A preparation method of free-cutting high-strength multi-phase non-quenched and tempered steel

Abstract

The invention provides a preparation method of high-strength complex-phase non-quenched and tempered steel easy to cut. Superfast cooling equipment is additionally arranged behind an outlet of a heating furnace, secondary heating is conducted in the heating furnace, conventional hot rolling is conducted, preheating treatment is conducted in advance, a steel blank can generate a large core-surfacetemperature difference under the superfast cooling condition, original thick austenite is converted into fine martensite tissue cut original austenite crystalline grains, the crystalline grain refining effect is generated, and by virtue of the tissue genetic characteristics, the secondary heating original austenite size is decreased, and a hot-rolled final tissue is obviously refined compared withthat in a conventional technology. The steel blank enters the superfast cooling equipment after being hot-rolled, the temperature is lowered to the bainite transformation temperature, heat preservation is conducted, then the steel blank enters the superfast cooling equipment to be cooled to the room temperature, the bainite-martensite complex-phase non-quenched and tempered steel tissue is obtained, and the strength is improved. The quenching and tempering treatment property level is achieved, the later-period heat treatment process is omitted, energy sources are saved, the production cost isreduced, and the production efficiency is improved.

Description

Technical field [0001] The invention belongs to the field of metallurgy and relates to a process method for preparing high-strength multiphase non-quenched and tempered steel. Background technique [0002] With the rapid development of machinery manufacturing and automotive fields, environmental protection has attracted more and more attention. Not only on the basis of emphasizing development, but also reasonable technological innovation. It is an effective way to use new materials to replace the original traditional materials for the manufacture of automobiles. According to data, the energy consumption of driving in automobiles accounts for 80%, the energy consumption of materials production accounts for 15%, and the energy consumption of automobile manufacturing accounts for 5%. By using non-modulated steel to replace traditional quenched and tempered steel, production energy consumption can be greatly reduced by more than 40%, while manufacturing costs can be reduced by more ...

AI Technical Summary

Problems solved by technology

[0004] In the traditional free-cutting non-quenched and tempered steel, due to the existence of MnS, it often forms long strips in the steel after rolling, which is easy to become the source of cracks and adversely affects the performance.

[0005] Moreover, the non-quenched and tempered steel has not been processed, and its mechanical properties are low. Under the traditional process, the final structure is pearlite and ferrite, with a tensile strength of 800-850MPa, a yield strength of 700-750MPa, and a hardness of 260-280HV.

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