High-elongation cold-rolled TRIP (Transformation-Induced Plasticity) steel plate and preparation method thereof

Abstract

The invention discloses a high-elongation cold-rolled TRIP (Transformation-Induced Plasticity) steel plate, comprising 0.15-0.25% of C, 0.4-1.5% of Si, 0.5-2.5% of Mn, 0.04-0.10% of P, less than or equal to 0.02% of S, 0.02-0.5% of Al, less than or equal to 0.01% of N, 0-0.5% of Nb, 0-0.5% of V, 0-0.5% of Ti, 0-2% of Cr, 0-1% of Mo, and the balance of Fe and inevitable impurities, wherein in the microscopic structure, the area ratio of ferrite is 10-80%, while the area ratio of residual austenite is 3-20% and the area ratio of martensite is 0-20%, and the rest part is bainite; the hot rolling heating temperature is 1100-1250 DEG C, the heat preservation time is greater than or equal to 2 h, the rolling starting temperature is equal to or higher than 1100 DEG C, the final rolling temperature ranges from 850 to 950 DEG C, and the coiling temperature is lower than 720 DEG C; the hot-rolled plate is 2-4 mm thick; accumulated compression quantity of cold rolling is 40-80%; the annealing temperature is 700-(Ac3+50) DEG C, the heat preservation time is 30-360 s, the cooling rate is 10-150 DEG C / s, the aging temperature is 300-600 DEG C, the aging time is 30-1200 s and the cooling rate is 5-100 DEG C / s; and finally, cooling is performed until the temperature reaches the room temperature.

Description

technical field [0001] The invention belongs to the field of cold-rolled automobile steel manufacturing, and relates to a low-cost high-elongation cold-rolled TRIP steel plate with a tensile strength greater than 780 MPa and an elongation greater than 24% and a preparation method thereof. Background technique [0002] With the continuous improvement of people's requirements for environmental protection, safety and energy saving of automobiles, the steel for automobiles is developing towards the direction of high strength and high elongation. Cold-rolled high-strength automotive steel above 780MPa, as the most widely used advanced high-strength steel, has become the research focus of scholars and steel companies in various countries. [0003] Patent CN1782116A introduces a high-strength automotive steel - dual-phase steel, its structure is ferrite + martensite, this steel has low yield strength, high tensile strength, low yield ratio, and rapid work hardening The disadvantag...

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Problems solved by technology

[0003] Patent CN1782116A introduces a high-strength automotive steel - dual-phase steel, its structure is ferrite + martensite, this steel has low yield strength, high tensile strength, low yield ratio, and rapid work hardening The disadvantage is that the elongation rate is between 15 and 24%, which limits the application range of this steel type in auto parts

[0004] Patent CN101353761A introduces a conventional C-Al-Mn series TRIP steel, whose tensile strength is greater than 780MPa. The disadvantage is that the Al content is too high, which makes continuous casting difficult and it is difficult to achieve stable mass production

At the same time, it will lead to a lot of inclusions in the continuous casting slab, and the surface quality of the cold-rolled sheet is poor, which is difficult to meet the needs of automobile factories for cold-rolled sheets for automobiles

[0005] Patent CN101429590A introduces a high-manganese TWIP steel, which has the advantages of high strength and high elongation, which can meet the requirements of most auto parts on strength and elongation. The disadvantage is that the Mn content is too high, resulting in high production costs. Continuous casting and rolling are difficult, and it is difficult to apply in large quantities in industry

[0006] Patent CN102304664 introduces a kind of TRIP steel with medium manganese, which is characterized in that the content of Mn is between 5 and 10%. The advantage is that the steel has good strength and elongation. The disadvantage is that the content of Mn is high and the production cost is high. , continuous casting and rolling are difficult, and it is difficult to achieve stable mass production

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