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Lean Duplex Austenitic/Ferritic Stainless Steels

Appearing on the market around the year 2000, lean duplex stainless steels were developed as alternatives both to more traditional duplex grades as well as duplex substitutions for standard austenitic stainless steels. A new standard for such steels, A1084, Test Method for Detecting Detrimental Phases in Lean Duplex Austenitic/Ferritic Stainless Steels, has just been approved. A1084 was developed by Subcommittee A01.14 on Methods of Corrosion Testing, part of ASTM International Committee A01 on Steel, Stainless Steel and Related Alloys.

According to Poul-Erik Arnvig, vice president, global market development, Outokumpu, and an A01 member, users of standard duplex grades have attempted to use A923, Test Methods for Detecting Detrimental Intermetallic Phase in Duplex Austenitic/Ferritic Stainless Steels, in testing lean duplex grades. However, the small amounts of molybdenum in many lean duplex grades created a need for A1084, which more specifically deals with lean duplex stainless steels.

“A1084 gives users and producers a tool to check if the product made out of a lean duplex alloy contains deleterious phases originating from improper heat treatment of the product,” says Arnvig. “When used, A1084 will give added information and comfort outside existing standard specifications that the material ordered and delivered is free from deleterious amounts of unwanted phases that, if present in significant amounts, often will deteriorate both corrosion resistance and toughness properties of the materials in question.”

Arnvig notes that currently the standard covers two alloys that had been submitted for documentation for its use. Further alloys should be incorporated and Arnvig encourages applications for alloys to be included in future revisions of A1084. An appendix in the standard outlines the documentation needed to apply for incorporation of a new alloy into the standard.

A01.14 is attempting to establish round robin testing to further evaluate and document the test methods contained in A1084. All interested laboratories are welcome to join in this testing activity.

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CONTACT Technical Information: Poul-Erik Arnvig, Outokumpu Stainless AB • Degerfors, Sweden • Phone: +46-(0) 586-47-255 | ASTM Staff: Kevin Shanahan • Phone: 610-832-9737 | Upcoming Meeting: May 5-8, 2014 • May Committee Week • Toronto, Ontario, Canada

This article appears in the issue of Standardization News.