Research On The Comparition Of Microstructures And Properties Of Some Kinds Of Electrical Heating Alloys

As nickel based electrical heating alloy,because of the high temperature oxidation resistance,high strength,little permanent elongation,high resistance and small temperature coefficient of resistance,Cr20Ni80 alloy and Cr20Ni35 alloy were widely applied.There are tens of specialized manufacturer in ours contury which produce electrical heating alloy.But the quality of electrical heating alloys are different from each other.And there are many steps and factors which influenced the life of Cr20Ni80 alloy and Cr20Ni35 alloy during the process.Comparing with imported products,the longevity of Cr20Ni80 and Cr20Ni35 produced by domestic firms is shorter than that of aborad.Based on these factors,we researched some kinds of Cr20Ni80 alloy and Cr20Ni35 alloy in china so as to put forward some measures about improveing the quality and increaseing of service life of electrical heating alloy.In this paper,the basic theory and correlation report of Cr20Ni80 and Cr20Ni35 alloy were introduced.Further more,the microstructure,chemical components, electrical resistance,mechanical properties and quick life of Cr20Ni80 alloy and Cr20Ni35 alloy from different manufacturers in china were comparied.And the influencing factors of properties were investigated.The results indicate that the chemical components,mechanical properties and electrical resistance of the samples of Cr20Ni80 alloys from different manufacturers reached the national standard.But the grain sizes of samples are different from each other.The results also show that the higher the content of Cr in alloy,the higher the electrical resistance;the smaller the grain sizes in alloy,the better the mechanical properties.When the content and the size of nonmetallic inclusions increased,the alloy's electrical resistance will be increased and the alloy's quick life will be reduced. In samples,large inclusions are dominated by carbides,while Al,Mg,N,Ti,Fe elements etc are rich in small inclusions.The chemical components,mechanical properties and electrical resistance of the samples of Cr20Ni35 alloys from different manufacturers also reached the national standard.And the distribution of inclusions is nonuniform.In samples,large inclusions are dominated by carbides,while Mg,N,Ti,Ca,0 elements etc are rich in small inclusions.No matter whether Cr20Ni80 alloy or Cr20Ni35 alloy,Electron microprobe analysis shows that the large inclusions which gathered easily and are easy to form larger inclusions are dominated by carbides.So it has a great effect on mechanical properties and corrosion resistance of electrical heating alloy.Meanwhile,the Titanium nitride which is a brittle,dot shaped and undeformable inclusion which will have a effect on fatigue property of alloy,so as to decrease the fatigues trength and life of alloys.In this artical the Cr20Ni80 alloy and Cr20Ni35 alloy were comparative researched.As we all known that nickel element was used as matrix elements in Cr20Ni80 alloy and Cr20Ni35 alloy.In Cr20Ni80 alloy Iron element was used as microelement element while used as major element in Cr20Ni35 alloy.Because the Cr20Ni35 alloy has high content of Iron element,its high temperatur strength, oxidation resistance,corrosion resistance and maximum operating temperature decreased.The high temperature mechanical properties and room temperature mechanical properties of Cr20Ni80 alloy is better than that of Cr20Ni35 alloy,because of its high content of nickel element.