Study Of The Intermittent Spray Quenching Of 42CrMo Cutting Picks Treated By Medium Frequency Induction

This topic comes from Qingdao HaiNa plasma technology Co., LTD, whose main product is plasma cladding strengthening cutting picks of shearer. The original body material of pick was 20CrMnTi. But the material between the head of cutting pick and the head of hard alloy gear existed softened zone, which leading to early failure of picks, so 42CrMo was selected as body material of cutting pick. With the change of material, heat treatment process was also changed from induction heating and lye quenching to medium frequency induction heating and intermittent spray quenching. So the new process that the as-forged picks were firstly reinforced using plasma jet surface metallurgy and then treated with the technology of mid-frequency induction heating plus intermittent spray quenching and tempering was proposed, which prolonged the working life of picks while saving large amounts of steel. In addition, the process broke up technical monopolies of international companies in this field and broke out the situation that key parts in our country depend on import.The paper studied the optimization of heat treatment of cutting picks, and discussed the feasibility of mid-frequency induction intermittent spray quenching of 42CrMo cutting picks. NC special quenching machine was used to optimize the structure and properties of picks. The samples of picks were observed under the optical microscope (OM) and scanning electron microscope (SEM) to analyze the structure. The chemical compositions were analyzed by energy dispersive spectrometry (EDS). An X-ray diffractometer (XRD) was used to identify the phase. Rockwell hardness tester and impact tester were used to measure the hardness and toughness. In addition, there were many dynamic features in the process of induction heating spray quenching. With the help of the computer, the paper simply simulated and analyzed the temperature field in cutting picks. And it played an auxiliary role in optimizing the process parameters.The experimental results showed that we can completely get the cutting picks conformed to the state standards. Direct spray quenching was not feasible, because the vale of the impact toughness was too low. But through the mid-frequency induction heating and intermittent spray quenching, the hardness of cutting pick was maintained on 40HRC. The value of impact toughness was 50.15J/cm2. Shear strength was 241 MPa. Each of the performance meets the requirements of the state standards. The head of cutting pick was composed of tempered martensite and a small quantity of residual austenite; the handle of cutting pick was composed of tempered martensite and bainite. we use Fe-Cr-Mn-Mo-C-Si-B-V system as Plasma jet surface metallurgy coating. Through the organization and performance of the coating, we can judge that before and after the heat treatment there was no big organization morphology change. The top of metallurgical coating was dentritic structure and equiaxial structure and the top metallurgical coating was typically denotative plane crystal structure.