Thermal deformation method of LSAW steel pipe

Thermal deformation in Longitudinally Submerged Arc Welding (LSAW) steel pipe production can significantly impact product quality. Proper management of thermal deformation involves several critical steps, from material selection to precise heat treatment and operational techniques.

1. Reasonable Material Selection

Choosing the right materials is essential. For precision molds that are prone to thermal deformation, select steel with minimal micro-deformation characteristics. For molds with severe carbide segregation, employ appropriate casting and heat treatment methods, such as quenching and tempering or solution heat treatment. Avoid using large double refining and casting mold steel, which is unsuitable for such treatments. Control the heating temperature and rate carefully, especially for complex precision molds, by using slow heating, preheating, and other techniques to ensure uniform heat distribution and minimize deformation.

2. Correct Heat Treatment Procedures

Implementing accurate heat treatment processes is crucial in reducing deformation in precision molds. Although deformation in complex precision molds can be challenging, understanding the deformation patterns and analyzing the causes can help in choosing methods to minimize and control abnormal deformation.

3. Pre-Heat Treatment and Stress Elimination

Perform pre-heat treatment on precision molds to eliminate residual stress from the machining process. When feasible, use cryogenic vacuum heating and hardening after quenching. Ensure mold hardness while employing pre-cooling, graded cooling, or quenching temperature quenching processes to manage thermal deformation effectively.

4. Rational Mold Design

Design molds with symmetrical shapes and avoid significant thickness disparities. For large and complex molds, plan for deformation by leaving allowances and considering combined designs. Employ pre-heat treatment, aging heat treatment, quenching, and nitriding to maintain mold accuracy. When repairing molds for defects such as blisters, porosity, or wear, use cold welding and other low heat-affected zone repair techniques to prevent further deformation.

By carefully managing these aspects, LSAW steel pipe production can achieve higher quality and consistency, reducing the impact of thermal deformation on the final product.