Overview of Heat Treatment and Surface Treatment Technology‌

----Alexy liu  2025-1-10

Heat treatment technology is an indispensable part of metal processing, covering a variety of processes such as quenching, tempering, annealing and normalizing. Each process aims to give metal materials specific performance.

‌Quenching Technology‌

Quenching, a key step in increasing the hardness and strength of metals, involves heating a part above a critical temperature, holding it for a period of time, and then rapidly cooling it. Although this process can significantly increase the hardness and strength of the steel, it also makes the workpiece more fragile. Therefore, tempering treatment is often required after quenching to balance hardness and toughness.

Tempering and annealing process

Tempering is heating the quenched workpiece to a temperature below the critical point, keeping it warm and then cooling it, in order to eliminate quenching stress, reduce brittleness, and adjust hardness and toughness to ensure that the workpiece has excellent comprehensive mechanical properties. Taking projectiles as an example, they are first quenched to increase the hardness, and then tempered to maintain the hardness while increasing toughness to prevent them from breaking during firing. Annealing is the process of heating the parts to an appropriate temperature and then slowly cooling them to eliminate residual stress, improve cutting performance, and prepare for subsequent heat treatment.

‌Normalizing

Normalizing, as another heat treatment method, requires heating the workpiece to above the critical temperature, keeping it warm and then cooling it in air. This process can enhance the strength and hardness of the workpiece, while improving the cutting performance and organizational structure, providing a more solid material foundation for parts manufacturing.

During the parts manufacturing process, the selection of heat treatment process needs to be comprehensively considered based on material, shape, size and performance requirements to ensure the stability and consistency of heat treatment quality.

Surface treatment technology

In addition to heat treatment, surface treatment technology is also crucial to improving part performance. Electroplating, phosphating, bluing and other processes are widely used to improve the corrosion resistance, wear resistance, lubricity and decorative properties of parts.

‌Electroplating process‌

Electroplating is done by coating the surface of parts with a metal or alloy layer, such as chrome plating, which improves the hardness, wear resistance and corrosion resistance of the projectile surface, while zinc plating enhances the corrosion resistance of the cartridge. During the electroplating process, the composition, temperature and current density of the plating solution must be strictly controlled to ensure uniform quality and thickness of the coating.

Phosphating and bluing treatment

Phosphating treatment forms a phosphate film through a phosphate solution to improve the corrosion resistance and lubricity of the workpiece. The bluing treatment is a process of heating and oxidizing the workpiece with a chemical solution to form a blue or black oxide film on the surface of the workpiece, which has both a decorative effect and a certain anti-rust function.

During the surface treatment process, the process regulations must be strictly followed to ensure quality standards, pay attention to environmental protection, and properly handle the waste generated.