| As-cast pearlite ductile iron is a kind of metal materials which has many advantages such as high strength, high hardness, high wear resistance, lower production costs and longer working life, it has been widely used to replace Mo-Cr alloy cast iron and other steel-casting, and to produce automotive panel die castings in recent years. However, in heavy section ductile iron such as automotive panel die castings, it easily appears spheroidization degeneration and inoculation degeneration in the final solidification central parts due to slow solidification rate, and the effective number of graphite crystal core is decrease quickly, so the heavy section ductile cast iron is easy to suffer from these defects such as reduction of nodular graphite, the nodular graphite coarsening, deformation of nodular graphite which leads to engender chunk graphite and exploded graphite, which making mechanical performance of ductile iron decrease and restricting the extensive application of heavy section ductile iron. The practice showed that it can effectively reduce or eliminate deformation of nodular graphite and improve the performance in heavy section ductile cast iron by adding the trace elements Sn and Sb.For aiming the problems existing in the production of heavy section ductile cast iron, on the basis of the existing laboratory conditions, a high-strength ductile iron has been successfully manufactured by adding trace amount of Sn and Sb to non-alloy ductile cast iron, and the complicated interaction of Sn,Sb and REin the ductile cast iron was investigated by the method of quadratic regression orthogonal design, so that making certain guidance to the trace elements alloy control in the ductile cast iron.The range of basis chemical components in this study is C:3.7%, Si:2.3%, Mn:0.55%, P:0.04%,S:0.03%. Liquid irons are melted in 10kg coreless medium frequency induction furnace, and the temperature is measured by optical pyrometer with controlling the tapping temperature around 1500℃. The reaction of spheroidization and inoculation are in the casting ladle with pour-over process, and the trace amount of Sn and Sb are added in the ladle with inoculants, knockout is operated about 40 minutes after pouring finished, and then air cooled to room temperature.The effects of the trace elements Sn, Sb and RE on microstructure, mechanical performance and wear resistance performance of ductile cast iron were investigated through multi group experiments in this study. The results showed that Sn and Sb not only increase the grade and decrease the graphite sphere size, but also increase pearlite content and decrease pearlite lamellar distance through observation of the microstructure, only the interaction between the Sn and Sb can significantly improve the pheroidization rate, the interaction among three alloy elements all not have a significant impact on pearlite content. The interaction among three alloy elements all have a significant impact on tensile strength, the tensile strength will be decline obviously when the alloy elements exceed a certain value, the interaction among three alloy elements all not have a significant impact on the elongation, only the interaction of Sn and RE or Sb and RE can improve the hardness and decrease the impact toughness significantly through the test on mechanical properties. The interaction between the Sn and Sb can significantly improve the wear mass loss and decrease the friction coeffiction remarkably, the wear mas loss will descend obviously and the friction coeffiction will remain in a stable range when the addition of alloyelements increasing.
|
PDF Full Text Request