High strength low alloy steel (HSLA steel) is an alloy that provides improved mechanical properties and greater atmospheric corrosion resistance than traditional carbon steel. These types of steels differ from ‘normal’ alloy steels as they are not designed to meet a specific chemical composition but to meet specific mechanical properties.
The Chemical Composition of HSLA Steel
The chemical composition of high strength low alloy steels consists of a low carbon content of between 0.05% – 0.25% for sufficient formability and weldability, and a manganese content of up to 2%.
The remaining chemical constituents can vary depending on the product thickness and mechanical property requirements, and small quantities of chromium, molybdenum, nickel, copper, vanadium, niobium, nitrogen, zirconium, and titration can be used in different combinations.
Strength is added to the HSLA steel with the addition of vanadium, niobium, copper, and titanium. HSLA steels can reach yield strengths of greater than 275 MPa or 40 ksi, but because of this high strength, high strength low alloy steels usually require 25% – 30% more power to form than traditional carbon steels.
Increased corrosion resistance is given to high strength low alloy steel by the addition of silicon, copper, chromium, and phosphorus. Formability is improved with the inclusion of zirconium, calcium, and other rare earth elements as they provide sulfide-inclusion shape control.
Classifications of HSLA Steel
There are six different classifications of high strength low alloy steels, which are all designed to provide specific combinations of mechanical properties to suit the application requirements.
Weathering steel, also known by the trade name Cor-Ten, is a type of HSLA steel that exhibit a high level of atmospheric corrosion resistance and tensile strength. This type of high strength low alloy steel is commonly used in outdoor structures such as bridges due to these properties.
This type of HSLA steel includes the addition of calcium, zirconium, titanium, or other rare earth elements, which change the shape of the sulfide inclusions from elongated stringers to small, dispersed, globules that are almost globules. This change provides this type of steel with improved through-thickness toughness and ductility.
Microalloyed Ferrite-Pearlite Steel
Microalloyed ferrite-pearlite steel contains strong carbide or carbonitride-forming elements, in very small quantities – often less than 0.10%. These elements could be titanium, niobium, and/or vanadium, and they provide the HSLA steel with precipitation strengthening, grain refinement, and the possibility of transformation temperature control.
These steels have a ferrite microstructure that contains uniformly distributed, small sections of martensite. This microstructure provides these high strength low alloy steels with ductility, high tensile strength, low yield strength, high rate of work hardening, and good formability.
Acicular Ferrite Steel
These HSLA steels are characterized by a very fine high strength acicular ferrite structure. They are low carbon steels, with high yield strengths, excellent weldability and formability, and good toughness.
As-Rolled Pearlitic Steel
As-rolled pearlitic steels often include carbon-manganese steels, but they may also have small additions of other alloying elements to provide enhanced strength, formability, weldability, and toughness.
HSLA Steel from Masteel
Masteel supply a large range of high strength low alloy steels, all of which are engineered to promote outstanding high yield characteristics, which provide a cost-effective option for buyers.
Our range of HSLA steel has a tensile strength of up to 1300 MPa and provides excellent impact resistance and formability. We can supply our high strength low alloy steel as heavy plates or sheets.
If you would like any more information about our range of HSLA steels, please contact us.