High-toughness, cold-roll and double-phase steel plate for automobile and manufacture method of steel plate

Abstract

The invention relates to a high-toughness, cold-roll and double-phase steel plate for an automobile and a manufacture method of the steel plate. The steel plate comprises chemical components in percentage by weight as follows: 0.07%-0.11% of C, 1.25%-1.35% of Si, 1.90%-2.20% of Mn, smaller than or equal to 0.003% of P, smaller than or equal to 0.003% of S and the balance of Fe and unavoidable impurities. The structure of the steel plate in the position of one fourth of the thickness adopts polygonal ferrite, 4-11vol.% of island-like martensite and a little bainite (2-5vol.%), the island-like martensite is dispersed in the ferrite, sigma b of the steel plate is larger than or equal to 540 MPa, sigma 0.2 is smaller than or equal to 380 MPa, A80% is larger than or equal to 30%, and the steel plate has higher strain hardening index n (larger than 0.2); according to the heat treatment temperature for the steel plate, the steel plate is heated to 730-750 DEG C at the heating speed of 20-60 DEG C / h, heat preservation is performed for 15-17 h, and the steel plate is cooled to below 150 DEG C for discharge at the speed of 30-50 DEG C / h; and finally, the steel plate is flattened at the flattening rate of 0.25%-0.35%. An alloy system is simple, the production technology is reliable, and the mechanical properties of products are excellent.

Description

technical field [0001] The invention relates to a dual-phase steel plate for automobiles and a heat treatment production process thereof. Background technique [0002] In recent years, due to the shortage of energy in the world, countries are trying to use high-strength toughness materials to make automobile components, so as to reduce the weight of automobiles and save energy. As a high-strength toughness steel, a dual-phase steel with ferrite plus martensite structure has attracted great attention. [0003] At present, all countries in the world have announced that the production of cold-rolled dual-phase steel sheets will contain 1.0-1.8% Mn, ≤ 1.2% Si or steel with a small amount of Cr, Ni, Ti, Nb and other elements added on the basis of Mn. In the continuous annealing furnace, heat rapidly to the α + γ zone for a short time, and then accelerate cooling to below the martensitic transformation point at a rate exceeding the critical cooling rate of the steel to obtain the...

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Problems solved by technology

The production of this kind of cold-rolled dual-phase steel plate must have continuous annealing equipment with a rapid cooling device, and the construction of this equipment requires a huge investment in equipment, and is limited by the technology and site of most metallurgical plants.

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