Mechanical Processing Technology – Heat Treatment Processes

With the advancement of aerospace, industrial, microelectronics, modern, and bioengineering technologies, the demand for highly precise mechanical components—whose feature sizes range from micrometers to millimeters—is becoming increasingly urgent. The specialization of their structural shapes, the diversification of component materials, and the continuous improvement in dimensional and surface-quality accuracy have become distinctive features of high-precision mechanical components as well as miniature devices and equipment. Consequently, the requirements in terms of functional performance, material properties, structural design, and overall characteristics are steadily rising.

With the rapid development of modern precision machining technologies, numerous advanced precision machining techniques have gradually emerged, such as micro-precision machining, rapid prototyping technology, and ultra-precision machining.

Inserting heat treatment at the appropriate stage during precision machining can ensure good coordination between cold and hot processes and prevent deformation caused by heat treatment. The arrangement of heat treatment, depending on its intended purpose, is generally categorized as follows:

1. The purpose of preliminary heat treatment is to eliminate internal stresses generated during the blank manufacturing process, improve the machinability of metallic materials, and prepare the material for subsequent heat treatments. Heat treatments that fall under this category include tempering, annealing, and normalizing. Typically, these treatments are scheduled either before or after rough machining. When performed before rough machining, they help enhance the machinability of the material; when carried out after rough machining, they effectively relieve residual internal stresses.

2. Heat treatment is generally scheduled after rough machining and semi-finishing, and before or after finishing. For heat treatments that cause significant deformation—such as carburizing and quenching, or tempering—these should be carried out prior to finishing, so that any deformation caused by heat treatment can be corrected during the finishing process. For heat treatments that cause minimal deformation—such as nitriding—these can be scheduled after finishing.