Stainless Steel

Stainless Steel 321 Pipe

Titanium-Stabilized Austenitic Stainless Steel Seamless, Welded & ERW Pipes, Exhaust Tubing, and Boiler Tubes

Grade SS 321 / TP321 (UNS S32100, Werkstoff 1.4541, X6CrNiTi18-10, SUS 321, 321S31) & SS 321H (UNS S32109 / 1.4878)
Standard ASTM A312, ASME SA312, ASTM A213, ASME SA213, ASTM A269, ASME SA269, ASTM A249, ASTM A358, ASTM A376, ASTM A409, ASTM A813, ASTM A814, ASTM A554, AMS 5570, ASME B36.19M, ASME B36.10M, EN 10216-5, DIN 17456 / 17458
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Product Overview

Om Export India Pvt Ltd is an internationally recognized manufacturer, stockist, and global exporter of high-temperature Stainless Steel 321 Pipes and Tubes (ASTM A312 TP321 / UNS S32100 / Werkstoff 1.4541). Grade 321 is a stabilized austenitic chromium-nickel stainless steel containing an intentional addition of Titanium at a minimum concentration of five times the carbon plus nitrogen content [Ti ≥ 5 × (C + N)]. This metallurgical stabilization binds carbon as harmless titanium carbides (TiC), completely suppressing chromium carbide precipitation at grain boundaries and granting exceptional immunity to intergranular corrosion during prolonged exposure within the carbide precipitation temperature range of 427°C to 816°C (800°F to 1500°F).

Engineered for high-temperature and high-stress environments, our SS 321 seamless, welded, and ERW pipes meet ASTM A312, ASTM A213, ASTM A358, and Indian Boiler Regulations (IBR) standards. Operating with a density of 8.027 g/cm³ and a melting range of 1398°C to 1446°C, Grade 321 delivers superior short-term tensile and long-term creep-rupture performance up to 870°C (1600°F). These pipes and tubes are essential across aircraft exhaust manifolds, jet engine components, furnace flue gas ducts, expansion bellows, chemical processing reactors, and thermal boiler pipelines.

  • Titanium Stabilization: Prevents sensitization and intergranular attack during service in the critical carbide precipitation range (427°C–816°C).
  • Elevated Creep & Stress Rupture Properties: Exhibits superior creep strength and mechanical stability compared to standard 304/304L in continuous high-temperature service.
  • Broad Structural Range & Finishes: Available in cold-drawn seamless, fusion-welded ERW/EFW, bright annealed (BA), pickled & passivated, and 120–600 Grit mirror-polished finishes.

Key Features

  • Intergranular Corrosion Immunity: Titanium stabilization eliminates chromium depletion and weld decay in the 427°C–816°C range.
  • Elevated Creep & Stress Rupture Strength: Preserves mechanical strength and structural stability under sustained cyclic thermal operations up to 870°C.
  • Thermal Shock & Exhaust Durability: Resists thermal fatigue, cyclic hot scaling, and exhaust gas erosion in aerospace and automotive manifolds.
  • Indian Boiler Regulations (IBR) Certified: Approved under Form III-A and III-D for utility steam boilers, headers, and superheaters.
  • Formability & Ductility: High elongation (≥40%) allows cold bending, expansion into tubesheets, and fabrication into complex hydroformed bellows.
  • Clean Surface Finishes: Supplied in pickled & passivated, bright annealed (BA), electropolished, and mechanical polish (120 to 600 Grit).

Product Specifications

Specification Parameter Standard Specification / Technical Value
Nominal Size Range (Seamless) 1/8" NB to 24" NB (Outer Diameter: 6.00 mm to 609.6 mm OD)
Nominal Size Range (Welded / ERW / EFW) 1/8" NB to 48" NB (Outer Diameter: 6.00 mm to 1219.2 mm OD / Custom up to 100")
Wall Thickness & Schedules 0.30 mm to 50.0 mm (SCH 5S, SCH 10S, SCH 40S/STD, SCH 80S/XS, SCH 160, SCH XXS)
Governing Standards ASTM A312 / ASME SA312, ASTM A213, ASTM A269, ASTM A249, ASTM A358, ASTM A376, ASTM A409
Manufacturing Methods Cold Drawn Seamless (CDS), Hot Finished Seamless, High-Frequency Induction ERW, Plasma/TIG Welded, LSAW
Heat Treatment & Delivery State Solution Annealed at 980°C – 1065°C followed by water quenching or rapid air cooling; Stabilizing Anneal available
Standard Lengths Single Random Length (SRL), Double Random Length (DRL), Custom Cut Lengths up to 26,000 mm (26m)
End Configurations & Protection Plain Square Cut End (PE), Beveled End (BE 30°/37.5° per ASME B16.25), Threaded Ends with Protective Plastic Caps

Dimensions & Sizes

  • Mill Test Certificate (MTC): Fully compliant with EN 10204 Type 3.1 and Type 3.2 inspection standards.
  • IBR Form III-A / III-D: Statutory inspection certificates issued and stamped by the Indian Boiler Regulations Directorate.
  • Chemical Composition Analysis: 100% Positive Material Identification (PMI) Spectro reports confirming Titanium stabilization ratio, Cr, Ni, and interstitial limits.
  • Mechanical Test Reports: Tensile strength, yield point (0.2% proof), elongation, flattening, flaring, and Rockwell/Brinell hardness verification.
  • Intergranular Corrosion Testing: Verified per ASTM A262 Practice E (Strauss Test) confirming zero intergranular sensitization.
  • Non-Destructive Testing (NDT): 100% Hydrostatic pressure testing per ASTM A530 and automated Eddy Current / Ultrasonic flaw examination.
  • Third-Party Inspection (TPI): Verified and endorsed by Bureau Veritas, TUV, DNV, SGS, Lloyd's Register, ABS, or client TPI representatives.

Chemical Composition

Element ASTM A312 TP321 (%) UNS S32100 (%) DIN 1.4541 / X6CrNiTi18-10 (%)
Carbon (C, Max) 0.08 0.08 0.08
Chromium (Cr) 17.00 – 19.00 17.00 – 19.00 17.00 – 19.00
Nickel (Ni) 9.00 – 12.00 9.00 – 12.00 9.00 – 12.00
Titanium (Ti) 5 × (C + N) Min – 0.70 Max 5 × (C + N) Min – 0.70 Max 5 × C Min – 0.70 Max
Manganese (Mn, Max) 2.00 2.00 2.00
Silicon (Si, Max) 0.75 (1.00 Max) 1.00 1.00
Phosphorus (P, Max) 0.045 0.045 0.045
Sulfur (S, Max) 0.030 0.030 0.015
Nitrogen (N, Max) 0.10 0.10 —
Iron (Fe) Balance Balance Balance

Mechanical Properties

Mechanical Property ASTM A312 TP321 Specified Limits Typical Production Values
Tensile Strength, Ultimate (Min) 515 MPa (75 ksi / 75,000 psi) 550 – 630 MPa
Yield Strength (0.2% Proof, Min) 205 MPa (30 ksi / 30,000 psi) 230 – 290 MPa
Elongation in 2 in. / 50 mm (Min) 35% – 40% Min 45% – 55%
Hardness (Rockwell B / Brinell, Max) 95 HRB Max / 217 HBW Max 80 – 88 HRB (150 – 185 HBW)
Density & Melting Range Density: 8.027 g/cm³ (8027 kg/m³) Melting Range: 1398°C – 1446°C (2550°F – 2635°F)
Modulus of Elasticity (Tension) 193 GPa (28 x 10⁶ psi) Electrical Resistivity: 720 nΩ·m
Thermal Expansion (0–100°C / 0–538°C) 16.6 µm/m·°C (0–100°C) 18.6 µm/m·°C (0–538°C)
Thermal Conductivity & Specific Heat 16.1 W/m·K at 100°C | 22.2 W/m·K at 500°C Specific Heat (0–100°C): 500 J/kg·K

Standards & Specifications

Standard Designation Governing Organization Scope & Product Description
ASTM A312 / ASME SA312 ASTM / ASME Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes (TP321 / UNS S32100)
ASTM A213 / ASME SA213 ASTM / ASME Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes (TP321)
ASTM A269 / ASME SA269 ASTM / ASME Seamless and Welded Austenitic Stainless Steel Tubing for General Service
ASTM A249 / ASME SA249 ASTM / ASME Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes
ASTM A358 / ASME SA358 ASTM / ASME Electric-Fusion-Welded Austenitic Chromium-Nickel Stainless Steel Pipe for High-Temperature Service
AMS 5570 / AMS 5557 Aerospace Material Spec Seamless and Welded Stainless Steel Tubing for Aerospace Hydraulic and Exhaust Lines
EN 10216-5 / DIN 17456 / 17458 European / German Standards Seamless Steel Tubes for Pressure Purposes (Grade 1.4541 / X6CrNiTi18-10)
Indian Boiler Regulations (IBR) Central Boilers Board IBR Certified Steam and High-Pressure Stainless Steel Boiler Piping

Applications

Stainless Steel 321 titanium-stabilized pipes and tubes are utilized across demanding aerospace, furnace, and elevated-temperature process systems:

  • Aerospace & Defense: Jet engine exhaust manifolds, turbine engine casing collectors, afterburner components, and aircraft bleed-air piping.
  • Automotive & Heavy Vehicle Exhausts: High-performance exhaust headers, turbocharger manifolds, flex pipes, and diesel engine catalytic converter piping.
  • Chemical & Petrochemical Processing: Reactor circuits, thermal hydrocrackers, high-temperature organic chemical transport lines, and waste gas incinerator ducts.
  • Thermal Power Stations & Utility Boilers: Superheater tube pendants, reheater loops, steam headers, boiler economizers, and IBR high-pressure steam distribution lines.
  • Furnace Hardware & Thermal Processing: Radiant heating tubes, annealing furnace fixtures, burner nozzles, expansion bellows, and thermocouple protection sheaths.
  • General Structural & Pressure Piping: High-pressure steam lines, expansion joints, and compensatory piping assemblies operating between 400°C and 900°C.

Frequently Asked Questions

Q1: Why is Titanium added to Stainless Steel 321?
Titanium has a stronger chemical affinity for carbon than chromium. By adding titanium [Ti ≥ 5 × (C + N)], carbon binds preferentially as titanium carbides (TiC) rather than chromium carbides. This prevents chromium depletion along grain boundaries, providing immunity to intergranular corrosion when operating within the sensitizing range of 427°C to 816°C (800°F to 1500°F).

Q2: What is the main difference between SS 321 and SS 304 in high-temperature applications?
While SS 304 suffers from intergranular corrosion and rapid loss of strength when held at temperatures above 425°C, SS 321 remains metallurgically stable and retains higher allowable design stresses, superior creep resistance, and higher stress-rupture strength up to 870°C (1600°F).

Q3: Why is Grade 321 widely specified for exhaust systems and bellows?
Automotive and aerospace exhausts experience severe thermal cycling and exposure to hot combustion gases and corrosive condensate. SS 321 withstands extreme exhaust temperatures, resists vibration cracking and fatigue, and prevents post-weld cracking in heat-affected zones.

Q4: What certifications accompany Om Export India Pvt Ltd SS 321 pipes?
All shipments are accompanied by EN 10204 Type 3.1 / 3.2 Material Test Certificates, IBR Form III-A or III-D statutory documents, 100% Positive Material Identification (PMI) spectro analysis, ASTM A262 Practice E intergranular corrosion testing, and 100% Hydrostatic / Eddy Current test certificates.

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