By -
Date 10-16-2000 18:19
For carbon and stainless welding where the person "walks the cup" over the wire, the wire size could affect the quality of the weld. This is usually when the wire is to big to allow the heat from the arc melt the underlying base metal. I have personally cut apart Sch 10 stainless welds in pipe 3,4,6,8,10 inch from vendors and I have been able to see lack of fusion between layers and in some cases you could plainly see the shape of the unmetled wire. This can also occur when a person doesnt walk the cup but feeds such an excessive amount of wire that the energy from the arc is used heating the puddle and keeping it molten.
This is related to the ratio of heat-input/current density to the diameter of the wire or the abount of deposited weld metal.
If a welder is going to extemes (5/32" wire 4" schedule 5S pipe) I would probably do a destructive test on a similar joint.
To me it's hard to nail down all the variables for the welding process when one big variable exists, the welder. I have met many with the skills and abilities to do thing I never would have imagined. And I'm a welder!
So I 'd check it out closely before making any major policy/procedure change that is not supported by the applicable code and the applicable welding procedure specification (WPS).
As a pipe welder of 18 years I would never be found holding a piece of .030 wire in my hand. I have never welded anything smaller than 1/4" od x .065 wall tubing.
Using one size for the range of 1/4" to 4" would not be at all practical to me. Possible but not practical.
