GTAW dissimilar thickness materials

Date 02-03-2002 01:09

Here's the question. When welding say a .125" thick bracket to a .250" thick steel plate (bracket 90 degrees to .250 plate, inside fillet weld). Do you set the amperage for the thinner material or higher for the thicker material and favor the thicker plate as you weld? I'd assume the latter as the amperage for the thicker material will simply melt the thinner away from too much heat.

Is there a general accepted practice for such welding conditions...again GTAW in this instance, but I'm sure it would apply to other welding processes as well.

TIA
Todd

By Goose

Date 02-03-2002 01:13

One more question on the same topic. If for example you normally use 120-130 amps to weld .125" thick material. Now your gonna weld a .125" thick bracket, again perpendicular to the base material, fillet weld, but this time your gonna weld down both sides of this bracket. Do you now only use say 60-75 amps to weld each side of the bracket as you only really need to penetrate 1/2 of the .125" bracket? I'd assume this would help keep from inducing too much heat into this bracket?

By MBSims

Date 02-03-2002 05:34

Sounds like you are welding a tee fillet joint. Setting the amperage about the same or 5-10 amps higher should be fine. The thicker material will absorb more heat than the thinner material, so favor the thicker side to keep from blowing through the thin side. By the time you complete one side of the joint the material temperature will be hotter, so less amperage will be needed on the other side of the joint or you can allow it to cool before finishing the weld. Using a foot control for the amperage is the best way to control heat input for GTAW in thin materials such as these. If you see the puddle getting out of control, just back off on the pedal to lower the amps (just like the gas pedal in a car!).

Hope this helps,
Marty