| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for accurately estimating a remaining service life of a heat resistant low Cr-Mo steel of STPA 20 to 24 or STBA 20 to 24 using a hardness method. SOLUTION: Hardness of a weld metal at a weld part of a material to be estimated is measured. An LMP value of the measured hardness represented by the following equation (1) is obtained based on the following equations (2) or (3) indicating a relationship between a preset hardness value of the weld metal and the LMP value. From the LMP value and an accumulated drive time, an actual use temperature is obtained based on the equation (1). A usable remaining time is obtained by subtracting the accumulated drive time from a sum of the use temperature and a service life of the material under a stressσ. LMP=T×(log t+C) (1), H=K<SB>1</SB>×LMP+H<SB>0</SB>(2), H=K<SB>2</SB>×(LMP-LMPC)+HC (3), wherein T: temperature (K), t: time (h), H: measured hardness of weld metal, K: constant, H<SB>0</SB>: hardness when LMP is 0, K<SB>2</SB>: constant, LMPC: LMP value when accelerated softening is started, HC: hardness of weld metal when accelerated softening is started. In this case, K<SB>2</SB>=f(σ), LMPC=g(σ), whileσdenotes a stress applied to a measured part. COPYRIGHT: (C)2004,JPO
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