High-carbon hot-rolled steel plate,cold-rolled steel plate and making method thereof
A technology for hot-rolled steel sheets and cold-rolled steel sheets, applied in high-carbon hot-rolled steel sheets, cold-rolled steel sheets and their manufacturing fields, can solve problems such as ductility, inability to ensure TS and tensile flanging properties stably at the same time
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Embodiment approach 1
[0031] Embodiment 1 provides that the composition contains C: 0.20-0.48%, Si: 0.1% or less, Mn: 0.20-0.60%, P: 0.02% or less, S: 0.01% or less, sol.Al: 0.1% or less in terms of mass percentage , N: 0.005% or less, B: 0.001-0.005%, Cr: 0.05-0.3%, and the rest are iron and unavoidable impurities. The average particle size of ferrite is below 6 μm, and the average particle size of carbide is 0.1 A high-carbon hot-rolled steel sheet having a micrometer of not less than 1.20 μm and a structure in which the volume ratio of ferrite grains substantially free of the aforementioned carbides is 10% or less. It is desirable that the average particle size of carbides be more than 0.5 μm and less than 1.20 μm. It is desirable that the volume ratio of ferrite crystal grains be 5% or less.
[0032] Furthermore, Embodiment 1 provides steel having the above composition, in (Ar 3 Transformation point -10°C) above the finishing temperature for hot rolling, then cooling at a cooling rate greater...
Embodiment 1
[0092]The continuous casting slab of steel with the chemical composition shown in Table 1 is heated at 1250°C, the finishing temperature of hot rolling is 880°C, the time from finishing rolling to the beginning of cooling is 0.7 seconds, and the cooling rate after hot rolling is Hot rolling was performed under conditions of 150°C / sec, cooling end temperature of 610°C, and coiling temperature of 560°C. Thereafter, it was pickled, and box annealed at 710° C. for 40 hours to manufacture a steel plate with a thickness of 5.0 mm. Among them, the chemical components (compositions) of Steel Nos. A to E and N are within the range of Embodiment 1, and Steel Nos. F to M are comparative examples whose compositions deviate from the range of Embodiment 1.
[0093] Samples were taken from these steel sheets, and the average particle size of ferrite, the average particle size of carbides, and the dispersion state of carbides were measured, evaluation of tensile flanging performance, and tens...
Embodiment 2
[0109] Among the steels shown in Table 1 above, after heating the continuously cast slabs of Steel No.A and C of Invention Example to 1250°C, hot rolling was carried out under the conditions shown in Table 3, pickled and annealed to produce A steel plate with a thickness of 5.0mm. Among them, steel plate Nos. 1 to 8 are inventive examples in which the manufacturing conditions are within the range of the first embodiment, and steel plate Nos. 9 to 16 are comparative examples in which the manufacturing conditions deviate from the range of the first embodiment.
[0110] Samples were taken from these steel sheets, and in the same manner as in Example 1, the average particle size of ferrite, the average particle size of carbides, and the dispersion state of carbides were measured, the tensile flanging performance was measured, and a tensile test was performed. Each test, measuring method and condition are the same as in Example 1. The results are shown in Table 4.
[0111] In Tab...
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