Continuous casting of steel — Japanese development

Japanese-led commercialization of continuous casting. Ten-story-tall casters; copper molds; 10-foot-high mold zone; horizontal cut-off as the slab moves at centimeters/minute. Yield jumped from 65% (ingot) to 90%+ (continuous). Breakouts (shell rupture) catastrophic — hundreds of tons of liquid on a billion-dollar facility, weeks of shutdown.

The other thing was continuous casting. When you pour an ingot of steel, it's usually slightly V-shaped — anybody know why? The mold is slightly V-shaped so you can get it out as it shrinks on solidification. You end up with a gap, and you can turn it over or lift it with a crane and take it out. If you put it in straight-sided walls, you're liable to just make a composite of cast iron and steel. So they have sloping walls. You pour the steel in, but as it shrinks on solidification, you get what we call a piping defect — shrinkage on solidification. You could throw away one-third of your steel and just remelt it because of the solidification piping. What people learned to do — the Japanese primarily, it took a while, you have to invest hundreds of millions of dollars — they developed continuous casting technology, so you're constantly feeding liquid in at the top. The continuous casters are about ten stories tall — you pour the steel in at the top, you have these copper molds that take the heat out, and they're about 10 feet high. You let the thing drop, pull it down, and the steel is soft enough that if you've got seven stories to go, you can actually turn that 10-inch-thick slab of steel sideways, horizontally, and cut it off as the whole thing is moving — at a few centimeters a minute, not very fast. The Japanese have cast continuously for several years on one machine. Now if you have a breakout — if the liquid in the center of the shell of solid steel fractures the shell — you dump not 300 tons but a couple hundred tons of steel on top of your $100 million or billion-dollar facility, and it shuts you down for a few weeks, which is pretty expensive. So breakouts are important.