Low-cost production method of cold-rolled low-carbon steel strip with high plastic deformation capacity

Abstract

The invention discloses a low-cost production method of a cold-rolled low-carbon steel strip with high plastic deformation capacity, and belongs to the field of manufacturing of household appliances and steel furniture. According to the method provided by the invention, chemical components and process parameters of the cold-rolled low-carbon steel strip are optimally controlled, so that the plastic deformation capacity of the cold-rolled low-carbon steel strip can be improved (the ductility is greater than or equal to 50.0%) while the cold-rolled low-carbon steel strip is kept to have relatively high strength, the production cost is reduced, and the profitability of a steel mill is further improved.

Description

Technical Field

[0001] The invention belongs to the field of household appliances and steel furniture manufacturing, and in particular relates to a low-cost production method of a cold-rolled low-carbon steel strip with high plastic deformation ability. Background Art

[0002] At present, most cold-rolled low-carbon steel products on the market are produced by traditional hood annealing, and the production process is relatively complicated. In order to improve the strength of the product, alloy elements such as Nb and Ti need to be added, and the alloy cost is relatively high. Some require the control of impurity S elements. Not only is it not conducive to production scheduling, but it also increases the cost of steelmaking, and the plastic deformation ability of the obtained cold-rolled low-carbon steel products is poor, which is not conducive to the manufacture of home appliances and furniture products. In the fierce market competition environment, it is particularly important to reduce the production cost of steel mills, save energy and reduce consumption, and develop low-cost, high-strength cold-rolled low-carbon steel suitable for the home appliance and steel furniture industries. Summary of the invention

[0003] The present invention aims to provide a low-cost production method for a cold-rolled low-carbon steel strip with high plastic deformation capacity while maintaining the high strength of the cold-rolled low-carbon steel strip. In order to achieve the above object, the present invention adopts the following technical solutions.

[0004] One aspect of the present invention provides a low-cost production method for a cold-rolled low-carbon steel strip with high plastic deformation ability, the production method of the cold-rolled low-carbon steel strip comprising the following steps: converter smelting, continuous casting, hot rolling, pickling, cold rolling, continuous annealing and smoothing, wherein:

[0005] The elongation of the cold-rolled low-carbon steel strip is ≥50.0%;

[0006] In the converter smelting process, the chemical composition of the cold-rolled low-carbon steel strip is controlled to be: C: 0.020-0.04%, Si: 0.005-0.010%, Mn: 0.15-0.20%, P: ≤0.020%, S: ≤0.010%, N: ≤50ppm, and the rest is Fe and unavoidable impurities;

[0007] In the hot rolling process, the heating temperature of the ingot is controlled to be 1160-1180°C, the soaking temperature is 1170-1190°C, the cold charging time in the furnace is 160-220min, the cold charging soaking time is 30-50min, the final rolling temperature is 845-885°C, and the coiling temperature is 660-680°C.

[0008] In the continuous annealing process, the annealing temperature is controlled to be 715-725°C, the over-aging temperature is 250-350°C, and the final cooling temperature is ≤100°C;

[0009] In the flattening process, the flattening machine elongation is controlled to be 0.9-1.0%.

[0010] In some embodiments, in the converter smelting process, the chemical composition of the cold-rolled low-carbon steel strip is controlled in weight percentage as follows: C: 0.022-0.024%, Si: 0.005-0.006%, Mn: 0.18-0.21%, P: ≤0.020%, S: ≤0.010%, N: ≤50ppm, Alt: 0.030-0.040%, and the rest is Fe and unavoidable impurities.

[0011] In some embodiments, in the converter smelting process, oxygen blowing, decarburization and heating are carried out during the top and bottom combined blowing smelting of the converter. Aluminum iron and manganese iron are added for deoxidation and alloying in the later stage of smelting to control the P and S components to prevent overoxidation of the molten steel. The tapping temperature is ≥1620°C, and the P and S content of the converter tapping steel is ≤0.020%, and ≤0.020%. The RH furnace refining adopts the RH full-process argon blowing process, and deep decarburization treatment is carried out according to the composition and temperature of the RH molten steel supplied by the converter. After decarburization is completed, aluminum particles are added for deoxidation and alloying according to the oxygen determination situation. After circulating for more than 4 minutes, manganese iron and other alloys are added to adjust the composition. After the composition adjustment is completed, the vacuum cycle is ensured to be ≥6 minutes.

[0012] In some embodiments, in the continuous casting process, the temperature of the molten steel entering the tundish is controlled to be 1530-1540° C., the superheat is 25-35° C., and the casting speed is 1.00-1.80 m / min.

[0013] In some embodiments, during the continuous casting process, the thickness of the cast strand is controlled to be 230 mm.

[0014] In some embodiments, in the hot rolling process, the hot rolling thickness h is controlled to satisfy: 3.8 mm ≤ h ≤ 4.5 mm.

[0015] In some embodiments, in the cold rolling step, the cold rolling reduction ratio is controlled to be greater than 60%.

[0016] In some embodiments, in the cold rolling process, the cold rolling thickness is controlled to be 0.8 to 1.2 mm.

[0017] In some embodiments, the strength of the cold-rolled low-carbon steel strip meets the following requirements: yield strength of 170-240 MPa, and tensile strength of ≥330 MPa.

[0018] Another aspect of the present invention provides a cold-rolled low-carbon steel strip with high plastic deformation capability, which is produced by the above method.

[0019] The beneficial effects of the present invention are as follows: the alloy cost and process cost of the present invention are both low, and only by optimizing the chemical composition design and process conditions, on the basis of ordinary cold-rolled low-carbon steel sheets, without considering the addition of alloy elements Nb and Ti, a low-cost, high-performance cold-rolled low-carbon steel product for home appliances that fully meets the requirements of home appliances and steel furniture is achieved. The low cost and good comprehensive performance balance are ensured, and the profitability of the steel mill is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Metallographic microstructure photographs of cold-rolled low-carbon steel strips obtained from test numbers 1# (A) and 2# (B). DETAILED DESCRIPTION

[0021] The present invention is described in detail below through specific examples. The examples are intended to help understand the present invention but are not intended to limit the present invention.

[0022] The low-cost production method of the cold-rolled low-carbon steel strip with high plastic deformation ability provided by the present invention mainly comprises the following steps:

[0023] 1. Smelting process

[0024] The smelting process includes: molten iron pretreatment - converter top and bottom combined blowing smelting - RH furnace refining - slab continuous casting - slow cooling, wherein oxygen blowing decarburization and heating are carried out in the converter top and bottom combined blowing smelting, and aluminum iron and manganese iron are added for deoxidation and alloying in the later stage of smelting to control the P and S components to prevent overoxidation of molten steel, and the tapping temperature is ≥1620℃, and the converter tapping P≤0.020%, S≤0.020%. The above-mentioned RH furnace refining adopts the RH full-process argon blowing process, and deep decarburization treatment is carried out according to the composition and temperature of the RH molten steel supplied by the converter. After decarburization, aluminum particles are added for deoxidation and alloying according to the oxygen setting situation, and after circulating for more than 4 minutes, ferromanganese and other alloys are added to adjust the composition. After the composition adjustment is completed, ensure that the vacuum cycle is ≥6 minutes. In the above-mentioned slab continuous casting, the temperature of the molten steel entering the tundish is controlled at 1530-1540℃, the superheat is 25-35℃, and the pulling speed is controlled at 1.00-1.80m / min. The ingot is inspected at low magnification. There shall be no shrinkage, bubbles, cracks, inclusions or white spots that may affect the product performance on the macrostructure test piece. The segregation of the continuous casting ingot shall not be greater than Class B 1.0, and the central porosity shall not be greater than Level 1. In this smelting process, the chemical composition of the ingot is controlled by weight percentage: C: 0.020-0.04%, Si: 0.005-0.010%, Mn: 0.15-0.20%, P: ≤0.020%, S: ≤0.010%, N: ≤50ppm, and the rest is Fe and unavoidable impurities.

[0025] 2 Hot rolling process

[0026] The hot rolling process includes: heating of the ingot - high-pressure water descaling - fixed width press - E1R1 roughing mill rolling - E2R2 roughing mill rolling - flying shear - high-pressure water descaling - F1~F7 finishing mill rolling - dense laminar cooling - coiling; this process adopts a walking heating furnace to heat the ingot (the heating process is shown in Table 1), the rough rolling adopts double-stand R1 and R2 reciprocating rolling, the rough rolling mode adopted is 3+3, and the finishing rolling adopts F1~F7 continuous rolling process. The specific hot rolling process is shown in Table 2.

[0027] Table 1: Billet heating process

[0028]

[0029] Table 2: Rolling process

[0030]

[0031] 3 Annealing process

[0032] The cold rolling process includes: pickling uncoiling-welding-stretching-pickling-rinsing-drying-edge trimming-continuous rolling machine cold rolling-slitting-coiling; the continuous annealing process includes: continuous annealing uncoiling-welding-cleaning-entry looper-annealing furnace-exit looper-leveling-loop inspection-edge trimming-surface inspection-oiling-coiling-weighing-sampling, inspection-packaging. The specific process of the continuous annealing process is shown in Table 3.

[0033] Table 3: Annealing process

[0034]

[0035] 4. Example Analysis

[0036] 4.1 Steelmaking ingredients

[0037] According to the above steelmaking process requirements, the actual slab chemical composition (mass percentage) is shown in Table 4 below.

[0038] Table 4: Example chemical composition wt.%

[0039]

[0040]

[0041] 4.2 Hot rolling process

[0042] According to the above hot rolling process requirements, the hot rolling thickness is 3.8mm and 4.5mm, and the actual process is shown in Table 5.

[0043] Table 5: Hot rolling process

[0044]

[0045] 4.3 Continuous Annealing Process

[0046] According to the above continuous annealing process requirements, the cold rolling thickness is 1.0mm and 1.2mm, and the actual process is shown in Table 6.

[0047] Table 6: Continuous Annealing Process

[0048]

[0049] The mechanical properties of the steel strip products obtained through the above process are shown in Table 7. The test method refers to GB / T228.1.

[0050] Table 7: Finished product tensile properties

[0051]

[0052] The cold-rolled low-carbon steel products obtained by the above process have no stamping cracking after use, and the product performance meets customer needs, with a yield strength of 170-240MPa, a tensile strength of ≥330MPa, and an elongation of ≥50.0%. The metallographic structure of the finished product is equiaxed ferrite with a grain size of 8.0-9.5. The organizational morphology of the cold-rolled low-carbon steel strips obtained in test 1# and 2# is as follows Figure 1 As shown in panels A and B.

[0053] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low-cost production method for cold-rolled low-carbon steel strip with high plastic deformation ability, the production method of the cold-rolled low-carbon steel strip comprising the following steps: converter smelting, continuous casting, hot rolling, pickling, cold rolling, continuous annealing and smoothing, characterized in that: The elongation of the cold-rolled low-carbon steel strip is ≥50.0%; In the converter smelting process, the chemical composition of the cold-rolled low-carbon steel strip is controlled to be: C: 0.020-0.04%, Si: 0.005-0.010%, Mn: 0.15-0.20%, P: ≤0.020%, S: ≤0.010%, N: ≤50ppm, and the rest is Fe and unavoidable impurities; In the hot rolling process, the heating temperature of the ingot is controlled to be 1160-1180°C, the soaking temperature is 1170-1190°C, the cold charging time in the furnace is 160-220min, the cold charging soaking time is 30-50min, the final rolling temperature is 845-885°C, and the coiling temperature is 660-680°C. In the continuous annealing process, the annealing temperature is controlled to be 715-725°C, the over-aging temperature is 250-350°C, and the final cooling temperature is ≤100°C; In the flattening process, the flattening machine elongation is controlled to be 0.9-1.0%.

2. The method according to claim 1, characterized in that In the continuous casting process, the temperature of the molten steel entering the tundish is controlled to be 1530-1540°C, the superheat is 25-35°C, and the pulling speed is 1.00-1.80 m / min.

3. The method according to claim 2, characterized in that In the continuous casting process, the thickness of the cast strand is controlled to be 230 mm.

4. The method according to any one of claims 1 to 3, characterized in that In the hot rolling process, the hot rolling thickness h is controlled to satisfy: 3.8 mm ≤ h ≤ 4.5 mm.

5. The method according to any one of claims 1 to 4, characterized in that In the cold rolling step, the cold rolling reduction ratio is controlled to be 60% or more.

6. The method according to any one of claims 1 to 5, characterized in that In the cold rolling process, the cold rolling thickness is controlled to be 0.8 to 1.2 mm.

7. The method according to any one of claims 1 to 6, characterized in that The strength of the cold-rolled low-carbon steel strip meets the following requirements: yield strength of 170-240 MPa, and tensile strength of ≥330 MPa.

8. The method according to any one of claims 1 to 7, characterized in that In the converter smelting process, the chemical composition of the cold-rolled low-carbon steel strip is controlled to be calculated by weight percentage as follows: C: 0.022-0.024%, Si: 0.005-0.006%, Mn: 0.18-0.21%, P: ≤0.020%, S: ≤0.010%, N: ≤50ppm, Alt: 0.030-0.040%, and the rest is Fe and unavoidable impurities.

9. A cold-rolled low-carbon steel strip with high plastic deformation capability, produced by the method according to any one of claims 1 to 8.

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