Vacuum Sintering Furnace Powder Metallurgy Technology
Requirements of powder metallurgy process for sintering furnace structure:
Sintering furnace is one of the most important equipments in powder metallurgy production. It is designed and manufactured according to the requirements of sintering process. Electric furnace is the most common sintering furnace for powder metallurgy.
Sintering of powder metallurgical products is essentially a heat treatment process, which is similar to traditional heat treatment of dense metals. However, due to the particularity of powder raw materials, powder metallurgical sintering has the following characteristics.
(1) Powder compacts have large free surfaces, and the sintering process generally needs to protect the atmosphere, and is sensitive to the reaction of various sintering atmosphere.
(2) There are oxide films on the surface of metal powders, which affect the contact between metals and hinder the sintering process. It is necessary to reduce the metal oxides during the sintering process.
(3) The stress produced in the forming process should be eliminated.
(4) The compact contains a certain amount of volatile additives, which need to be burned at the heating stage before sintering.
(5) There may be liquid phase in the sintering process of compact.
(6) The compact strength is low, it can't collide in sintering process, and the material transmission in sintering should be stable.
(7) The sintering temperature is higher than the general heat treatment temperature, and the temperature control should be more accurate.
The sintering process of powder metallurgy requires the structure of sintering furnace as follows:
(1) Muffle sheaths with sealed shell are needed to maintain the reducing atmosphere in the furnace and prevent air from entering.
(2) A stable and reliable material transfer mechanism;
(3) Pre-tropical zone to remove lubricants and adsorbed gases in the compact;
(4) High-temperature sintering zone, so that products have sufficient sintering and thermal insulation process;
(5) There are water jacket cooling belts to prevent oxidation and to form final metallographic structure. The products must be cooled out after sintering.
(6) There are devices for adjusting and controlling heating speed, sintering temperature, holding time, cooling speed, etc.
(7) There is a strict temperature control system, which requires sintering temperature to be controlled below 1000 C and below 3 C and above 1000 C. Therefore, the furnace temperature control system should have measures to ensure that the indicating temperature does not lag behind the time.
(8) The temperature distribution in the cross section of the furnace chamber is uniform.
(9) Heating elements must meet the sintering temperature requirements, some need to be separated from the gas in the furnace, and some need to be protected by protective atmosphere.
(10) Opening or closing of the electric furnace without air backflow into the furnace. There should be no water vapor in the furnace.