On The Preparation Processes,Microstructure And Properties Of The Heat-resistant Stainless Steel Vortex Shell Castings

The automotive industry is a pillar industry of the national economy.Improving engine power and reducing the content of harmful substances such as CO,HC and NO_X in exhaust gas is the inevitable trend of the development of the automotive industry.Turbocharger is an effective way to improve engine efficiency,reduce fuel consumption and reduce exhaust emissions,and vortex shell is one of the main component of turbocharger.With the rapid development of automobile industry,and compared with the volute casings made by conventional ductile iron and high silicon molybdenum ductile iron material,the heat-resistance temperature of new austenitic heat resistant stainless steel vortex shell can reach above 1050?and meet the requirements of the using ambient temperature of volute,therefore,it has a strong market competitiveness.In this paper,the typical specification of austenitic stainless steel(GX40CrNiSi25-12)vortex shell casting is studied firstly.By using 3D drawing software Pro/E and solidification simulation software ProCAST,the casting process design and solidification simulation optimization analysis of volute castings were carried out,and the trial production validation was proceeded.Then,with the help of the methods of metallographic microanalysis(OM),mechanical properties test,X ray diffraction(XRD)and Electro-Probe Microanalyzer(EPMA)test,the effects of modification on the microstructure and properties of austenitic heat-resistant stainless steel(GX40CrNiSi25-20)were studied.At last,the high temperature oxidation resistance of two kinds of austenitic heat-resistant stainless steels was studied.The main conclusions are as follows:The solidification simulation analysis of the typical size of vortex shell casting was carried out by the ProCAST solidification simulation software,and the casting process was designed.The austenitic stainless steel vortex shell castings of GX40CrNiSi25-12 were prepared successfully.The deterioration test of the heat-resistant stainless steel of GX40CrNiSi25-20shows that the addition of the modifier can effectively improve the mechanical properties of the material.Comparison with unspoiled material,After the modification of WS-1 silicon free modifier was carried out by the penetration method and Bell Hood method,the tensile strength,yield strength and elongation of GX40CrNiSi25-20 austenitic stainless steel increased by 44.3%,15.3%,77.2%and40.4%,18.6%,61.3%,respectively.And after modification of YBZW-4 refining agents by the penetration method,the tensile strength,yield strength and elongation of austenitic stainless steel increased by 38.7%,11.6%and 74.4%respectively.The high temperature oxidation resistance of two kinds of austenitic stainless steel GX40CrNiSi25-20 and GX40CrNiSi25-12 at different temperatures was studied contrastively.The result shows,the kinetic curve of high temperature oxidation follows the parabolic law,and the increase of oxidation weight increases with the increase of oxidation temperature and the time of oxidation.Comparing the oxidation kinetics of the two materials,we know that when the other elements are basically the same,the GX40CrNiSi25-20 austenitic stainless steel with higher Ni content has better high-temperature oxidation resistance.