Effect Of Grain Size On The Resistivity Of Several Electric Heating Alloys

Electrical alloys is the resistance alloy heater using resistance characteristic of the material manufacture heating element. It is divided into two categories:the Ni-Cr-(Fe) type and the type Fe-Cr-Al;(1) Ni-Cr-(Fe) alloy with Ni (or iron) as the base, which contain15%～30%Cr,29%～80%Ni, is the austenite, Cr20Ni80alloys are widely used, its highest use temperature is1100℃;(2) Fe-Cr-Al type alloys based on iron, which contain12%～30%Cr,4%～8%Al, the remaining Fe. is the ferrite.0Cr25Al5alloys are widely used, its highest use temperature is1200℃. Alloy0Cr25Al5and alloy Cr20Ni80has the following advantages:①They should have good oxidation resistance at high temperatures (or anti-media sentiment erosion) and adequate creep resistance.②They should have high resistivity, temperature coefficient of resistivity as low as possible, and can withstand large current.③They should have good metallurgical production process performance and manufacturing and processing performance. They are widely used in household appliances, industrial furnaces, machinery, and other buildings, and occupy an important position in the national economy. Meanwhile, the performance of the same material composition is mainly determined by the final crystal structure, which contains the grain size. Currently, however, the majority of domestic manufacturers in the manufacturing process, rarely consider the effect of grain size on resistivity.Therefore, In this paper, through the study of comparative research over the grain size and the corresponding change in resistivity to identify the relationships between this alloy0Cr25Al5and alloy Cr20Ni80after tensile deformation and annealing,it provide such research a basis data for the electrothermal alloy of the production.This paper describes alloy0Cr25Al5and alloy Cr20Ni80related basic research, influence factors of metal resistivity as well as relevant research report.On this basis, the author makes different tensile deformation,uses the same recrystallization annealing process, Finally, the paper study The two phase resistivity change and the change of oxidation.and basically understand the grain size of alloy0Cr25Al5and alloy Cr20Ni80impacingt on their resistivity and oxidative changes of these two alloys, and their in-depth analysis.The results showed that the alloy0Cr25Al5and alloy Cr20Ni80after different tensile deformation and using the same recrystallization annealing process, they have a grain size variation, the larger tensile deformation of the alloy Cr20Ni80, the smaller the grain size after recrystallization annealing, the value of resistivity is relatively high; The grain of alloy0Cr25A15is inversely proportional with tensile deformation.In five groups samples,the grain of VI sample is minimum, the grain size of Ⅱ, Ⅲ, Ⅳ, Ⅴ sample increase in turn. Resistivity is the No.1sample resistivity maximum, Ⅴ, Ⅳ, Ⅲ, Ⅱ in turn reduce.Whether the alloy0Cr25A15or alloy Cr20Ni80, after various tensile deformation and the same recrystallization annealing process, They had a resistivity decreases with increasing grain size and grain boundary is small, relatively speaking,effect of grain size on resistivity changes significantly.Meanwhile, the paper make a comparative study about the alloy0Cr25A15and alloy Cr20Ni80. Alloy0Cr25A15and alloy Cr20Ni80after stretching deformation, their resistance rates will be reduced, but also in the beginning stages of deformation, The resistivity decreased relatively obvious, but the degree of reduction in resistivity of the alloy0Cr25A15is less than the alloy Cr20Ni80, so the effect of cold working ratio is less than the alloy Cr20Ni80.The alloy0Cr25A15and alloy Cr20Ni80are uneven solid solution, after the plastic deformation.The change of crystal grain has nothing to do with the change of resistivity, but the alloy Cr20Ni80also contain the uneven tissue more than the alloy0Cr25A15.Although the oxidation resistance of alloy0Cr25A15is better than alloy Cr20Ni80,However,the experimental samples after heat treatment is in the oxide film forming stage,this time, the oxidation degree of the alloy0Cr25A15was greater than the oxidation degree of the alloy Cr20Ni80.