I’ve been thumbing through various online forums (dangerous thing I know). The Brits really moved the bar with the Tornado, and that project has stimulated build from scratch efforts on this side of the pond. All that aside I was struck by some commentary regarding building brand new boilers in particular the quality of contemporary steel for use in boilerplate. Not being in the steel business, an engineer, nor a metallurgist, I am a bit puzzled by the thought of steel from 60 years ago being superior to contemporary steel. If true is this an issue of raw material, or because steam locomotives went away, the type of steel needed for locomotive boilers simply went out of demand thus driving the price for suitable plate steel through the roof?

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The slow disappearance of the steam engine also meant the need for its raw materials like for flues, which may have raised prices. And also the regular suppliers not getting orders take it off their supply list. Which meant metal makers for flues stopped making them and adjusted their metallurgy for other things.

When I went to the Owosso steam fest PM 1225 was fired and running, I left and learned they had a flue failure, later learned the metal in the flues was inferior for real flue material (IE china made you might say), the folks for the Milwaukee road 261 got the right flues for 1225.

Its a matter of knowing your metal and where what to do and the cost. You better be more careful about trying to buy something -off the shelf- not knowing its true distinction.
Same for rolling your own boiler plate, better have your metal right. There are folks out there making boilers, including custom steam locomotives, and they better have it right also.

Kelly, Thanks a bunch for the discussion link (Just didn't get the search string right.)

Like most things the answer is a hybrid. Part raw material - the prevalence of scrap, part processing - using aluminiun v silaca to "kill" the steel, and a heaping dose of market driven industry change.