Study on Alloying of China cast steel parts

As we all know, the performance of steel casting parts comes from casting materials, guaranteed by manufacturing process and improved by heat treatment. China’s research on the quality of steel casting parts also focuses on the material, casting process and heat treatment process of steel casting parts. With the development of science and technology and the rapid growth of China’s economy, the upgrading of equipment manufacturing industry has higher and higher requirements for the material of steel casting parts. The traditional steel casting materials can no longer meet the upgrading requirements of equipment manufacturing industry. In order to improve the performance of steel casting parts, the foundry author carries out optimization design and alloying research on the material composition on the basis of raw materials. The composition optimization design is mainly based on Mn series, Mn Si series and CR series steel casting materials. Through composition adjustment and optimization, it can meet the service requirements under different working conditions.

Alloying research is to add one or more alloy elements to the raw steel casting materials, through the solid solution strengthening, second phase strengthening and interaction of each alloy element on the steel casting materials, give full play to the role of each alloy element in improving the microstructure and steel casting properties, and meet the service requirements of steel casting parts in special environments such as heat resistance, wear resistance and corrosion resistance. The main alloying elements often added in the alloying of steel casting parts are Cr, Mn, Si, W, Mo, Ni, Cu, V, Nb, Ti, etc. For example, after alloying with cr-v-ti-re, cr-v-ti, cr-re or v-ti-nb-re, the grain of high manganese steel is refined by 1 ~ 2 grades, the size, morphology and distribution of inclusions are significantly improved, and the hardness, impact toughness and wear resistance of high manganese steel are greatly improved. Compared with high manganese steel without alloying treatment, the hardness and impact toughness are increased by 12.4% and 32.5%, 217hbs and 155 J / cm2 respectively, and the wear resistance is increased by 13.9% ~ 45.4%; After alloying with 0.4-0.5% Mo and 0.04% ~ 0.06% Nb in low alloy steel (0.33-0.37c%, 1.1-1.3% Mn, 0.3-0.4% Ni, 0.7-0.9% Si), the tensile strength increases from 630mpa to 766mpa, the hardness increases from 230hb to 285hb, and the elongation reaches 12%. After alloying with Si, Mn, Cr, Cu and Mo in low carbon steel (A3 steel), bainite structure can be obtained by normalizing at 900 ℃, which increases the hardness and notchless impact toughness of the steel to 40.7hrc and 185.5j/cm2, and the wear resistance is significantly improved. In order to improve the heat resistance and wear resistance of steel casting parts at 1000 ℃, based on the composition of zg40cr25ni20 heat-resistant steel, after multi-element alloying with Mo, Nb, N and re, the lasting strength of steel at 1000 ℃ is stable at 16.9mpa, which is significantly higher than that of zg40cr25ni20 heat-resistant steel, and the oxidation resistance is equivalent, but higher than that of zg35cr18ni25si2 heat-resistant steel. The service life of the nozzle made of this steel is 3.5 times that of zg30cr22ni4mn7si2re heat-resistant steel.