Bellows Material Specification

Stainless Steel, Inconel and Hastelloy

UNAFLEX® standard bellows material is A/SA240 321ss. Other materials available to UNAFLEX® to manufacture bellows are:

  • A/SA240 304ss

  • A/SA240 304Lss

  • A/SA240 316ss

  • A/SA240 316Lss

  • A/SA240 310S

  • B/SB443 Alloy 625 (Inconel® 625)

  • B/SB168 Alloy 600 (Inconel® 600)

  • B/SB575 Alloy C276 (Hastelloy® C276)

  • B/SB575 Alloy C22 (Hastelloy® C22)

  • B/SB127 Alloy 400 (Monel® 400)

  • B/SB409 Alloy 800

  • Duplex Alloy 2205

  • Hastelloy® X

  • Nickel 200

  • Alloy 20

  • AL6XN

UNAFLEX® welders are qualified in accordance with ASME Section IX latest edition (available as required). We stock various types of bellows materials, flanges, plates, pipe and threaded rods for fast response and delivery times.

Materials Defined

Stainless Steel

In metallurgy, stainless steel is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass. Stainless steel does not stain, corrode, or rust as easily as ordinary steel, but is not stain-proof.


Inconel® is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based super alloys. Inconel® alloys are typically used in high temperature applications.


Hastelloy® is the registered trademark name of Haynes International, Inc. The trademark is applied as the prefix name of a range of 22 different highly corrosion-resistant metal alloys loosely grouped by the metallurgical industry under the material term "super alloys" or "high-performance alloys". The predominant alloying ingredient is typically the transition metal nickel.

The primary function of the Hastelloy® super alloys is that of effective survival under high-temperature, high-stress service in a moderately to severely corrosive and/or erosion prone environment where more common and less expensive iron-based alloys would fail, including the pressure vessels of some nuclear reactors, chemical reactors, distillation equipment and pipes and valves in chemical industry.

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