Welding: when should a slug be used?

[bcware]

How do you decide when to use a slug when joining two sections of pipe together? When is ok not to do this?

What is this technique officially called? Doing searches for things including the words "slug" and "frame" have not gotten me anywhere with google.

I stole this photo from LuckyEight. It demonstrates what I am talking about, but also shows additional holes that were drilled. I am assuming the holes are to increase the surface area of the slug so more welds can be done. What is this technique called?

 

[16VGTIDave]

I think it is called plug welding when you drill holes and weld then. But I'm not positive.

 

[Scorpio1963]

That's cool method of welding pipes together,this way they stay aligned.The last time my welder friend welded my old set of mufflers they weren't very straight and I had to cut them off and have it redone.

 

[Tombo]

That pipe looks befuddled #iseefaces

 

[Charles]

I would recommend using slugs any time any lateral stress will be seen. Bevel both ends of the pipe you're welding together so you're filling in the valley with your weld material (which isn't done in the pic you posted), then, like in the pic, drill holes for welding rosettes, and weld them up too. If you do it properly, that $hit will never break.

 

[LuckyEight]

Well I dont know how to call it but it works fine. At this picture I used it just because I wasn't able to bend the pipes to this shape... But I think in this case, it wasn't necessary... I used it also where the hoop is connected to the frame. There it seems to be quite appropriate...Especially in cases when it will be loaded with passenger (not your case)

 

[bcware]

Yes, I'm looking to make a loop for the rear of my frame, but it is aft of the rear shocks and will not be bearing any weight. I don't have a lathe or anything, so I cannot make a slug. I could buy a solid rod and chop it up, but this would all depend on being able to find the right sizes off the shelf (proper od/id pipe and proper size rod to fit inside). I don't have any experience shopping for metal from more serious sources, but I know I will have to start. The prices at the big box hardware stores are pretty high.

 

[LuckyEight]

or you can try this

 

[bcware]

A rolled sheet or a split pipe? That is clever.

 

[LuckyEight]

splitted pipe would be better for sure...some thin sheets could be burned through during the welding. And with thicker sheet it's harder to roll them in desired shape. As you said...it all depends what sizes of rods/pipes you are able to find.

Frame pipes under the seat are 22mm OD and 19 or 18mm ID ?(not sure). Maybe you will be able to find some pipes with this OD. Good luck! Looking forward to see your final seat setup.

 

[drewpy]

I slugged the Gilera frame as it was snapped
I also slugged the rear hoop in to the frame as It gave a better weld.

check out chopperunderground

http://www.thechopperunderground.co...=0&p=283973&hl=slug&fromsearch=1&#entry283973

important that its the same thickness as the tubing,as solid creates a folding stress where the solid bit ends

 

[bcware]

I'll just re-post this from the link because it's good information and I don't want it to go anywhere. Thanks Drewpy. That's a good enough answer for me!

"Going off of what I've learned from certifications, a slug is not technically necessary. I can't speak for "black pipe' as being the proper material for the job, but the slug mainly serves the purpose of making sure the joint is properly welded 100% with no slag inclusions...

Here's what I mean... when you weld a pipe with no slug, and you don't purge the pipe with argon or some other gas, you risk the weld becoming defective from the inside out. Sometimes they call this "sugaring'. When taking my 6G cert on the tig, which is a fixed pipe 45 degrees, I was able to weld around the fixed pipe 360 degrees with no problems, but when it came to the inside of the pipe, they were unable to purge the inside, so there was a defective weld surface on the inside of the pipe, and I was unable to ever turn in a sample.

Putting a slug into the tubing joint prevents this from happening, because you essentially have a backer, the slug, to prevent air from getting to the backside of your weld.

So basically the welds you encountered, could possibly have been ok, but it's hard to say given that we don't know how they were welded. I would think two obvious methods would be to purge the inside of the tubing, or to just stick weld them, or flux core them, where the flux would eliminate the problem of "sugaring" inside.

Feel free to disagree if anyone is reading this and has some input, but this is what I have learned from previous welding instruction.

Mathius"

 

[XSLeo]

Let me start by saying I'm not a great welder. That being said from what I understand a tubular slug is better than a solid slug. A solid slug takes more heat to weld than a tubular slug. This excess heat can weaken the tubing outside the weld.
I have seen many things welded break, not so much at the weld but right next to it. From what I understand the heat of the weld weakens the steel next to the weld.
I also hear that heating the tubing back away from the weld a few feet can lessen the stress on the weld.
Leo

 

[drewpy]

Let me start by saying I'm not a great welder. That being said from what I understand a tubular slug is better than a solid slug. A solid slug takes more heat to weld than a tubular slug. This excess heat can weaken the tubing outside the weld.
I have seen many things welded break, not so much at the weld but right next to it. From what I understand the heat of the weld weakens the steel next to the weld.
I also hear that heating the tubing back away from the weld a few feet can lessen the stress on the weld.
Leo

true, but it also causes stress where the solid slug ends as, being solid, it doesn't flex.