980mpa grade cold-rolled alloyed galvanized quenched partition steel and preparation method thereof

Abstract

The invention relates to a 980MPa grade cold-rolled, alloyed, galvanized, quenched and partitioned steel and a preparation method thereof. The chemical components in the steel are calculated by weight percentage as follows: C: 0.1%-0.17%, Si: 0.60%-1.0%, Mn: 1.50% %~2.50%, P≤0.05%, S≤0.05%, Als≤0.05%; one of Nb, Ti, V, and Nb≤0.02%, Ti≤0.02%, V≤0.05%; the balance is Fe and unavoidable impurities; at the same time satisfy: C+Si / 4≤0.4%; the metallographic structure is ferrite+tempered martensite+retained austenite structure, and the austenitizing temperature of the steel is ≤840℃. The production process includes: smelting, hot rolling, pickling and cold rolling, and galvanizing. Through the alloy and process design, the invention realizes a hole expansion rate of more than 60% at a lower alloy cost, and makes the product more competitive in the market.

Description

technical field [0001] The invention relates to the technical field of automobile steel manufacturing, in particular to a 980MPa grade cold-rolled alloyed galvanized quenched partition steel and a preparation method thereof. Background technique [0002] With the development of the automobile industry, automobile high-strength steel is used in the body-in-white (referring to the welding assembly of body structural parts and covering parts, including front fenders, doors, hoods, trunk lids, but excluding uncoated accessories and decorative parts). The proportion of application on the painted body) is gradually increased, and the intensity level is also gradually increased. For example, the application ratio of steel plates with strengths above 980MPa on domestic vehicles has increased from less than 3% in 2014 to about 10% at present. At the same time, the application ratio of hot-dip galvanized steel sheet and alloyed galvanized steel sheet is also increasing continuously. ...

AI Technical Summary

Problems solved by technology

The technical solution adopts the technological idea of ​​reducing the hardness difference between soft and hard phases through bainite, and obtains mechanical properties with a yield strength of more than 700MPa, a tensile strength of more than 980MPa, an elongation after fracture of more than 12%, and a hole expansion rate of 25-32%. However, a large increase in the proportion of microalloying significantly increases the cost of the alloy, and at the same time, the inhomogeneity of its own bainite phase structure is not conducive to the uniform distribution of strain in the hole expansion stage.

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