The stainless steel material 304 is the most common grade in industry field.In steel piping systems,there are pipes,fittings,flanges and other products are made from 304 stainless steels.
They are from different material standards,like the ASTM A213,A312,A182 and A403 etc.There are three 304 grades materials in these standards:304,304L,304H,they are looks very familiar,only different from the carbon content in chemical composition.(ASTM A403 WP304 pipe fitting)
From followings technical data,we can know the difference between the 3 grades:
| C | Mn | P | S | Si | Cr | Ni | N | |
| 304 | 0.08 | 2 | 0.045 | 0.03 | 0.75 | 18.00-20.00 | 8.00-10.50 | 0.1 |
| 304L | 0.03 | 2 | 0.045 | 0.03 | 0.75 | 18.00-20.00 | 8.00-12.00 | 0.10 |
| 304H | 0.04-0.10 | 2 | 0.045 | 0.03 | 0.75 | 18.00-20.00 | 8.00-10.50 |
| T.S（MPa） | Y.S（MPa） | Elongation | Hardness | ||
| % | HB | HR | |||
| 304 | ≥515 | ≥205 | ≥40 | ≥201 | ≥92 |
| 304L | ≥485 | ≥170 | ≥40 | ≥201 | ≥92 |
| 304H | ≥515 | ≥205 | ≥40 | ≥201 | ≥92 |
304L means low carbon,304H means high carbon.Because of the difference of carbon content,the 304H have a better heat and corrosive resistant,and the 304L material has a good welding performance.
This is the most important difference between the three grades.
