Introduction
If you’re working on a project involving high temperatures, pressure, or corrosive environments—think power generation, petrochemical processing, or refining—you’ve likely encountered AISI 316H stainless steel. But what makes this particular alloy stand out from the crowd of stainless steels?
Here’s the straightforward answer: AISI 316H is a high-carbon variant of the popular 316 alloy, specifically designed for extreme high-temperature service. Its unique composition—with a controlled carbon range of 0.04–0.10%—enhances creep resistance and high-temperature strength, making it the material of choice for components that must perform reliably at temperatures up to 760°C for continuous operation .
Unlike standard 316 or low-carbon 316L, 316H maintains its mechanical properties under long-term stress at elevated temperatures, resisting the gradual deformation (creep) that can lead to catastrophic failure in boilers, reformers, and heat exchangers.
This guide breaks down everything you need to know—from chemical composition and mechanical properties to welding guidelines, available product forms, and real-world applications.
What Are the Key Specifications of AISI 316H?
Chemical Composition
The AISI 316H composition is precisely controlled to deliver high-temperature performance. The key differentiator is its carbon content:
| Element | 316H Range | 316L Range (for comparison) |
|---|---|---|
| Carbon | 0.04–0.10% | ≤0.03% |
| Chromium | 16.0–18.0% | 16.0–18.0% |
| Nickel | 10.0–14.0% | 10.0–14.0% |
| Molybdenum | 2.0–3.0% | 2.0–3.0% |
| Manganese | ≤2.0% | ≤2.0% |
| Silicon | ≤0.75% | ≤0.75% |
| Phosphorus | ≤0.045% | ≤0.045% |
| Sulfur | ≤0.03% | ≤0.03% |
This higher carbon content (compared to 316L’s <0.03%) is what gives 316H its superior creep resistance—a must for long-term use at elevated temperatures .
Designations and Standards
AISI 316H is recognized under multiple international standards:
| Standard | Designation |
|---|---|
| UNS | S31609 |
| ASTM A240 | 316H plate, sheet, and strip |
| ASME SA-240 | 316H pressure vessel plates |
| EN | 1.4918 (European equivalent) |
Mechanical and Physical Properties
At room temperature:
| Property | Value |
|---|---|
| Density | 7.98 g/cm³ |
| Melting point | 1390 °C |
| Minimum tensile strength | 515 MPa |
| Minimum yield strength | 205 MPa |
| Minimum elongation | 35% |
Real-world example: A power plant in Texas specified 316H ASTM A240 plates for a boiler’s high-pressure section, citing the alloy’s ability to meet the 515 MPa tensile strength requirement even at 600°C .
How Does 316H Perform at High Temperatures?
Creep Resistance
AISI 316H’s biggest advantage is its performance under heat. The higher carbon content improves 316H high-temperature strength and resistance to creep—the gradual deformation that occurs under long-term stress at high temperatures.
Critical high-temperature metrics:
| Parameter | Value |
|---|---|
| 100,000-hour creep strength at 650°C | ~100 MPa |
| Oxidation resistance | Up to 925°C |
| Steam oxidation rate at 800°C | ≤0.1 mm/year |
| Maximum continuous service temperature | 760°C |
| Maximum short-term service temperature | 870°C |
The 316H 100,000-hour creep strength benchmark means the material can withstand approximately 100 MPa of stress for over a decade at 650°C without failing—critical for power plant components designed for 20+ year service lives .
Oxidation Resistance
316H resists oxidation up to 925°C, with a slow 316H steam oxidation rate (≤0.1 mm/year at 800°C in pure steam). This makes it suitable for boiler tubes and superheater components exposed to aggressive steam environments.
Sigma Phase Embrittlement
One potential risk: 316H sigma phase embrittlement after long-term exposure in the 800–900°C range. This phase can make the material brittle and prone to cracking.
Prevention: Avoid prolonged heating in this temperature range. Proper solution annealing and controlled cooling rates minimize sigma phase formation .
Case study: A European refinery’s 316H refinery hydrogen reformer tubes operating at 750°C showed no significant creep deformation after 15 years—a testament to the alloy’s robust creep resistance when properly specified and operated .
What Heat Treatment Does 316H Require?
Proper heat treatment ensures AISI 316H maintains its strength and corrosion resistance. The goal is to control grain size and prevent harmful phase formation.
Solution Annealing
| Parameter | Specification |
|---|---|
| Temperature | 1040–1100°C |
| Hold time | 30–60 minutes |
| Cooling | Water quench |
This process dissolves carbides and restores a uniform austenitic microstructure, ensuring optimal mechanical properties.
Grain Size Control
Standards like ASME SA-240 require a 316H grain size ASTM 7 minimum (finer grains = higher strength). Finer grains also improve creep resistance by inhibiting dislocation movement.
Residual Stress Relief
For welded parts, a stress relief anneal at 450–600°C relieves fabrication stresses without causing sensitization.
Sensitization Behavior
316H sensitization behavior at elevated carbon is a concern: if cooled too slowly from 800–1000°C, carbon can combine with chromium to form carbides at grain boundaries, reducing corrosion resistance.
Solution: Proper solution annealing prevents this by keeping carbides dissolved in the austenitic matrix .
How to Weld and Fabricate 316H?
Welding and machining AISI 316H require careful technique to preserve its properties.
Welding Best Practices
| Parameter | Recommendation |
|---|---|
| Consumables | 316H welding consumables ER316H (matching carbon content) |
| Preheat | Not required for thin sections |
| Post-weld heat treatment (PWHT) | 600–650°C for thick sections |
| Heat input | ≤1.5 kJ/mm (to minimize HAZ size) |
| Interpass temperature | ≤150°C |
Critical: 316H filler metal carbon matching is essential—using 316L filler (with lower carbon) will compromise creep strength in the weld metal.
The 316H HAZ (heat-affected zone) creep strength can drop by 10–15% if welding parameters are poor. Using low heat input and proper PWHT restores properties .
Machining Tips
| Parameter | Recommendation |
|---|---|
| Cutting speed | 100–120 m/min (15–20% lower than carbon steel) |
| Tool coating | TiAlN-coated carbide |
| Tool life | 2–3x longer with coated tools |
| Coolant | Flood coolant recommended |
316H distortion control during welding is key for large fabrications. Use:
- Backstepping welding sequence
- Intermittent welding where possible
- Fixturing to restrain movement
What Product Forms Are Available?
AISI 316H is available in a wide range of forms from global stockists.
Common Product Forms
| Form | Specifications | Typical Sizes |
|---|---|---|
| Plates | ASTM A240 / ASME SA-240 | 3 mm to 200 mm thick |
| Seamless tubes | ASTM A213 | Various diameters |
| Pipes | Schedule 40 to 160 | 1/8″ to 24″ nominal |
| Round bars | 10 mm to 300 mm diameter | |
| Flat bars | 5×20 mm to 20×100 mm | |
| Forged fittings | Elbows, tees, reducers |
Supply Chain Tips
- Work with 316H global stockists to ensure quick delivery
- Many suppliers offer 316H custom cut plate to reduce waste
- 316H coil suppliers provide coils for large-scale fabrication
What Industries Use 316H?
Power Generation
- 316H boiler tubes for superheaters and reheaters
- 316H superheater headers distributing steam to turbine
- 316H power plant headers operating at 600–750°C
Petrochemical and Refining
- 316H refinery hydrogen reformer tubes (resisting hydrogen attack at 700–800°C)
- 316H ethylene cracking coils for olefin production
Other Applications
- 316H heat exchanger shells for high-temperature processes
- 316H steam distribution manifolds in industrial plants
- 316H flare stack tips resisting oxidation and weathering
Real-world example: A Japanese petrochemical plant replaced their 316L ethylene cracking coils with 316H ethylene cracking coils. Maintenance costs dropped by 40% because 316H resisted creep and cracking better at 800°C .
How Does 316H Compare to Other Grades?
| Grade | Carbon Content | Best For | Limitations |
|---|---|---|---|
| 316H | 0.04–0.10% | High-temperature creep resistance | Not for low-temp corrosion service |
| 316L | ≤0.03% | Corrosion resistance, welding | Poor creep strength above 500°C |
| 316 | ≤0.08% | General purpose | Intermediate creep performance |
| 304H | 0.04–0.10% | High-temperature service | No molybdenum (less corrosion resistance) |
The bottom line: Choose 316H when your primary concern is long-term performance at elevated temperatures (above 500°C). Choose 316L when corrosion resistance at ambient temperatures is the priority.
Conclusion
AISI 316H stainless steel offers a proven solution for high-temperature applications where standard stainless grades would creep and fail. Its controlled carbon content, combined with chromium, nickel, and molybdenum, delivers:
- Excellent creep resistance up to 760°C continuous service
- Good oxidation resistance to 925°C
- Compatibility with hydrogen service in refineries
- Available in all common product forms
- Weldable with proper techniques and matching consumables
For power plants, petrochemical facilities, and high-temperature industrial processes, 316H represents a cost-effective choice when long-term reliability is the goal.
FAQ About AISI 316H Stainless Steel
What is the difference between 316H and 316L stainless steel?
The main difference is carbon content: 316H has 0.04–0.10% carbon (for high-temperature strength), while 316L has <0.03% carbon (for better corrosion resistance in low-heat environments). 316H is better for creep resistance; 316L is ideal for food processing or marine applications.
Can AISI 316H be used in hydrogen service?
Yes—316H refinery hydrogen reformer tubes are a common application. Its molybdenum content resists hydrogen embrittlement, and its high carbon content maintains strength at 700–800°C, typical for hydrogen reformers.
What is the maximum service temperature for AISI 316H?
The 316H service temperature limit is 870°C for short-term (hours) use and 760°C for continuous (years) use. Exceeding these temperatures can lead to oxidation, creep, or sigma phase embrittlement.
What welding consumables should I use for 316H?
Use 316H welding consumables ER316H for TIG/MIG welding. 316H filler metal carbon matching is critical—using 316L filler will lower creep strength in the weld.
Does 316H require post-weld heat treatment?
For thick sections, 316H post-weld heat treatment (PWHT) at 600–650°C is recommended to restore creep resistance in the heat-affected zone. Thin sections may not require PWHT if welding parameters are optimized.
What is sigma phase embrittlement in 316H?
316H sigma phase embrittlement after long-term exposure in the 800–900°C range can occur, forming a brittle phase. Avoid prolonged heating in this range and ensure proper solution annealing.
What grain size is required for 316H?
Standards require a 316H grain size ASTM 7 minimum. Finer grains provide higher strength and better creep resistance.
Discuss Your High-Temperature Projects with Yigu Rapid Prototyping
At Yigu Rapid Prototyping, we recognize the critical role that AISI 316H stainless steel plays in high-temperature industrial applications. Whether you’re designing power plant components, petrochemical processing equipment, or specialized high-heat machinery, we can help you source and fabricate with this premium alloy.
Our team works with trusted global suppliers to source:
- 316H seamless tube ASTM A213 for boiler applications
- 316H pressure vessel plate meeting ASTM/ASME standards
- Custom-fabricated components with proper heat treatment
We also provide technical support for welding and heat treatment, helping clients avoid common pitfalls like sigma phase embrittlement.
Let’s discuss your project. We’ll provide a free assessment and help you determine whether AISI 316H is the right material for your high-temperature requirements.