Steel

—A compound of iron containing 0.25 to 3% of carbon, usually with small quantities of silicon and manganese. The carbon causes it to harden when cooled suddenly from a red heat, and to soften again when cooled slowly. Steel cla ed as miid or ingot steel, is so made by a fusion proce , which frees it from intermingled slag. The more highly carbonized varieties, such as crucible and shear steel are used for tools, weapons and springs, their properties of hardening and tempering being invaluable. Modern research has led to the employment of le highly carbonized or mild steels in a variety of forms, either as castings or as forgings or rolled sections, thus displacing cast and wrought iron. Other metals, such as chromium and nickel are mixed with steel, increasing its tenacity ane toughne to a remarkable extent. Be emer steel, open hearth proce , mild steel, nickel steel, etc., are varieties.