THE PROPERTIES OF UNDERWATER WELDED MILD STEEL AND HIGH STREINGTH STEEL JOINTS

This thesis is divided into two parts, the first being an investigation into the multipass underwater welding of mild steel, and the second an investigation into the feasibility of underwater welding HY-80 steel. With the former, current underwater shielded metal-arc welding technology was employed, while with the latter, current shielded metal-arc air welding technology was adapted to underwater welding. Multipass underwater mild steel welds are very often required and are commonly employed during underwater repair and salvage operations. However the physics, and even the basic properties of multipass welding are not well known. Experimental results showed that multipass underwater butt welds can be fabricated with marginally satisfactory tensile and impact strength. It appears that weld metal embrittlement due to rapid quenching causes the weld metal to become most susceptible to brittle fracture. This is significantly different from air welding, where the heat affected zone is more susceptible to brittle fracture. There are presently a substantial number of naval vessels afloat with all or part of their hull structure fabricated with HY-80 steel. However no investigation has been made into the feasibility of welding HY-80 underwater in order to perform voyage repairs or carry out salvage operations. Simple lap and tee joints were fabricated underwater from HY-80 steel of various thicknesses, and tests conducted to determine joint strength and ductility as well as overall weld quality. Both single and multipass joints were fabricated. It was found that acceptable joints could be fabricated, with joint performance comparable to that of underwater welded mild steel joints.

• Corporate Authors:

  Massachusetts Institute of Technology

  Department of Ocean Engineering, 77 Massachusetts Avenue
  Cambridge, MA  United States  02139
• Authors:
  • Meloney, M B
• Publication Date: 1973-6

Subject/Index Terms

• TRT Terms: Butt welds; HY 80 steel; Weld tests; Welding
• Uncontrolled Terms: Weldability
• Old TRIS Terms: Multipass welds; Underwater welding
• Subject Areas: Bridges and other structures; Construction; Marine Transportation;

Filing Info

• Accession Number: 00048387
• Record Type: Publication
• Source Agency: Massachusetts Institute of Technology
• Report/Paper Numbers: MS Thesis
• Files: TRIS
• Created Date: Nov 14 1973 12:00AM