Thefollowing is a discussion of the various types of stainless steel. For otherterms and their definitions you will encounter when dealing with stainlesssteel .
18-8: 300 series stainless steel having approximately (not exactly)18% chromium and 8% nickel. The term "18-8" is used interchangeablyto characterize fittings made of 302, 302HQ, 303, 304, 305, 384, XM7, and othervariables of these grades with close chemical compositions. There is littleoverall difference in corrosion resistance among the "18-8" types,but slight differences in chemical composition do make certain grades moreresistant than others do against particular chemicals or atmospheres. "18-8"has superior corrosion resistance to 400 series stainless, is generallynonmagnetic, and is hardenable only by cold working.304: The basic alloy. Type 304(18-8) is an austenitic steel possessing a minimum of 18% chromium and 8%nickel, combined with a maximum of 0.08% carbon. It is a nonmagnetic steelwhich cannot be hardened by heat treatment, but instead. must be cold worked toobtain higher tensile strengths.
The 18% minimum chromium content providescorrosion and oxidation resistance. The alloy's metallurgical characteristicsare established primarily by the nickel content (8% mm.), which also extendsresistance to corrosion caused by reducing chemicals. Carbon, a necessity ofmixed benefit, is held at a level (0.08% max.) that is satisfactory for mostservice applications.
Thestainless alloy resists most oxidizing acids and can withstand all ordinaryrusting. HOWEVER, IT WILL TARNISH. It is immune to foodstuffs, sterilizingsolutions, most of the organic chemicals and dyestuffs, and a wide variety ofinorganic chemicals. Type 304, or one of its modifications, is the materialspecified more than 50% of the time whenever a stainless steel is used.
Because of its ability to withstand thecorrosive action of various acids found in fruits, meats, milk, and vegetables,Type 304 is used for sinks, tabletops, coffee urns, stoves, refrigerators, milkand cream dispensers, and steam tables. It is also used in numerous otherutensils such as cooking appliances, pots, pans, and flatware.
Type304 is especially suited for all types of dairy equipment - milking machines,containers, homogenizers, sterilizers, and storage and hauling tanks, includingpiping, valves, milk trucks and railroad cars. This 18-8 alloy is equallyserviceable in the brewing industry where it is used in pipelines, yeast pans,fermentation vats, storage and railway cars, etc. The citrus and fruit juiceindustry also uses Type 304 for all their handling, crushing, preparation,storage and hauling equipment.