1. Annealed steel heat treatment
The purpose of the annealing process is to do the opposite of hardening. Annealing the metal to release stress, increase ductility, soften the metal, and improve its grain structure. When there is no appropriate preheating stage, welding can lead to uneven temperature of metal components, even in areas where melting occurs and near room temperature.
In this case, welding will weaken the metal; As the weld seam cools, interna; Stress is generated together with hard and brittle points. Annealing is the best solution to solve such common problems and eliminate internal stress.
2. Normalized steel heat treatment
Normalized steel is crucial for eliminating any internal stress during machining, heat treatment, forming, forging, casting, or welding processes. Uncontrolled stress can lead to metal failure, so normalizing the steel before any hardening will help ensure the success of the project.
3. Heat treatment of hardened steel
The purpose of hardening is not only to make steel harder, but also to make it stronger. Hardening increases strength, but also reduces ductility, making the metal more brittle. After the hardening process, the metal may need to undergo some tempering to eliminate some brittleness.
Most steel is hardened through the first two stages of heat treatment (slow heating, then soaking to a uniform temperature within a specified time), while the third stage is different.
After the metal hardens, it quickly cools by immersing it in oil, water, or salt water. Most steels require rapid cooling (known as quenching) to harden, but only a few can be air-cooled. As alloys are added to the steel, the cooling rate required for hardening the steel will decrease. If the cooling rate slows down, the risk of warping or cracking will be reduced.
4. Tempered steel heat treatment
After hardening the metal through flame or shell and introducing internal stress after the inherent rapid cooling process, the steel becomes both harder and too brittle than needed. The solution may be to temper the steel to reduce brittleness and reduce or eliminate internal stress. When steel parts undergo tempering treatment, the hardness caused by hardening will decrease and certain physical properties will be produced.
Tempering always occurs after hardening, reducing brittleness while also softening the steel. Unfortunately, tempering and softening of steel is inevitable. However, the amount of hardness loss can be controlled based on the temperature during the tempering process. Tempering is always carried out at a temperature lower than the critical point on the metal, which is different from other heat treatment processes, which are carried out at a temperature higher than the critical point on the metal.
