Underwater Welding of High Tensile Strength Steel

Abstract

With improvement of .shielding method and prevention of heat dissipation from the surface of the mother metal, the study on the possibility of underwater welding of HT50 and HT60 was undertaken.
The results obtained are as follows.
1) With the use of water curtain, surrounding water did not intrude the welds and fluxtuation in welding thermal cycle curve shown in the usual underwater welding was not recongnized.
2) With improvement of shielding method under water, the cooling rate was moderated and resembled to that in the air.
3) The method covering the surface of the mother metal with tape was available for prevention of heat dissipation from the surface and moderated the cooling from the side of the bead.
4) The hardness of the weld metal and HAZ decreased with increasing of heat input and showed the qualitative correlation with the cooling rate.
5) The maximum hardness of HT50 was less than 38OHv and would not cause the actual problem.