^ Marine Welding is a Tough Job
Welding is the ultimate permanent fastener, connecting materials at the molecular level and endowing joints with tensile strength, toughness, hardness, and ductility similar to that of the bonded materials.
Van der Willingen formulated waterproof electrodes in 1946 and harnessed the long-known potential of electric arcs to weld under water. British Admiralty first executed marine welding for ships.
Industrial welding engages diverse processes. Marine welders prefer arc welding because the flux or inert gases used in the process protect the molten weld pool. Steel remains the most welded material, above or below water.
Superbly economical as it saves the titanic cost and effort of pulling mammoth structures out of water, marine welding is tougher to execute. Higher pressures, greater hydrogen content in weld joints, and faster cooling rates:
- destabilize arcs
- weaken joints
- escalate joint porosity
Marine welding can use only direct current (DC) because alternating current (AC) can electrocute diver-welders. Plus, maintaining AC arcs under water is harder. Industrial welding uses both. Inspecting underwater welds is tougher.
Unlike industrial welding, marine welding joins a limited range of metals. Favorites include:
- carbon steels
- low-alloy steels
- austenitic and duplex steels
Underwater welding dislikes:
- high-strength steels with over 0.4% carbon equivalent
- dissimilar metals and high-strength-low-alloy steels
- totally austenitic stainless steels
Industrial welders don’t, but marine welders may feel Nitrogen Narcosis i.e. drowsiness as nitrogen enters bloodstream on inhaling compressed air 100feet below water.
Types of Underwater Welding
Wet environs heighten the risk of electric shocks and explosions in marine welding. Restrictions on free movement exhaust the diver-welder and aggravate the electric shock hazard. Hydrogen and oxygen pocket build-up intensifies the explosion threat.
Research on marine welding targets:
- minimizing effect of wet ambience on weld-joint quality
- welding at greater depths
- improving existing processes
- evaluating new processes and materials
- boosting automation
- advancing inspection techniques
Differences aside, both welding types constitute a fundamental joining process the manufacturing world cannot do without.