Analysis of T23 Steel Weld-Joint on the Stress Relaxation Crack at Medium Temperature

Abstract This paper issues a new type of reheat-crack of T23 steel weld which is deferent to the cracks occurred at higher temperature above 550 degree as literatures reported. The specimen to be studied taken from a unit with long service time is analyzed by means of metallographic, scanning electron microscopy and energy dispersive spectroscopy. When further in-depth analysis is carried out on the test results, we find that Ti (Al) -N compounds are precipitated at grain boundaries, promote the formation of cavities, and finally become crack. Although the temperature of the crack is only about 380 degree which is much lower than the reheat-crack sensitivite temperature limit of T23 steel, but we also regard this crack as a type of stress relaxation crack which is another form of reheat-crack in coarse grained region of T23 steel weld-joint under specific service environment.