What TP304 / 304L is
Type 304 is an 18% chromium, 8% nickel austenitic stainless steel. The L grade carries lower carbon so that welding does not sensitize the heat-affected zone and invite intergranular corrosion. Dual-certified material meets the chemistry of 304L and the mechanical minimums of 304, which is why most tube is now supplied that way.
Seamless or welded
ASME SA213 covers seamless tube; SA249 covers welded tube made from strip and then annealed. For most heat exchanger and process service, welded tube performs identically at lower cost. Where the specification, the customer, or the pressure class demands seamless, we supply SA213. Tell us which, or ask us which.
Chemical composition, 304L
| Element | Requirement |
|---|---|
| Carbon | 0.035% max |
| Chromium | 18.0 to 20.0% |
| Nickel | 8.0 to 12.0% |
| Manganese | 2.00% max |
| Silicon | 0.75% max |
Mechanical properties
| Property | 304 | 304L |
|---|---|---|
| Tensile strength, min | 75,000 psi | 70,000 psi |
| Yield strength, min | 30,000 psi | 25,000 psi |
| Elongation in 2", min | 35% | 35% |
Where it is used
- Shell-and-tube exchangers on fresh cooling water and mild process streams.
- Food, beverage, and pharmaceutical process tube.
- Chemical plant piping and instrumentation tube.
- Boiler feedwater heaters and low-chloride condensers.
When 304 is not enough
Chlorides above about 200 ppm, seawater, or acidic condensate: move to TP316L or duplex SA789. Sustained temperatures above 1000 degrees F: TP321H or TP347H.
Seamless (SA213) or welded (SA249), OD, wall, length or U-bend schedule, quantity, finish, whether dual certification 304/304L is acceptable, and any supplementary tests such as ASTM A262 Practice E.