ambiguous

Tom produces the ~18-inch-thick, 400–600-pass weld sample. Tells the story: forging press broke after 60 years of service; competent welders, no weld defects, but high residual stress; cracked off the welding platform on first attempt; on second attempt the press cracked the first time they tried to forge an aluminum truck wheel. Tom specifies "not Alcoa, the other plant," ~8,000-ton press.

[Tom produces a thick weld sample.] Speaking of armor plate — we'll pass this one around, it's a little heavier. Let me put it up here first. It's not dirty, I just don't like to scratch everything up. This is a weld that came out of a forging press. It's about an 18-inch thick weld. This is the type of weld they would have been making. I counted once — somewhere between 400 and 600 passes. There are some sharp edges on this, so be careful, don't cut yourself. [Tom hands the weld sample around the class.] That's how they welded battleship armor, which could be 14, 16, in some cases 18 inches thick.