Seal Weld Dissimilar Metal Joints Material
Where a transition from one tube material to another must be made in a header-type furnace, the connecting header may be the same as either of the two tube materials.
But when a transition is made from ferritic (carbon steel or chrome-moly) to austenitic (stainless steel) tubes, the connecting header will necessarily involve a ferriticto-austenitic rolled joint. This joint is likely to leak in service because the austenitic material has a much greater coefficient of expansion. Seal weld such a joint.