Effect Of Graded Solid Solution On The Microstructure And Mechanical Properties Of Ti-V-Nb Alloyed Ultra-High Manganese Steel

High manganese steel is widely used in the fields of metallurgy,mining,building materials,railway and other mechanical equipment because of its good anti-impact abrasive wear and anti-chisel wear performance under the condition of strong impact and high stress.Large carbides are often formed in the internal structure of high manganese steel after water toughness treatment.It has a large impact on the performance of high manganese steels.In order to enhance the work-hardening ability of high manganese steels,Ti-V-Nb alloyed ultra-high manganese steels are prepared,and the size and distribution of carbides in alloyed ultra-high manganese steels can be regulated by heat treatment in order to improve the organisation and mechanical properties.Therefore,it is particularly important to study the influence of heat treatment process on the organisation and mechanical properties of cast alloyed ultra-high manganese steel,which is of great theoretical significance and industrial application value for the development and industrialisation of high wear-resistant cast austenitic manganese steel with excellent overall performance and high cost performance.In this paper,the optimized composition of Fe-0.976C-19.86Mn-1.89Cr-0.998Si-0.923Mo-0.18Ni-0.59Cu-0.091Ti-0.582V steel was used as the research object,and the effects of temperature gradient design(450°C-1100°C),heating rate(75°C/h-150°C/h)and holding time(2h-4h)on the organisation and properties of alloyed ultra-high manganese steels,with a view to preparing cast alloyed ultra-high manganese steels with well-matched mechanical and wear resistance properties.The as-cast organization of the alloyed ultra-high manganese steel consists of an austenitic matrix,in situ precipitated cladding structure of(Ti,V,Nb)C carbides and M₂₃C₆ carbides distributed along the grain boundaries,and the dissolution of the large size and grain boundary distributed M₂₃C₆ carbides precipitated in situ after graded solid solution treatment.The most significant organisational improvement and property enhancement of the high manganese steel was achieved with a grain size of 253?m,a second phase particle size of 5.08?m,a tensile strength of603.37MPa,an elongation of 23.33%and an intrinsic impact toughness of 620 k J/m².The mechanical properties of the alloyed ultra-high manganese steel could be improved by reducing the holding time or accelerating the heating rate,Both changes at the same time have a more obvious enhancement effect.Accelerating the heating rate and shortening the holding time at 550?-650?-950?-1100?can reduce the grain size by 25?m,increase the tensile strength by 150.63 MPa,and increase the elongation.13.21%higher,impact toughness increased by 26.8J.This was due to the graded solid solution eliminating large carbide sizes and casting This is due to the fact that the graded solid solution prevents grain coarsening while eliminating large carbides and casting stresses,and the improved organization leads to improved mechanical properties.The alloyed ultra-high manganese steel has the best impact abrasive wear resistance at a heating rate of 150?/h,550?-650?-950?1100?each heat 2h preservation process.The wear morphology shows that the plastic deformation zone is the largest,the microhardness at the impact surface is 578 HV,the thickness of the working hardening layer is 3400?m,the wear mechanism is microploughing,peeling pit and fatigue,and the precipitation phase of small particles produced by solid solution treatment effectively hinders the dislocation movement,The pinning of the precipitated phase makes the dislocation gather around the precipitated phase and improves the work hardening ability.The strengthening mechanism mainly includes solid solution strengthening,second phase strengthening and grain boundary strengthening,among which solid solution strengthening is the most obvious.