Steel for 300MPa-grade automobile structural part and production method for steel

Abstract

The invention relates to steel for a 300MPa-grade automobile structural part and a production method for the steel. The steel comprises the following main components in percentage by weight: 0.06-0.08 percent of C, 0.05-0.09 percent of Si, 0.30-0.45 percent of Mn, 0.025-0.055 percent of Al, 0.015-0.025 percent of P, less than or equal to 0.006 percent of S, 0.010-0.019 percent of Nb, less than or equal to 0.006 percent of N and the balance of Fe and impurities. The production method comprises the production steps of molten iron desulfurization, converter smelting, ladle argon blowing, continuous casting, heating of a casting blank, hot rolling, winding, conventional pickling, cold rolling, continuous operation and flattening for later use. The production method disclosed by the invention has the advantages of short process flow, lower energy consumption and stable mechanical property; and in addition, on the premise that the yield strength of 300-340MPa and the tensile strength of 390-445MPa are met, the elongation percentage is not lower than 31 percent, the plastic strain ratio r is 1.45-1.80, a strain hardening index n is 0.16-0.20, a wide-cold test bending is 180 degrees and a bending diameter d is equal to 0; and in a metallographic structure, an equiaxed ferrite is 85-90 percent and a granular pearlite is 10-15 percent.

Description

technical field [0001] The invention relates to a steel material for automobiles and a production method thereof, in particular to a steel for 300MPa grade automobile structural parts and a production method thereof. Background technique [0002] 300MPa grade micro-alloyed steel is widely used in the automobile, especially the car manufacturing industry because of its appropriate strength and plasticity, good formability and weldability, and the amount used for each vehicle reaches 40-60 kg. [0003] After searching, the Chinese patent (ZL99111533.3) disclosed "A Method for Manufacturing Low Carbon Microalloyed Steel", and its chemical composition (wt %) is C: 0.04~0.11, Si: 0.1~0.3, Mn: 1.0~1.5 , P: 0.001~0.015, S: 0.001~0.01, Al: 0.001~0.05, Nb: 0.03~0.06, Ti: 0.01~0.04, and the balance is Fe. Its disadvantages are: since Ti contains 0.01-0.04%, and Ti is easy to oxidize, it is necessary to increase the RH vacuum treatment process during steelmaking, resulting in high ene...

AI Technical Summary

Problems solved by technology

Its disadvantages are: due to the content of 0.01~0.04% Ti, and Ti is easy to oxidize, it is necessary to increase the RH vacuum treatment process during steelmaking, resulting in high energy consumption, reduced production efficiency, and low yield of Ti

In addition, due to the high content of Mn, the difficulty of welding increases

In addition, the Si content is also high, which makes it easy to form Mn on the surface of the steel plate. 2 SiO 4 Oxide, unfavorable galvanizing performance, prone to dezincification

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