Hot Deformation Behavior And Processing Maps Of Cr20Ni80Electrothermal Alloy

Cr20Ni80alloy, the typical of the nickel chromium in electric heating alloy series, with the advantages of high temperature strength, resistivity uniformity and good stability, convenient maintenance and so on, is widely used in kinds of heating equipments of industrial and civil industry. However, the quality of electric heating alloy manufactured in home is far worse than that produced in developed countries. What’s more, the international competitiveness of domestic electric heating alloy is restricted by the high costs of production. The cause of crackle emerged in the production of Cr20Ni80in a certain factory is studied in this paper. Furthermore, the production parameters are optimized by thermal processing map. Therefore, the practical significance and applied value are possessed by the study in this paper.With the condition of deformation temperature of900℃～1220℃and strain rate of0.001s-10s, the true stress-true strain curve under high temperature of Cr20Ni80alloy is acquired by the way of single channel isothermal compression on the gleeble thermal/mechanics simulator. Based on the dynamic material model and plastic instability criteria, the thermal processing map of Cr20Ni80alloy is build. The results of study show as flows.(1) Cr20Ni80alloy belongs to the anti-temperature sensitive material. The flow stress decreases with the increase of deformation temperature in certain strain rate. In addition, the gap value of flow stress between adjacent curves at high temperature is less than that at low temperature.(2) The thermal deformation constitutive equation of Cr20Ni80alloy can be described by the revised hyperbolic sine model. The activation energy Q of thermal deformation is371.29KJ/mol. The constitutive equation is written as follows:(3) In the process of high temperature deformation, the organizational evolution of Cr20Ni80is more sensitive to temperature than strain rate. With high temperature and low strain rate, the atom has enough time and energy to spread, which benefits the organizational evolution.(4) According to the requirements of product quality and production efficiency in practical production, the forging process parameters are given by the analysis of processing map. The deformation temperature is1050℃～1200℃, the strain rate is 0.03s-1-0.08s-1.(5) According to the analysis of forging sample inclusion, microstructure and thermal processing map, the large inclusion, carbide and sulfide inclusion probably bring about the crackle emerged in the production of Cr20Ni80. The suggestion of decreasing deformation rate moderately based on the existing thermal processing parameters is proposed.