Research On The Welding Behavior Between The WC-10co Cemented Carbide And The B318 High-strength Steel

Cemented carbide,due to its high hardness,good wear resistance and corrosion resistance,is widely applied in aerospace,machining,oil drilling,mining tools and other wear-resistant components.In order to reduce the influence of intrinsic brittleness as well as control cost,cemented carbide is usually embedded in the matrix of high-strength high-toughness steel to form a cutting tool with high strength,high toughness,high hardness and wear resistance.Compared with brazing,resistance spot welding technology has a good metallurgical bonding,which can ensure a higher bonding strength and overcome the limitations of high-energy beam welding,such as laser welding for small joints.Resistance spot welding is a new type of semi solid-phase connection technology,which has been widely studied and applied.However,resistance spot welding connection of cemented carbide and high-strength steel has not been reported.This research lays a foundation for the research and application of cemented carbide wear-resistant workpiece connection.This paper systematically studied the resistance spot welding process of cemented carbide grits WC-10Co and high-strength steel strip B318,and explored the internal relationship between welding current and welding time,microstructure(interface bonding type),bonding strength and fracture mode.The excellent mechanical properties were obtained under suitable process conditions.The process of the evolution of ? phase,five interface bonding types and fracture modes under different heat inputs were discussed.It is observed by high-speed photography that the deformation of the middle region of the weld increased with the increase of heat input in the pool of resistance spot welding between WC-10Co cemented carbide and B318 high-strength steel.The temperature field distribution of welded joint under different heat input was analyzed by commercial finite element software and colorimetric pyrometer.The maximum temperature of welded joint increased with the increase of heat input.However,the high temperature duration of the same area under different welding current increased at first and then decreased with the increase of welding current,while the high temperature duration of the same area increased with the increase of welding time under different welding time,and the temperature field distribution of the welding center was larger than that of the welding surface.According to the microstructure and characteristics of the weld,the whole weld was divided into five interface bonding types,the microstructure and phase of the five interface bonding types were explored,and the effects of different heat inputs on the relative proportion of the five interface bonding types were studied.Based on the theoretical generation mechanism of ? phase and the distribution of temperature field,the generation path of ? phase in actual resistance spot welding was deduced,and the evolution rules of five interface bonding types were deduced.The effects of different heat inputs on the bonding strength and fracture mechanism and microhardness distribution of welded joints were studied,and combined with the relative proportion of five interface bonding types of welded joints under different heat inputs,the contribution of each interface bonding type and crack to the bonding strength of welded joint was determined:type B and type C>type D>>type E>type A>>crack.After annealing at 300A/20ms pre-welding current and 800A/95ms welding current and in nitrogen atmosphere at 400?/15 min,the maximum shear strength can reach 924MPa,18%more than that of friction stir welded joints.