Heat treatment process for eliminating white-mouth defects of spheroidal graphite cast iron

Abstract

The invention relates to a heat treatment process for eliminating white-mouth defects of spheroidal graphite cast iron, and belongs to the technical field of metal cast iron graphitization treatment.The heat treatment process comprises the following steps of S1, temperature rising, wherein a to-be-treated spheroidal graphite cast iron part is heated to an annealing temperature along with a furnace, the annealing temperature ranges from 820 DEG C to 860 DEG C, and the heating time is controlled to be 2 to 4 hours; S2, heat preservation, wherein the spheroidal graphite cast iron part is kept atthe annealing temperature for 2 to 4 hours; S3, slow cooling and cooling, wherein the spheroidal graphite cast iron part is subjected to slow cooling for 2 to 3 hours along with the furnace; and S4,air-cooling, wherein after slow cooling and cooling is carried out, the spheroidal graphite cast iron part is taken out and air-cooled. The present application is directed to cast defect tissue features that are substantially spherical or partially short worm-like in graphite morphology, the heat treatment process for eliminating defects of the ductile iron white mouth at low temperature and shorttime is proposed, and finally graphite tissue features with globular and small clusters of flocculent are obtained, so that castings meet the application requirements, and the production loss is effectively saved.

Description

technical field [0001] The invention belongs to the technical field of cast iron graphitization treatment, and in particular relates to a heat treatment process for eliminating white defects of nodular cast iron. Background technique [0002] Ductile iron is a high-strength cast iron material developed in the 1950s. During the smelting process, spheroidal graphite is obtained through spheroidization and inoculation treatment, so that its comprehensive properties are close to those of steel. It has been successfully used to cast some parts with complex stress, high strength, toughness and wear resistance. The basic structure components in ordinary ductile iron (cast state) are: graphite, ferrite and pearlite. [0003] However, due to the influence of many factors such as product structure, composition control, casting process, gating system design, cooling conditions, etc., carbon atoms in ductile iron often diffuse toward the direction of precipitation of unstable phases, t...

AI Technical Summary

Problems solved by technology

This kind of process is mainly based on the graphitization annealing of traditional malleable cast iron. Its main characteristics are long-term high temperature and separate temperature zone treatment, which will easily lead to a large amount of energy consumption, high process repair costs, difficult control of process parameters, and process cycle. Long time affects delivery time, castings are easy to deform and produce oxidative decarburization, and directly affect the service life of heat treatment equipment

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