Type 304—the most common grade; the classic 18/8 stainless steel. Also referred to as "A2" in accordance with ISO 3506.[14]
Type 304L— same as the 304 grade but contains less carbon to increase weldability. Is slightly weaker than 304.
Type 316—the second most common grade (after 304); for food and surgical stainless steel uses; alloy addition of molybdenum prevents specific forms of corrosion. It is also known as marine grade stainless steel due to its increased resistance to chloride corrosion compared to type 304. 316 is often used for building nuclear reprocessing plants.[14]
Type 316L—extra low carbon grade of 316, generally used in stainless steel watches and marine applications due to its high resistance to corrosion. Also referred to as "A4" in accordance with ISO 3506.
Type 409—cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
Type 416—easy to machine due to additional sulfur
Type 440—a higher grade of cutlery steel, with more carbon, allowing for much better edge retention when properly heat-treated. It can be hardened to above Rockwell 55 hardness,[citation needed] making it one of the hardest stainless steels. Due to its hardness and relatively low cost, most display-only and replica swords or knives are made of 440 stainless. Available in four grades: 440A, 440B, 440C, and the uncommon 440F (free machinable). 440A, having the least amount of carbon in it, is the most stain-resistant; 440C, having the most, is the strongest and is usually considered more desirable in knifemaking than 440A, except for diving or other salt-water applications.
