Ti microalloyed ultra-fine grained cold rolling dual-phase steel of 1,000MPa level and preparation method thereof

Abstract

The invention relates to Ti microalloyed ultra-fine grained cold rolling dual-phase steel of a 1,000MPa level and a preparation method thereof, belonging to the technical field of cold rolling ultra-high strength steel for automobiles. The steel comprises the following chemical compositions in percentage by weight: 0.03-0.20 percent of C, 0.20-0.80 percent of Si, 1.2-2.0 percent of Mn, 0.03-0.15 percent of Ti, less than 0.15 percent of S, less than 0.020 percent of P, 0.02-0.15 percent of Als and the balance of Fe. In the invention, C-Si-Mn-Ti is used as a basic alloy system, low-price Ti is adopted, and alloy elements such as Cr, Mo, Nb, V, and the like are not added, thereby reducing the production cost; through a flexible continuous annealing process, the size of a martensite island can be controlled to be 1-2 micrometers or increased to about 5 micrometers under the condition that the quick cooling speed is lower than 50 DEG C / s in continuous annealing so as to obtain the following three different types of dual-phase steel: a high strength type (Rm is 980-1,200MPa, and A50 is 10-13 percent), a high plasticity type (Rm is 980-1,100MPa, and A50 is 14-18 percent) and a synthesizing type (Rm is 980-1,150MPa, and A50 is 12-15 percent); and the yield ratio is 0.47-0.65.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled ultra-high-strength steel sheets for automobiles, and relates to the development of high-strength, high-plasticity and comprehensive cold-rolled dual-phase steels, in particular to a 1000MPa Ti microalloyed ultrafine-grained cold-rolled dual-phase steel The preparation process thereof is used for door anti-collision beams, bumpers, etc. and complex parts, such as seat frames and B-pillars. Background technique [0002] In order to reduce vehicle weight and improve safety, it has become a trend to develop high-strength steel sheets for automobiles in recent years. The use of high-strength structural steel to replace the original materials can improve the energy absorption capacity and expand the elastic strain area, increase the deformation resistance of the components, and improve the strength and dent resistance while maintaining high formability, which is a contribution to the thinning and d...

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Problems solved by technology

[0010] At present, the highest level of cold-rolled dual-phase steel plate available internationally reaches 1180MPa, while only Baosteel in my country successfully produced 980MPa and 1180MPa-grade dual-phase steel in 2009, and most domestic steel mills do not yet have high-strength steel continuous annealing The conditions of the production line, on the basis of not using water quenching (cooling rate ≥ 1000 ℃ / s) + tempering continuous annealing line, how to use the existing continuous annealing equipment of domestic steel mills to adopt rapid cooling (cooling rate < 50 ℃ / s) +The production of ultra-high-strength cold-rolled dual-phase steel above 980MPa by the over-aging method has become the focus of public relations for domestic scientific researchers

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