Welding radius to flat?

[T_i_m]

Hi all,

I am in the process of re-furbishing a take-down motorcycle trailer and need to weld some 120X60X3mm box section steel tube with rounded corners to some 50x50x6mm steel angle. This is what the structure looks like (there is more of it than this but it highlights the welding question):

I'm thinking I'd like to run a fillet around all 4 touching edges but where the external radius on the box touches the flat angle leaves quite a large hollow / overhang?

Questions. Should I first build up the external (10mm) radius so I can grind it back to a form a square corner, presenting touching faces for a fillet and should it be something I should be able to do with my little Lincoln SP170 MIG or should I drag the SIP150 stick welder out?

Cheers, T i m

 

[123hotchef]

hit it with the mig it will be fine I did similar at the weekend if you need to make more han 1 pass so be it

 

[Paul.]

Turn the power up on the mig and weld it vertical down, you will get a nice flat or concave bead and is fast too so will reduce distortion, dont start building up corners, it will look a real mess and will distort the section.

 

[tom2207]

just weld round it , all will be grand.

 

[bricol]

I'd be thinking the radius has given me a good prep for the weld without any work!

 

[123hotchef]

I'd be thinking the radius has given me a good prep for the weld without any work!

yell yeah fill the void

 

[T_i_m]

Turn the power up on the mig and weld it vertical down, you will get a nice flat or concave bead and is fast too so will reduce distortion, dont start building up corners, it will look a real mess and will distort the section.

I appreciate these things aren't absolutes but to get me close, what sort of power settings (and wire size would I be using ideally using) be 'up' for this gauge of work please Paul?

As you mentioned distortion ... would it be 'better' to just weld the last (say) 30mm at either end of the 120mm face of the box to angle (given the middle probably wouldn't be doing much strength wise), especially as I'll be doing the same both sides of the angle?

 

[T_i_m]

I'd be thinking the radius has given me a good prep for the weld without any work!

I think I'll need to get some practice in first. ;-)

 

[T_i_m]

yell yeah fill the void

I guess my trepidation re doing that efficiently is a function of potentially not welding much heavy stuff yet with my MIG and secondly not being sure I would be able to see where I was going and end up miles away (and this needs to be strong, given it's role).

Re visibility, I think I've pinned my new shield down to a ESAB Savage A40 .... or a Parweld XR938H ... or ... ;-)

 

[pedrobedro]

Do the flat bits first then aim into the join where the two pieces touch and it should fill itself in. .8 wire should do it easily enough.

 

[T_i_m]

Do the flat bits first then aim into the join where the two pieces touch and it should fill itself in. .8 wire should do it easily enough.

OK and thanks. I'll check what wire I have in there tomorrow (I think I've only replaced the spool once in the 30 years I've had the welder). ;-(

 

[123hotchef]

OK and thanks. I'll check what wire I have in there tomorrow (I think I've only replaced the spool once in the 30 years I've had the welder). ;-(

if u feel more confident with stick then do that

 

[T_i_m]

if u feel more confident with stick then do that

No, I don't think I do specifically and have used the MIG more than the stick over the last 20 (probably) years (and prefer it for the continuity of control etc), it was more a question of which solution might be the better for this task and so subsequently better for me?

Assuming my MIG is up to it (sufficient current for the metal gauge etc) and I can see what I'm doing (getting closer to clicking on the 'buy' button for the A40 since I found the Parweld XR938H is 1/3/1/2) and with a bit of practice to get me back up to speed, I'm happy to give it a go.

And I've always got the angle grinder(s). ;-)

 

[Ubique]

If you're not too confident, I'd say use a stick welder - get some offcuts the same size & thickness to practice on first. You'll get better penetration with stick, even if the weld looks a bit ugly.
I'd say those radiussed corners are crying out for some stick pushed into them as a root weld, overlay with more stick or MIG if you want, to build up the strength if required.

 

[T_i_m]

If you're not too confident, I'd say use a stick welder -

I think today I'm as confident with the stick as I am the MIG and would have to practice more with the stick because it I feel it needs more 'technique' than the MIG?

get some offcuts the same size & thickness to practice on first. You'll get better penetration with stick, even if the weld looks a bit ugly.

That's the thing ... if all other things are equal ... if stick is 'better' for some technical reason (even as you say I can't make it look as pretty) then I'd rather go for what's most likely to give me the strongest outcome, even if it's more faf (getting the stick weder out and getting the rods in the oven). ;-)

I'd say those radiussed corners are crying out for some stick pushed into them as a root weld, overlay with more stick or MIG if you want, to build up the strength if required.

Understood.

I see the lovely welds on things and wonder just how many would have been automated?

 

[Ubique]

Well you've got dissimilar thicknesses and an awkward fillet due to the radius, the thing with rods is that you know the arc and therefore the weld puddle will be in exactly the place the rod is pointed at, it won't be off to the side. Use the angle of the rod to steer the weld to where it needs to be, because of the length, it 'points' more obviously than a Mig or Tig torch.

 

[T_i_m]

Well you've got dissimilar thicknesses and an awkward fillet due to the radius,

Quite, things that would be 'automatically' accommodated for by a skilled operator. ;-)

the thing with rods is that you know the arc and therefore the weld puddle will be in exactly the place the rod is pointed at, it won't be off to the side. Use the angle of the rod to steer the weld to where it needs to be, because of the length, it 'points' more obviously than a Mig or Tig torch.

Thanks for the explanation and that was the sort of thing I was eluding to. ;-)

Just thinking out loud on this point ... When you are good at something, especially when you are 'professional' at it it can sometimes be difficult to imagine all the holes someone not so experienced might fall into.

I have experienced this many times myself, assuming that a logical / mechanical procedure could be completed by anyone who is reasonably intelligent who has access to the right tools, forgetting just how much experience and technique are often also involved (when that nut is seized or that stud snaps).

I'm not suggesting anyone has done that here (certainly not intentionally and I really appreciate all the feedback I've been given) just that it's easy to do when something is (appears) easy to do when you are skilled / experienced at it (like plastering, roofing or gearboxes) and why I mentioned de-radiusing the radius because whilst that might be time consuming, unnecessary or even counter-productive to a skilled person, may possibly have made things easier to someone who isn't?

How many un-mentored practice welds might someone who may be able to run a good weld under ideal conditions have to do to be able to ensure success on this radius for example?

I'm also not suggesting that anyone should be able to pick up a welding torch and be able to weld, of course it takes time, practice and a certain level of hand-eye-coordination plus knowing what all the rules are re materials, machine settings, lighting and access etc. How many times have we seen someone struggling against something that we might have sorted without even thinking / trying.

Continuing to think out loud, I wonder if there might be any welding courses running at the (my) local Technical College with the Covid issue atm? I understand the basic principals and can complete the more basic welding jobs reasonably well (and I'm very self critical), it's just when the going gets tough a good mentor can (or typically does for me) shortcut many hours of trial and error and there is only so much you can learn from Youtube. ;-)