Study On Microstructure And Mechanical Property Of H11 Steel Prepared In Solid State Recycling By Powder Metallurgy Technology

The solid state recycling technology can be used to prepare the molding material from the metal return material in the form of solid state conversion without remelting the metal.Compared with the traditional liquid state recycling technology,the solid state recycling technology has the advantages of low energy consumption and high recovery efficiency,and retaining the excellent microstructure of the raw material.At present,there are many researches on the light alloys,such as magnesium and aluminum,but there are few researches on the direct recycling of the steel materials by the solid state recycling technology.The main reason is that the deformation resistance of the steel material is larger and the cold plastic can not make the plasticity greater deformation,hot compression process is complex,more difficult to achieve.In this paper,using H11 steel shavings as raw materials,crush it into powder,and then use multi-purpose powder consolidation system that made by our research group for powder compaction and forging.The microstructure and properties of the materials were studied by density meter,hardness tester,tensile tester,optical microscope,scanning electron microscope,energy dispersive spectrometer and XRD.Specific content and results are as follows:(1)The effect of different particle size and impurity content on the microstructure and properties of solid state recycled H11 steel was studied under the same solid state recycling technology.The results showed that the hardness,tensile strength and elongation of solid-state recycled H11 steel increased with the increase of the particle size and the decrease of the content of oxidized inclusions.(2)The effect of different extrusion forging temperatures in the range of 1100?-1220?on the microstructure and mechanical properties of solid state recycled H11 steel was studied.The results show that with the increase of extrusion forging temperature,the hardness and tensile strength of solid recycled H11 steel increase,but the elongation decreases.(3)After isothermal nodular annealing treatment,the material microstructure and mechanical properties of solid state recycling of H11 steel was studied.The results show that after isothermal nodular annealing treatment,the microstructure of solid recycled H11 steel becomes uniform and the elongation increases,but the strength and hardness decrease.(4)The microstructures and mechanical properties of solid recycled H11 steel and primary H11 steel were compared and found that the hardness of solid recycled H11 steel(192 HV)reached the level of raw materials(188 HV),but the yield strength,tensile strength,elongation of solid recycled H11 steel(254 MPa,541 MPa,12.78%,respectively)were lower than the raw materials(298 MPa,662 MPa,23.06%).The main reason for the poor performance of recycled H11 steel is that the impurity SiO2 mixed in the milling process leads to the discontinuity of the matrix,and the impurity particles tend to be the source of cracks during the drawing process.