316H Stainless Steel: High-Temperature Grade with Enhanced Creep Strength

What Is 316H Stainless Steel?

316H is a high-carbon version of type 316 stainless steel intended primarily for elevated-temperature service. The H suffix designates a controlled carbon range of 0.04-0.10%, which is significantly higher than the 0.03% maximum of 316L. Higher carbon content increases the creep rupture strength and stress-to-rupture life of the material at temperatures above about 500°C, making 316H a common choice for pressure vessels, boiler components and piping systems governed by high-temperature design codes such as ASME Boiler and Pressure Vessel Code Section VIII. The grade is specified in ASTM A240 (plate, sheet and strip), ASTM A312 (pipe) and ASTM A213 (boiler and superheater tubes).

Chemical Composition (wt%)

Element	Specified Range (ASTM A240/A312, UNS S31609)
Carbon	0.04 - 0.10
Silicon, max	1.00
Manganese, max	2.00
Phosphorus, max	0.045
Sulfur, max	0.030
Chromium	16.00 - 18.00
Nickel	10.00 - 14.00
Molybdenum	2.00 - 3.00
Iron	Balance

Equivalent designations: UNS S31609 (ASTM), EN 1.4407 / X6CrNiMo17-12-2 (EN 10088), SUS316H (JIS G4303/G4304).

Mechanical Properties (Annealed)

Property	Minimum Value	Reference Standard
Tensile strength	515 MPa	ASTM A240 / A312
Yield strength (0.2% offset)	205 MPa	ASTM A240 / A312
Elongation	40% (plate), 35% (pipe)	ASTM A240 / A312
Hardness	217 HBW max	ASTM A240

High-Temperature Behavior and Corrosion Resistance

Creep strength

The controlled carbon range is the key to high-temperature performance. Carbon provides solid-solution and carbide strengthening that raises creep rupture strength compared with low-carbon 316L, which loses strength rapidly above about 500°C. In practice 316H is specified for continuous service in the range of about 500-870°C, where design is governed by creep rather than short-term tensile properties.

Corrosion resistance

The 2-3% molybdenum content gives 316H substantially better resistance to pitting and crevice corrosion in chloride-bearing media than molybdenum-free grades such as 304 and 304H. In sulfur-bearing high-temperature environments, molybdenum also contributes to a more protective scale, which is why 316H is frequently selected for flue-gas and sulfur-containing process streams. As with all austenitic grades, 316H remains susceptible to chloride stress corrosion cracking in hot, wet chloride service, so it should not be treated as a seawater or brine grade.

Welding of 316H

Welding should be performed with matching filler metal, typically ER316H, so that the weld metal has carbon and molybdenum contents consistent with the base metal. Using a low-carbon filler such as ER316L in high-temperature design can reduce the creep strength of the weld below the design requirement. No preheat is required, and post-weld heat treatment is not normally performed for 316H; where sensitization is a concern in welded construction, a stabilized grade such as 316Ti or 321 may be preferred.

Typical Applications

Boiler and superheater components, hot-reheat steam piping, high-temperature chemical reactors, furnace radiant tubes, waste-incineration heat exchangers, and power-plant piping in coastal or sulfur-bearing environments. The grade is also used for flanges, valve bodies and fittings in high-temperature process lines where molybdenum-bearing corrosion resistance and creep strength are both required.

Selection Guidance

316H is the appropriate choice when the service temperature is in the 500-870°C range and the environment contains corrosive species such as chlorides, sulfur dioxide or process acids. For non-corrosive high-temperature service above 900°C, a heat-resisting grade such as 309S or 310S offers better oxidation resistance. For welded components held statically at 400-900°C where intergranular corrosion resistance is the priority, a titanium-stabilized grade such as 316Ti is often preferred.

FAQ

Q1: What is the difference between 316H and 316L? 316H has a controlled carbon content of 0.04-0.10% versus 0.03% maximum for 316L. The higher carbon raises creep rupture strength for service above about 500°C, whereas 316L is preferred for welded room-temperature and mildly elevated-temperature service because of its resistance to sensitization.

Q2: Which filler metal should be used to weld 316H? ER316H filler wire is recommended so that the weld deposit matches the carbon and molybdenum content of the base metal. Low-carbon fillers such as ER316L are not suitable where the weld is required to carry creep loads at high temperature.

Q3: Can 316H be used in sulfur-containing high-temperature environments? Yes. The molybdenum addition improves resistance to sulfur-bearing gases at elevated temperature, and 316H is commonly specified for flue-gas ducts, heat-recovery equipment and sulfuric acid plant components operating within its temperature limits.

Q4: What is the difference between 316H and 316Ti? 316Ti is stabilized with titanium for intergranular corrosion resistance and suits long-term static service at 400-900°C. 316H offers higher creep strength for dynamically loaded components such as shafts, valve stems and pressurized piping at 500-870°C.

Q5: How does carbon content affect 316H performance? Below 0.04% carbon, creep resistance is reduced; above 0.10%, the risk of sensitization and intergranular corrosion increases. The standard range of 0.04-0.10% balances creep strength against weldability and corrosion resistance.

Q6: 316H or 309S for a high-temperature component? Choose 316H when the environment is corrosive (chlorides, sulfur gases) and the temperature is at or below 870°C. Choose 309S for non-corrosive oxidizing service at 900-1000°C, where oxidation resistance is the governing requirement.