SHS butt joint.

[Mick B]

Sometimes I find it easier to draw a picture rather than try and explain what I want, so ........... I was welding some 35 X 35 X 2 mm SHS in a butt joint (flair bevel ?) today and wasn't too sure which way to go about the weld. I ended up angling the torch as in "A" because I thought if I used "B" it might put too much heat into the open end of the piece on the right hand side and maybe blow through it.
Am I on the right track ? It seemed to work OK.

Another question while I'm at it, I didn't weave the weld (as in little eeee s or zig zags) I just ran the bead straight. What is the advantage of weaving anyway, just to spread the heat, or does it make the weld stronger ?

 

[AdrianH]

I am definitely not an expert, just a hobby welder, but would have gone B or even slightly more over to the left going into the open face by about 10 to 15 degrees.

My thinking is that from the A angle you show you could left col welds, or lack of fusion on the face of the tube to the right in the picture.
Moving to B or even slightly over would have meant better fusion to the 2mm of the Square hollow section and down to the point of the join.

I know that the typical radius is 4 or 5 mm, but do not think to much metal would go under. Straight beads would have been what I would also do.

Lets see what more experienced welders would do as we all live and learn.

Adrian

 

[Kent]

A is correct
The bead size will or rather should catch the open edge with full penetration no probs
You could go straight in also and still get a perfectly good weld in
If there was good fit up no need to weave especially on the flat

 

[backpurge]

B

 

[Kent]

B

Why? It's mig on 2mm wall box and on its open edge so one side. The open edge one needs less than the other
Like I said though either will get it

 

[BrokenBiker]

I would have favoured position b but slightly offset to the square edge so as to wash material Into the joint but that's just me

 

[Richard.]

I would be more inclined to head somewhere between the two. I'd certainly be looking for pen into the radius but you need a good bit of filling into the B side to avoid cutting the thin edge away.
I vote "C". Inbetween the two more towards B

 

[Richard.]

In answer to your other Q. Weaving does not make the weld stronger

 

[BrokenBiker]

I was always told weaving was for vertical up only and even then only if you have trouble controlling the puddle

 

[Kent]

I would be more inclined to head somewhere between the two. I'd certainly be looking for pen into the radius but you need a good bit of filling into the B side to avoid cutting the thin edge away.
I vote "C". Inbetween the two more towards B

Agreed

 

[backpurge]

↑
B
Why? It's mig on 2mm wall box and on its open edge so one side. The open edge one needs less than the other
Like I said though either will get it


The arc is going to take its shortest root to earth so there is the danger of it simply blowing away the square edge in an uncontrolled fashion and merely "pouring" molten metal into the bottom of the radius rather than the arc energy going where it's supposed to

 

[Mick B]

Thanks for the replies. I counted 2 for A, 4 for B and 2 for C. Looks like more practice for me using the B position and I might even cut it through and have a look at it after welding.