| As a cutting tool,it is used to cut coal and rock in mining machinery.Severe cutting conditions seriously affect working life.Wear resistance is a key indicator for checking the quality of concrete,and it is also a hot and difficult problem in picking research.The effect of improving the wear resistance of the pick by conventional heat treatment at an early stage becomes more and more limited.At present,more and more experiments have proved that cryogenic treatment can significantly improve the wear resistance of the pick and prolong the service life.Research on the technology of picking material reinforcement is of great significance.According to the coal industry recommended standard(MT/T246-2006),the typical tooth material YG11C and the tooth material 42 Cr Mo were selected as research objects.Cryogenic treatment can effectively improve the wear resistance of high-speed steel materials,for example,but there are few studies on pick-up materials.In addition to the experimental cryogenic treatment process,this paper will also explore the magnetic field cryogenic treatment process.The parameters of different heat treatment process groups are selected and the following comparison process group is set to carry out integrated heat treatment test.Conventional group process: 870? insulation 20 min + oil quenching 15 min + 360? tempering 2 h + air cooling;Cryogenic group process: a cyclic deep crying treatment of-160? is inserted between quenching and tempering of a conventional process;Magnetic cooling group process: On the basis of the cryogenic group,the whole process of the sample is exposed to a uniform magnetic field of 0.3T.Macroscopically measure the hardness,impact toughness and wear resistance of the specimen and analyze the wear scar,fracture,metallographic structure and XRD pattern at the microscopic level.Cross-contrast analysis of the strengthening effect of each process group,the new picking process and its mechanism of action were obtained.The main research contents and conclusions are as follows:(1)The magnetic field cryogenic treatment needs to provide a uniformmagnetic field environment of more than 1000 Gs.For this purpose,a uniform static magnetic field generating device is designed and the magnetic field distribution simulation is performed by using COMSOL.After measuring with a Gauss meter,a uniform magnetic field air field with a magnetic field size of 0.3T and a space size of 60×30×15 mm was obtained.(2)The macroscopic results of the tooth material 42 Cr Mo show that compared with the original conventional process,the cryogenic treatment improves the wear resistance of 42 Cr Mo by about 5.7%;the magnetic cooling treatment improves the wear resistance by about 26.7%;The tooth material YG11C: cryogenic treatment improves the wear resistance of YG11C by about35.26%,and the magnetic cooling treatment reduces the wear resistance by about 21.21%.(3)After cryogenic treatment of the tooth material 42 Cr Mo,the supersaturated martensite precipitates a large amount of carbon and returns to ferrite.The precipitated carbon turns to form more cementite,and the cementite and ferrite mechanically mix to form tempered troostite;The precipitation process of carbon causes the grains to be refined,and the tempered troostite distribution is more uniform to improve the wear resistance.The deep cooling of the magnetic field weakens the precipitation ability of the carbide but the precipitation direction is optimized,and the precipitation distance is closer,so that the tempered troostite is more accumulated on the surface of the substrate to further improve the wear resistance.(4)After the cryogenic treatment of the tooth material YG11C,the number of ? phase carbides increases and the distribution is more uniform,which improves the wear resistance;After the magnetic cooling treatment,the transformation of the alloy ?-Co to ?-Co increases,making the binder phase brittle and the plastic deformation ability is reduced,thereby reducing the wear resistance. |
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