600 MPa grade high-yield-ratio high-plasticity cold-rolled steel plate and manufacturing method thereof

Abstract

A disclosed 600 MPa grade high-yield-ratio high-plasticity cold-rolled steel plate is characterized by comprising the following compositions in percent by mass: 0.06%-0.12% of C, 0.02-0.10% of Si, 1.40%-2.00% of Mn, 0.015% or less of P, 0.010% or less of S, 0.02%-0.10% of Al, 0.0050% or less of N, 0.015-0.045% of Nb, 0.020-0.055% of Ti, at the same time 0.035%<= Nb+Ti<= 0.100%, and the ferrite balance is Fe and other some unavoidable impurities.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled high-strength thin plates for automobiles, and provides a 600MPa grade high-yield ratio high-plasticity cold-rolled steel plate and a manufacturing method thereof. Background technique [0002] Low energy consumption, weight reduction and high safety have become the development trend of modern and future automobiles. In order to adapt to this development trend of the automobile industry, automobile manufacturers, steel companies and research institutes are actively working on the "lightweight" design and development of automobile bodies. Research and development of high-strength steel for automobiles. At present, the developed cold-rolled high-strength steels for automobiles, such as dual-phase (DP) steels and phase transformation-induced plasticity (TRIP) steels with strengths ranging from 590MPa to 980MPa, have been industrialized and mass-produced, and are used in automobile skeleton member...

AI Technical Summary

Problems solved by technology

In order to obtain such a steel plate with a strength greater than 600MPa and a yield ratio greater than 0.80, during the annealing process, the steel plate is heated to 780-850°C and then cooled to below 200°C through two-stage rapid cooling. Cooling is easy to control, and the second stage is rapidly cooled from a lower temperature of 400-500°C to below 200°C, which is very difficult for an annealing line that relies on gas-vapor cooling, and is not practical.

[0004] CN101558178A provides a kind of cold-rolled steel plate with high yield strength ratio and excellent weather resistance, the alloy elements such as Nb, Ni, Co, Cr, Cu and B have been added in the steel composition, and the steel plate after cold rolling is heated at 500 ℃ Continuous annealing within the temperature range to the A1 transition point, the yield ratio of the steel plate is greater than 0.85, and the tensile strength is greater than 800MPa. It is mainly used in construction, rail vehicles and containers, and products with high yield ratio cold-rolled high-strength steel plates for automobiles Not comparable to the annealing process

However, this annealing process requires a higher cooling rate in the overaging section of the continuous annealing furnace

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