SEDL / STP / STP706-EB / STP38208S

Toughness Properties of Vacuum Induction Melted High-Chromium Ferritic Stainless Steels

Deverell, HE
Research specialist, Stainless and Alloy Metallurgy, Allegheny Ludlum Steel Corp., Research Center, Brackenridge, Pa.

Pages: 18    Published: Jan 1980

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Abstract

Impact transition behavior of commercial heats of three low interstitial vacuum induction melted high-chromium ferritic stainless steels was studied as a function of gage. A 50 percent shear fracture (FATT⁵⁰) (fracture appearance transition temperature) of Charpy V-notch impact specimens was used as the transition criterion.

E-BRITE alloy, a 26Cr-1Mo alloy, was studied as formerly melted using electron beam refining and as currently melted by vacuum induction melting. With either melting, E-BRITE shows substantially lower impact transition at a given gage than a titanium-stabilized 26Cr-1Mo alloy made to conventional interstitial levels. Gage was observed to affect impact transition, with light gages showing lower FATT⁵⁰. Slow cooling from anneal is observed to substantially increase FATT⁵⁰ in comparison with water quenching. This effect is also seen in the heat-affected zone of welds. Using proper shielding and preparation, however, weld metal and base metal away from the weld show similar transition temperatures.

The other two alloys studied are high-purity materials containing 29Cr-4Mo and 29Cr-4Mo-2Ni, respectively. These are similar to E-BRITE alloy in impact behavior with the exceptions (1) that 2 percent nickel can lower water-quenched FATT⁵⁰, and (2) that these alloys are sensitive to precipitation of σ and χ phases.

Full-size (10 mm) impact specimens of each alloy can show FATT⁵⁰ below room temperature if satisfactorily heat-treated.