Mill Terms: General
Rimmed Steel—A type of steel characterized by a gaseous effervescence when cooling in the mold. This results in a relatively pure iron outer rim.
Capped Steel—This is a type of steel with characteristics similar to those of rimmed steels, but to a degree intermediate between those of rimmed and semikilled steels. It can be either mechanically capped or chemically capped when the ingot is cast, but in either case the full rimming action is stopped, resulting in a more uniform composition than rimmed steel.
Semikilled Steel—Steel that is partially deoxidized so that there Is greater degree of gas evolution than in killed steel, but less than in capped or rimmed steel. The uniformity in composition lies between that of killed steel and rimmed steel.
Killed Steel—Steel deoxidized with certain deoxidizing elements, such as aluminum, silicon, etc. The term “killed” is used because such additions cause the steel to lie quietly in the molds during solidification.
Strand Casting—The direct casting of steel from the ladle into slabs, blooms or billets.
In strand casting a heat of steel Is tapped into a ladle in the conventional manner. The liquid steel is then teemed into a tundish which acts as a reservoir to provide for controlled casting rate. The steel flows from the tundish into the casting machine and rapid solidification begins in the open-ended molds. The partially solidified slab, bloom or billet is continuously extracted from the mold. Solidification is completed by cooling the moving steel surface.
Ingot—A mass of metal cast In a form convenient for storage or transportation. The cross section of most ingots approximates a square or rectangle with rounded corners. All ingots are tapered and are commonly cast big-end-down. For certain purposes, however, ingots are cast big-end-up.
Blooms—A semi-finished product rectangular in cross-section, the width not being more than double the thickness and the cross-section usually not less than 36 square inches.
Billets—Usually associated with a solid semi-finished product for further rerolling, reprocessing or reshaping, in dimensions of 2 1/2, square inch minimum to 36 square inch maximum.
Hot-rolled—Products in the “as-rolled condition” from any hot mill operation.
Cold-drawing—The process of pulling a “conditioned’ bar (pickled and-limed or grit blasted) through a die for the purpose of producing a bright, smooth surface finish and close tolerances.
Centerless Grinding—Grinding the surface of a bar mounted on rollers rather than centers.
Turning—A method of cold-finishing by machining to size in a lathe or turning machine to remove surface metal formed during hot-rolling.