In the previous investigation (ref.1), the authors examined the thermal behaviour of single pass welding of Zeron 100 super duplex stainless steel. This study was extended to a simple dual pass model.

This work was carried out to investigate the effect of welding variables on the thermal behaviour in the weld and heat affected zone (HAZ) areas of a multi-pass weldment in a super duplex stainless steel. The investigation included the effect on cooling time, D t_8/5(cooling time from 800 ° C to 500 ° C), peak temperature distribution and to establish a relationship between thermal characteristics and phase balance.

The cooling time, D t_8/5 and peak temperature achieved were compared using an existing heat flow model (Rosenthal Equation)(ref. 2,3) and by direct measurement of the thermal cycle in the HAZ. Generally, there was good qualitative agreement between the theoretical solution (Rosenthal Equation) and experimental measurement. In some cases, however, the deviations between the theoretical solution and the experimental measurement may be quite substantial with values up to twice the experimental value being obtained.

Changes in thermal condition caused by welding variables will affect the microstructure and consequently the material properties. Supporting tests, including microstructure analysis and pitting corrosion resistance were investigated. Microstructure analysis consisted of measurement of phase balance and examination for the occurrence of deleterious phases. From these tests, various empirical correlation’s have been proposed to relate the thermal characteristics to welding variables