The sintering and heat treatment process operations of the metal sintered mesh filter element include: charging, vacuuming, degassing, heating, filling with argon, heat preservation, cooling, and discharging.
Furnace loading is the first load of the compacts in trays or boxes for sintering. The tray or material box is made of high-temperature resistant materials such as molybdenum sheet, heat-resistant steel, or graphite to avoid deformation during sintering. When charging, it is required that the compacts are not in direct contact to prevent the compacts from sticking to each other during sintering. Molybdenum sheets can also be used to separate the compacts from each other. Then push the loaded tray or material box into the furnace, cover the furnace cover and seal it.
Start the vacuum unit to evacuate to remove the air in the sintering chamber and the gas attached to the compact. Use a mechanical pump to evacuate to the vacuum degree required by the high vacuum pump population, and then turn on the high vacuum pump. Generally, the secondary vacuum is required to 1.3XlO-Pz.
The furnace is energized and heated, and the gas is continuously pumped at a temperature of 400-500℃. This process can reduce the residual stress of the compact, and gradually decompose and volatilize the gas adsorbed inside and outside the compact and the organic media such as lubricants and granulating agents added during pressing.
After degassing, the furnace was brought up to the sintering temperature. For different materials, the sintering temperature is also different, and the sintering temperature should be measured and controlled. If the temperature is too high, the product will be softened and deformed, and the grains will be coarse or even scrapped. If the sintering temperature is too low, the densification speed of the compact will be slowed down, the sintering time will be prolonged, the equipment utilization rate will be reduced, and the product performance will not meet the requirements.
As the temperature increases, under the action of vacuuming, the gas removal in the compact tends to be accurate. For sintering in a protective atmosphere, the sintering chamber should be filled with argon at this time to complete the sintering in the protective atmosphere. Stop the vacuum unit after filling it with argon to reduce power consumption.
The metal sintered mesh filter element is kept at the sintering temperature for a period of time so that the densification of the green body during the sintering process is fully carried out, and the pores of the product are contracted and transformed into crystals with enough time. The length of the holding time depends on the number and size of the sintered products. Appropriate sintering temperature and holding time can be determined by measuring the density and magnetic properties of the article.
The temperature of the sintered metal sintered mesh filter element is very high. If it is directly released from the furnace, it will cause combustion and pulverization, so it must be cooled before it is released from the furnace. The cooling rate has a certain influence on the performance of the magnet. During slow cooling, the phase structure in the magnet will change, resulting in some phases that are unfavorable to the magnetic properties. Therefore, it should be cooled rapidly to maintain the phase structure in the sintered state. In production, the cooling of the sintered body is carried out in conjunction with the heat treatment.
