Steel House India is a manufacturer, supplier, and stockist of ASTM A276 AISI Stainless Steel 347 Square Bar in India, serving refineries, fabricators, power plants, and OEM buyers across the country and export markets. We hold ready stock in multiple sizes and finishes, backed by full test certificates and fast dispatch.
AISI 347 is a niobium (columbium) stabilized austenitic grade (UNS S34700 / EN 1.4550) built for sustained high heat. Buyers choose it for elevated-temperature strength, oxidation resistance, weld stability, and resistance to sensitization. Our SS 347 Square Bar comes in bright, hot rolled, cold drawn, and forged conditions, with custom cutting on request.
Whether you need one project lot or a bulk export order, we supply material that matches the spec on paper and on the bench.
What Is ASTM A276 AISI 347 Stainless Steel Square Bar
Stainless Steel Square Bars
Stainless Steel Square Bars
Stainless Steel Square Bars
AISI 347 is an austenitic stainless steel stabilized with niobium (also called columbium). That niobium addition ties up free carbon, which stops chromium carbide from forming at the grain boundaries during welding or long heat exposure.
The result is strong resistance to intergranular corrosion and sensitization, even after prolonged high-temperature service. This is why Stainless Steel 347 Square Bar holds up where heavy welded sections face repeated thermal cycling.
Here is the key difference buyers ask about. Grade 347 uses niobium as its stabilizer, while 321 uses titanium. Niobium gives 347 stronger creep performance and a higher service ceiling, with useful intermittent performance approaching 925°C. That makes 347 the preferred pick for refinery-grade continuous heat and thick welded assemblies where 321 reaches its limit.
A square profile adds flat, parallel faces that seat cleanly into frames, fixtures, and machined parts. The grade is recognized worldwide as UNS S34700 Square Bar and EN 1.4550 Square Bar, so it drops easily into international procurement specs.
Key Features and Benefits of SS 347 Square Bar
The value of 347 square bar comes down to how it behaves under heat and after welding. Niobium stabilization prevents weld decay, so you can fabricate heavy or welded sections without mandatory post-weld annealing.
■ Niobium stabilization prevents weld decay and intergranular attack in welded sections.
■ High-temperature strength with superior creep resistance during sustained heat.
■ Oxidation resistance that holds through repeated thermal cycling.
■ Reliable weldability without forced post-weld annealing on heavy gauges.
■ Consistent square dimensions and controlled tolerances for predictable machining.
Compared to 321, the ASTM A276 347 Square Bar holds elevated-temperature strength better in continuous high-heat service. That extra margin matters when the part runs hot for years, not hours.
ASTM A276 AISI 347 Square Bar Specifications
Here is a quick reference for the core specifications we supply against.
| Property | Detail |
|---|---|
| Standard | ASTM A276 / ASTM A479 / ASME SA276 |
| Grade | AISI 347 / UNS S34700 / EN 1.4550 |
| Product Form | Square Bar |
| Size Range | 4 mm – 500 mm side (custom available) |
| Length | 2–6 m or custom cut lengths |
| Finishes | Bright, Hot Rolled, Cold Drawn, Forged, Polished |
| Manufacturing Process | Hot Rolled, Cold Drawn, Forged, Machined |
| Tolerance | h8 / h9 / h11 as required |
If your drawing calls for a size outside this range, send it through. We cut and finish to order.
Chemical Composition of AISI 347 Square Bar
The composition gives 347 its corrosion resistance and stability. Chromium and nickel build the austenitic, corrosion-resistant base, while niobium does the stabilizing work that defines the grade.
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.08 max |
| Manganese (Mn) | 2.00 max |
| Silicon (Si) | 1.00 max |
| Phosphorus (P) | 0.045 max |
| Sulfur (S) | 0.030 max |
| Chromium (Cr) | 17.00 – 19.00 |
| Nickel (Ni) | 9.00 – 13.00 |
| Niobium + Tantalum (Nb+Ta) | 10 x C min |
| Iron (Fe) | Balance |
The niobium + tantalum content (10 x C min) is the detail that sets 347 apart from 321. Where 321 relies on titanium, 347 uses niobium for a more robust hold on carbon under heat.
Mechanical Properties of Stainless Steel 347 Square Bar
SS 347 Square Bar balances good tensile strength with high ductility, which suits both structural and machined parts. Values shift with product form and heat treatment, so the figures below represent the typical annealed condition.
| Property | Value |
|---|---|
| Tensile Strength | 515 MPa min |
| Yield Strength (0.2% Proof) | 205 MPa min |
| Elongation | 40% min |
| Hardness (Brinell, HB) | 201 max |
| Hardness (Rockwell B, HRB) | 92 max |
| Density | 7.96 g/cm³ |
| Elastic Modulus | 193 GPa |
For specific creep or stress-rupture data tied to a design temperature, we can share figures on request.
Physical Properties of UNS S34700 Square Bar
Physical properties help engineers plan for thermal expansion, heat transfer, and fabrication behavior. The data below supports applications involving elevated temperatures and welded assemblies.
| Property | Value |
|---|---|
| Density | 7960 kg/m³ |
| Melting Range | 1398–1454 °C |
| Thermal Conductivity (100°C) | 16.3 W/m·K |
| Specific Heat (0–100°C) | 500 J/kg·K |
| Thermal Expansion | 17.3 µm/m·°C |
| Electrical Resistivity | 0.73 µΩ·m |
| Elastic Modulus | 193 GPa |
| Magnetic Permeability | 1.02 |
Equivalent Grades and International Standards
AISI 347 is accepted across most major procurement specs, which keeps cross-border sourcing simple. The table maps the grade to its regional equivalents.
| Region / Body | Grade | Standard |
|---|---|---|
| USA (ASTM/ASME) | AISI 347 / UNS S34700 | ASTM A276, A479, A182, ASME SA276 |
| Europe (EN) | 1.4550 / X6CrNiNb18-10 | EN 10088-3 |
| Germany (DIN) | X6CrNiNb18-10 | DIN 17440 |
| UK (BS) | 347S31 | BS 970 |
| Japan (JIS) | SUS 347 | JIS G4303 |
| Russia (GOST) | 08Х18Н12Б | GOST 5632 |
If your project documents reference one of these regional codes, we can supply matching certification.
Available Sizes and Finishes for SS 347 Square Bar
We stock 347 square bar across a wide size band and in several finishes, so you can match the bar to the job rather than reworking it. Hot rolled bars cover larger sections for structural and high-temperature frameworks, while cold drawn bars give tighter tolerances and a smoother surface.
Bright bars suit precision machining, forged bars handle large or custom sections, and polished finishes work where surface appearance matters. Beyond standard stock, we offer custom cutting, cut-to-length service, and ready stock for faster turnaround.
Send your size and finish requirement, and we will confirm availability and dispatch time on the same Stainless Steel 347 Square Bar order.
High-Temperature Performance of Stainless Steel 347 Square Bar
Grade 347 is specified for sustained elevated-temperature service because niobium stabilization protects corrosion resistance and the structure resists creep under load. This is where 347 stretches past the typical 321 working range.
The table below shows how performance holds across rising temperatures, with useful intermittent service approaching 925°C.
| Temperature °C | Strength Retention | Oxidation Resistance | Thermal Stability | Service Recommendation |
|---|---|---|---|---|
| 300 | Excellent | Excellent | Excellent | Continuous Service |
| 500 | Very High | Excellent | Excellent | Continuous Service |
| 650 | High | Excellent | Excellent | Continuous Service |
| 750 | High | Excellent | Very High | Continuous Service |
| 850 | Moderate | Excellent | High | Intermittent Service |
| 925 | Moderate | High | Moderate | Limited Exposure |
That higher ceiling is the practical reason engineers reach for 347 over 321 in refinery and furnace work.
Testing and Certification for ASTM A276 347 Square Bar
Every batch is verified before it leaves our facility, and full documentation travels with the material. Our standard testing covers the checks most buyers and inspectors ask for:
■ PMI (Positive Material Identification) to confirm grade and niobium content.
■ Material Test Certificates (MTC) as per EN 10204 3.1.
■ Tensile, hardness, and chemical analysis per ASTM standards.
■ Intergranular corrosion test per ASTM A262 and ultrasonic testing per ASTM A388.
Third-party inspection from agencies such as SGS, TÜV, BV, or Lloyd's is available on request. We also provide 100% dimensional and visual inspection along with complete material traceability.
Industrial Applications of AISI 347 Square Bar
The grade earns its place wherever heat and welding meet corrosive service. In refineries and petrochemical plants, it goes into furnace assemblies, heater components, and welded process equipment exposed to thermal cycling.
Power generation relies on 347 for boiler and superheater components, where elevated-temperature strength is non-negotiable. Aerospace work draws on it for exhaust manifolds, heat exchangers, and high-temperature structural parts.
You will also find Stainless Steel 347 Square Bar in general fabrication and pressure equipment, including frames, supports, machined parts, and pressure-retaining assemblies. The common thread is weld stability and steady performance under high heat.
Why Choose Steel House India for ASTM A276 347 Square Bar
We work as a manufacturer, supplier, and stockist of ASTM A276 AISI Stainless Steel 347 Square Bar in India, which means you deal with one source from inquiry to dispatch. Ready stock across common sizes keeps lead times short.
■ Custom cutting and cut-to-length service to match drawings exactly.
■ Full MTC, PMI reports, and third-party inspection support on request.
■ Multiple finishes and supply conditions in one place.
■ Seaworthy export packing with complete documentation.
For export buyers, we handle packing and paperwork end to end. As an ASTM A276 AISI Stainless Steel 347 Square Bar supplier in India with pan-India reach, we support both single-project orders and bulk volumes without dropping the quality checks.
Frequently Asked Questions — ASTM A276 AISI 347 Square Bar
What is ASTM A276 AISI 347 stainless steel square bar?
It is a niobium-stabilized austenitic stainless steel bar (UNS S34700 / EN 1.4550) produced to the ASTM A276 specification, supplied in a square profile for structural, welded, and high-temperature applications.
What is the difference between 347 and 321 stainless steel square bar?
Both are stabilized austenitic grades, but 347 uses niobium (columbium) while 321 uses titanium. Niobium gives 347 stronger creep resistance and a higher service-temperature ceiling, which is why it is favored for heavy welded sections and continuous high-heat service.
Why is niobium (columbium) stabilization used in 347 square bar?
Niobium ties up free carbon so chromium carbide cannot form at the grain boundaries during welding or sustained heat. This protects corrosion resistance and prevents weld decay in demanding thermal environments.
Is SS 347 square bar suitable for high-temperature applications up to 925°C?
Yes. It delivers continuous service through the mid-temperature range and useful intermittent service approaching 925°C, which makes it common in furnaces, refinery heaters, and superheater parts.
What sizes and finishes are available in ASTM A276 347 square bar?
We stock sides from roughly 4 mm to 500 mm in bright, hot rolled, cold drawn, forged, and polished finishes, with custom cutting available on request.
Do you provide MTC and third-party inspection for 347 square bar?
Yes. Every order ships with Material Test Certificates as per EN 10204 3.1, and third-party inspection from agencies like SGS, TÜV, or BV can be arranged on request. As a supplier in India, we keep full documentation with the material.
Are you a manufacturer, supplier, and stockist of 347 square bar in India?
Yes. Steel House India is a manufacturer, supplier, and stockist of ASTM A276 AISI Stainless Steel 347 Square Bar in India, with ready stock and pan-India delivery.
How quickly can you dispatch and deliver across India?
Standard sizes held in ready stock ship quickly after order confirmation. Custom sizes and finishes depend on dimensions and quantity, and we confirm a dispatch timeline with every quote.
Request a Quote for ASTM A276 AISI 347 Square Bar
Tell us what you need and we will get you a clear, competitive quote. To speed things up, share the shape, dimensions (side and length), finish, and quantity.
Reach us by email or WhatsApp to inquire about ready stock, custom cutting, and pan-India delivery. As a leading stockist of ASTM A276 AISI 347 Stainless Steel Square Bar in India, we are ready to supply the exact material your project specifies.
If your application prioritizes free-machining performance over high-temperature stabilization, you may also want to review our ASTM A276 AISI 303 Stainless Steel Square Bar as part of your material selection.