What is alloy steel?
Alloy steel is a steel that is alloyed with various elements, usually with alloying element content between 1.0% and 50% by weight, in order to improve the mechanical properties of the steel. According to the different alloying elements, alloy steel can be divided into two categories: low alloy steel and high alloy steel. However, there is some controversy about the specific difference between the two. For example, Smith and Hashemi defined the difference as 4.0%, while Degarmo et al. defined it as 8.0%. In most cases, when we refer to the term "alloy steel", we usually mean low alloy steel.
Strictly speaking, every type of steel can be considered an alloy because steel is made by alloying iron with carbon (C) and other elements. However, not all steel is classified as "alloy steel". The simplest steel is alloyed with carbon (C) and iron (Fe), with a carbon content of about 0.1% to 1%, depending on the type of steel. However, when we say "alloy steel", we mean steel that has been deliberately added with other alloying elements in addition to carbon. Common alloying elements include manganese (which is the most common), nickel, chromium, molybdenum, vanadium, silicon, and boron. Less common alloying elements include aluminium, cobalt, copper, cerium, niobium, titanium, tungsten, tin, zinc, lead, and zirconium.
Compared to carbon steel, alloy steel has a range of improved properties, including strength, hardness, toughness, wear resistance, corrosion resistance, hardenability and thermal hardness. In order to obtain these properties, the metal may need to be heat treated.
Some of these alloys have excellent properties and can be used in particularly demanding applications, such as jet engine turbine blades and nuclear reactors. Due to the ferromagnetic properties of iron, the response of certain steel alloys to magnetism is important in important applications, including applications in electric motors and transformers.
The following are several common low alloy steels:
- D6AC
- 300M
- 256A
see also Types of steel for construction
[edit] Related articles on Designing Buildings
Featured articles and news
Electrical contractors welcome crackdown on late payment and push for clean energy.
Cyber Security in the Built Environment
Protecting projects, data, and digital assets: A CIOB Academy TIS.
Managing competence in the built environment
ITFG publishes new industry guide on how to meet the ICC principles.
The UK's campaign to reduce noise pollution: Mythbusting, articles and topic guides.
Setting Expectations on Competence Management
Industry Competence Committee.
New Scottish and Welsh governments
CIOB stresses importance of construction after new parliament elections.
The sad story of Derby Hippodrome
An historic building left to decay.
ECA, JIB and JTL back Fabian Society call to invest in skills for a stronger built environment workforce.
Women's Contributions to the Built Environment.
Calls for the delayed Circular Economy Strategy
Over 50 leading businesses, trade associations and professional bodies, including CIAT, and UKGBC sign open letter.
The future workforce: culture change and skill
Under the spotlight at UK Construction Week London.
A landmark moment for postmodern heritage.
A safe energy transition – ECA launches a new Charter
Practical policy actions to speed up low carbon adoption while maintaining installation safety and competency.
Frank Duffy: Researcher and Practitioner
Reflections on achievements and relevance to the wider research and practice communities.
The 2026 Compliance Landscape: Fire doors
Why 'Business as Usual' is a Liability.
Cutting construction carbon footprint by caring for soil
Is construction neglecting one of the planet’s most powerful carbon stores and one of our greatest natural climate allies.