Mass General subway stop welding investigation

Used as the exemplar case where 1900-era steel chemistry matters for solidification cracking — Tom checks manganese-to-sulfur ratio on old steels, not just hardenability/hardness.

Solidification cracking — it says keep the proper manganese-to-sulfur ratio. Well, this was a problem back in 1920, when we had high sulfur like 0.05 sulfur. The proper ratio, if you go back and read a metallurgy text from 1920 or 1930, is that the manganese-to-sulfur ratio has to be greater than six. If I have 0.05 sulfur, six times that is 0.3 manganese. Most steels have 0.3 manganese; many of them today have one percent manganese. So it's not really a problem, unless you're doing something like the Mass General subway stop. When they call me up, I say, what's the composition? If it's a 1900 piece of steel, I would also start worrying about the manganese-to-sulfur ratio. It wasn't just hardenability and hardness — I would start worrying about some of this in the really old steels.

1910-vintage subway station; engineering firm chipped half-inch-thick rust off structural beams down to white metal. Tom's recommendation: plug it back up — the rust was structural and stopping further corrosion.

They were redoing the subway station down here at Mass General right across the river. The guys doing it were at the firm I used to consult with — civil engineering, back 60 years ago — and they called me up. They said, this is 1910, they built this subway station, the old rhythms, sealants up. They had areas of rust that were half an inch thick. It replaced the beams — in some cases it held the concrete. They go in there and chip out all the rust down to white metal. They called me up, said, Tom, now what do we do? I said, you better plug it up with something, because that rust is keeping it from growing. It's kept it from growing for the last 18 years.