Research on induction tempering heat treatment process of cutter ring of gradient hardness

Under the complex geological conditions of high quartz content, high compressive strength and composite strata, the full-section hard rock tunnel boring machine (TBM) cutter ring is prone to fracture and wear when subjected to a large impact load, which seriously reduces the tunneling efficiency of the TBM and increases the construction cost. In order to solve the above problems, this paper aims to improve the hardness of the cutter ring while taking into account the high toughness of the cutter ring as the goal, based on the DFEORM to establish a gradient hardness cutter ring induction tempering heat treatment finite element simulation model, to study the tempering process parameters of the cutter ring hardness and toughness of the influence of the law, and through the induction tempering experiments on its verification, and ultimately get the edge part of the high hardness and high tenacity of the high performance of the gradient hardness of the cutter ring heart part. The results show that increasing the heating time, current density and current frequency can effectively expand the softening area of the cutter ring to improve the toughness of the cutter ring heart, and increasing the air gap can effectively reduce the softening degree of the cutter ring to improve the hardness of the cutter ring. The optimal combination of the induction tempering parameters is as follows: current density between 5.31 A/mm² and 5.94 A/mm², current frequency between 5 kHz and 10 kHz, induction tempering time between 6 min and 8 min, and air gap between 4 mm and 8 mm.