Heat treatment method for improving yield strength of steel casting

Abstract

A heat treatment method for improving the yield strength of steel castings, comprising the following steps: a. heating the steel castings to an austenitizing temperature of 880°C-950°C and keeping them warm; b. heating the austenitized steel castings out of the furnace, adopt air cooling + water mist cooling or tap water quenching or polymer quenching to cool the steel castings rapidly, and the cooling speed of the steel castings reaches 30°C / min-120°C / min; c. The cooled cast The steel piece is heated and tempered to 580°C-650°C, and kept warm; the chemical composition of the steel casting and the mass percentage of each component element are as follows: C%=0.12~0.35, Si%=0.20~1.0, Mn%= 0.5~1.8, P%≤0.035, S%≤0.035, Cr%≤2.20, Mo%≤1.20, Ni%≤0.50, the rest are Fe and unavoidable impurity elements.

Description

technical field [0001] The invention relates to the technical field of heat treatment of steel castings, in particular to a heat treatment method for improving the yield strength of steel castings. Background technique [0002] Intrinsic factors affecting the yield strength of steel castings include the characteristics of the material itself, such as bond, structure, structure, and atomic nature; external factors include test temperature, strain rate, stress state, sample size and precision, and sample processing methods, etc. influences. [0003] When the external factors remain stable or unchanged, for steel castings, if the yield strength is increased from the internal factors, the technical means adopted are to improve by adjusting the chemical composition or heat treatment process or the joint action of the two. The increase of most chemical elements will increase the yield strength, such as C, Si, Mn, Ti, Cu, Al, V, Nb, etc. However, what element content to increase,...

AI Technical Summary

Problems solved by technology

However, what element content to increase, how much to increase, and how much to increase the yield strength need to be determined according to the specific composition standard requirements and tests. The test verification cycle is long, the interaction of elements is more complicated, and the increase in composition content will increase the smelting cost, especially It is a large-tonnage casting, and the cost increase is more obvious

At the same time, the increase of the content of most elements will increase the carbon equivalent, reduce the weldability, and increase the difficulty of welding and repairing defects in steel castings.