Hiroo Koide

Residual Stress Improvement in Repair Welded Plates Using Water-Shower Cooling During Welding Process

To reduce tensile residual stress at a repair-welded area, a method that applies water-shower cooling behind a torch was developed. The width of the repair-welded area in this study was 27 mm, while the maximum width of welded areas in previous studies was 18 mm. To examine how much the welding method reduced residual stress at large-width welds, we first applied the method to multipass bead on plate specimens. The first layer consisted of a five-pass bead. A single large-width weld pass was applied with water-shower cooling. To cover the five-pass bead on plate area with a large-width weld, the torch was moved in a weaving motion. Residual stresses were measured. The measurements showed that tensile stresses remained in the five-pass bead on plate specimen. The tensile residual stresses were improved to compressive when our welding method was applied at the large-width weld pass. Then, we applied our method to a repair-welded specimen. The specimen was a butt-welded joint with an X-shaped groove. Repair welding was performed around the boundary of the welded area. A single large-width weld pass with water-shower cooling was applied at the surface. Residual stresses were measured. The measurements showed that tensile stresses remained on the surface of the X-shaped groove welding. Tensile residual stresses increased around the repair-welded area. When our welding method was applied, residual stresses were improved to compressive. Therefore, our welding method can reduce tensile stress in a repair-welded plate.© 2007 ASME

Effect of water-shower cooling during welding on tensile residual stress improvement in multi-layer welding of austenitic stainless steel plates

Abstract A new welding method that uses a water shower behind the welding torch has been developed in order to reduce tensile residual stress in a welded region. When this method is applied to the welding of austenitic stainless steel, the welding and cooling conditions mainly determine how much the residual stress can be reduced. To optimize these conditions, we first used the robust design technique to determine the effects of the interpass temperature, the heat input quantity and the water-shower area on the residual stress distribution of bead-on-plate. We found that, to decrease the tensile residual stress, the interpass temperature should be high, the heat input low, and the water-shower area large. Effect of the water-shower cooling on multi-layer welding was examined analytically and experimentally. It was found that the residual stresses were tensile without water-shower cooling, but compressive with water-shower cooling under the optimized conditions. It can therefore be concluded that the new welding method is appropriate for reducing tensile residual stress in multi-layer welding of austenitic stainless steel.

Residual Stress Improvement in Multi-Layer Welding of Austenitic Stainless Steel Plates by Using Water-Shower Cooling During Welding Process

To reduce tensile residual stress in a welded region, we have developed a new cooling method that applies a water-shower behind the welding torch. When this method is applied to multi-layer welding of austenitic stainless steel plates, cooling conditions mainly determine how much the residual stress can be reduced. To determine the conditions, we first used FEM to evaluate the effects of water-shower cooling and interpass temperature on the residual stress. In addition, we found effective conditions for reducing tensile residual stress. To verify the validity of the conditions, three plates were welded with or without water shower cooling. Residual stresses of the plates were measured experimentally. It was found that tensile residual stresses occurred on the surface of the welds and that they were reduced when the water-shower was applied at the last pass. These measurement results agree well with the FEM analyses. It can therefore be concluded that water-shower cooling during the last welding pass is appropriate for reducing tensile residual stress in austenitic stainless steel at a multi-pass weld.Copyright