In the 1920s, weld strength, ductility, and reliability were godawful by modern standards. The Master Boilermakers' Association (a railroad industry group) published annual convention proceedings annually. The proceedings are verbatim transcriptions of the official presentations and subsequent discussions. There was a lot of discussion about locomotive boiler welded repairs over the years. In the 1920s, welds had to be at least 25% as strong as the base metal... on the official welder qualification test. In the field, under typical sub-optimal conditions (i.e. the foreman barking at you, hot and tired, difficult access to the weld area, etc) you can bet the welds were <20% of the base metal strength. That's >5X weaker than a modern weld.
Also the crack-detection methods were crude at best. So often the entire crack wasn't even detected. Modern methods (dye penetrant test, for example) are far more capable of definitively locating cracks than the old slosh-it-with-black-oil-and-kerosene, wipe clean, then dust-it-with-whiting-and-hit-with-a-brass-hammer test.
So the ICC had very good reasons to discourage welding as a safe repair technique, unless it was used only to help seal the edge of a riveted joint. That way you might develop a small leak if the weld failed, but the rivets would hold everything together.
Just before WW2, the U.S. Navy switched from riveted submarine hulls (dangerous when depth-charged - the rivets tend to break under shock and become projectiles inside the hull) to welded sub hulls. Ditto for merchant ship construction. The WW2-emergency Liberty Ships had welded hulls, but they had a lot of trouble at first with steel quality, cracking, and strain relief. At first designers didn't realize how much stress could build up in a huge welded assembly from the hot welds cooling and contracting, and they failed to provide stress relief structures for this. The earlier Liberty ships were nicknamed "Kaiser coffins" for a grim reason. Similarly, locomotive boiler welds only start to become trustworthy starting in the late 1930s under unusually well-controlled conditions. General adoption of recognizably "modern" welding techniques, training, and equipment is generally a post-WW2 phenomenon.
- Doug Debs
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