Sindo Kou - Welding Metallurgy

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1 3.1 Experimental results show that the depth/width ratio of stainless‐steel welds increases with increasing electrode tip angle. How does the angle affect the effective radius of the electric current at the pool surface (the anode spot)? How does this radius in turn affect weld pool convection and the weld depth/width ratio?

2 3.2 It has been suggested that the weldability of stainless steels can be improved by oxidizing the surface by subjecting it to an elevated temperature in an oxidizing environment. From the penetration point of view, do you agree or disagree, and why?

3 3.3 Consider Marangoni convection in a simulated weld pool of NaNO3 such as that shown in Figure 3.22a. As the laser beam diameter is reduced at the same power from 5.9 mm to 1.5 mm, does Marangoni convection in the pool become faster or slower and shallower or deeper, and why?