Alloy Steels

Alloy steel is a class of steel that, in addition to carbon, is alloyed with other elements, ranging from 1 wt.% to 50 wt.%, which are used to enhance the material’s various properties.

These elements commonly include manganese, nickel, chromium, molybdenum, vanadium, silicon, and boron. Less common elements include aluminium, cobalt, copper, cerium, niobium, titanium, tungsten, tin, zinc, lead, and zirconium.

Types of alloy steel

There are multiple subcategories of alloy steel. These include:

• Low-alloy steel

• High-strength low alloy (HSLA) steel

• High-alloy steel

• Stainless steel

• Microalloyed steel

• Advanced high-strength steel (AHSS)

• Maraging steel

• Tool steel

Low alloy steels generally contain less than 8 wt.% non-iron elements, whereas high-alloy steels contain more than 8 wt.% non-iron elements. Both typically have superior mechanical properties in comparison to carbon steels.

Properties of alloy steel

Alloy steels can contain a wide variety of elements, each of which can enhance various properties of the material, such as mechanical thermal and corrosion resistance. Elements added in low quantities of less than around 5 wt.% tend to improve mechanical properties, for example increasing hardenability and strength, whereas larger additions of up to 20 wt.% increase corrosion resistance and stability at high or low temperatures.

Applications & examples

As the term alloy steel encompasses numerous types of steel, its application area is broad.

Low alloy steels are used in a wide range of industries due to their extreme strength, machinability, cost-effectiveness and availability. They are found in military vehicles, construction equipment, ships, pipelines, pressure vessels oil drilling platforms and in structural components. Examples include HY80 and HY100.

High-alloy steels can be expensive to manufacture and difficult to process. Nevertheless, their superior hardness, toughness and corrosion resistance make them ideal for structural components, automotive applications, chemical processing and power generating equipment. Examples of high-alloy steels include the grades HE, HF, HH, HI, HK, and HL.