Manufacturing method for controlling large inclusion of non-quenched and tempered steel

Abstract

The invention relates to a manufacturing method for a large inclusion smelting control technology of sulfur and nitrogen controlled non-quenched and tempered steel with the S content being 0.050%-0.065%, the N content being 0.010%-0.018% and the Ti content being 0.008%-0.025%, wherein the size of the inclusion is larger than 50 microns but smaller than 1 millimeter. According to the manufacturingmethod, the forming amount of Al and Ca contained brittle inclusion is reduced by controlling the Al content and the Ca content in the steel, the stable running of the casting cycle is ensured by controlling crystallizer casting powder selection, crystallizer liquid level fluctuation in the casting cycle and nozzle stopper rod curve fluctuation, and therefore the large cluster-shaped inclusion with the size being about 50 microns-200 microns is restrained from forming in the steel, and the service life of a crankshaft is prolonged.

Description

technical field [0001] The invention belongs to the technical field of special steels, and in particular relates to a smelting and manufacturing method for controlling large-size inclusions of sulfur-containing non-quenched and tempered steels. Background technique [0002] As the service life requirements of domestic automobiles are getting higher and higher, the steel for automobile crankshafts also has higher requirements on the internal quality of the steel. The main purpose is to check the inclusions through ultrasonic flaw detection of round steel. Larger inclusions will lead to unqualified ultrasonic flaw detection. , resulting in unqualified round steel quality and increased production costs. At present, more and more non-quenched and tempered steels are used for domestic crankshafts. Non-quenched and tempered steels contain high sulfur and are prone to produce more sulfides during the smelting process. The slender sulfides will not actually reduce the internal quali...

AI Technical Summary

Problems solved by technology

Due to the large number of these clustered inclusions in the steel, the pass rate of round steel flaw detection is less than 70%

[0006] To sum up, the current control of large-sized inclusions in non-quenched and tempered steels with sulfur content ≥ 0.050% has seriously affected the quality of steel for automobile crankshafts. Poor castability, or even stop pouring, so the number of consecutive pouring furnaces is difficult to exceed 4 furnaces, which affects production efficiency

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