SS Schenectady

The SS Schenectady was a World War 2 tanker, the first built by Kaiser Shipbuilding Company of Portland Oregon. The ship was launched on the 24th of October, 1942 and completed on December 31. 16 days later, while being loaded, with a loud crack, the ship broke in half. Suggested causes at the time were just guesses, faulty welding, "locked in" stresses, design flaws... Later as metallurgy improved, it was determined that the buttwelded plates had become brittle due to the forming processes and the chemical makeup of the annealed metal near the welds had become weaker. The crack started at the corner of a hatch and quickly travelled to the keel. 
The ship was repaired and was in regular use till it was scrapped in 1962