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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.
stainless steels, ferritic stainless steels, vacuum induction melting, 26Cr-1Mo, 29Cr-4Mo, 29Cr-4Mo-2Ni, gage, impact properties, toughness, Charpy V-notch, impact transition, fracture appearance transition temperature, fracture toughness
Research specialist, Stainless and Alloy Metallurgy, Allegheny Ludlum Steel Corp., Research Center, Brackenridge, Pa.