The relative merits of rivets and welds dominate opinions about ship construction. Rivets are cylindrical metals shafts with a head at one end. These provide a watertight join when pushed glowing hot through drilled holes in two pieces of metal. Once in place, the plain end is deformed to nearly twice its size. The rivet contracts as it cools and holds the metal pieces together. Welding fuses two pieces of metal together. An external high heat source melts the pieces where they join. Filler is added to the molten material that cools to form a strong joint.
The installation of each rivet requires two workers. On one side, a person pushes the rivet through the metal piece and on the other side, a second person hammers the rivet’s plain end in place. Shipyards making riveted ships were famous for their banging noise and large payroll. The doomed Titanic liner that sank in 1912 required 3 million rivets weighing a total of 1,200 tons. It was built at a Northern Ireland shipyard that employed over 30,000 people.
The introduction of welding into shipbuilding during World War II permitted faster and cheaper ship construction. Larger pieces of metal could be joined together to make the ship’s hull than was possible with riveting. The manufacturing process required a smaller and less-skilled workforce. The joints were more water tight and oil tight than rivets. The vessel was lighter and with a smooth hull. It moved through water with less friction than a riveted ship.
The Titanic sank because substandard rivets failed to hold its hull together. These popped on impact with the ice and allowed icy seawater to flood inside the ship. Forty years later, poorly understood welding on Liberty ships, welded cargo ships produced by the United States during World War II, caused a number of these to break in half at sea. Low temperatures in the northern oceans made the steel hull brittle and crack, concentrating stress on poor welds.
Rivet installation has limited application in modern shipbuilding. Workforces skilled in riveting exist only in the aircraft manufacturing sector. Naval engineers still dispute the relative strength of joins between the hull and decks of ships where rivets could be stronger and superior to welds. Most modern vessels are produced exclusively of welded steel. Improved steel design has eliminated the brittle fracture and weld failure that affected the Liberty ships.