Crucible Steel

: The Working Of Steel

Crucible steel is still made by melting material in a clay or graphite

crucible. Each crucible contains about 40 lb. of best puddled iron,

40 lb. of clean mill scrap--ends trimmed from tool steel bars--and

sufficient rich alloys and charcoal to make the mixture conform to

the desired chemical analysis. The crucible is covered, lowered

into a melting hole (Fig. 4) and entirely surrounded by burning

coke. In about four h
urs the metal is converted into a quiet white

hot liquid. Several crucibles are then pulled out of the hole, and

their contents carefully poured into a metal mold, forming an ingot.

If modern high-speed steel is being made, the ingots are taken

out of the molds while still red hot and placed in a furnace which

keeps them at this temperature for some hours, an operation known

as annealing. After slow cooling any surface defects are ground

out. Ingots are then reheated to forging temperature, hammered

down into billets of about one-quarter size, and 10 to 20 per

cent of the length cut from the top. After reheating the billets

are hammered or rolled into bars of desired size. Finished bars are

packed with a little charcoal into large pipes, the ends sealed,

and annealed for two or three days. After careful inspection and

testing the steel is ready for market.