On 2018-08-08 14:48:54
Heat treatment process of metal in Box Furnace
The heat treatment process of box furnace generally includes three processes: heating, heat preservation and cooling, sometimes only heating and cooling. These processes are interrelated and uninterrupted. Heating is one of the important processes of heat treatment. There are many heating methods for metal heat treatment. Charcoal and coal are used as heat sources, and then liquid and gas fuels are used. Electrical application makes heating easy to control and Environmentally friendly, these heat sources can be used for direct heating, or indirect heating of molten salts or metals or floating particles.
When the metal of the box furnace is heated, the workpiece is exposed to the air, which often occurs oxidation and decarburization (that is, the carbon content on the surface of the steel parts), which has an adverse effect on the surface performance. As a result, metals should generally be heated in a controlled or protective atmosphere, in molten salt and vacuum, or protected by coating or packaging.
Tempering is the rapid cooling of the workpiece in a quenching medium such as water oil or other inorganic salts or organic aqueous solutions after heating and holding the workpiece. After quenching, the steel becomes hard but brittle at the same time. In order to reduce the brittleness of the steel, the quenched steel is kept warm for a long time at a suitable temperature higher than the room temperature and lower than 650 ℃, and then cooled. This process is called tempering, annealing, normalizing, quenching and tempering. Among them, quenching and tempering are closely related and often used together. They are indispensable. The "four fire" has evolved different heat treatment processes with different heating temperatures and cooling methods.
In order to obtain certain strength and toughness, the process of combination of quenching and high temperature tempering is called quenching and tempering. After some alloys are quenched to form supersaturated solid solution, they are kept at room temperature or slightly higher temperature for a longer time to increase the hardness, strength or electromagnetic properties of the alloy. This heat treatment process is called aging treatment.