304 and 304L Chemistry
Type 304 and 304L stainless steels share the same basic alloy system—roughly 18% chromium and 8% nickel—but they differ in one key element: carbon.
- 304 allows up to 0.08% carbon.
- 304L is restricted to 0.03% carbon maximum.
Aside from carbon, the chemical ranges for chromium, nickel, and other constituents are essentially the same across both grades. The lower carbon level is the defining distinction.
Why 304 is not an ideal alloy for welding
When stainless steel is heated into the range typical of welding (roughly 450–850°C), carbon becomes mobile and can combine with chromium near grain boundaries to form chromium carbides. These carbides “steal” chromium from the surrounding metal. 304 has up to .08% carbon. More carbon means more chromium carbides.
Because stainless steels depend on dissolved chromium to maintain their corrosion-resistant surface film, any region that becomes chromium-depleted becomes more vulnerable to attack. This localized loss of corrosion resistance at grain boundaries is known as sensitization, and it can lead to intergranular corrosion.
Why 304L is the right choice for welding
By limiting carbon to very low levels (0.03%), 304L drastically reduces the amount of chromium carbides that can form during welding. With little carbon available, carbide precipitation is minimized, allowing the heat-affected zone to retain adequate chromium in solid solution.
This gives 304L two advantages:
- It can be welded without needing post-weld heat treatment.
- It maintains better corrosion resistance in and around welds.
Contact us today for a more information or a quote on 304 or 304L precision slit coil, blanks, custom sheet, or coil to coil polishing.
