Long-Term Creep Rupture Testing at NRIM

Abstract

For the preparation of creep data sheets, a systematic and coordinated test program was planned at National Research Institute for Metals in 1964. The plan was to obtain creep and rupture strengths up to 100000hrs by performing long-term tests on high-temperature materials produced in Japan.To carry out this program a new creep laboratory was built at NRIM in 1967 and the installation of testing facilities was completed in 1968.According to the program the tests were started in 1968 and the program is now under way for about 30 kinds of steels.More recently, on 6 kinds of steels (1Cr-1/2Mo, 11/4Cr-1/2Mo, 21/4Cr-1Mo, 18Cr-8Ni, 18Cr-8Ni-Ti, and 18Cr-12Ni-Mo steels), the data up to 10000hr rupture-times were obtained, and these data were published as NRIM Creep Data Sheet No. 1∼6.The creep rupture-times of 21/4Cr-1Mo, 18Cr-8Ni and 18Cr-8Ni-Ti steels showed larger scatter than those of the other 3 kinds of steels. The elongation of ruptured specimens decreased with increasing rupture-time and showed relatively large scatter for 18Cr-12Ni-Mo steel.Furthermore, with regard to the 100000hr rupture stress a comparison was made between the estimated values obtained from the regression curves for logarithmic stress versus logarithmic rupture-time plots and other published data.