Welding light gauge to heavy

[Dick Skinner]

I am rebuilding a trailer on a new chassis. The chassis is made up from 76 x 38 RSC (about 6 mm thick on the flanges) but I have to weld on an existing superstructure of 25 x 25 x 2(?) mm box section. The box sections will land end on onto the RSC flanges. Any advice on welding techniques would be appreciated. At present I have only a 150 Amp arc welder but think that MIG would be more appropriate. I will have to hire, borrow or scrounge a suitable welder.

 

[the snooper]

just use your arc welder but prep the joints first and start off welding on the heavier steel i dont see any problem using the arc welder

 

[piman]

Hello D.S.,

I don't see any problem with using your existing arc set? If you can practice with some scrap as far as welding the 2mm to 6mm. Keep the gaps as tight as possible or it will burn through very easily.

Alec

 

[Drains]

You should be ok using the arc welder with small rods - 2mm should do it, but if you have any verticals to weld you would be better off either turning the chassis so they're not verticals, or getting a mig.

If you go the mig route, keep the joints tight (as above- you'll need to do this anyway), adjust the volts so you're getting good fusion on the thick stuff and wash over to the thin stuff as you slightly weave along. You're looking to aim the torch, and the heat, towards the thick side of the joint, sort of 70/30 stylee.

 

[troppo]

What they said^^^^^^^^^^^