Application of heat treatment technology in the production of mechanical blades Ⅱ
1.Deformation heat treatment
By effectively combining pressure processing with heat treatment, the dual effects of deformation strengthening and heat treatment strengthening can be exerted at the same time, and comprehensive mechanical properties that cannot be achieved by a single strengthening method can be obtained. This comprehensive strengthening process is called deformation heat treatment. In addition to obtaining excellent mechanical properties, deformation heat treatment can save the reheating process of heat treatment by closely combining pressure processing and heat treatment, thereby saving a lot of energy consumption, heating equipment and workshop floor space, and at the same time can reduce the oxidation and burning of materials and heat treatment defects such as decarburization and deformation. Therefore, the deformation heat treatment process has both excellent strengthening and toughening effects and huge economic benefits. After the blade is quenched at 550℃ in the furnace and taken out of the furnace, the copper slag and other residues on the surface are quickly removed, and it is repeatedly rolled on the rolling machine to straighten and level it while hot. This deformation during the martensitic transformation process is also called low-temperature deformation heat treatment. In-depth research and application of deformation heat treatment can combine pressure processing and heat treatment more closely, which will cause a series of major changes in the process flow, process division, equipment layout, etc. of the machinery manufacturing industry. At the same time, it will also promote the scientific development of pressure processing and heat treatment technology. It is a thermal processing process with great application prospects.
2.Phase transformation superplastic straightening technology
After normal quenching, high-alloy tool steels such as high-speed steel contain 25%~30% retained austenite (FR) in the organization. If FR is unstable, it will further transform into martensite (M). During the martensitic phase transformation, when the stress is lower than the yield strength of the soft phase (austenite), plastic deformation can occur. This phenomenon is called martensitic phase transformation plasticity. According to the author's many years of experimental research, it is proved that steel has a significant phase transformation superplastic effect during the heat treatment phase transformation process, that is, the plasticity during the phase transformation process is several times or even dozens of times higher than the plasticity of the new and old organizations before and after the phase transformation. For many years, it has been believed that the correction of quenched parts while hot can achieve significant results. Although it includes the factors of thermoplasticity and the contribution of good r plasticity, the most important effect is the role of phase transformation superplasticity. The superplastic effect of phase transformation occurs in the whole process of TR→M phase transformation, but this effect is transient. When the phase transformation is most intense, the superplastic effect of phase transformation is most significant, so the frequency curve of plasticity should show a peak value. Obviously, the condition corresponding to this peak value should be the best time for correction. Correctly grasping and using this best time will have practical significance for guiding the process and operation of quenching while hot correction. Due to its thinness and length, the mechanical blade is bent by 10~30mm after normal quenching. It is easy to correct it by using the principle of phase transformation superplasticity. The superplasticity of steel during quenching and cooling is several times higher than the plasticity of austenite in a state slightly above the Ms point temperature. Therefore, when quenching while hot correction, correctly understanding and making full use of the principle of phase transformation superplasticity will have a guiding role in the actual production of heat treatment. Straightening at temperatures below the Ms point is not only feasible but also very applicable. It can correct deformation caused by thermal stress and structural stress at the same time, which is beneficial to ensuring the high hardness requirement of the workpiece, improving working conditions, reducing the pressure on the correction equipment and working conditions requirements, and has good correction quality and high production efficiency. It should be vigorously promoted and applied.
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