Salt bath and application thereof as well as heat treatment method of high-strength steel weld joint

Abstract

The invention discloses a salt bath formula containing KOH, NaOH and H2O. The invention discloses application of the salt bath formula to the heat treatment of a high-strength steel weld joint. Moreover, the invention also discloses a heat treatment method of the high-strength steel weld joint. The heat treatment method comprises the steps of placing the high-strength steel weld joint in the heat treatment salt bath, cooling till reaching the holding temperature and holding the temperature, wherein the holding temperature is higher than the martensite transformation starting temperature 20-50 DEG C of the high-strength steel weld joint and the salt bath formula is adopted in the heat treatment salt bath. The salt bath formula disclosed by the invention has the characteristics of stronger cooling capacity, stable chemical property, difficulty in resolving and little residue. The heat treatment method of the high-strength steel weld joint, disclosed by the invention, has the advantages that the weld joint is cooled by using the salt bath formula, so that the toughness and the strength of the weld joint can be improved.

Description

technical field [0001] The invention relates to the field of heat treatment, in particular to a salt bath and its application and a heat treatment method for high-strength steel welds. Background technique [0002] Salt bath heat treatment is a common heat treatment process, which is used to optimize the metallographic structure of materials to improve the performance of workpieces. [0003] High-strength steel is widely used in engineering construction and mechanical fields. Because high-strength steel contains more carbon and alloy elements, high-strength steel has a greater tendency to harden. During the welding process, martensitic hardened structures are easily produced in the welded joints, causing cold cracks. The sensitivity increases, and the mechanical properties of the welded joint decrease. [0004] Therefore, the method of salt bath heat treatment is considered to control the formation of hardened structure of high-strength steel. Specifically, after high-stren...

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Problems solved by technology

[0005] At present, the common low-temperature heat treatment salt bath is mainly based on the nitrate system, for example, the composition and proportion are 50% by weight of KNO 3 and 50% by weight NaNO 2 The salt bath, its working temperature is 150-500 ℃, and composition and proportioning are the KNO of 55% by weight 3 and 45% by weight NaNO 2 The salt bath, its working temperature is 230-550 ℃, and the composition and ratio are 50% by weight of NaNO 3 and 50% by weight KNO 3 The working temperature of the salt bath is 300-550°C. However, within the working range, the cooling capacity of these salt baths cannot reach the rapid cooling of the high-strength steel weld to a temperature slightly higher than the martensitic transformation start temperature. ; and the fluidity of these salt baths is relatively poor, which brings inconvenience to the recovery and reuse of salt baths

Therefore, the existing salt bath is not suitable for heat treatment of high-strength steel welds with welding salt bath

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