Thermodynamics Calculation And Structure Properties Research Of Heat-Resistant Steel GX12

In this paper, mechanical property and welding performance heat-resistant steel G-X12CrMoWVNbN10-1-1 were researched in order to prove that this kind of steel can be used for elevated steam parameter thermal generator set, therefor increase generating efficiency and reduce exhaust gas. So it has great benfit to economy and society.In this paper, equilibrium precipitated phases in heat-resistant steel GX12 were studied,Gibbs free energy of carbides in Fe-Cr-W-V-C system of GX12 were calculated ,tension tests were proceed at different temperature of room temperature ,550℃, 600℃, 650℃, 700℃and the tensile fractures were scanned. the welding tests were proceed under different electric current of 80A,100A,120A,140A and temper at 735℃.According to thermodynamics result, in Fe-Cr-W-V-C system, when the temperature was higher than 1770K, after alloy became fused mass, the Gibbs free energy of Cr₂₃C₆ precipitated phase was the lowest, the Gibbs free energy of Cr₇C₃ followed by Cr₂₃C₆.In the fused mass, the precipitated phase were Cr₂₃C₆,Cr₇C₃,MX etc. Because of iron liquid environment, there was a little cementite appeared. The major equilibrium precipitated phases in base corpuscle were Cr₂₃C₆,Cr₇C₃,Fe3C etc. When the temperature between 1770K and 1938K, Cr₂₃C₆ and Cr₇C₃ were priority generated, because of chromiun carbon ratio was large quantity, Cr₂₃C₆ generated more easily, arborescent cyystal generated sometimes. The casting temperature can't be higher than the melting point of alloy (<1938K).Room temperature tensile indicated, compared with carbon steel (ZG20MnSi) and stainless steel (ZG0Cr13Ni4Mo), GX12 steel showed better mechanical property; high temperature tensile indicated, GX12 steel showed the best mechanical property at high temperature, tensile fracture TEM pictures showed that the tensile fracture mode of GX12 steel was ductile rupture at testing temperature.According to weld result, no weld crack was found that show GX12 steel had welding capacity; the structure of melting zone were martensite, the structure of overheated zone were martensite. The weld difference of structure was partly eliminated by heat treatment, after heat treatment, the structure of melting zone was martensite, the structure of overheated zone were tempered martensite, after the high temperature tempering, the performance of material became gentle, it was in favor of the use of material.