Powder metallurgy sintering furnace is a kind of heat treatment equipment which uses metal powder (or mixture of metal powder and non-metal powder) as raw material to form and sinter metal or alloy parts. It is mainly used for pressing iron base, copper base and other related P / M products. Type of sintering furnace is mainly divided into resistance sintering furnace and induction sintering furnace. Resistance sintering furnace is widely used. Electric resistance sintering furnace is an electric furnace which transforms electric energy into heat energy through electric heating elements, while induction sintering furnace is an electric furnace which uses electromagnetic induction to excite electric current in metal to heat it.
According to the atmosphere and vacuum degree used in the furnace, resistance sintering furnace can be divided into ordinary atmosphere resistance sintering furnace and vacuum resistance sintering furnace, induction sintering furnace can also be divided into ordinary atmosphere induction sintering furnace and vacuum induction sintering furnace; according to the furnace structure, resistance sintering furnace can be divided into vertical resistance sintering furnace and horizontal resistance sintering furnace, induction sintering furnace can also be divided into vertical induction sintering furnace and horizontal induction sintering furnace According to the nature of operation, resistance sintering furnace can be divided into intermittent resistance sintering furnace and continuous resistance sintering furnace. Induction sintering furnace can also be divided into intermittent induction sintering furnace and continuous induction sintering furnace. In addition, induction sintering furnace can be divided into medium frequency induction sintering furnace (500hz-10khz) and high frequency induction sintering furnace (70-200khz) according to the frequency of use.
According to the heating mode, resistance sintering furnace is divided into indirect heating resistance sintering furnace and direct heating resistance sintering furnace. Indirect heating type resistance sintering furnace means that the current sends heat through the electric heating element, which makes the furnace temperature rise by radiation heat transfer, and then heats the products; direct heating type resistance sintering furnace means that the current flows directly through the joints of the heated products to heat them, for example, the high temperature vertical furnace used for high temperature sintering of refractory metals such as tungsten, molybdenum, tantalum and niobium is a typical direct furnace Heating resistance sintering furnace.
Pressure sintering furnace is needed in sintering. This furnace is mainly used for sintering thin-layer products such as powder metallurgy friction plates. Bell jar furnace is a typical pressure sintering furnace.
The electric heating elements of resistance sintering furnace can be divided into metal electric heating elements and non-metal electric heating elements. There are two kinds of metal heating elements: pure metal and alloy. Pure metal electric heating elements include platinum (maximum use temperature 1400 ℃), molybdenum (maximum use temperature 1600 ℃), tungsten (maximum use temperature 21 () () ~ 2500 ℃), tantalum (maximum use temperature 2500 ℃); alloy electric heating elements include nickel chromium system (maximum use temperature 1050 ~ 1100 ℃), iron chromium aluminum system (maximum use temperature 1300 ~ 1400 ℃). Nonmetal electric heating elements include silicon carbide (maximum service temperature 1450 ℃), molybdenum silicide (maximum service temperature 1700 ℃), graphite (maximum service temperature 3000 ℃), etc.
According to the material and shape of the electric heating element, the resistance sintering furnace using metal and alloy as electric heating element can be divided into molybdenum wire furnace, tungsten wire furnace, tungsten rod furnace, molybdenum sheet furnace, tantalum sheet furnace, nickel chromium wire furnace and iron chromium aluminum wire furnace. One of the most representative is molybdenum wire furnace, which is also widely used. The structure diagram of molybdenum wire sintering furnace is shown in Figure 1. The working temperature is 1500 ℃, which is commonly used to sinter powder metallurgy materials and products, especially sintered hard alloy. If vacuum is needed, it can be made into vacuum molybdenum wire furnace, vacuum tungsten rod furnace, etc.
