The metals that are characterized as steel are a diverse class of materials that are an integral part of modern society. Steel is an alloy that is made by combining iron with carbon as well as other elements that provide it with unmatched strength. Since its beginnings in the early 20th century, steel has proliferated into hundreds of types, each with its own unique material profiles. To help organize these steels, The American Iron & Steel Institute (AISI) and the Society of Automotive Engineers (SAE) have distinguished certain steel types, and this article will explore a steel class from the stainless steels or those which are more resistant to stains, corrosions, and rust. This stainless steel class is known as the 440 steels, and it is a highly popular material thanks to its hardness and resistance to wear.
Physical Properties of 440 Steel
440 steel is part of the stainless steels or those alloy steels which contain a minimum of 10% chromium, imbuing these alloys with increased resistance to corrosion. The AISI has created a three-digit naming index for the stainless steels (as opposed to the typical four-digit names given to other, non-stainless steels; see our article about the types of steels for more information), where the first digit represents the type of steel and alloying elements. The stainless steels have also been designated based on their molecular structure, where stainless steels can be austenitic, ferritic, martensitic, or duplex types. The differences between these types lie in their crystal lattice structures, which give the stainless steels certain beneficial working characteristics such as increased hardness, malleability, or resilience to fracture.
