Heat treatment is one of the methods that are commonly used to alter the mechanical and physical properties of metals used in making knives and other tools without necessarily changing their shape. This is an essential process in metal manufacturing that can be used to increase the characteristics of metals so that further processing can take place. The heat treatment process entails controlling the heating and cooling process of the metals. Steel can be heated so as to prepare it to be used in a variety of industrial and commercial applications. When heated, metals increase their hardness and strength and improve their toughness. In addition, heating improves formability, improves elasticity, and increases ductility.
The cooling process plays an important role as well. Steel hardens when it is cooled rapidly. This process is popularly referred to as annealing. It softens makes other metals hard. It softens the aluminum hence makes the knife making the process easy.
Annealing
This is where steel is heated to a specified temperature before it is cooled at a controlled rate and temperature. The process has three effects: improves the machinability of the metal, softens the metal and enhances the electrical conductivity of the metal. Annealing plays an important role in restoring ductility of the metal and plays a critical role in allowing for cold working to take place without cracking. The process of annealing releases any mechanical stress that is produced during grinding and machining.
Annealing can be used in steel even though other metals such as brass, aluminum, and copper can be annealed as well. In most of the cases, large ovens may be used in annealing, however; the oven must be large enough to allow air to fully circulate around the metal. Smaller pieces can be annealed in car-bottom furnaces while large pieces can be annealed in conveyor furnaces.
Normally, during the process, the metal is heated to a specified temperature before recrystallization is allowed to take place. When this happens, all defects that cause deformation of metal could be repaired. The metal should be held to a fixed temperature for some time before it is allowed to cool down at a room temperature. The cooling process must be monitored and done slowly if you are looking forward to obtaining refined metals that maximize on softness.
Tempering
It is used to increase the toughness of an alloy. It is particularly used in steel. Normally, tempering will be carried out after hardening to help reduce hardness. Tempering changes:
- The strength
- The hardness
- Strength
- Structural stability
- Ductility
Tempering entails heating the metal to a specified temperature below a certain critical point to reduce the hardness and brittleness while maintaining the hardness of the metals. Higher temperature help to reduce hardness while increases the metals plasticity and elasticity. However, it has been observed tempering may cause tensile stress to be lost.
If you want to use the metal to make a knife, it is important that you heat the metal gradually to avoid instances of cracking it. The metal should then be maintained at a predetermined temperature for a stated period of time. Every inch should take an hour after which the metal should then be cooled in still air and forged into a knife.