21 replies to this topic

[Stu.]

Firstly, I.m very sorry for the long post, but I need to expalin things correctly -

 

I've been plug welding the inner wing this weekend. I'm (fairly) new to mig welding and up to now have done patch repairs with, well lets say 'fair' results.

 

I'm well aware that weld penetration is key to ensuring a good strong weld, and that when plug welding, a higher power and wire speed are required than say butt welding.

 

While I'm (mostly) happy regarding the weld penetration I'm getting, I'm having difficulty preventing the top panel blowing around the edges of the weld hole. I'm trying to keep the wire in the centre of the hole to build up the pool, but on most of them I cant stop it happening, and have to follow up filling the gap where it's blown on the edge, which I dont like doing for obvious reasons regarding integrity.

 

I'm running 0.8 wire (it also happens using 0.6) on a Clarke 135TE, using Argon / Co2 mix. Ive tried different power, wire combinations but still struggle with the problem. If I weld with less power I dont get enough penetration. To be fair I am learning to use a higher setting to get good penetration as I realised from reading one of Soniks posts that you need to 'crank it up' for plug welding, but this is coming at a cost with the edges of the hole blowing.

 

I've seen some really good plug weld examples on the forum (sonik, Ben-O to name a few), and when I plug weld on the bench with new metal offcuts to test they come out really good too. I even tried a new offcut and plug welded it to some old rusted offcut from the car, set in the vice vertically, and even that came out good,  but I just cant seem to get it right on the car.

 

Unfortunately I dont have any photos to explain the blowing around the edge of the hole, but I'm sure you know what I mean. This is a photo up to show my bench welds. I pulled it apart and the plug weld held together, ripping the steel around it, so the penetrations ok I think.

 

 

I know its something I'm not doing right, but wondered if anyone else has had this problem, and if anyone has any tips I could try.

 

Many thanks.

Edited by Stu., 14 March 2015 - 06:01 PM.

[Ben_O]

How close are you holding the nozzle to the workpiece

[Tupers]

It seems like the problem you're having is caused buy a lack of heat making it into the holed panel resulting in little to no weld penetration. 

 

 

When ever I plug weld I start in the middle but spiral outwards and around the edge of the hole. This results in a relatively flat plug weld with a little dimple in the middle. 

 

I rarely change settings between butt welds and plug welds as the way I plug weld is really more like a very short seam.

[sonikk4]

Hole size plays a big part here. I use 1/4" holes where I can then max power setting and wire speed at 9 on the same welder. The only difference is I use 0,6mm wire.

[sonikk4]

http://www.theminifo...rebuild/page-21

You can see all of the plug welds on the rear panel.

[midridge2]

Check you have a good earth.

[Ben_O]

I find that you get better results if you hold the tip of the shroud about 1/4" away from the workpiece. Hold your torch so that the tip of the shroud square in to the workpiece instead of at a slant like you would for seam/stitch welding.

 

The wire should start in the centre of the hole and then fairly quickly but as steady as you can, rotate the torch up to the top edge of the hole  and then round in a circle to fill the hole and then back to the centre creating the 'dimple'

 

As well as hole size being a factor, it also depends what you cleaned back the flange with. You might find if you are using a flap disc that you might be thinning the metal too much.

 

Practice, Practice, Practice and even then, you probably won't get every single one perfect all of the time. Cleanliness is also a key factor as any contaminants will always cause problems

 

Ben

[Stu.]

Great advice thank you fellas. All comments noted. Using 0.8 wire, I've had the mig set on 1 / Max with a wire speed of about 6. It lays a flatter weld and I get penetration but still get hole edge blow. Are these settings still to low then ?

[Ben_O]

Great advice thank you fellas. All comments noted. Using 0.8 wire, I've had the mig set on 1 / Max with a wire speed of about 6. It lays a flatter weld and I get penetration but still get hole edge blow. Are these settings still to low then ?

Sounds ok to me.

 

I also use 0.8 wire, always have as it was what i always used at work when i first learnt welding for my apprenticeship. To be honest though, i have used 0.6 on my resto as my first welder came set up for 0.6 and i found it no different really. Just need to slightly adjust your weld times and technique 

[Stu.]

You might be onto something about the flap disc Ben. On the test welds I did on the bench (which came out fine) I just hand filed the burrs off the back of the drilled hole. When I prepped the inner wing panel for the car, I took a 60 grit flap wheel to it to dress the holes and remove the etch primer on both sides. I've also realised the metal pushes out a little as the drill bit is pushed through, which would have been removed by the flap wheel leaving a very thin edge around the hole. I recon this is the problem, so I'm going to test the theory tonight. There are other things you guys have mentioned that I'll take onboard too so thank you. I'll let you know how I get on.

Edited by Stu., 14 March 2015 - 09:09 PM.

[Stu.]

Well, I gave it a try and got inconclusive results really. Both holes gave good welds with no edge blowthrough. I think I'll need to ensure the back panel of the holes are really clean and totally free from rust etc. I got a bit dispondant today as I was worried that my welds were not good enough, but I'll apply all your advice and try to keep positive.

[humph]

Given that you get good results with metal clamped in a vice, are the panels on the car clamped together tight to make sure there is no gap between them? Gaps cause blown holes.

[Stu.]

Humph, you're spot on. I realised this was the cause of my problem this morning. I did another bench test on a row of four. The first three were clamped tight with no gaps and were perfect with good penetration, but the last one had a slight gap between the panels, which caused the edge of the hole to blow when I tried to plug weld it.

In some areas of the inner wing it was difficult to get a clamp in to get the panels really tight up and due to the inner wing being quite stiff it was hard to pull them up tight. I suppose skin pins would help but I dont have any (on my list).

Thanks for your help.

[minidaves]

.6 wire is the key .8 needs so much power to melt

[sonikk4]

As I said I use and 2 and Max wire speed at 9 with 0.6mm wire. I do get the occasional edge blow but then using a 3/16 th hole instead of a 1/4 helps to reduce that.

To be honest you do need skin pins or similar to pull metal together if you cannot get a clamp in place. I also use a hammer and dolly to ensure as far as possible the mating surfaces are flat.