Study Of Vacuum Quenching Process Of Cr12MoV Steel

In recent years, the industrial development of China is transforming from OEM(Original Equipment Manufacturer) to manufacturing with independent research and development. Therefore, as a key technology to improve the mechanical property of parts, heat treatment is getting more and more attention from machine part manufacturing companies. However, some industrial developed countries have already made the road map of their heat treatment technical development, in which the indexed plan of reducing energy consumption, manufacturing time and cost has been determined. The road map of heat treatment technical development of the United States indicates that free distortion of heat treatment part and minimum mass dispersion should be achieved by 2020. This kind of demand is not only excitation, but also a challenge to heat treatment. As the most advanced technology in bulk heat treatment, vacuum heat treatment has many advantages as non-oxidation, less distortion, no pollution and lower cost. The cold treatment has many advantages as well, including less energy consumption, no pollution and lower cost. They are key technologies to achieve the demand of heat treatment technical development. In this essay, these two technologies will be researched based on Cr12 MoV to provide data support for production practice.Vacuum quenching is divided into vacuum oil quenching, high pressure gas quenching and vacuum water quenching. In practical manufacturing, vacuum water quenching is used less than the previous two technologies. The quenching process of vacuum oil quenching and high pressure gas quenching are studied. The microstructure and properties of the quenched specimen are analyzed in this work. To compare the difference of quenching process, practical temperature measurement and computer numerical simulation are used. In comparing the difference of structure and properties of Cr12 MoV after different quenched process, we observe and compare the metallography of different test specimens, scan electron micrograph, X-ray diffraction results and micro hardness. The conclusion of the analysis is that after the process of the two quenching methods, the structure of Cr12 MoV are all consist of martensite, carbide and retained austenite. The hardness of the material are all remarkably increased after the quenching process and the specimen of high pressure gas quenching has better appearance and lower cost for manual operation.In this essay, after vacuum oil quenching, tempering and cold treatment are combined into many kinds of process programs based on the properties of Cr12 MoV. Effects of different process program on the structure and properties of the products are studies by metallography, scanning electron micrograph, X-ray diffraction, micro hardness and friction machine. In the experiment there are two processes with cold treatment, the specimens of which have better strength, hardness and abrasive resistance. When the two processes with cold treatment are compared, directly cold treatment and two times of tempering after the quenching has better strength and hardness. While the specimen treated by tempering + cold treatment + tempering after quenched has better abrasive resistance. Therefore, in practical manufacturing the process can be chosen based on the demand of the properties.The process of high pressure gas quenching is combined with tempering and cold treatment into different kinds of process programs as well. The method of experiment and result analysis is as same as the experiment of vacuum oil quenching. The final results are also similar. The specimens of the processes with cold treatment have better strength, hardness and abrasive resistance. When compare these results, the order of tempering and cold treatment had little effect on hardness of the specimens, while the specimen with cold treated after tempering has better abrasive resistance.The research process combines theory and practical manufacturing, it has great significance to chosen of manufacturing processes.