by the skin pass roll since the skin pass roll was put into use.

[0056] As the service distance of the skin pass roll increases, the surface of the skin pass roll will be continuously worn and the surface roughness will decrease. In order to ensure that the surface of the strip has a certain roughness, the reduction of the skin pass process needs to be increased when the service distance of the skin pass roll is >50km.

[0057] In addition, within the soaking temperature range of 780-800℃ of the continuous annealing process, as the annealing temperature increases, the strength of the cold-rolled strip will decrease, and increasing the reduction of the skin pass process will increase the strength of the cold-rolled strip.

[0058] Preferably, if the soaking temperature of the continuous annealing process is 780-800℃, the reduction of the skin pass process is controlled to be 0.8-1.0%;

[0059] If the soaking temperature of the continuous annealing process is 800-820℃, the reduction of the skin pass process is controlled to be 1.0-1.2%.

[0060] By synergistically controlling the soaking temperature of the continuous annealing process and the reduction of the skin pass process, the surface roughness of the skin pass roll can be prevented from being excessively attenuated, which can cause slipping during production and thus affect the leveling effect on the cold-rolled strip.

[0061] (8) Oil coating treatment process

[0062] The oil coating machine uses double knife beams arranged in front and back for oil coating, and the knife slit of one knife beam gradually widens from the transmission end to the operation end, and the knife slit of the other knife beam gradually narrows from the transmission end to the operation end.

[0063] On the one hand, the gradually widening or gradually narrowing of the knife slit of the knife beam from the transmission end to the operation end can avoid the uneven distribution of the oil amount of the cold-rolled strip at the two ends and the middle part of the knife beam due to the fastening mode and the like at the transmission end and the operation end; on the other hand, the knife slit of the double-knife beam has opposite change rules in the same direction, thereby avoiding the uneven distribution of the oil amount of the cold-rolled strip along the width direction.

[0064] Preferably, the absolute value of the difference between the width of the knife slit of each knife beam at the transmission end and at the operation end is 0.02-0.06 mm. In this way, the difference in the oil amount of the cold-rolled strip at the two ends of the knife beam can be avoided.

[0065] Preferably, if the knife slit at the transmission end is narrower than the knife slit at the operation end, the width of the knife slit at the transmission end is 0.04-0.06 mm, and the width of the knife slit at the operation end is 0.06-0.12 mm.

[0066] If the knife slit at the transmission end is wider than the knife slit at the operation end, the width of the knife slit at the transmission end is 0.06-0.12 mm, and the width of the knife slit at the operation end is 0.04-0.06 mm.

[0067] By setting the width of the knife slit at the transmission end and at the operation end, the oil amount requirement of the cold-rolled strip can be ensured, so that it can be cleaned in the subsequent processing process, thereby improving the surface quality of the cold-rolled strip.

[0068] The so-called transmission end is one end of the knife beam where the power mechanism is located, and the so-called operation end is the end away from the transmission end, and the operator operates the oiling machine on the side of the operation end.

[0069] Specifically, the double-knife beam includes a front knife beam and a rear knife beam arranged in front and behind.

[0070] In this embodiment, the width of the knife slit of the front knife beam at the transmission end is 0.04-0.06 mm, and the width of the knife slit of the front knife beam at the operation end is 0.06-0.12 mm; the width of the knife slit of the rear knife beam at the transmission end is 0.06-0.12 mm, and the width of the knife slit of the rear knife beam at the operation end is 0.04-0.06 mm, and the width of the knife slit of the front knife beam at the transmission end is the same as the width of the knife slit of the rear knife beam at the operation end, and the width of the knife slit of the front knife beam at the operation end is the same as the width of the knife slit of the rear knife beam at the transmission end.

[0071] In other embodiments, the front beam and the rear beam can also be arranged reversely to the present embodiment, that is, the width of the knife slit of the front beam at the operating end is 0.04-0.06 mm, the width of the knife slit of the front beam at the driving end is 0.06-0.12 mm; the width of the knife slit of the rear beam at the operating end is 0.06-0.12 mm, the width of the knife slit of the rear beam at the driving end is 0.04-0.06 mm, and the width of the knife slit of the front beam at the driving end is the same as the width of the knife slit of the rear beam at the operating end, and the width of the knife slit of the front beam at the operating end is the same as the width of the knife slit of the rear beam at the driving end.

[0072] Preferably, the single-side oiling amount of the cold-rolled strip steel is 300-800 mg / m 2 .

[0073] In summary, the production method of the cold-rolled strip steel and the cold-rolled strip steel prepared by using the production method have the following advantages: through the chemical composition scheme design and the process design of each process, the finally prepared cold-rolled strip steel has excellent mechanical properties, the yield strength is 185-230 MPa, the tensile strength is 290-370 MPa, and the elongation is ≥37%, and the situation that the finally prepared cold-rolled strip steel has water washing spots after silane treatment is avoided, and the application requirements of the downstream customers on the surface quality of the cold-rolled strip steel and the apparent beautification after silane treatment can be met.

[0074] The detailed description listed above is only a specific description of the feasible embodiments of the present application, and is not used to limit the protection scope of the present application, and equivalent embodiments or changes made without departing from the spirit of the present application should be included in the protection scope of the present application.

[0075] The beneficial effects of the present application will be further illustrated by the following two embodiments and one comparative example, and of course, the three embodiments are only part of the numerous changed embodiments of the present application, but not all.

[0076] Embodiment 1

[0077] The cold-rolled strip steel is prepared by the following processes:

[0078] (1) Molten steel smelting process

[0079] The molten iron is smelted into molten steel by sequentially performing the molten iron pre-desulfurization, converter smelting and refining steps, and the chemical composition of the obtained molten steel includes, in mass percent: C: 0.016%, Si: 0.03%, Mn: 0.15%, P: 0.014%, S: 0.003%, and the rest is Fe and inevitable impurities.

[0080] (2) Continuous casting process

[0081] The molten steel obtained in the molten steel smelting process is used to produce a continuous casting billet with a thickness of 200 mm by using a continuous casting machine, and the continuous casting speed is 1.2 m / min. The chemical composition of the continuous casting billet is consistent with the chemical composition of the molten steel obtained in the molten steel smelting process.

[0082] (3) Hot rolling process

[0083] After the continuous casting billet obtained in the continuous casting process is heated in a heating furnace, rough rolling, finish rolling, laminar cooling and coiling are sequentially performed to obtain a hot-rolled coil with a thickness of 4 mm. The discharge temperature of the continuous casting billet in the heating furnace is 1210°C, the finish rolling temperature is 870°C, and the coiling temperature is 672°C.

[0084] (4) Pickling process

[0085] The hot-rolled coil after hot rolling is pickled.

[0086] (5) Cold rolling process

[0087] The hot-rolled coil after pickling is rolled into a cold-rolled strip with a thickness of 1 mm by using a five-stand cold rolling mill, wherein the surface roughness of the roller of the fifth stand is 1.2-2.0 μm by means of roughening treatment, and the roller surface of the remaining stands is not subjected to roughening treatment.

[0088] (6) Continuous annealing process

[0089] The strip obtained by cold rolling is subjected to product annealing by using a continuous annealing furnace, and the soaking temperature is 810°C.

[0090] (7) Leveling process

[0091] After leveling is performed on the leveling machine, drying is performed in the blowing unit, wherein the surface roughness Ra of the leveling roller of the leveling machine is 3.1 μm, the RPc peak count value of the leveling roller is 78, the blowing unit has 4 rows of nozzles, the last row of nozzles uses normal temperature compressed air for drying, and the remaining rows of nozzles use hot air for drying, and the hot air temperature is 102°C. In this embodiment, since the service stroke of the leveling roller is ≤50 km, the reduction rate of the leveling process is controlled to be 1.2%.

[0092] (8) Oil coating treatment process

[0093] The oil coating machine uses double knife beams arranged in front and back for oil coating, the width of the knife slit at the transmission end of the front knife beam is 0.05 mm, the width of the knife slit at the operating end of the front knife beam is 0.07 mm; the width of the knife slit at the transmission end of the rear knife beam is 0.07 mm, and the width of the knife slit at the operating end of the rear knife beam is 0.05 mm, and the single-sided oil coating amount of the cold-rolled strip is 400 mg / m 2 .

[0094] In terms of mechanical properties, the yield strength, tensile strength and elongation of the cold-rolled strip product were tested according to the test method and definition in GB / T 228.1-2021, and the yield strength of the cold-rolled strip of the present example was measured to be 196 MPa, the tensile strength was 304 MPa, and the surface reduction rate was 43.5%.

[0095] After the cold-rolled strip prepared in the present example was treated with silane, its apparent picture is shown in Figure 1 As can be seen from Figure 1 , the cold-rolled strip prepared by the production method of the present example has almost no water spot after silane treatment.

[0096] Example 2

[0097] The cold-rolled strip was prepared by the following processes:

[0098] (1) Molten steel smelting process

[0099] The molten iron was smelted into molten steel by sequentially performing the molten iron pre-desulfurization, converter smelting and refining steps, and the chemical composition of the obtained molten steel included, by mass percent: C: 0.031%, Si: 0.02%, Mn: 0.22%, P: 0.012%, S: 0.0032%, and the balance of Fe and unavoidable impurities.

[0100] (2) Continuous casting process

[0101] The molten steel obtained from the molten steel smelting process was used to produce a continuous casting billet with a thickness of 200 mm using a continuous casting machine, and the continuous casting speed was 1.05 m / min. The chemical composition of the continuous casting billet was consistent with that of the molten steel obtained from the molten steel smelting process.

[0102] (3) Hot rolling process

[0103] After the continuous casting billet obtained from the continuous casting process was heated in a heating furnace, rough rolling, finishing rolling, laminar cooling and coiling were sequentially performed to obtain a hot-rolled coil with a thickness of 4.5 mm. Among them, the discharge temperature of the continuous casting billet in the heating furnace was 1210℃, the finishing rolling temperature was 866℃, and the coiling temperature was 668℃.

[0104] (4) Pickling process

[0105] The hot-rolled coil after hot rolling was pickled.

[0106] (5) Cold rolling process

[0107] The hot-rolled coil after pickling was rolled into a cold-rolled strip with a thickness of 1.2 mm using a five-stand cold rolling mill, wherein the surface roughness of the fifth stand roller was 1.2-2.0 μm by roughening treatment, and the surface of the rollers of the remaining stands was not roughened.

[0108] (6) Continuous annealing process

[0109] The cold-rolled strip steel is subjected to finish annealing using a continuous annealing furnace, and the soaking temperature is 830°C.

[0110] (7) Leveling process

[0111] After leveling in the leveling machine, the strip steel enters the blowing unit for drying, wherein the surface roughness Ra of the leveling roll of the leveling machine is 2.5 μm, the RPc peak count value of the leveling roll is 89, the blowing unit has 6 rows of nozzles, the last row of nozzles uses normal temperature compressed air for drying, and the rest of the rows of nozzles use hot air for drying, and the temperature of the hot air is 89°C. In this embodiment, since the service stroke of the leveling roll is > 50 km, the reduction rate of the leveling process is controlled to be 1.5%.

[0112] (8) Oil coating treatment process

[0113] The oil coating machine uses double knife beams arranged in front and back for oil coating, the width of the knife slit at the transmission end of the front knife beam is 0.04 mm, the width of the knife slit at the operating end of the front knife beam is 0.10 mm; the width of the knife slit at the transmission end of the rear knife beam is 0.10 mm, and the width of the knife slit at the operating end of the rear knife beam is 0.04 mm, and the single-sided oil coating amount of the cold-rolled strip steel is 500 mg / m 2 .

[0114] In terms of mechanical properties, the yield strength, tensile strength, and elongation of the cold-rolled strip steel product are tested according to the test method and definition in GB / T 228.1-2021, and the yield strength of the cold-rolled strip steel of this embodiment is measured to be 217 MPa, the tensile strength is 327 MPa, and the area reduction is 40.0%.

[0115] After the cold-rolled strip steel prepared in this example is subjected to silane treatment, its apparent picture is as shown in Figure 2 From Figure 2 it can be seen that the cold-rolled strip steel prepared by the production method of this embodiment has almost no water washing spots after silane treatment.

[0116] Comparative Example

[0117] The cold-rolled strip steel is prepared by the following processes:

[0118] (1) Molten steel smelting process

[0119] The molten iron is smelted into molten steel by sequentially performing the steps of molten iron pre-desulfurization, converter smelting, and refining, and the chemical composition of the obtained molten steel includes, by mass percent: C: 0.043%, Si: 0.03%, Mn: 0.20%, P: 0.016%, S: 0.0032%, and the rest is Fe and unavoidable impurities.

[0120] (2) Continuous casting process

[0121] The molten steel obtained in the molten steel smelting process is used to produce a continuous casting billet with a thickness of 200 mm, and the continuous casting speed is 1.05 m / min. The chemical composition of the continuous casting billet is consistent with that of the molten steel obtained in the molten steel smelting process.

[0122] (3) Hot rolling process

[0123] After the continuous casting billet obtained in the continuous casting process is heated in a heating furnace, rough rolling, finish rolling, laminar cooling and coiling are sequentially performed to obtain a hot-rolled coil with a thickness of 4.5 mm. Among them, the discharge temperature of the continuous casting billet in the heating furnace is 1200℃, the finish rolling temperature is 858℃, and the coiling temperature is 664℃.

[0124] (4) Pickling process

[0125] The hot-rolled coil after hot rolling is pickled.

[0126] (5) Cold rolling process

[0127] The hot-rolled coil after pickling is rolled into a cold-rolled strip with a thickness of 1 mm by using a five-stand cold rolling mill, and the surface of the roll of each stand is not roughened.

[0128] (6) Continuous annealing process

[0129] The strip obtained by cold rolling is annealed by using a continuous annealing furnace, and the soaking temperature is 820℃.

[0130] (7) Leveling process

[0131] After leveling on the leveling machine, drying is performed in the blowing unit, wherein the surface roughness Ra of the leveling roll of the leveling machine is 2.3μm, the RPc peak count value of the leveling roll is 72, the blowing unit has 4 rows of nozzles, the nozzles use hot air drying, the hot air temperature is 64℃, and the reduction rate of the leveling process is 1.2%.

[0132] (8) Oil coating treatment process

[0133] The knife slit width at both ends of the knife beam of the oil coating machine is 0.08mm, and the single-sided oil coating amount of the cold-rolled strip is 500mg / m 2 .

[0134] In terms of mechanical properties, the yield strength, tensile strength and elongation of the cold-rolled strip product are tested according to the test method and definition in GB / T 228.1-2021, and the yield strength of the cold-rolled strip of the present example is 239MPa, the tensile strength is 356MPa, and the area reduction is 37.5%.

[0135] After the cold-rolled strip prepared in the present example is treated with silane, its apparent picture is as followsFigure 3 The production method of the comparative example prepared the cold-rolled strip steel, and then the surface was treated by silane. It can be seen that there are a large number of obvious water washing spots on the surface, which seriously affects the appearance quality and beauty of the product. Figure 3

[0136] It should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be combined appropriately to form other embodiments that those skilled in the art can understand.

[0137] The detailed description listed above is only a specific description of the feasible embodiments of the present application, and is not used to limit the protection scope of the present application. Any equivalent embodiments or changes made without departing from the spirit of the present application shall be included in the protection scope of the present application.​

Claims

1. A method of producing a cold-rolled steel strip, characterized in that, The production method comprises sequentially performing the following processes: molten steel smelting, continuous casting, hot rolling, pickling, cold rolling, continuous annealing, skin passing and oiling treatment; The chemical composition of the molten steel obtained by the molten steel smelting process includes, in mass percent: C: 0.01-0.04%, Si≤0.08%, Mn: 0.10-0.40%, P≤0.015%, S≤0.015%, and the balance of Fe and inevitable impurities; The cold rolling process adopts a five-stand cold rolling mill to cold roll the hot-rolled coil into a cold-rolled strip, wherein the surface roughness of the roller of the fifth stand is 1.2-2.0 μm; In the skin passing process, after skin passing is performed on the skin passing mill, drying is performed on the blowing unit, wherein the surface roughness of the skin passing roller of the skin passing mill is 2.5-3.5 μm, the RPc peak count value of the skin passing roller is 70-100, the blowing unit has 4-6 rows of nozzles, the last row of nozzles adopts normal-temperature compressed air drying, and the remaining rows of nozzles adopt hot air drying, and the temperature of the hot air is 80-120 °C; In the oiling treatment process, the oiling machine adopts double knife beams arranged in front and back to perform oiling, wherein the knife slit of one knife beam gradually widens from the transmission end to the operation end, and the knife slit of the other knife beam gradually narrows from the transmission end to the operation end.

2. The production method of cold-rolled steel strip according to claim 1, characterized in that, In the oiling treatment process, the absolute value of the difference between the width of the knife slit of each knife beam at the transmission end and at the operation end is 0.02-0.06 mm.

3. The production method of cold-rolled steel strip according to claim 1, characterized in that, In the oiling treatment process, if the knife slit at the transmission end is narrower than the knife slit at the operation end, the width of the knife slit at the transmission end is 0.04-0.06 mm, and the width of the knife slit at the operation end is 0.06-0.12 mm. If the knife slit at the transmission end is wider than the knife slit at the operation end, the width of the knife slit at the transmission end is 0.06-0.12 mm, and the width of the knife slit at the operation end is 0.04-0.06 mm.

4. The production method of cold-rolled steel strip according to claim 1, characterized in that, In the oiling process, the single-side oiling amount of the cold-rolled steel strip is 300 to 800 mg / m 2 .

5. The production method of the cold-rolled strip according to claim 1, wherein If the service stroke of the skin passing roller is ≤50 km, the soaking temperature of the continuous annealing process is controlled to be 780-820 °C, and the reduction of the skin passing process is controlled to be 0.8-1.2%. If the service stroke of the skin passing roller is >50 km, the soaking temperature of the continuous annealing process is controlled to be 820-840 °C, and the reduction of the skin passing process is controlled to be 1.2-1.5%.

6. The production method of the cold-rolled strip according to claim 5, wherein If the soaking temperature of the continuous annealing process is 780-800 °C, the reduction of the skin passing process is controlled to be 0.8-1.0%. If the soaking temperature of the continuous annealing process is 800-820 °C, the reduction of the skin passing process is controlled to be 1.0-1.2%.

7. The production method of cold-rolled steel strip according to claim 1, characterized in that, The thickness of the continuous casting billet obtained by the continuous casting process is 180-220 mm, and the continuous casting pulling speed is 1.0-1.5 m / min.

8. The production method of cold-rolled steel strip according to claim 1, characterized in that, In the hot rolling process, the continuous casting billet obtained from the continuous casting process is heated in a heating furnace, and then rough rolling, finish rolling, laminar cooling and coiling are sequentially performed to obtain a hot-rolled coil with a thickness of 2-6 mm, wherein the discharge temperature of the continuous casting billet in the heating furnace is ≥1200℃, the finish rolling temperature is 840-900℃, and the coiling temperature is 660-720℃.

9. The production method of cold-rolled steel strip according to claim 1, characterized in that, In the cold rolling process, the hot-rolled coil after pickling is cold-rolled into a cold-rolled strip with a thickness of 0.5-1.5 mm, wherein the reduction rate of cold rolling is 75-85%.

10. A cold-rolled steel strip, characterized in that, The cold-rolled strip is prepared by using the production method according to any one of claims 1-9.

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