Are there special welding precautions to be taken when welding duplex stainless Steels?
Duplex Stainless Steels are generally user friendly but do require some care. General Guidelines involve the following precautions: • Heat Input • Joint design • Interpass Temperature Heat Input – The range of heat input varies with the grade of duplex. There is both a minumum heat input range as well as a maximum. At the point of solidification duplex steels are 100% ferrite. There is a phase transformation that takes place as the weld metal cools. The final structure is roughly 50-50 ferrite and austenite. Too low a heat input will not give the ferrite a chance to transform and corrosion problems may result. Joint Design – Duplex weld metal does not flow quite as well as a standard 300 series. The flow is somewhere between 300 Series and Nickel Base Alloys. For this reason it is generally recommended to design joint to give generous room for the weld metal to flow. This may be in the form of a 60 degree included angle or use of U grooves. Interpass Temperature – The maximum Interpass
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