800 MPa grade cold-rolling dual-phase steel and manufacturing method thereof

Abstract

The invention discloses 800 MPa grade cold-rolling dual-phase steel and a manufacturing method thereof. The steel contains the following chemical compositions in percentage by weight: 0.10-0.18% of C, 0.03-0.19% of Si, 2.6-3.0% of Mn, 0.01-0.04% of Als, 0.15-0.9% of Cr, and the balance of Fe and other inevitable impurities. The manufacturing method for the steel comprises the following steps sequentially: heating billet steel to 1150-1250 DEG C along with a furnace and preserving the temperature for 1.5-3 hours under heat insulation condition, then performing hot rolling, wherein the rough rolling start rolling temperature is controlled within the range from 1050 DEG C to 1110 DEG C, the precision rolling finish rolling temperature is controlled within the range from 860 DEG C to 900 DEG C, and the simulation curling temperature is controlled within the range from 560 to 600 DEG C; washing a hot rolled plate with acid and then carrying out cold rolling; wherein the cold rolling pressing rate is controlled to be 45-75%, then performing the annealing treatment, wherein the annealing temperature is controlled within the range from 760 DEG C to 860 DEG C; and slowly cooling the hot rolled plate to 630-680 DEG C after keeping for 1-5 minutes under heat preservation condition and then rapidly cooling to be below 350 DEG C at a speed more than 25 DEG C/s for ageing treatment lasting for 5-10 minutes. The practice proves that the steel has the advantages of low yield strength, low yield ratio, high coefficient of elongation, and excellent forming property, and the manufacturing method has simple process and low cost.

Description

technical field [0001] The invention belongs to the technical field of high-strength steel production, and specifically refers to an 800MPa grade cold-rolled dual-phase steel and a manufacturing method thereof. Background technique [0002] With the continuous development of lightweight automobile bodies and the continuous improvement of passenger safety requirements, ultra-high-strength steels of 800 MPa and above have been more and more used in structural parts and reinforcements of mid-to-high-end cars to achieve energy saving and emission reduction and improve vehicle crash safety. In recent years, the proportion of ultra-high-strength steel plates used by international automakers in newly developed models has reached about 20%, and the proportion of high-strength steel plates used in international award-winning models is generally around 70%. The adoption rate of high-strength steel plates for new models is also increasing year by year. The cold-rolled dual-phase stee...

AI Technical Summary

Problems solved by technology

However, the Mo element is expensive and the production cost is high, while the addition of Nb, V and other micro-alloying elements increases the difficulty of process control in the production process, requires high equipment capabilities and control levels, and process fluctuations have a greater impact on final performance. , while adding Nb and V, the precipitation strengthening effect will increase the tensile strength and the yield strength will also increase significantly, which is unfavorable for stamping forming and unfavorable for industrial production

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