Alloy steel

Alloy steel

Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low-steel/" target="_blank" class="keylink">alloy steels and high-steel/" target="_blank" class="keylink">alloy steels. The difference between the two is somewhat arbitrary: Smith and Hashemi define the difference at 4.0%, while Degarmo, et al., define it at 8.0 %. Most commonly, the phrase "steel/" target="_blank" class="keylink">alloy steel" refers to low-steel/" target="_blank" class="keylink">alloy steels.

Every steel is truly an alloy, but not all steels are called "steel/" target="_blank" class="keylink">alloy steels". Even the simplest steels are iron (Fe) (about 99%) alloyed with carbon (C) (about 0.1% to 1%, depending on type). However, the term "steel/" target="_blank" class="keylink">alloy steel" is the standard term referring to steels with other alloying elements in addition to the carbon. Common alloyants include manganese (the most common one), nickel, chromium, molybdenum, vanadium, silicon, and boron. Less common alloyants include aluminum, cobalt, copper, cerium, niobium, titanium, tungsten, tin, zinc, lead, and zirconium.

The following is a range of improved properties in steel/" target="_blank" class="keylink">alloy steels (as compared to carbon steels): strength, hardness, toughness, wear resistance, hardenability, and hot hardness. To achieve some of these improved properties the metal may require heat treating.

Some of these find uses in exotic and highly-demanding applications, such as in the turbine blades of jet engines, in spacecraft, and in nuclear reactors. Because of the ferromagnetic properties of iron, some steel alloys find important applications where their responses to magnetism are very important, including in electric motors and in transformers.

Low-alloy Steels

Low-steel/" target="_blank" class="keylink">alloy steels are usually used to achieve better hardenability, which in turn improves its other mechanical properties. They are also used to increase corrosion resistance in certain environmental conditions.
With medium to high carbon levels, low-steel/" target="_blank" class="keylink">alloy steel is difficult to weld. Lowering the carbon content to the range of 0.10% to 0.30%, along with some reduction in alloying elements, increases the weldability and formability of the steel while maintaining its strength. Such a metal is classed as a high-strength low-steel/" target="_blank" class="keylink">alloy steel.
Some common low steel/" target="_blank" class="keylink">alloy steels are:
D6AC
300M
256A