A 1000mpa cold-rolled dual-phase steel with excellent local formability and its preparation method

Abstract

The invention discloses a 1000MPa cold-rolled dual-phase steel with excellent local formability and a preparation method thereof. The chemical composition of the steel is: C: 0.06-0.11%, Si: 0.1-0.3%, Mn : 1.5~2.4%, Cr: 0.2~0.6%, Mo: 0.2~0.6%, P: ≤0.010%, S: ≤0.006%, Ti: 0.01~0.04%, Al: 0.1~0.3%, B: 0.0001~ 0.005%, the rest is iron and unavoidable impurities, and Mn+Cr+B>2.1%; the present invention limits the addition of easily segregated element Mn through rational design of chemical composition, refines grains and forms in ferrite Nano-precipitated phase strengthens the ferrite structure and achieves a balance of strength, elongation and hole expansion performance, and the product has excellent local forming performance.

Description

technical field [0001] The invention relates to the technical field of steel preparation, in particular to a 1000MPa cold-rolled dual-phase steel with excellent local formability and a preparation method thereof. Background technique [0002] As the automotive industry has increasingly stringent requirements for lightweight, safety, and low emissions, the proportion of high-strength steel used in new automotive models continues to increase. A typical representative, in the body structure designed by the project of "ultra-light steel car body-advanced car concept", high-strength steel with a tensile strength of 1000MPa accounts for the largest proportion, accounting for 29% to 30% of the weight of the car body about. [0003] The traditional dual-phase steel structure is mainly composed of a soft ferrite matrix and a high-strength martensite. The performance of this structure is characterized by a low yield ratio and excellent elongation. It is suitable for stamping parts P...

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Problems solved by technology

However, it is undeniable that the dual-phase steel has a high cracking rate in the forming of parts required for hole expansion and flanging, while the prior art multi-phase steel shows that the improvement of hole expansion performance plays a positive role in the improvement of edge ductility, however In the prior art, selective oxidation during the annealing process due to the addition of alloying elements is ubiquitous, which eventually causes surface defects such as poor phosphating; therefore, on the basis of traditional dual-phase steel, its local formability is further optimized to achieve excellent The development of dual-phase steel with hole expansion performance can further meet the requirements of different users

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