440MPa of precipitation strengthening-type cold rolled interstitial free (IF) steel containing niobium and production method thereof

Abstract

The invention discloses 440MPa of precipitation strengthening-type cold rolled interstitial free (IF) steel containing niobium and a production method thereof. The deep drawing forming property of the IF steel is improved when high strength is obtained. The IF steel comprises the following chemical components: 0.005-0.008% of C, 0.05-0.08% of Si, 1.5-2.0% of Mn, less than 0.04% of P, less than 0.004% of S, 0.003% or less of N, 0.08-0.12% of Nb, 0.0005-0.002% of B, 0.01-0.03% of Ti, and the balance of Fe and inevitable impurities. The production method comprises the following processes: smelting, hot rolling, cold rolling, continuous annealing or hot galvanizing; the technological parameters of rolling are as follows: the heating temperature of a plate blank is 1150-1250 DEG C; the finish rolling temperature is 880-900 DEG C; the plate blank is formed into 4mm from 35mm in a hot rolling manner; the coiling temperature is 620-660 DEG C / s; reduction in cold rolling is 80-85%; the continuous annealing temperature is 830-870 DEG C; the continuous annealing heat preservation time is 100-200 seconds; the cooling speed is 15-25 DEG C / s after annealing. By adopting the production method, the 440MPa of high-strength IF steel with good deep drawing property, of which the strength is greater than or equal to 440MPa, the yield ratio is smaller than 0.6, the ductility is 33-36%, and an r value is greater than or equal to 1.7 can be obtained.

Description

technical field [0001] The invention relates to the technical field of high-strength steel for automobiles, and in particular provides a 440MPa niobium-containing precipitation-strengthened cold-rolled IF steel and a production method thereof. technical background [0002] With the continuous increase of car ownership and rising fuel prices, the automotive industry has higher and higher requirements for lightweight, safety, environmental protection and fuel economy. The production of IF steel as the outer panel of automobiles has become a symbol of a country's automobile steel plates. Reducing production costs and further improving product grades are the current research and production directions for IF steel. [0003] IF steel (Interstitial Free Steel), also known as interstitial-free steel, is added trace alloy elements (mainly Ti, Nb) to ultra-low carbon (generally, the carbon content is below 0.005%) to make the C and N in the steel The interstitial atoms are completely...

AI Technical Summary

Problems solved by technology

Although the bell-type optimized annealing process can improve the secondary processing brittleness resistance of the bell-type annealed IF steel, the annealing time of the bell-type production process is longer than that of the continuous annealing process, and the performance after annealing is far inferior to that of the continuous annealing process.

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