Low alloy steel

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Low alloy steel is steel alloyed with other elements, usually molybdenum, manganese, chromium, vanadium, silicon, boron or nickel, in amounts of up to 10% by weight to improve the hardenability of thick sections. Steel with higher alloy contents are generally called stainless steel, tool steel, or simply high alloy steel depending on the alloying elements.

Some of the more common low alloy steels in North America are identified by AISI four-digit codes. The first two digits indicate the alloy group, and the last two digits indicate the carbon content in hundreths of a percent by weight. Some common low alloy steels are:

• 4130
• 4140
• 4330V
• 4335V
• 4340
• 8630
• 8735
• 8740
• D6AC
• 300M

The most common these low alloy steels, particularly the 41xx series, have chromium and molybdenum as their main alloying element and are referred to as chromoly.