Heat Treating Process
Heat treating is a process used to change the physical and chemical properties of any material. It is used by metals in particular to alter the hardness, strength, elasticity, and elasticity of components. Heat treat processes are divided into three stages: preheating, austenitizing and quenching, and tempering. Each of these processes has a corresponding temperature range, and in some cases, a certain pattern or temperature is used to optimize the process.
Preheating
The first step of heat treating, which is called preheating, involves heating the material to a certain temperature range. This temperature range is determined by the material, the desired properties of the material, and the type of process the material is to undergo. In the case of a standard steel alloy, the ideal preheating temperature range is between 1000°F and 2000°F. This range allows the material to warm evenly, allows the impurities to rise to the surface, and prevents cracks from forming due to rapid cooling.
Austenitizing and Quenching
The second step of the heat treating process is called austenitizing and quenching. That involves placing the material in an austenitizing furnace and heating it to a specific temperature range. With steel alloys, the typical austenitizing temperature range is between 1600°F and 1900°F. This temperature range allows the steel to become austenitized, meaning the carbides and other impurities the material contain will dissolve and become supersaturated. Following the austenitizing step, the material is then quenched either in water, oil, or gas. This process cools the material rapidly and locks in the desired properties.
Tempering
The last process of the heat treating cycle is tempering. During tempering, the material is heated to a certain temperature range beyond its quenching temperature. With steel alloys, the ideal tempering temperature range is between 600°F and 900°F depending on the desired material properties. Tempering allows for the steel to reach equilibrium between hardness, strength and ductility. It also allows for any residual carbon or other impurities to adjust during the tempering process and refine the desired properties.
After each of the above steps, the material may be reheated, cooled, held at a certain temperature, and reheated again. These processes are called normalizing, annealing, and stress relieving and they are used to refine the material further and create specific material properties.
Overall, heat treating is a process used to alter the physical and chemical properties of a material by repeating a cycle of preheating, austenitizing and quenching, and tempering. Each stage of this process corresponds to a certain temperature range and pattern to optimize the process. Other processes such as normalizing, annealing and stress relieving may be used to refine the material further and create unique material properties.
