What are the general processes of metal heat treatment

Heat treatment of metals, China is the world's first invention and use of pig iron country. As early as in the spring and Autumn period (476 BC) and the Warring States period (221 BC), our ancestors used pig iron to cast production tools and living utensils. This kind of pig iron is similar to modern white iron. In pig iron, all carbon exists in the form of Fe3C, which is hard but brittle but can not be used.

Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing technologies, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but endows or improves the performance of the workpiece by changing the microstructure inside the workpiece or the chemical composition on the surface of the workpiece. Its characteristic is to improve the internal quality of the workpiece, which is generally not visible to the naked eye.

Heat treatment process generally includes three processes: heating, heat preservation and cooling, sometimes only heating and cooling. These processes are interlinked and uninterrupted. Heating is one of the important processes of heat treatment. There are many heating methods for metal heat treatment, which use charcoal and coal as heat source, and then use liquid and gas fuel. The application of electricity makes heating easy to control and no environmental pollution. These heat sources can be used to heat directly, or indirectly through molten salt or metal, or even floating particles.

In addition, the distortion of the workpiece in the heating process can not be measured, so the distortion of the heating process is little known and easy to be ignored. In fact, the distortion is not only caused by thermal stress, but also by the release of internal stress itself. In the process of manufacturing high-precision gear products, the distortion of gear heat treatment in the heating process should also be paid attention to.

Generally speaking, heat treatment process is the process of heating, heat preservation and cooling. It is an important part of the mechanical industry. It is an indispensable part of the production chain of modern manufacturing industry. It is a key processing procedure to promote the full potential of metal materials and improve the internal quality and service life of mechanical parts. It is also the basic technology of manufacturing industry.