Analysis Of Relationship Between Creep Deformation And Rupture Life Of Heat-resistant Steel Based On Zc Method

Heat-resistant steel is a kind of material serving at high temperature,which is widely used in aerospace,boilers,power plants,petrochemical and other important industrial areas.The accident failure of high temperature components will bring serious economic damage and casualties,so the accurate life assessment of high temperature components is particularly important.Two main kinds of life prediction methods were used in engineering.One is extrapolated based on the life of creep rupture experiment,however,this kind of method requested long-time experiment,and a large amount of information was ignored in the process of creep,the other is based on creep data,but the method can't evaluate the dispersion of the data,it is unable to realize the reliability assessment meanwhile.Based on the problems existing in life prediction method,the high temperature creep experiment of 25Cr35 NiNbM alloy was carried out.The relationship between creep deformation and long-term life based on 25Cr35 NiNbM alloy creep lasting results was investigated,then a kind of life prediction method combined with creep information was put forward,which can analyze the dispersity of creep life results.The creep strain and life prediction of 25Cr35 Ni alloy were evaluated by the Zc method proposed,meanwhile the reliability prediction results were also given.At the same time,L-M,M-H parameter method,theta and ? method were applied to evaluate the creep life of the alloy for objective analyzing the traditional life evaluation methods and proposed Zc method.Further more,the application and influencing factors of Zc method were analyzed based on NIMS creep data tables.This paper mainly analyses.Effect of creep longest lasting time and creep rupture elongation on Zc method were discussed.The results showed that:(1)With the increase of the creep strain,the ?-P parameter curves gradually incline to fracture master curve,the estimated standard error of the data(?-P parameter data points in the corresponding dispersion)on either side of the master curve decreases.The difference between predicted rupture life and actual rupture life based on Zc method is small,when a suitable creep strain is selected.(2)Compared with other life prediction methods,TTP method can only predict creep rupture life.? method cannot realize the correct life prediction because there are too many fitting parameters,meanwhile it cannot evaluate the distribution of high temperature creep rupture data.? method is a kind of empirical method,the predicted rupture life based on this method have a big difference with actual rupture life.The advantage of Zc method is that the creep process information can be used to make prediction on creep strain and creep rupture life,and the reliability prediction can be evaluated based on Zc method.(3)The rule described by Zc method exists for the long creep data of different maximum creep data.The reliability prediction results obtained are consistent with the distribution of data,through statistical analysis of the high temperature creep duration data of 25Cr35 NiNbM alloy.When 5% is selected to make rupture life prediction on 25Cr35 NiNbM and 13Cr4.5Mo-cast state alloy based on Zc method,the predicted rupture life is close to actual rupture life.When the creep rupture elongation of material is large,5% is failure to predict the rupture life.The mean creep rupture elongation rate of material should be selected to reduce the rupture life prediction error.