304 / 304H / 304L stainless steel is the most common stainless steel. The steel contains both chromium (between 18% and 20%) and nickel (between 8% and 10.5%)
304 / 304H / 304L is an austenitic stainless steel. It is less electrically and thermally conductive than carbon steel and is essentially-magnetic but less magnetic than steel. It has a higher corrosion resistance than regular steel and is widely used because of the ease in which it is formed into various shapes
The carbon content of 304H (UNS S30409) is restricted to 0.04–0.10%, which provides optimal high temperature strength
The carbon content of 304L (UNS 30403) is restricted to a maximum of 0.03%, which prevents sensitization during welding. Sensitization is the formation of chromium carbides along grain boundaries when a stainless steel is exposed to temperatures in the range of approx. 900–1,500 °F (480–820 °C). The subsequent formation of chromium carbide results in reduced corrosion resistance along the grain boundary leaving the stainless steel susceptible to unanticipated corrosion in an environment where 304 would be expected to be corrosion resistant. This grain boundary corrosive attack is known as intergranular corrosion
The carbon content of 304 (UNS 30400) is restricted to a maximum of 0.08%. Thus 304 is not useful for corrosive applications where welding is required such as tanks and pipes where corrosive solutions are involved, thus, 304L is preferred. And its lack of a minimum carbon content is not ideal for high temperature applications where optimal strength is required, thus, 304H is preferred. Thus 304 is typically restricted to bars that will be machined into components where welding is not required or thin sheets that are formed in articles such as kitchen sinks or cookware that are also not welded.
304 Stainless Steel diameters range from 0.125″ to 14.00″ diameter.