APPLICATION OF VACUUM SUCTION CASTING OF IRON-CARBON ALLOYS FOR THE PRODUCTION OF ENGINE PARTS

Abstract

The use of vacuum suction casting technology for iron-carbon alloys for the production of internal combustion engine parts will improve their quality and wear resistance, preserve metal, and reduce emissions. The technology is widely used for non-ferrous alloys. At the same time, its implementation for iron-carbon alloys (including cast iron) in modern engine construction requires careful scientific and practical preparation. Problematic tasks arise when improving the pneumatic system of vacuum suction (large volumes of gas release), the stability of the metal pipeline (thermal overload in a high-temperature cast iron melt), and the stabilization of the casting microstructure (high-speed crystallization). The authors suggest using a specialized titanium alloy VT3-1 for the metal pipeline, for which the article calculates thermal loads during cyclic operation in the “Deep – take-out” mode for the use of cast irons of the SCH25 and VCH50-1.5 grades. For reliable operation of the metal pipeline and the absence of solidification of the melt on its inner surface, a thermal calculation method was develop, which allows determining the time of heat removal of overheating of the melt according to the diameter of the metal pipeline. The pneumatic system of the vacuum unit is supplement with a patented gas jet ejector, which, in combination with a powerful shop compressed air system, provides a full gas outlet. Applying the developed law of change in the discharge between atmospheric pressure and pressure in the mold cavity, the authors of the article regulate the rate of crystallization of castings, which makes it possible to form much smaller phases of perlite in the microstructure and reduce the presence of Ferrite. At the Enterprise "Pervomaiskdizelmash" using vacuum casting technology, blanks of guide bushings of engine valves 6CHN25/34 made of cast iron SCH25 and VCH50-1,5, as well as oils of piston rings made of cast iron VCH50-1,5 were obtained. The obtained parts showed an increased service life by 15-30%. Vacuum casting technology is recommend for iron-carbon alloys in the production of engine parts.