Super-high strength cold rolled steel and manufacturing method thereof

Abstract

The invention discloses super-high strength cold rolled steel or steel plate, which comprises the following chemical components in percent by weight: 0.08 to 0.18 percent of C, 0.1 to 0.6 percent of Si, 1.4 to 2.4 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.005 percent of S, 0.01 to 0.05 percent of A1, less than or equal to 0.006 percent of N, 0.2 to 0.77 percent of B / N and the balance of Fe and inevitable impurities. A manufacturing method for the super-high strength cold rolled steel comprises the following steps: performing hot rolling, wherein the finishing temperature is between 830 and 930 DEG C and the coiling temperature is between 550 and 650 DEG C; performing cold rolling, wherein the rolling reduction is 40 to 70 percent; performing continuous annealing, namely holding the temperature between 780 and 880 DEG C, cooling the steel to be between 700 and 750 DEG C with air at a rate of between 10 and 30 DEG C / s, cooling the steel to be between 550 and 640 DEG C by air blast at the cooling rate of between 60 and 200 DEG C / s, cooling the steel to be below 100 DEG C at the cooling rate greater than 500 DEG C / s and heating the steel to be between 150 and 250 DEG C to perform tempering for 60 to 300s; washing the steel with weak acid; and levelling the steel by 0 to 0.6 percent. Thus the obtained super-high strength band steel or steel plate with high processability can be applied to structures or enhanced parts for automobile manufacturing.

Description

technical field [0001] The present invention relates to ultra-high-strength cold-rolled steel, especially ultra-high-strength cold-rolled strip or steel plate with high workability, and their manufacturing methods. Background technique [0002] In the automobile industry, a large number of cold-rolled steel sheets are used in the production of cars. In order to reduce the weight, it is required to thin the steel plate. At the same time, due to the requirements for safety, the requirements for the rigidity of the vehicle body are also continuously increasing. Therefore, cold-rolled high-strength steel plates have good application prospects in automobile manufacturing. Cold-rolled ultra-high-strength steel is especially suitable for the manufacture of automotive safety parts, such as door bumpers and bumper reinforcements. At present, ultra-high-strength steels adopt phase transformation strengthening methods, and adopt relatively rapid cooling during continuous annealing t...

AI Technical Summary

Problems solved by technology

Due to the poor shape, high hardness, and large internal stress of ultra-high-strength steel, it is easy to warp during slitting or blanking, and the tool wears too quickly or is damaged, which will cause subsequent processing failure or increase processing difficulty.

Images