Detailed explanation of heat treatment process of aluminum alloy bushing
Stainless Steel Tray Stainless Steel Tray Stainless Steel Tray,Stainless Steel Mesh Tray,Stainless Steel Drying Tray,Stainlesss Steel Dehydrator Trays Anping County Comesh Filter Co., Ltd , http://www.comeshfilter.com
The bushing is one of the main parts of the gear pump, and is mounted on the two ends of the high-speed gear to support the bearing. It must have sufficient strength and good wear resistance. In order to ensure the performance requirements of the parts, our factory uses non-standard aluminum-tin alloy, and the role of Cu is to strengthen the matrix. Sn can form a softer low melting point Al-Sn eutectic, which increases wear resistance. The original heat treatment process is 515 ° C solid solution 6h water cooling, 180 ° C aging 8h air cooling. There are two problems with this process:
(1) The Al-Sn eutectic was over-fired to form tin to form an Al-Sn eutectic containing 99.5% of tin, and its melting point was 229 °C. When the workpiece is heated to 515 ° C, the Al-Sn eutectic is over-fired and a remelted pellet is formed upon quenching and cooling. In the process of forming the remelted pellets, on the one hand, the grain boundary is oxidized, the grain strength is decreased, and on the other hand, many microvoids are generated, the grain boundary energy is increased, the strength of the metal is lowered, and it is easy to use during use. Early failure.
(2) The production time of the process is long, up to 16 hours, the production efficiency is low, and the energy consumption is large.
It can be seen from the metallographic observation and mechanical property test data that the treatment process at 250 ° C × 7 h is ideal. The Al-Sn eutectic crystal is distributed along the grain boundary in a broken network. On the one hand, the Al-Sn eutectic distribution is relatively uniform, ensuring good wear resistance. On the other hand, the Al-Sn eutectic does not have a split matrix, which makes the alloy better. Plasticity and toughness. The use of 250 ° C × 7h treatment process can obtain higher hardness, because the alloy contains less Cu, the metal mold cooling rate is fast, in the casting cooling process, Cu has been ensured to melt into the solid solution, played a quenching effect. This is also evidenced by the increased hardness through natural aging. The tensile strength of the 250 ° C × 7 h air-cooling process is 47% higher than that of the 515 ° C × 6 h water cooling + 180 ° C × 8 h air cooling process. The 250 ° C × 7 h air cooling process temperature is slightly higher than the melting point of the Al-Sn eutectic crystal, in order to obtain the mesh-like distribution of the Al-Sn eutectic crystal by a short holding time without pre-sintering the eutectic. On the basis of the process test, a small batch (400 pieces) of trial production was carried out, and all the products were tested by hardness, metallographic examination and test bench. The process was officially put into production in 1996, and has produced hundreds of thousands of bushings, all of which are qualified. The work efficiency is increased by 1.3 times, and the annual savings can be about 70,000 yuan, and the power saving is over 80,000 kW.h.
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