Creep‐rupture strength of a martensitic chromium steel after annealing between 750 and 950 °C

The influence of various temperature transients on the tirne‐to‐rupture of a martensitic chromium steel was investigated in tests in which the transient temperature and transient time, cooling rate, and test temperature were varied systematically. Above a temperature of approximately 800 °C an austenitic structure is produced which can be transformed back into martensite by rapid cooling to a temperature below approximately 200 °C. The time‐to‐rupture of this martensite may be reduced by a factor of five compared to the initial condition. At annealing temperatures below 780 °C (A c1b ) this loss in time‐to‐rupture is either less pronounced or non‐existent. If austenite produced above some 800 °C is cooled slowly, pearlite of very low creep‐rupture strength is generated, or the austenite remains in existence above 300 °C and, depending on the test temperature, also may have an unsatisfactory creep‐rupture strength.