DAIKOFCW 5CrMo

5%Cr-½%Mo steel for elevated temperature service up to 600°C.

In the PWHT condition the microstructure consists of tempered bainite.

• EN W.Nr.: 12CrMo 19 5 (1.7362), X7CrMo 6 1 (1.7373), X11CrMo 6 1 (1.7374), GS-12CrMo 19 5 (1.7363)
• ASTM: A387 gr. 5, A335 gr. P5, P5b, A234 gr. WP5 (fittings), A199 gr. T5, A213 gr. T5, T5b, A182 gr. F5, F5a, A336 gr. F5, A217 gr. C5

Given the hardness of the deposited metal (up to 400 HV) and its bainitic microstructure with relatively reduced fracture toughness, 5CrMo requires preheating and a minimum interpass temperature of 200 °C to prevent hydrogen-induced cold cracking. The use of controlled and well-maintained electrodes ensures a hydrogen content in the weld metal of <5 ml/100 g. For root TIG welds or when fully employing TIG welding, a lower preheat of below 150 °C may be acceptable, although faster cooling may result in partially martensitic and harder deposits. The transformation of 5CrMo during welding is completed within the operating range of 200-350 °C, allowing direct transition (at > 150 °C) to post-weld heat treatment (PWHT), followed by non-destructive examinations (NDE). If PWHT is applied after full cooling and NDE, maintaining the preheat temperature for a set period, according to thickness, is essential to aid in the dispersion of residual hydrogen. This precaution is less critical in solid wire TIG and MAG processes. The PWHT temperature for weld tempering usually varies between 705-760 °C (in accordance with ASME B31.3 705-760 °C). The minimum recommended holding time is two hours. For castings, the minimum recommended temperature for PWHT is lower, reaching temperatures up to 670 °C.