This paper studied the creep curves of 12CrMoV heat resistant steel served as main steam pipes in power plant.By comparing constant-stress creep with constant-load creep

it was found that the method of θ Projection Concept could describe constant-stress creep successfully

but it was not applicable for the constant-load creep.Based on the constant-load creep curves of 12CrMoV steel

a modified θ method has been developed

which could describe both the constant-stress creep and constant-load creep successfully.Thereby

the extrapolations of creep curves can be made effectively with a lot of tested data of constant-load

Furthermore

on the basis of damage mechanics analysis and normalization treatment

a new concept of step-by-step extrapolation on the basis of extrapolation from creep curves was put forward to assess the residual life of high temperature components in power plants.The new step-by-step life extrapolation method gives a more accurate creep life estimation of certain components without considering uncertainties of classical extrapolation under conditions such as operation variations

microstructure alternation

and deference of test specimen from real components etc.creep