Development of Optimal Technological Modes for Production of Composite Materials by Lost Foam Casting Process

Processy litʹâ, 2020, Tom 140, №2, p.37-42

Abstract

Received 05.05.2020

UDC 621.74.074:546.261

Technological modes of bushing casting from composite materials by the ligature method have been developed using lost foam casting process. The lost foam casting process is currently one of the most effective and promising methods for producing high-quality castings having a predetermined dimensional accuracy, and the required surface smoothness which is no worse than the lost wax casting. The lost foam casting process is becoming more widespread in the production of foundry products from aluminum alloys. For aluminum alloys casting, polystyrene foam of lower density and a larger residual pressure (at a level of 40−50 kPa) in vacuum form are used in contrast to the steel, cast iron and copper alloys casting. The base alloy for producing of composite materials was cast aluminum alloy AK7. The cemented carbide ВК6 wastes and silicon carbides as large as 60−600 microns were used as reinforcing elements; they were introduced into the aluminum melt using ligatures. The ligatures were preliminarily obtained by the method of forced impregnation of  dispersed particles in vacuum using aluminium alloy AK7 melt. The melting was carried out in an induction furnace in a graphite crucible. The melt temperature was above 150−200 0C the liquidus temperature. An analysis of the experimental results showed that in order to obtain high-quality castings by the lost foam casting process, it is necessary to follow the melting and casting parameters: the overheat temperature is tover = 880− 890 0С (for АK7 – 5 mass % ВК6) and the overheat temperature is tover = 910−920 0С (for АK7 – 5 mass % SiC), holding time is 8−10 min and the casting 
temperature is tcast = 820−830 0С, the density of polystyrene foam models should be in the range from 0.022 g/cm3 to 0.024 g/cm3. An experimental batch of plain bearings was manufactured and their industrial testing was carried out at the TzDV «GAL-KAT» industrial enterprise. Tests have shown that the developed composite materials can be used in friction units as an alternative substitute for bronze. A reduction in the plain bearings mass is achieved by a factor of 3, as well as a reduction in cost due to the lower price of the composite materials.