Material Grade Specification

Stainless Steel 321/347 Flanges — Stabilized Grades

SS 321/347 flange manufacturer, Mumbai. Ti/Nb-stabilized for high-temp welded service, refinery furnace outlet piping. Class 150-2500. Quote in 30 min.

Material Specification & Overview

ASTM A182 F321 (Titanium stabilized) and F347 (Niobium stabilized) forged flanges are specifically alloyed to eliminate intergranular corrosion in high-temperature service between 425°C and 815°C.

UNS DesignationS32100 (321) / S34700 (347)
Governing StandardASTM A182 / ASME SA-182 Grade F321 / F347

Chemical Composition (wt %)

Governing specification limits per ASTM / ASME standards. Actual values provided on EN 10204 3.1 MTC.

ElementSpecification Limit / Composition
Titanium (Ti)5x C min, 0.70% max (F321)
Niobium + Tantalum (Nb+Ta)N/A
Chromium (Cr)17.0 - 19.0%
Nickel (Ni)9.0 - 12.0%

Mechanical Properties

PropertySpecification Limit
Yield Strength205 MPa min
Tensile Strength515 MPa min

Pressure-Temperature Rating Reference

Service TempClass 150Class 300Class 600Class 900
Ambient (-29 to 38°C)275 psi720 psi1440 psi2160 psi

Primary Industry Applications

Refinery furnace tube outlet piping
High-temperature exhaust manifolds and thermal oxidizers
Chemical reactors operating in the sensitization range
Power plant superheater steam piping loops

Related Products & Industry Guides

Frequently Asked Procurement Questions

Q: What makes 321 and 347 'stabilized' grades?

A: Titanium (in 321) and Niobium (in 347) have a higher affinity for carbon than chromium. They form stable carbides (TiC / NbC) during thermal exposure, preventing chromium depletion at grain boundaries.

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