Effect of temperature on high‐cycle fatigue and very high cycle fatigue behaviours of a low‐strength Cr–Ni–Mo–V steel welded joint

Axially push–pull fatigue tests of a low‐strength Cr–Ni–Mo–V steel welded joint were conducted up to very high cycle fatigue regime at room temperature and 370 °C. The S–N curve at room temperature shows a duplex shape, while the S–N curve at 370 °C is continuously decreasing with lower fatigue strength. The welds at 370 °C undergoes dynamic strain ageing and has an enhanced load–defects interaction, leading to equal distribution of failures among different parts of the welds. The Z parameter model, with micro‐defect location incorporated, having sound physical representation, is life‐controlling of the welds at high temperature.