High Speed Pulse TIG for Edge Welding 

Hot rolled steel sheet/plate/bar is formed into shape by rollers when it's red hot. Cold rolled is formed when it's (relatively speaking) cold. Hot rolled steel typically has a tough, dark oxide coating on it called mill scale, from the rolling process. For TIG welding you should grind that off, at least in the weld area, before welding. You can also remove mill scale with an acid soak, even with a mild acid like vinegar-it's called "pickling." Some other welding processes and rods can weld ok through mill scale. Cold rolled doesn't require the removal of mill scale and it is more dimensionally correct but sometimes the cold rolling leaves residual stresses that can be revealed by welding or other heating. This is separate from the usual heat shrinking/warping that happens with welding.

@@benz-share9058 makes sense, thanks for the detailed response!

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Hi have you tried it yet? I also need to weld on an edge and I would like to try it too. My machine has a setting "Ratio of pulse duration to base current duration" and its factory setting is 5%. That would mean for a pulse frequency of 40 Hz the period is 25ms and the pulse is only active for 1.25ms. Does your machine have this setting too? What has worked for you?

I've just read the specifications for his MT200-AC/DC machine. The pulse width setting on his machine is fixed at 50%. Well 50% is also possible on my machine. Let's try that first. Maybe later a lower pulse duration might have advantages but Amp settings need to be adjusted as well I assume.