Ferritomartensite hot-rolled dual phase steel with high surface quality and manufacturing method thereof

Abstract

The invention discloses ferritomartensite hot-rolled dual phase steel with high surface quality and a manufacturing method thereof. The steel comprises, by weight percent, 0.04 to 0.08% of C, not larger than 0.1% of Si, 1.0 to 1.4% of Mn, 0.3 to 0.8% of Al, 0.15 to 0.60% of Cr, 0.01 to 0.03% of Nb, not larger than 0.015% of P, not larger than 0.002% of S, and not larger than 0.005% of N, one or more of not larger than 0.03% of Ti, not larger than 0.03% of V, and not larger than 0.005% of Ca and the balance Fe and inevitable impurities. The conditions that the sum of Si+2Al+Cr is larger than orequal to 1.0 and Al/Cr is smaller than or equal to 2.5 need to be met at the same time, according to the hot-rolled dual phase steel, after acid pickling, the surface is bright and clean and free offigures, the tensile strength of the steel can be up to 600 MPa or above, the yield ratio is 0.7 or below, the hole expansion rate is 50% or above, the easy forming high hole expansion property is achieved, the steel can be used for producing parts like car wheel spokes, in addition, a production process is wide in window, industrial large production is easy, and performance is stable.

Description

technical field [0001] The invention belongs to the field of low-alloy steel manufacturing, and relates to a high-surface-quality ferritic-martensitic hot-rolled dual-phase steel and a manufacturing method, which are suitable for automotive appearance parts such as automobile wheels. Background technique [0002] Based on the demand for emission reduction and consumption reduction, automobile weight reduction is a global trend. Many high-strength advanced high-strength steels have been developed to meet the demand for new steel materials with good processability such as automobiles. Among them, ferrite + martensitic dual-phase steel has the characteristics of low yield strength ratio, no yield platform, easy forming, high work hardening rate, high bake hardening, and long fatigue life, and has become the preferred choice for automotive parts such as wheel spokes. preferred material. [0003] In order to obtain the desired microstructure of ferrite + martensitic dual-phase ...

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Problems solved by technology

In addition, the ferrite formation process window of the C-Mn-Cr system is narrow, and the production difficulty and performance fluctuation are relatively large.

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