Research On Influential Factors Of Longevity Of Cr20Ni80 Electric-resistance Alloy

Cr20Ni80 is a kind of nickel based alloy which contain Nickel by 80 percent and Chromium by 20 percent.Cr20Ni80 is an Electric-resistance alloy.Recent year,the requirement of Electric-resistance alloy is increasing. It was more concerned about Cr20Ni80 as it has a lot of excellent performance.Experimentations show that the longevity of Cr20Ni80 produced by domestic firms is shorter than that by abroad.Nickel and Chromium are valuable strategically material.So the factor which influences the performance of Cr20Ni80 has been researched.Through this research we wanted to study the factor which influences the longevity of Cr20Ni80 and can make some advices for improving the Longevity of Cr20Ni80.So it is much significative to research the microstructure and properties of Cr20Ni80 alloy.In this paper,basic theory and correlation report of the Cr20Ni80 alloy were introduced.Recent researches show that inclusions and the structure and property of oxide film of Cr20Ni80 alloy are two important factors which influence the longevity of Cr20Ni80 alloy.So the surface defect, inclusions,oxide film of Cr20Ni80 alloy has been investigated and researched in this paper.The results indicate that there are many micro-cracks on the surface of Cr20Ni80 alloy rod.There are many air vents and shrinkage cavities in Cr20Ni80 alloy casting also。Those defects can reduce finished product quotiety.It exists many inclusions in Cr20Ni80 alloy rod.The composition of those inclusions is complex,mainly consists of C,O,Al,Si,Ca,Ti and Fe elements and so on.They are commonly alumina silicate,calcium aluminate and calcium silicate and so on.Integrity shape of inclusions can be seen by means of electrolyte.It include nubby,rotundity,strip and floccule.The size can be obtain about 200um.Those inclusions can produce micro-cracks during the procedure of rolling and dragging.Furthermore,it can influence the longevity of Cr20Ni80 alloy.The oxidation behavior of Cr20Ni80 alloy in air over the temperature range of 700 to 1100℃for period up to 100h has been studied.The results indicate that oxidation kinetics obey parabolic law.The scales on the surface were determined by SEM and EPMA equipped with an EDS.The results show that oxide film is mainly composed of Cr₂O₃.There is a little of NiO and NiCr₂O₄ in oxidation film also.Their scales depend on calefaction temperature and time.At the temperature of 700℃,the oxide film is desquamating after 20h.Under the oxidation layer,it appears internal oxidation film.Oxidation film's forming and falling is influenced by electricity at a certain extent.The defect on the surface of Cr20Ni80 alloy is first cradle land of oxide film.Inclusions can lead to desquamation of Cr20Ni80 alloy.Oxide film desquamation can accelerate oxidation rate, influence oxidation resistance at high temperature,influence longevity of Cr20Ni80 alloy.Compare with our own Cr20Ni80 production,there is not crack on importation surface;There are little inclusions in importation alloy; Importation alloy has excellent oxidation-resistance performance at high temperature;The size of crystal grain of importation alloy is fine and uniformity.These factors can make importation alloy more durable than homemade production。...