Effects Of Gadolinium(Gd) Addition On Microstructure And Mechanical Properties Of 5Cr5MoSiV1 Steel

5Cr5Mo Si V1 steel is a new type of hot work die steel, which is often used as the material for shield tools. But 5Cr5 Mo Si V1 steel is a kind of eutectoid steel, there are coarse grains and serious segregation in its cast microstructures, which can easily lead to brittle fracture and greatly reduce the mechanical properties of the material, as well as shorten the life of the shield tools. Thus the construction efficiency is reduced, the progress of the project is slowed and construction costs increase. What is worse, it is difficult to eliminate these defects by conventional heat treatments.The rich rare earth resources attract our attention to solve this problem. The addition of rare earth elements can deeply purify the steel liquid, refine steel microstructures and eliminate inclusions segregation. Therefore, the comprehensive mechanical properties of the steel will be improved. In order to make the 5Cr5 Mo Si V1 steel can adapt to the bad working conditions of strong extrusion, high torque, strong impact and high abrasion, in this paper, how to improve comprehensive performance of 5Cr5 Mo Si V1 steel by the addition of rare earth elements was studied. The main contents are as follows:1. The preparation method of rare earth 5Cr5 Mo Si V1 steel was studied from several aspects as the choice, addition form, method and amount of the rare earth element. The optimal preparation route of rare earth steel is that the Gd prefabricated blocks were added to 5Cr5 Mo Si V1 steel under Ar vacuum conditions;2. Effects of different rare earth contents on the cast microstructures(including grain size, inclusion morphology and distribution etc.) and mechanical properties(including hardness, tensile strength and elongation) of 5Cr5 Mo Si V1 steel were studied and it was determined that the optimal rare earth content is 0.131 wt. %.3. Effects of different rare earth contents on the microstructures and mechanical properties of 5Cr5 Mo Si V1 steel for different heat treatment conditions(including spheroidizing annealing, quenching and tempering) were studied and confirmed that the optimal rare earth content is 0.131 wt. %.