Stainless steel is an essential material in modern industry, used in applications ranging from chemical processing to marine equipment and medical devices. Among the many grades available, 316 vs 347 stainless steels are widely used due to their excellent corrosion resistance and mechanical properties. Understanding their differences is crucial for engineers, procurement specialists, and manufacturers to select the right stainless steel grade for their applications.
At Huaxiao Metal, we specialize in supplying high-quality stainless steel materials, including sheets, plates, bars, and pipes. This comprehensive guide compares 316 and 347 stainless steels in terms of chemical composition, mechanical performance, international equivalents, applications, and FAQs to help you make informed decisions.
What Is 316 Stainless Steel?
316 stainless steel is one of the most commonly used grades of stainless steel due to its broad applicability, good corrosion resistance, and favorable mechanical properties. It is suitable for a wide range of environments and applications, making it a popular choice in various industries.
What Is 347 Stainless Steel?
347 stainless steel has many advantages over 316 stainless steel, but its main advantage is its ability to withstand higher temperatures without losing strength or becoming brittle. This makes it an excellent choice for extreme temperature applications, such as turbines or boilers where temperatures may exceed 1000°F (537°C). It has higher corrosion resistance than 316 stainless steel due to its higher chromium, nickel, molybdenum, titanium, and aluminum content. Additionally, 347 stainless steel is non-magnetic and has good ductility (can be easily formed into a variety of shapes).
316 vs 347 Stainless Steel – What’s the Difference
| Property | 316 Stainless Steel | 347 Stainless Steel |
|---|---|---|
| Key Alloying Element | Molybdenum (Mo) | Niobium (Nb) |
| Main Advantage | Excellent resistance to chlorides, cost-effective | Superior intergranular corrosion resistance, excellent high-temperature performance |
| Corrosion Resistance | Excellent | Outstanding, especially in post-welded condition |
| High-Temperature Performance | Good | Better, maintains strength and stability at higher temperatures |
| Weldability | Good, but thick sections may require solution annealing | Excellent, no post-weld heat treatment needed to prevent intergranular corrosion |
| Cost | Relatively lower, widely available | Higher, due to the addition of expensive niobium |
| Typical Applications | Chemical industry, marine equipment, food processing, pharmaceuticals | Aircraft exhaust systems, boilers, heat exchangers, and heavy-duty welded equipment |
316 and 347 are both stainless steel alloys, but they have different compositions and are designed for different applications. Here are the key differences between 316 and 347 stainless steel:
Chemical Composition of 316 vs 347 Stainless Steel:
| Element | 316（ASTM A240） | 347（ASTM A240） |
|---|---|---|
| Cr | 16.0–18.0% | 17.0–19.0% |
| Ni | 10.0–14.0% | 9.0–13.0% |
| Mo | 2.0–3.0% | —— |
| Nb/Ta | —— | ≥ 10 × (C+N)%（Min），0.6–1.0% |
| C | ≤ 0.08% | ≤ 0.10%（347H）/0.08% |
| Mn | ≤ 2.0% | ≤ 2.0% |
| Si | ≤ 1.0% | ≤ 0.75% |
| P | ≤ 0.045% | ≤ 0.045% |
| S | ≤ 0.03% | ≤ 0.03% |
Note: 316 has molybdenum added to enhance pitting resistance in chloride ion environments, and 347 has niobium/tantalum stabilization to improve intergranular corrosion resistance and high-temperature performance.
Corrosion Resistance of 316 vs 347 Stainless Steel:
| Corrosion Type | 316 | 347 | Notes |
|---|---|---|---|
| General / Atmospheric | Excellent | Excellent | Both resist oxidation and rust in normal environments |
| Pitting (Chlorides) | Very High | Moderate | Mo in 316 improves pitting resistance in seawater or saline environments |
| Crevice Corrosion | High | Moderate | 316 preferred in confined wet areas |
| Stress Corrosion Cracking | Moderate | Low | 347 slightly better in high-temperature chloride stress conditions |
| Intergranular Corrosion | Moderate | Excellent | Nb stabilization in 347 prevents sensitization at grain boundaries |
- Both 316 and 347 stainless steel offer good corrosion resistance, but 316 is particularly well-suited for applications involving exposure to corrosive environments, such as marine or chemical processing.
High-Temperature Performance:
| Maximum Service Temperature (Intermittent) | 870°C | 925°C | 347 can handle slightly higher intermittent temperatures due to Nb stabilization |
| Maximum Service Temperature (Continuous) | 925°C | 920°C | Continuous exposure slightly favors 316 in some references, but 347 resists intergranular corrosion at high T |
| Resistance to Intergranular Corrosion | Moderate | Excellent | 347 contains Nb to prevent carbide precipitation at grain boundaries |
| Thermal Aging / Sensitization | Susceptible above 425°C | Resistant up to ~900°C | 347 preferred for welded or long-term high-temperature components |
| Oxidation Resistance | Good | Very Good | Both form protective Cr-oxide layer; 347 slightly better at higher T |
Key Takeaways:
316: Better overall in general high-temperature service, especially in oxidizing environments below ~870°C.
347: Superior for welded components and long-term exposure above 500°C due to niobium stabilization.
Mechanical Properties Comparison
| Property | 316 | 347 | Notes |
|---|---|---|---|
| Tensile Strength | 515 MPa | 515 MPa | Similar strength |
| Yield Strength | 205 MPa | 205 MPa | Both offer good mechanical stability |
| Elongation | 40% | 40% | Excellent ductility |
| Hardness | 95 HRB | 95 HRB | Suitable for fabrication |
Summary: Both 316 and 347 provide similar mechanical performance, making them versatile for industrial applications requiring corrosion resistance and high strength.
Physical Properties Comparison
| Property | 316 | 347 | Notes |
|---|---|---|---|
| Density | 8.0 g/cm³ | 8.0 g/cm³ | Both austenitic steels, with similar mass |
| Thermal Conductivity | 16 W/m·K | 16 W/m·K | Relatively low, typical for austenitic steels |
| Thermal Expansion (20–100°C) | 16 ×10⁻⁶ /°C | 16 ×10⁻⁶ /°C | Both expand similarly with heat |
| Magnetic Properties | Non-magnetic (annealed) | Non-magnetic (annealed) | May show slight magnetism after cold working |
International Equivalents
| Grade | 316 | 347 |
|---|---|---|
| EN | 1.4401 / 1.4404 | 1.4550 |
| JIS | SUS316 | SUS347 |
| GB / China | 0Cr17Ni12Mo2 | 0Cr18Ni9Nb |
| UNS | S31600 / S31603 | S34700 |
This table helps engineers and buyers identify equivalents across different international standards.
Sensitization and Intergranular Corrosion:
- 316 Stainless Steel: It can be susceptible to sensitization, especially during welding, which may lead to intergranular corrosion in certain environments.
- 347 Stainless Steel: The niobium content in 347 stainless steel helps prevent sensitization, making it less prone to intergranular corrosion after exposure to high temperatures.
Applications: 316 vs 347 Stainless Steel
316 Stainless Steel Applications:
Chemical processing equipment
Marine environments and offshore structures
Medical instruments and food processing equipment
Pharmaceutical machinery
347 Stainless Steel Applications:
Boilers, steam piping, and high-temperature equipment
Chemical and petrochemical plants
Aerospace and power generation components
Weldability, Fabrication & Machinability
| Feature | 316 Stainless Steel | 347 Stainless Steel | Notes |
|---|---|---|---|
| Weldability | Excellent | Excellent | Both can be welded with conventional techniques; 347 is preferred for welded high-temp service |
| Post-Weld Sensitization | Susceptible | Resistant | 347 resists intergranular corrosion due to Nb stabilization |
| Machinability | Moderate | Moderate | Both are more difficult to machine than ferritic steels; use sharp tools and cutting fluids |
| Forming / Bending | Good | Good | Both are ductile, suitable for cold and hot forming |
| Surface Finish | Smooth achievable | Smooth achievable | Polishing to 400–600 grit is common; a mirror finish is achievable with proper treatment |
Takeaways:
Use 347 if the material will be welded extensively in high-temperature service.
316 is easier to source and commonly used in chemical and marine fabrication.
Heat Treatment and Annealing of 316 vs 347 Stainless Steel:
| Process | 316 | 347 | Notes |
|---|---|---|---|
| Annealing Temperature | 1010–1120°C | 1040–1120°C | Both require rapid cooling in water or air to prevent sensitization |
| Hardening | Not hardenable by heat | Not hardenable by heat | Both are austenitic, strengthened by cold working |
| Stress Relief | 425–870°C | 425–900°C | 347 can handle slightly higher stress-relief temperatures due to Nb stabilization |
Cost of 316 vs 347 Stainless Steel：
The cost of stainless steel can vary based on a variety of factors, including specific grades, market conditions, and supplier pricing. Generally speaking, 316 stainless steel is more commonly used and has been on the market longer, which helps it cost less than some of the more specialized alloys.
316 stainless steel is generally less expensive than 347 stainless steel. The main reason for this cost difference is the presence of more complex alloying elements in 347 stainless steel, specifically the addition of niobium, which helps enhance its high-temperature properties.
However, it is important to note that prices may fluctuate based on market conditions, supply and demand, and other factors. For the most accurate and up-to-date information on the cost difference between 316 and 347 stainless steel, it is recommended to contact us directly or other stainless steel suppliers, distributors, or manufacturers. We can provide current pricing based on the specific quantity, size, and other requirements of your application.
By comparison, 316 is superior in chloride corrosion resistance, while 347 is more advantageous in high temperature and welding performance. Huaxiao Metal provides a variety of 316/316L and 347 stainless steel products with sufficient inventory and quality assurance. Contact us now to get the best price and delivery time.
How to Choose: 316 VS 347 Stainless Steel
You should choose 316 stainless steel if:
Your application environment involves chlorides, but does not require high-temperature welding.
Budget is the primary consideration.
The workpiece is thin, or can be solution annealed after welding.
Typical projects: marine railings, chemical storage tanks, food processing countertops, pharmaceutical pipelines.
You should choose 347 stainless steel if:
Equipment needs to operate at high temperatures (>500°C) for a long time.
Thick-section parts need to be welded, and heat treatment cannot be performed after welding.
The equipment will repeatedly experience sensitization temperature zones during operation.
Typical projects: aircraft engine parts, boiler shells, heavy exhaust systems, high-temperature chemical reactors.
Simply put: choose 316 for conventional corrosion resistance, and choose 347 for high temperature or post-welding corrosion protection.
FAQ: 316 vs 347 Stainless Steel
Can 316 stainless steel withstand seawater?
Yes, 316 stainless steel has excellent resistance to chloride-induced corrosion, making it suitable for marine applications.
Is 347 stainless steel better for high-temperature applications?
Yes, 347 is stabilized with niobium, which enhances resistance to intergranular corrosion during high-temperature exposure, ideal for boilers and steam piping.
What are the differences in welding 316 vs 347?
Both are weldable, but 347 provides better resistance to intergranular corrosion in welded areas due to Nb stabilization.
Can I use 347 instead of 316?
Performance-wise, it is OK in almost all cases. The 347 covers most of the performance of the 316 and improves on it. But it is “over-engineered” and will cause unnecessary cost waste.
Is 347 stainless steel better than 316?
There is no absolute “better”, only “more suitable”. 347 is better than 316 in high temperature and post-weld corrosion resistance, but the cost is higher and unnecessary. The choice depends on the specific application.
What is the relationship between 316L and 347?
316L is a low-carbon version of 316. It reduces intergranular corrosion by reducing the carbon content, but the effect is not as thorough as 347 with the addition of the stabilizing element Nb, especially under long-term high-temperature service.
In Conclusion: 316 vs 347 Stainless Steel
In summary, the choice between 316 vs 347 stainless steel depends on the application’s specific requirements, particularly regarding corrosion resistance and high-temperature performance. If you need excellent corrosion resistance in a variety of environments, 316 may be more suitable. If you’re dealing with high temperatures and want to avoid sensitization issues, 347 might be a better choice.
Our team of technical experts is ready to work with you to gain a deep understanding of your application, budget, and performance requirements to help you find the perfect balance among 316, 347, and hundreds of other stainless steel grades. We offer high-quality 316 and 347 stainless steel plates, coils, tubes, and bars, and can provide you with expert selection advice.
Don’t compromise on material selection. Contact us today to ensure your project is built on a solid and reliable foundation from the start.
