How to weld this basic joint? pics

[MisterCruiser]

This pic is of 2 pieces of box steel, to weld these together would one weld in the direction of the red line over and back the 2 pieces or like the blue line straight down the middle?

I have been trying to do the red line, but the problem I have is I don't seem to be able to weld across the gap, how does one go about welding this joint with the gap?

The 2nd pic is the same, just without my red + blue lines as the blue line covered up the gap a bit so iposted the orig pic for clarity.

Also, just a general question, but why does box steel come with that chamfer at the sides, why isn't it proper square so you don't have that gap when trying to weld it? Is this chamfer called rolled steel? Can you get box steel that is proper square straight sides with no chamfer?

 

[Towpack]

When I've welded such joints I've either profiled the end on the tube to closely fit the rounded edges (a lot of filing!) or just turned up the welder and used a faster wire feed rate. A properly profiled joint will be stronger.
AFAIK square section steel tube is (usually) made from sheet steel which is folded and seam welded which gives the rounded corners. That looks like the seam weld in the middle of the vertical piece. Tubing in softer metals like aluminium can be extruded through dies which can give sharper corners.

 

[Tractionman]

+ 1.
Agree with Towpack, I've always profiled stuff like that with a bench grinder if enough access or a 41/2" angle grinder. The thicker grinding disc used on edge - the H&SE is non existant here, just PPE and common sense, if that's not a contradiction.
Using same said grinder flat, make sure areas to be welded are clean shiney steel and degreased for a strong weld with maximum penetration.

 

[BobMurphy]

@MisterCruiser - Are we right in assuming you are using a MIG welder, or is it perhaps a MMA (stick) or a TIG ??

I've bridged a gap by running a weld bead along both edges and then a third bead to join the two. Profiling the cut edge to give a close fit to the side of the box and then using a high current to give a deep penetration will give a stronger joint.

My problem is that every job I do is different and when I finish I wish I was that good when I started .

Remember: "Grinder and paint make me the welder I ain't" .

Best of luck.

Bob.

 

[Shayne]

I use more grinder blades than Bob but penetration really isn't an issue with my dodgy stick welder given i find the amp i need by burning through spare metal then turning amps down a little until it sticks instead of burns .

So with your joint i'd just tack it at the sides where it joins flush then weld to the weld bead so it fills at the same time .

 

[Tractionman]

All good suggestions so far, but filling joints to get a weld will take more time and use more rods/gas/wire of whichever welder type you use.
Penetration is always an issue, poor penetration = poor welds that break.

 

[Shayne]

If your using an arc welder its probable your earth is only running to the bar its clamped to which can be remedied by polishing to a shine where the joint meets .

Or have the clamp touch both pieces while you get a start .

 

[Michael80]

Welding that joint in the flat position is ok, just keep the heat or weld pool closer to the rolled edge of the box and allow it to fuse with the cut edge of the other box.
You can use the same settings as for the fillet weld but just move a little faster.

 

[MisterCruiser]

I should have said I meant in the context of an arc welder.

Which pattern would you weld by though, the red line or the blue line? If standing at the right hand end of the blue line and facing the joint in this direction, would you weld across the 2 pieces of steel like the red pattern or would you try and run a weld straight along the joint like with the blue line? Which is the correct method?

 

[Shayne]

Right or wrong i don't know but if i can get it to pool i draw tiny circles to touch both sides while pulling it towards me .

 

[Andy]

I wouldn’t go just straight like the blue line, would be more like the red one, with gentle side to side movements, have a practice on some scrap bits first & youll soon get the hang of it.
a nice continual fizzy sort of sound as you weld is a good sign,
is it mig or arc you have Got? If it’s arc, make sure you chip off the slag between passes, with a good arc weld it’ll come off, peel away quite easily.
I’m not a welder but have done plenty!
Andy

 

[MisterCruiser]

Quote BobMurphy "I've bridged a gap by running a weld bead along both edges and then a third bead to join the two. Profiling the cut edge to give a close fit to the side of the box and then using a high current to give a deep penetration will give a stronger joint."

This made me laugh becuase I do this too but by accident, What happens me is, I fail to get my pool to stay in the middle, ir falls through the gap or such and I end up with weld only on each side and nothing in the middle. I then weld the 2 beads together as it's easier now that there's a smaller gap now. I often thought of what you describe, is this a proper weld? I suppose it is as effectively all 3 beads are individually sound. Interesting method I might try in future

 

[Michael80]

It’s a fine line with too big or too small rods and then having enough current to strike an arc but then too much current which makes a hot weld pool.
Keep the rods warm and dry.
Also run them along a piece of steel to warm them up makes things a little easier before welding the job.
I would recommend just welding in the flat position until you can lay a weld uniform along its length with a raised profile.
The slag will peel up when the temp etc is about right.
2-2.5mm rods.