SS 321 / 321H
SS 321/321H: Specifications | Grades & Standards | Product Types | Equivalent | Chemical | Mechanical | BW Fittings | Forged Fittings | Flanges | FAQ
SS 321 Buttweld Fittings, SS 321H Forged Fittings, and SS 321 Flanges – ASTM A403 / A182 Certified, including Elbows, Tees, Reducers, Stub Ends, and Crosses. Supplied as UNS S32100 / S32109 Fittings & Flanges with WNRF & SORF Flanges SS 321 / 321H, serving as trusted SS 321 / 321H Fittings Exporter to Middle East, Europe, and USA for high-performance, chemical- and heat-resistant piping applications worldwide.
Best Export Prices: sales@midlandforgefittings.com
At Midland Forge and Fittings Pvt. Ltd., we are committed to delivering excellence in the manufacturing and supply of high-quality stainless steel 321/321h fittings, flanges, and piping solutions. Backed by a team of experienced engineers and technical experts, our company operates with a structured workflow that ensures precision, efficiency, and adherence to international standards such as ASTM and ASME.
Over the years, we have built a strong reputation for reliability, durability, and timely delivery, earning the trust of clients across chemical, petrochemical, power, marine, and industrial sectors. Our customer-centric approach emphasizes tailored solutions, from standard sizes to customized components, ensuring each project receives the exact specifications and quality it demands. With state-of-the-art facilities, stringent quality control, and a dedication to innovation.
Stainless Steel 321 Buttweld Fittings, Forged Fittings, and Flanges are stabilized austenitic stainless steel components containing titanium for enhanced resistance to intergranular corrosion. Designed to perform in continuous service temperatures up to 870°C, SS 321 offers excellent oxidation and creep strength. These fittings—available as elbows, tees, reducers, stub ends, and crosses—are manufactured as per ASTM A403 and ASTM A182 standards, ensuring superior weldability and mechanical integrity. SS 321 Flanges, including WNRF and SORF types, are ideal for use in chemical processing, power generation, and high-temperature piping systems where corrosion resistance and thermal stability are essential.
Stainless Steel 321H Buttweld Fittings, Forged Fittings, and Flanges are the high-carbon version of SS 321, offering improved high-temperature strength and resistance to creep and stress rupture. With a controlled carbon content (0.04–0.10%), SS 321H is specifically designed for service in environments exceeding 500°C. Manufactured to ASTM A403 and ASTM A182 specifications, these fittings ensure exceptional durability, corrosion resistance, and metallurgical stability under thermal cycling. SS 321H Flanges, such as WNRF, SORF, and Blind types, provide robust joint integrity in refining, petrochemical, and heat exchanger applications, making them a preferred choice for high-pressure, heat-intensive industrial systems.
ASTM A403 SS 321h Pipe Fittings - Specifications
Stainless Steel 321 Forged Fittings – Grades & Standards
| Grade | Buttweld Fittings Standards | Forged Fittings Standards | Flanges Standards |
|---|---|---|---|
| 321 | ASTM A403 / ASME B16.9 / MSS-SP-43 | ASTM A182 / ASME B16.11 | ASTM A182 / ASME B16.5 / B16.47 |
| 321H | ASTM A403 / ASME B16.9 / MSS-SP-43 | ASTM A182 / ASME B16.11 | ASTM A182 / ASME B16.5 / B16.47 |
SS 321/321h – Industrial Flanges, Fittings & Piping Products
ASTM A182 SS 321 Flange - Equivalent Grades
| Grade | UNS | ASTM | EN (DIN) | JIS | GOST | BS | AFNOR |
|---|---|---|---|---|---|---|---|
| 321 | S32100 | A240 / A276 / A312 | 1.4541 (X6CrNiTi18-10) | SUS321 | 08Х18Н10Т (08X18H10T) | 321S31 | Z6CNT18-10 |
| 321H | S32109 | A240 / A276 / A312 | 1.4878 (X6CrNiTi18-10) | SUS321H | 03Х18Н11 (03X18H11) | 321S51 | Z6CNT18-10 |
321h SS Buttweld Fittings - Chemical Composition
| Element | SS 321 (%) | SS 321H (%) |
|---|---|---|
| Carbon (C) | ≤ 0.08 | 0.04 – 0.10 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 0.75 | ≤ 0.75 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 |
| Chromium (Cr) | 17.00 – 19.00 | 17.00 – 19.00 |
| Nickel (Ni) | 9.00 – 12.00 | 9.00 – 12.00 |
| Titanium (Ti) | ≥ 5 × C up to 0.70 | ≥ 5 × C up to 0.70 |
| Iron (Fe) | Balance | Balance |
UNS S32100 Pipe Fittings & Flanges - Mechanical Properties
| Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness (HB) | Hardness (HRB) |
|---|---|---|---|---|---|
| 321 | 515 – 750 | ≥ 205 | ≥ 40 | ≤ 217 | ≤ 95 |
| 321H | 515 – 750 | ≥ 205 | ≥ 40 | ≤ 217 | ≤ 95 |
ASTM A403 WP321 / WP321H Buttweld Pipe Fittings – Seamless & Welded
ASTM A182 F321 / F321h SS Flanges – Types and Industrial Applications
ASTM A182 Stainless Steel 321 / 321h Forged Fittings – Complete Range
How does titanium stabilization in SS 321/321H enhance high-temperature performance?
Titanium in SS 321 and 321H binds with carbon to form titanium carbides, preventing chromium carbide formation at grain boundaries during welding or high-temperature exposure.
This ensures intergranular corrosion resistance, which is critical in furnace, boiler, and heat exchanger piping systems.
Titanium also maintains mechanical strength and ductility at temperatures above 800°C, preventing cracking in high-temperature process lines.
Why is SS 321H preferred over SS 321 for high-temperature pipelines?
SS 321H contains higher carbon (0.08–0.10%), which improves creep strength for sustained high-temperature operation.
It minimizes the risk of softening under prolonged heat, making it ideal for steam pipelines, superheaters, and high-pressure boilers.
While SS 321 is sufficient for moderate temperatures, 321H ensures long-term reliability in extreme heat environments.
Can SS 321/321H flanges and fittings be used in offshore applications?
Yes, they are suitable for offshore pipelines, chemical process lines, and marine environments, provided water and chloride exposure is controlled.
Titanium stabilization ensures grain boundary integrity, reducing the risk of stress corrosion cracking in chloride-rich environments.
321H is preferred for long-term high-temperature offshore pipelines, where creep and thermal fatigue resistance are critical.