Metal Heat Treatment Defect Analysis and Cases

Author: Wang Guangsheng / et al.
Editor-in-Chief: Han Huimin
Publisher:
Publish Date: 2000-06-01
Features: This book provides a comprehensive and systematic discussion on heat treatment defects, focusing on common defects such as heat treatment cracks, excessive deformation, excessive residual stress, organization, performance, and brittleness. It combines theoretical analysis with practical experience to discuss the characteristics, causes, hazards, and preventive measures for various heat treatment defects. It specifically introduces defects that may occur in vacuum heat treatment, protected heat treatment, and heat treatment of non-ferrous metals. From a preventive perspective, it also introduces comprehensive quality control of heat treatment. The final chapter lists case studies on analyzing various types of heat treatment defects. This book is suitable for engineering technicians and management personnel engaged in heat treatment research, production, and inspection. It also serves as an important reference for mechanical product design, cold and hot processing technology, maintenance personnel, and faculty and students of metal materials and heat treatment at universities and colleges.
Excerpt: Residual stress, organization, performance, brittleness, and other defects, in terms of occurrence frequency and severity, rank third compared to cracks and deformation, and are generally referred to as the third category of heat treatment defects. The characteristics of this category of defects are that they generally require specialized instruments and methods for detection, with a high likelihood of being missed. They pose significant potential hazards to use, so special attention must be paid to comprehensive quality control in heat treatment production, strengthening inspections, reducing such defects, and strictly preventing missed detections.
The causes of heat treatment defects are multifaceted and can be summarized into three categories: before heat treatment, during heat treatment, and after heat treatment. Before heat treatment, defects may arise due to poor design, material or billet flaws, which then develop or expand into heat treatment defects during the process, with responsibility not lying with the heat treatment itself. In part design, unreasonable design choices such as improper material selection, inappropriate heat treatment technical requirements, abrupt changes in cross-section, sharp transitions, and stress concentrations at marking points may lead to heat treatment defects. Defects in raw materials and various processing defects before heat treatment can also cause heat treatment defects. Possible raw material defects that may lead to heat treatment defects include fluctuations and unevenness in chemical composition, excessive impurity elements, severe segregation, non-metallic inclusions, porosity, banded structure, folds, surface marks, white spots, micro-cracks, oxidation and decarburization, and scratches. Possible casting, forging, welding, and mechanical processing defects that may lead to heat treatment defects mainly include cracks, poor organization, and surface defects.