Microalloyed (High-Strength, Low-Alloy) Steels

Microalloying is a term applied to steels that contain small additions of alloying elements that retard austenite recrystallization and pin austenite grain boundary movement by the formation of small carbide and/or nitride precipitates. These elements include vanadium, niobium, and titanium. These HSLA steels are produced for a variety of plates, structural shapes, bars, and sheet applications with yield strength varying from 290 to 690 MPa. These steels are covered under numerous SAE and ASTM specifications. The SAE high-strength, low-alloy steels are covered under specifications J410, J1392, and J1442 and the ASTM high-strength, low-alloy steels are covered under various specifications, including A242, A440, A441, A572, A588, A606, A607, A618, A633, A656, A690, A709, A714, A715, A808, A812, A841, A860, and A871. These HSLA

steels have found wide application in areas such as bridge construction (structural beams), off-shore oil and natural gas platforms, ship hull and deck plate, and electrical transmission towers and poles. In the  automobile, HSLA steels are used for safety (ultrahigh-strength impact door beams and energy-absorbing bumper assemblies) and for increasing fuel economy through thinner (lighter weight) chassis structural sections. Microalloyed HSLA steels are also employed in large-diameter gas transmission pipelines.

Bruce L. Bramfitt

International Steel Group, Inc.

Research Laboratories

Bethlehem, Pennsylvania

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