Study Of Bearing Bush Material Of Zinc-Based Alloy And Its Forming Technology

For its low price energy saving and high quality, Zinc alloy, a new type material, has been used increasingly at home and abroad in recent years. As its wide raw material source, low price, low energy consumption, no pollution and long service life, the alloy is developing rapidly at home and abroad. The material and components of Zn-Al alloy have an important influence on the properties and application. In addition, bottom-shrinkage will occur at the bottom of the alloy during casting process. The shrinkage not only has a serious impact on the properties of the alloy, but also may cause production accidents, reduce the production efficiency. Therefore, the research of zinc alloy material and forming technology has an important significance. This paper firstly designed the pouring process of large ZA30 bearings.According to the structure characteristics of bearing, the top open gating system was designed, and the rain type riser was using for shrinkage. In order to strengthen the bottom-up solidification order and reduce the bottom-shrinkage, water-cooled metal mould was used in the inner cavity of the bearing. Then, the solidification process of the design project was simulated and optimized in this paper by using China casting CAE software to simulate the temperature field during the cast solidification process. The results showed that: setting a chilled iron at bearing bush bottom and using water-cooling metal core in inner cavity simultaneously can effectively changed the temperature field distribution of hot section parts, and the bottom-up solidification order was strengthened. At last, the isolated liquid was effectively prevent, and so to the shrinkage hole and porosity.This paper also studied the chemical composition of zinc alloy, mainly the effect of copper and lanthanum content on the microstructure and properties of the alloy. The results indicated that the critical point ofε-phase precipitation is between 1.5%; increase the copper content suitably will refinement the alloy's matrix, improve density and reduce the tendency of shrinkage. Considering various factors, to the ZA27, ZA30 and other high aluminum zinc based alloy, the copper content can be controlled between 1.8 to 3.5%, and the alloy strength and elongation were increased with high hardness. Adding0.1% La can refined the alloy casting organization and improved the mechanical property of high aluminum zinc alloy, thus its tensile strength reached to 423MPa, elongation was increased for 13%, hardness was enhanced to118HB and the re-abrasion ability was advanced for 6%.Finally, the low-temperature impact toughness of the alloy in different state (cast, hot treatment and aging) was studied in this paper. The results show that: impact toughness of alloy decreases sharply with temperature decrease. After 360℃heat treatment, low temperature impact toughness of the alloy increased, the plastic - brittle transition curve move up; After aging 250℃, the impact toughness of alloy is low than casting and plastic - ductile transition curve move down.