HT PIPE is a SS 316H Pipe supplier with 15+ export experience. Contact us for more information and quotes for free!
316H is an austenitic stainless steel pipe grade with a carbon content between 0.04% and 0.10%. That matters because at temperatures above roughly 425°C (800°F), the creep strength of an austenitic stainless drops significantly. The higher carbon allows a specific solution heat treatment that produces a stable austenitic grain structure, which is what gives 316H its resistance to creep deformation under sustained thermal load.
Chemical Composition (weight %)
| Element | 316H Requirement | 316L Cap |
|---|---|---|
| Carbon (C) | 0.04 – 0.10 | 0.030 |
| Manganese (Mn) | 2.00 max | 2.00 |
| Phosphorus (P) | 0.045 max | 0.045 |
| Sulfur (S) | 0.030 max | 0.030 |
| Silicon (Si) | 0.75 max | 0.75 |
| Chromium (Cr) | 16.0 – 18.0 | 16.0 – 18.0 |
| Nickel (Ni) | 10.0 – 14.0 | 10.0 – 14.0 |
| Molybdenum (Mo) | 2.00 – 3.00 | 2.00 – 3.00 |
| Nitrogen (N) | 0.10 max | 0.10 |
Mechanical Properties at Room Temperature
| Property | ASTM A312 Requirement |
|---|---|
| Tensile Strength | 515 MPa min (75 ksi) |
| Yield Strength (0.2% offset) | 205 MPa min (30 ksi) |
| Elongation in 2" | 35% min |
| Hardness | 217 HB / 95 HRB max |
The 316H vs 316L Decision: What Actually Matters
Most comparisons stop at carbon content. Here's the part that usually gets skipped:
Operating temperature is the primary driver.
Below 425°C: 316L is usually adequate. Its lower carbon gives better resistance to intergranular corrosion in the heat-affected zone of welds.
Above 425°C (sustained): 316H is the standard choice. The higher carbon combined with proper solution annealing gives creep-rupture strength that 316L simply cannot match at those temperatures.
Cyclic thermal conditions (thermal cycling between high and low temperatures): Both grades need careful evaluation. 316H handles sustained creep better, neither grade eliminates the risk of thermal fatigue cracking if the design doesn't account for differential thermal expansion.
Welding complexity is real with 316H.
The higher carbon makes the HAZ (heat-affected zone) more susceptible to chromium carbide precipitation if the weld cools too slowly. In practice, this means:
- Weld procedure qualifications need to address post-weld heat treatment requirements for thick sections.
- For thin-walled pipe (schedule 10S or below), autogenous TIG or orbital welding without filler may be acceptable without PWHT, depending on the project's NDE requirements.
- For heavy wall (above 19mm), PWHT is often required by the engineering design code, which means you need to account for furnace capacity or in-situ heat treatment logistics on site.
Pipe Dimensions and Schedules Under ASME B36.19M
ASME B36.19M covers dimensions for stainless steel pipe. Unlike B36.10M (carbon steel), B36.19M primarily covers schedules 5S, 10S, 10, 20, 30, 40S, 40, 80S, 80, 120, 160, and XXS.
Commonly ordered 316H pipe sizes for industrial projects:
| NPS (inch) | Schedule | OD (mm) | Wall (mm) | Application |
|---|---|---|---|---|
| 1/2 | 40S | 21.34 | 2.77 | Instrument air, minor process |
| 1 | 40S | 33.40 | 3.38 | Utility piping |
| 2 | 40S | 60.33 | 3.91 | Main process headers |
| 4 | 40S | 114.30 | 6.02 | Major process lines |
| 6 | 40S | 168.28 | 7.11 | Unit transfer lines |
| 8 | 40S | 219.08 | 8.18 | High-temp hydrocarbon |
| 10 | 40S | 273.05 | 9.27 | Fired heater outlet |
| 12 | 40S | 323.85 | 9.53 | Reactor effluent |
| 16 | 40S | 406.40 | 9.53 | Main column bottoms |
For refinery and petrochemical projects where API 660 or plant engineering specifications apply, schedule 40S is common but always confirm against your line class. Some projects specify schedule 80S or 160 for high-pressure/high-temperature combinations on the same nominal size.
