The AISI defines the following grades among others:
200 Series—austenitic iron-chromium-nickel-manganese alloys
300 Series—austenitic iron-chromium-nickel alloys
Type 301—highly ductile, for formed products. Also hardens rapidly during mechanical working.
Type 303—equivalent to ISO A1. Free machining version of 304 via addition of sulfur
Type 304—the most common; the classic 18/8 stainless steel; equivalent to ISO A2.
Type 316—for food and surgical stainless steel uses; Alloy addition of molybdenum to prevent specific forms of corrosion; equivalent to ISO A4.
400 Series—ferritic and martensitic alloys
Type 408—heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel.
Type 409—cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
Type 410—martensitic (high-strength iron/chromium); equivalent to ISO C1.
Type 420—"Cutlery Grade" martensitic; similar to the Brearley's original "rustless steel". Also known as "surgical steel".
Type 430—decorative, e.g. for automotive trim; ferritic.
Type 440—a higher grade of cutlery steel, with more carbon in it, which allows for much better edge retention when the steel is heat treated properly.
Tool Steels: Tool steel refers to a variety of carbon and alloy steels that are particularly well-suited to be made into tools. Their suitability comes from their distinct toughness, resistance to abrasion, their ability to hold a cutting edge and/or their resistance to deformation at elevated temperature (red-hardness).
HSLA Steel: HSLA Steel (High Strength Low Alloy Steel) is a type of steel alloy that provides many benefits over regular steel alloys. In general, HSLA alloys are much stronger and t ougher than ordinary carbon-based steel. They are used in cars, trucks, cranes, bridges and other structures that are designed to handle a lot of stress.
HSLA Steel only contains a very small percentage of carbon (less than one percent) and only small amounts of other added metals.