How can I weld very thick material to thin?

[Thebeast]

I’m abit confused on welding thicker material so an example would be:

I have a 100x50x 3.5mm thick mild steel box section. I want to weld a 50mm (solid) steel tube. So basically that’s 50mm thick steel.

how would I weld that thick of steel to 3.5mm thick material? i only have a 200amp mig welder

Would it need to be multi passes or could I do it in 1 pass? Would the 50mm solid tube be just as strong as welding a 3mm (hollow) tube to the box section?

Sorry if this is abit confusing I have been trying to find info on this for a while now and can’t find anything. anyone would could help me out I appreciate it soo much!

 

[chrismac]

Hi, there could be various work arounds to help, if just welding it does not work. orientation of parts to be welded, ie having the 50mm solid bar on the lower section so you can direct your weld pool up to the 3.5mm thick box, some pre heat on the 50mm bar,

TBH just go for it and see what happens, how big a run are you looking for?

 

[Mark 2]

50mm solid tube? Or solid round.

 

[Thebeast]

Hi, there could be various work arounds to help, if just welding it does not work. orientation of parts to be welded, ie having the 50mm solid bar on the lower section so you can direct your weld pool up to the 3.5mm thick box, some pre heat on the 50mm bar,

TBH just go for it and see what happens, how big a run are you looking for?

 

[Thebeast]

Its just a solid tube that’s going to be welded in that position as in photo

 

[Thebeast]

50mm solid tube? Or solid round.

Solid round sorry

 

[Bornfree]

The strongest way of doing this is drill the box and weld both sides.

 

[Thebeast]

The strongest way of doing this is drill the box and weld both sides.

So drilling a 50mm hole through both walls welding the underneath and top?

 

[Bornfree]

So drilling a 50mm hole through both walls welding the underneath and top?

Yes 3.5mm wall box is easily drilled with a holesaw

 

[Thebeast]

Yes 3.5mm wall box is easily drilled with a holesaw

Thanks so a single pass on both sides will do it?

 

[Bsmith]

Sounds like one of these jobs, if it's not important risk doing it, if it is important get someone who knows to weld it.
Calling it solid tube tells me that you have not done very much steel work?

 

[Bornfree]

Thanks so a single pass on both sides will do it?

Yes you can run your welder hot by concentrating most of the heat onto the round bar and washing the puddle onto the box.

 

[Pigeon_Droppings2]

As above I'd drill and weld...but context is important. If this is part of a bird feeder for the garden...then have a go by all means. If it's safety critical then make sure it's fit for purpose.

It might be difficult to avoid a cold weld on the solid bar.

 

[DAPPH]

Perhaps heat the bar to cherry red , insert it in the two holes then weld both sides whilst it's still red hot ?

 

[Pigeon_Droppings2]

Could you redesign the joint maybe....add a sleeve thro the square section (same wall thickness) and then pin the bar perhaps (lots of other possibilities too). May be a bit OTT for a bird feeder though

 

[Brad93]

The thinnest piece of metal is the limiting factor. That 3mm steel will fail before a 4mm leg fillet weld.

No point putting 50mm of weld on a 3mm plate that will just bow it, adding a ton of stress.