High yield ratio cold-rolled steel sheet excellent in hole expansion and bending properties and production method thereof

Abstract

The invention discloses a high yield-tensile ratio cold-rolled steel plate with good reaming and bending properties and a production method thereof. The cold-rolled steel plate is prepared from the following chemical components in percentage by mass: 0.06 to 0.10 percent of C, 0.40 to 0.60 percent of Si, 1.45 to 1.65 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.008 percent of S, 0.020 to 0.060 percent of Als, 0.040 to 0.055 percent of Nb, 0.035 to 0.050 percent of Ti, less than or equal to 0.0040 percent of N and the balance of iron and unavoidable impurityelements. By reasonable component design and cooperation with corresponding processes of hot rolling, acid rolling and continuous annealing, the yield strength of the produced steel plate is more thanor equal to 650 MPa, the tensile strength is more than or equal to 720 MPa, and the ductility A80 is more than or equal to 11 percent; when bent at 180 degrees and then flattened, the steel plate cannot crack; the hole expansion rate is more than or equal to 45 percent; the high yield-tensile ratio cold-rolled steel plate is high in intensity and good in forming property.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a high yield ratio cold-rolled steel plate with excellent hole expansion and bending properties and a production method thereof. Background technique [0002] In order to adapt to the development trend of low energy consumption and high safety in the automobile industry, automobile manufacturers and iron and steel enterprises are actively committed to the design of lightweight body and the development of high-strength steel for automobiles. At present, both cold-rolled dual-phase steel and transformation-induced plasticity steel have been realized. Industrial production, but this type of steel usually has poor bending performance or hole expansion performance, which limits its wide application. Therefore, the steel sheet is expected to have high strength and better formability at the same time. [0003] Invention patent CN200710045334.0 discloses a high-strength, ...

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Problems solved by technology

[0003] Invention patent CN200710045334.0 discloses a high-strength and high-yield ratio cold-rolled steel plate and its manufacturing method, involving a steel plate with a yield strength ≥ 500 MPa. In order to obtain this steel plate, the steel plate is heated to 780-850°C during the annealing process Finally, through two-stage rapid cooling to below 200°C, the first stage of this process is easy to control from high temperature and rapid cooling, while the second stage is cooled from a lower temperature of 400-500°C to below 200°C, which greatly affects the cooling capacity of the annealing line The requirements are high, the operability is not strong, and the yield strength of the steel plate involved in this patent is 100MPa lower

[0004] Invention patent CN201210560597.6 discloses a high-strength cold-rolled steel plate with excellent stretch flangeability and spot weldability and its manufacturing method. The tensile strength is above 800 MPa, but the precious element Mo is added, and the cost is high; it contains more V. Because its strengthening effect is closely related to the N content, it is difficult to control; the reduction rate of acid rolling is 60-80%, the reduction rate is high, and the cold rolling is difficult

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