Hybrid welding of duplex steels for chemical vessels

摘要

Duplex stainless steels represent very attractive alternative compared to currently broadly use of austenitic stainless steels in manufacturing of vessels for chemical plants. The article deals with the use of laser-arc hybrid welding (LHAW) to weld two types of duplex steels (EN 1.4410 and EN 1.4462), when the both welding sources operated in pulsing modes. The aim of the experiments was to gain insights into the effect of pulse parameters on properties of welded joints. The tensile strength of the welds reached the predicted strength of the base material even in those cases, where fracture occurred in the weld metal or in heat affected zone. Analysis of the phase composition of the weld metal indicated a balanced ferrite-aus-tenite ratio. For the analysed sample, the austenite content was on average 61%. The micro-hardness measurements showed no significant inhomogeneities in the micro-hardness of weld metal and heat affected zone with respect to base material. The results showed that LAHW in pulsed mode could provide the balanced thermal cycle that would ensure to avoid the embrittlement of the weld associated with non-equilibrium transformation of ferrite to austenite in the temperature interval between 1200 and 800 °C.