Superhigh-strength cold rolling band steel with anti-tensile strength above 880Mpa and its production

Abstract

High strength cold-strip steel whose tensile strength is over 880Mpa , its component is ( weight percentage): C:0.14-0.24%;Si:0.2-1.2%;Mn:1.5-2.5%;P:<0.02%; S:<0.02%;N:<=0.005%;Ti:0.03-0.1%;Nb:0-0.04%;B:0.002- 0.006%;Al:0.02-0.08%;the other is composed of Fe and other inevitable impurity. Its method is as following: Steel billet-> hot-rolling-> acid-washing-> cold rolling-> continuous annealing; its main manufacture technological parameter is as following: The anneal temperature is between750DEG C-850DEG C, heat preservation time is controlled to between 40s-150s; Air cooling speed is 30-60DEG C / s, cooling down to350-500DEG C; The hydrocooling temperature is below 200DEG C; The drawing-back temperature is 150-300DEG C, drawing-back time is 100-300s; the unknit rate is 0-0.8%.

Description

technical field [0001] The invention relates to an ultra-high-strength cold-rolled steel strip and a manufacturing method thereof, in particular to an ultra-high-strength cold-rolled steel strip with a tensile strength above 880Mpa and a manufacturing method thereof. Background technique [0002] In order to reduce weight and save energy, the automobile industry requires the steel plate to be thinned. At the same time, due to the requirements for safety, the requirements for the rigidity of the vehicle body are also continuously increasing. Ultra-high-strength steel is especially suitable for the manufacture of automotive safety parts that require high strength but low molding requirements. Therefore, ultra-high-strength steel plates (>800Mpa grade) have good application prospects in automobile manufacturing. At present, ultra-high-strength steel is manufactured by rapid cooling process to obtain a certain amount of martensite. However, ultra-high-strength steel require...

AI Technical Summary

Problems solved by technology

In order to avoid the strength decrease caused by the reduction of carbon content, this method inevitably needs to greatly increase the content of alloying elements, so the cost is very high, and the tendency of cold and brittle is obvious

[0011] In short, the above inventions involving ultra-high-strength steel plates greatly increase the cooling rate and reduce the amount of alloying elements added. The technical requirements for equipment are extremely high, the shape of the plate is difficult to control, and in the welding process, it is easy to occur due to insufficient hardenability. The resulting softening of the heat-affected zone of the weld causes the strength of the weld to be lower than that of the base metal, which is not conducive to the improvement of the overall strength of the welded member

Another invention is to reduce the carbon content and increase the content of alloy elements, which not only increases the cost, but also easily causes hardening and embrittlement of the welding zone, which is not conducive to welding performance.