Determining the optimum speeds for welding and for the filler wire begins with a review of the weld specification. For example, for a butt weld, we want to know the depth of penetration; weld width at the top, mid-thickness, and back of the weld; and crown on both the top and back surfaces.
We will typically start by creating a ‘bead on plate’ weld without filler material to find the welding speed that gives full penetration. From there, we will modify the weld speed to obtain the specified widths of the top bead, waist (center of the weld), and bottom bead. This is considered the baseline weld from which we also define the wire speed.
For reference, the example pictured below is a butt weld of 4 mm thick Inconel 718. We determined that if there was no gap in the butt joint, a welding speed of 1 m/min and wire speed of 1 m/min would produce the required weld profile.
Since there was a gap (0.1-0.2 mm) in the real parts, we increased the wire speed and reduced the welding speed. In this case (with a 0.1-0.2 mm gap), we found through a few combinations of lower weld speed and higher wire speed that a weld speed of 1.5 m/min and wire speed of 0.7 m/min consistently produced the required weld profile without any porosity.
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