Medium-carbon steels-Aisi-Sae 1030 -1050-1055-1040Medium-carbon steels are the grades AISI 1030 to 1055. They usually are produced as killed, semikilled, or capped steels and are hardenable by heat treatment. However, hardenability is limited to thin sections or to the thin outer layer on thick parts. Medium-carbon steels in the quenched and tempered condition provide a good balance of strength and ductility. Strength can be further increased by cold work. The highest hardness practical for medium-carbon steels is about Brinell 550 (Rockwell C 55). Because of the good combination of properties, they are the most widely used steels for structural applications, where moderate mechanical properties are required. Quenched and tempered, their tensile strengths range from about 75,000 to over 150,000 lb/in2 (517 to over 1,034 MPa).
Medium-carbon steel 1035 in cold-drawn bar 0.625 to 0.875 in (16 to 22 mm) thick has minimum tensile properties of about 85,000 lb/in2 (586 MPa) ultimate strength, 75,000 lb/in2 (517 MPa) yield strength, and 13% elongation. Strength increases and ductility decreases with increasing carbon content to, say, 100,000 lb/in2 (689 MPa), 90,000 lb/in2 (621 MPa), and 11%, respectively, for medium-carbon steel 1050. Properties decrease somewhat with increasing section size to, say, 70,000 lb/in2 (483 MPa), 60,000 lb/in2 (414 MPa), and 10%, respectively, for 1035 steel 2- to 3-in (50- to 76-mm) thick.
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