TBM Hob Tool Ring With H13 Steel Surfacing Remanufacturing Preheating And Tempering Process Research

When the full-section rock tunnel boring machine(TBM)is working,due to the harsh geological conditions and complex load conditions,the loss of the TBM cutter cutter ring is serious.Currently,the failed tool ring is removed and scrapped,so it cannot be repaired and reused.Under the background of "double carbon",the research group carried out a feasibility study on the remanufacturing of the tool ring surfacing in the early stage.On this basis,this paper further aims at the bottleneck problems of the traditional surfacing and remanufacturing process such as easy cracking of the base material,low strength of the binding layer,unreasonable hardness and toughness regulation,etc.,in order to meet the physical and mechanical properties of the material required for the rock breaking conditions of the knife ring,and carried out the research on the preheating and tempering process before and after the H13 steel overlay welding and remanufacturing of the TBM hob tool ring.The important contents and conclusions of this paper include:(1)Comprehensively analyzed the advantages and disadvantages of the commonly used remanufacturing repair technology in the project,combined with the actual load conditions of the TBM hob and the comprehensive cutting performance requirements,the surfacing remanufacturing repair method based on MAG(melting pole active gas shielded arc welding)welding was proposed,and the remanufacturing repair route of the hob tool circle was formulated accordingly.(2)The key performance parameters of H13 steel were calculated by JMATPRO,a metal material calculation software,and the heat treatment performance chart including thermal equilibrium phase diagram and continuous cooling curve was obtained;In addition,in order to simulate the actual heat treatment state of the engineering tool ring,the heat treatment process route for the preparation of the tool ring specimen is proposed.(3)Based on the thermodynamic finite element analysis theory,the simulation model of the heat treatment process before and after the overlay welding of the tool ring base metal was established,among which: First,in order to verify the rationality of the heat treatment process line prepared by the knife ring specimen,based on the performance parameters obtained by JMATPRO,in the SYSWELD environment,a simulation model of the heat treatment process of the base metal was established,and the heat treatment process line route described above was used for heat treatment of the base metal in the initial annealing state.The simulation results show that the samples prepared by the aforementioned heat treatment process line are roughly consistent with the engineering knife ring in terms of metallographic composition and hardness indexes;Secondly,for several important physical and mechanical parameters that affect the rock breaking of the knife circle,such as wear resistance,shear strength,impact toughness,hardness performance,design normal tool ring and preparation of the specimen comparison test,the test results show that the physical and mechanical properties of the sample prepared by the aforementioned heat treatment process line are basically the same as the normal knife ring.(4)On the basis of SYSWELD,a simulated finite element model of heat treatment base material under preheating before welding and post-weld tempering process was established,and a comprehensive study of heat treatment performance was carried out from three aspects:temperature,phase transition and stress,and its simulation results showed that no preheating would accelerate the cooling speed of the weld,and would produce greater residual stress and equivalent force,which would lead to cracking of the overlay remanufactured workpiece;In addition,the higher the preheating temperature,the more uniform the cooling rate will be throughout the weldment,so that the residual stress and the equivalence force will be lower,but it will also make the size and grain of the heat affected zone and the molten pool larger,which will lead to unstable mechanical properties;Tempering temperature has a greater impact on the stress after welding,the higher the tempering temperature,the smaller the residual stress,but with the increase of tempering temperature,its decrease will decrease each time.After comprehensive trade-off analysis,it is recommended to take 150°C,200°C and 250°C as the preheating temperature for subsequent tests,450°C,550°C and 650°C as the tempering temperature,and 1h,2h and 3h as the post-weld tempering time.(5)In order to verify the influence of preheating temperature and tempering temperature on the remanufacturing performance of the tool ring in the aforementioned simulation test,based on the Yaskawa MOTOWELD-RD500 welding machine,a test platform for H13 steel plate surfacing and remanufacturing of the knife ring was built.Through the self-developed slide rail heating furnace,the platform realizes the seamless docking of pre-weld preheating and post-weld tempering process,which meets the high requirements of accurate temperature control.Based on the platform test bench,with metallographic structure,residual stress,wear resistance,shear strength,impact toughness and hardness performance as the evaluation index of the physical and mechanical properties of the tool ring,the preheating temperature before welding,the tempering temperature after welding and the tempering time after welding were selected to examine the factors,and the three-factor three-level orthogonal test was designed,and the research results showed that: In terms of a single factor,the tempering temperature has the greatest impact on the evaluation indicators of surfacing and remanufacturing.In order to comprehensively evaluate the performance of remanufacturing under different processes,two analysis methods of comparison and weight are further proposed.Among them,the optimal combination of repair process parameters obtained by comparing the normal tool circle is 150°C preheating before welding,550°C after welding tempering and 2h after welding tempering.By setting the relevant weights,the optimal combination of repair process parameters is 150°C preheating before welding,450°C after welding tempering,and 1h after welding tempering.