Classification of vacuum furnaces for powder metallurgy
With the development of science and technology, vacuum furnace is widely used in the process of powder metallurgy and heat treatment of metal materials. There are many kinds of vacuum furnaces:
(1) It can be divided into vacuum carbonization furnace, vacuum sintering furnace, vacuum annealing furnace, vacuum quenching furnace, vacuum tempering furnace and vacuum carburizing furnace.
(2) According to the heat source, it can be divided into resistance heating vacuum furnace, induction heating vacuum furnace, arc heating vacuum furnace, plasma arc heating vacuum furnace and electron beam heating vacuum furnace.
(3) According to the vacuum degree, it can be divided into low vacuum furnace, high vacuum furnace and ultra vacuum furnace.
(4) According to the working temperature, it can be divided into low temperature vacuum furnace (below 700 ℃), medium temperature vacuum furnace (700-1000 ℃) and high temperature vacuum furnace (above 1000 ℃).
(5) According to the nature of operation, it can be divided into periodic vacuum furnace and continuous vacuum furnace.
(6) According to the form of furnace, it can be divided into vertical vacuum furnace and horizontal vacuum furnace.
From the point of view of the structure and heating mode of the vacuum furnace, it can be divided into two categories: one is the external heat vacuum furnace, the other is the internal heat vacuum furnace, both of which are mainly vacuum resistance furnace. External heated vacuum furnace is usually called hot fireplace, also known as muffle furnace. The heating part and the heat insulation part of the furnace, namely the electric heating element and the heat insulation layer, are arranged outside the vacuum chamber, the workpiece is placed inside the vacuum chamber, and the workpiece is heated indirectly.
Vacuum annealing furnace is usually external heat vacuum heat treatment furnace. Internal heated vacuum furnace is usually called cold fireplace. The heating chamber composed of the electric heating elements and the heat insulation layer of the furnace is all placed in the vacuum furnace shell of the water-cooled sandwich structure. Compared with the external heat vacuum furnace, the internal heat vacuum furnace has complex structure, but it has high temperature, high thermal efficiency and high productivity, which can realize rapid heating and cooling. Therefore, the internal heated vacuum furnace has developed rapidly and has become the main furnace for vacuum sintering, vacuum annealing, vacuum quenching and vacuum tempering.