Distortion and its Control in Welding of Stainless Steel Structures - Case Studies

摘要

In the present study, two circular components made of stainless steel have been taken up for control of welding induced distortion. The first structure is the labyrinth used in hydro turbine assembly that consists of a ring type of flange made of martensitic stainless steel (ASTM grade A240 S41500) welded with a shell type web using grooved fillet welds. The size of the welded assembly is huge and the quantum of weld is very high leading to heavy distortion that often required to be corrected by way of weld build-up and subsequent machining. The second one is the vortex finder assembly, which is a part of cyclone separator that is used to separate the fine particles of coal from coarse ones for use in the combustion chamber of typical Circulating Fluidised Bed Combustion (CFBC) boilers' This is again a cylindrical structure with three shells joined with three flanges and supported by stiffeners. The structure is made of special grade austenitic stainless steel to withstand high temperature. In both the structures, a suitable welding procedure using an appropriate weld sequence was evolved after studying the weld details of the components. This weld sequence was implemented in-situ in actual components. After implementation of the weld sequence, it was found that the distortion of the component could be reduced and contained well within the permissible limits. This made the extra rework redundant, thus leading to a significant reduction in the cycle time of manufacture of the component. The details of the methodology adopted are described in this paper.