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Can SS 304 be used instead of SS 304H at high temperature?
Short answer
No, not for pressure parts in the creep range. SS 304H requires carbon of 0.04–0.10% and a grain size of ASTM No. 7 or coarser, which together guarantee creep-rupture strength above about 500 °C. Standard SS 304 has no minimum carbon or grain requirement, so its creep strength is not assured.
SS 304 vs SS 304H at a glance
| Property | SS 304 | SS 304H |
|---|---|---|
| UNS | S30400 | S30409 |
| EN | 1.4301 | 1.4948 |
| Family | Austenitic stainless steel | Austenitic stainless steel |
| C (%) | 0.07 max | 0.04 – 0.10 |
| Cr (%) | 17.5 – 19.5 | 18.0 – 20.0 |
| Ni (%) | 8.0 – 10.5 | 8.0 – 10.5 |
| N (%) | 0.10 max | — |
| Tensile strength | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Yield strength | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| PREN | 18 – 20 | — |
| Density | 7.93 g/cm³ | 7.93 g/cm³ |
| Magnetic | Essentially non-magnetic when annealed; cold work can make it slightly magnetic. | Essentially non-magnetic when annealed; cold work can make it slightly magnetic. |
| Typical use | Food, dairy and beverage processing equipment | Superheater and reheater tubes |
Which should you choose?
There's no universal "winner": the right choice depends on service conditions, codes and cost. Share your conditions with us for a recommendation.
Dual-certified SS 304/304H
Some mills produce material that meets both SS 304 and SS 304H. That is useful for stock, but the certificate must show the carbon and grain-size results for the SS 304H claim.
Sensitisation trade-off
Products in both grades
Related guides, comparisons and articles
Frequently asked questions
Which specifications include SS 304H?
ASTM A213 (tube), A312 and A376 (pipe), A240 (plate) and A182 (forgings).
How is grain size checked?
By metallographic examination per ASTM E112 on samples from the heat-treated lot.
What is the main difference between SS 304 and SS 304H?
SS 304H requires 0.04–0.10% carbon and a coarse grain size for creep strength above about 500 °C. Standard SS 304 has no minimum carbon or grain requirement.
When should I choose SS 304?
General service below the creep range.
When should I choose SS 304H?
Pressure parts in the creep range (boilers, heaters).
Can SS 304 replace SS 304H?
Only when the design, code and specification allow it. Strength, corrosion resistance and temperature limits differ, so substitution must be approved by the design authority.