The influence of delta ferrite on forged austenitic stainless steel

Abstract

Within the stainless steel family, austenitic steel can be considered as the one with the best weldability and greatest application in the processing industry. However, the properties of this type of steel can be easily degraded during welding operations or plant service. The solidification cracks can be avoided when there is a moderate presence of Δ ferrite in the welded metal, as described in technical literature. On the other hand, Δ ferrite is seldom discussed when applied to base metals, since austenitic stainless steel, annealed and quenched, probably presents only traces of it at this phase. Forged austenitic stainless steel components have presented high amounts of Δ ferrite, sometimes appearing in the intermetallic phases, creating serious concerns for equipment and pipe manufacturers. Herein, a case study is presented where Δ ferrite and intermetallic precipitates, especially the σ phase, hindered the application of ASTM A182 F 317L forged flanges in processing plants.

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