HSLA steel (high strength low alloy steel) is a type of steel alloy that provides many benefits over regular steel alloys. In general, HSLA alloys are much stronger and tougher than ordinary plain carbon steels. They are used in cars, trucks, cranes, bridges and other structures that are designed to handle a lot of stress, often at very low temperatures.


HSLA steels are so called because they only contain a very small percentage of carbon. A typical HSLA steel may contain 0.15% carbon, 1.65% manganese and low levels (under 0.035%) of phosphorous and sulphur[1]. It may also contain small amounts of copper, nickel, niobium, nitrogen, vandium, chromium, molybdenum, silicon or zirconium. HSLAs are therefor also referred to as 'microalloyed', as they are indeed alloyed in extremely small amounts by comparison to other main commercial alloy steels. As little as 0.10% niobium and vanadium can have profound effects on the mechanical properties of a 0.1%C, 1.3% Mn steel. These added elements are intended to utterly alter the microstructure of plain carbon steels, which is usually a ferrite-pearlite aggregate, to produce a very fine dispersion of alloy carbides in an almost pure ferrite. This eliminates the toughness-reducing effect of a pearlitic volume fraction, yet maintains and even increases the material's strength by precipitation strengthening and by refining the grain size, which in the case of ferrite increases yield strength by 50% for every halving of the mean grain diameter.