Machinery's Handbook, 31st Edition
High-Strength, Low-Alloy Steels 417 High-Strength, Low-Alloy Steels.— High-strength, low-alloy (HSLA) steel represents a specific group of steels in which enhanced mechanical properties and, sometimes, resis tance to atmospheric corrosion are obtained by the addition of moderate amounts of one or more alloying elements other than carbon. Different types are available, some of which are carbon-manganese steels and others contain further alloy additions, governed by spe - cial requirements for weldability, formability, toughness, strength, and economics. These steels may be obtained in the form of sheet, strip, plates, structural shapes, bars, and bar size sections. HSLA steels are especially characterized by their mechanical properties, obtained in the as-rolled condition. They are not intended for quenching and tempering. For certain applications, they are sometimes annealed, normalized, or stress relieved with some in - fluence on mechanical properties. Where these steels are used for fabrication by welding, care must be exercised in selec tion of grade and in the details of the welding process. Certain grades may be welded without preheat or postheat. Because of their high strength-to-weight ratio, abrasion resistance, and, in certain com positions, improved atmospheric corrosion resistance, these steels are adapted particu - larly for use in mobile equipment and other structures where substantial weight savings are generally desirable. Typical applications are truck bodies, frames, structural mem- bers, scrapers, truck wheels, cranes, shovels, booms, chutes, and conveyors. Grade 942X: A niobium- or vanadium-treated carbon-manganese high-strength steel similar to 945X and 945C except for somewhat improved welding and forming properties. Grade 945A: A HSLA steel with excellent welding characteristics, both arc and resis tance, and the best formability, weldability, and low-temperature notch toughness of the high-strength steels. It is generally used in sheets, strip, and light plate thicknesses. Grade 945C: A carbon-manganese high-strength steel with satisfactory arc weld- ing properties if adequate precautions are observed. It is similar to grade 950C, except that lower carbon and manganese improve arc welding characteristics, formability, and low-temperature notch toughness at some sacrifice in strength. Grade 945X: A niobium- or vanadium-treated carbon-manganese high-strength steel similar to 945C, except for somewhat improved welding and forming properties. Grade 950A: A HSLA steel with good weldability, both arc and resistance, with good low-temperature notch toughness, and good formability. It is generally used in sheet, strip, and light plate thicknesses. Grade 950B: A HSLA steel with satisfactory arc welding properties and fairly good low-temperature notch toughness and formability. Grade 950C: A carbon-manganese high-strength steel that can be arc welded with spe cial precautions, but is unsuitable for resistance welding. The formability and toughness are fair. Grade 950D: A HSLA steel with good weldability, both arc and resistance, and fairly good formability. Where low-temperature properties are important, the effect of phosphorus in conjunction with other elements present should be considered. Grade 950X: A niobium- or vanadium-treated carbon-manganese high-strength steel similar to 950C, except for somewhat improved welding and forming properties. Grades 955X, 960X, 965X, 970X, 980X: These are steels similar to 945X and 950X with higher strength obtained by increased amounts of strengthening elements, such as carbon or manganese, or by the addition of nitrogen up to about 0.015 percent. This increased strength involves reduced formability and usually decreased weldability. Toughness will vary considerably with composition and mill practice. The formability, composition, and minimum mechanical properties of the HSLA steel grades are shown in Table 7 through Table 9 on page 418.
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