Abstract
In underwater welding by the use of commercial covered austenitic stainless steel electrode, the mechanical properties are not so good and the hot crack occurs in the weld metal.
This study is investigated the mechanical and metallurgical properties with trial covered stainless steel electrode (RMl).
The following results are obtained:
(1) The compositional analysis of weld metal with RMl rod are the same as Schaeffler's diagram (penetration 40%) using trial covered stainless steel electrode.
(2) The quantity of diffusible hydrogen collected in mercury reaches to a constant volume in about 500 hr, it is about 8 ml/100 g Fe in case of RMl rod. The hydrogen embrittlement and the delayed cracking are hard to occur because of the lower quantity of diffusible hydrogen, so the RMl rod is adapted for the underwater welding rod.
(3) The weld metal seldom has blowholes, and no cracks are observed to the weld metal in X-ray inspection.
(4) The vicker's hardness in heat-affected zone is about Hv250 and that of weld metal is about Hv220 when used RMl rod, it does not have quench hardenability in underwater welding.
(5) In notched tensile test, the tensile strength of weld metal is about 660 MPa and that of bond about 645 MPa.
(6) In the impact test, the RMl rod is good for notch toughness because of the lower transition temperature.
