440MPa grade niobium-containing high-strength IF steel and manufacturing method thereof

Abstract

The invention relates to a 440MPa niobium-bearing high-strength IF steel and a preparation method thereof, which belong to the high-strength automobile steel technical field. The chemical compositions in weight percent are 0.005 to 0.007 percent of carbon, 0.02 to 0.03 percent of silicon, 1.2 to 2.1 percent of manganese, less than 0.08 percent of phosphor, less than 0.006 percent of sulfur, less than or equal to 0.003 percent of nitrogen, 0.05 to 0.11 percent of niobium, 0.0005 to 0.002 percent of boron, 0.2 to 0.5 percent of chromium, 0.005 to 0.01 percent of titanium, 0.01 to 0.04 percent of aluminum, and the balance being iron and unavoidable impurities. The manufacturing technique is smelting, hot rolling, cold rolling and continuous annealing or hot galvanizing. The controlled technological parameters are as follows: the heating temperature of a hot-rolled slab is between 1,200 and 1,250 DEG C; the heat preservation time is between 0.5 and 1.5 hours; the finishing temperature is between 910 and 920 DEG C; the coiling temperature is between 640 and 680 DEG C; the cold rolling reduction is 80 percent; the annealing temperature is between 840 and 860 DEG C; and the annealing heat preservation time is between 100 and 120 seconds. The preparation method has the advantage of capability of obtaining the 440MPa high-strength IF steel with the strength more than or equal to 440MPa, an r value more than or equal to 1.5 and good deep drawability.

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 high-strength IF steel and a preparation method thereof. The 440MPa niobium-containing high-strength IF steel with excellent deep drawing performance is obtained through the combination of P, Mn and Cr Solid solution strengthening, and the combination of precipitation strengthening and fine-grain strengthening of niobium-containing carbonitrides, so as to obtain excellent comprehensive mechanical properties. Background technique [0002] With the development of industrial technology, energy and environmental issues have become major social issues, and the automobile industry is no exception. Therefore, in the structural performance of modern automobiles, reducing weight and consumption, reducing environmental pollution and improving safety have become research hotspots. Steel for automobiles is constantly developi...

AI Technical Summary

Problems solved by technology

[0009] The purpose of the present invention is to provide a 440MPa niobium-containing high-strength IF steel and its preparation method, which solves the problems of reduced formability as the strength increases

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