Big plug welds

[fizzy]

Just been practicing. Drilled a 16mm hole through a 100x100 column - 10mm thick. piece of channel underneath clamped. Filled the hole with weld to see how well it would stick.

Well it stuck extremely well. Very happy with the strength. It is to give extra strength to cross members for my trailer.

The puzzling thing was - the edges of the hole seemed to crater or collapse. In 10mm steel - where did the metal go? Does it matter?

In the photos it is the edges AROUND the plug I am talking about. I hit the piece of channel a few times with a big sledge hammer and it held - only secured by the one plug.

 

[fizzy]

Oh forgot to add 230 amps - high wire speed and CO2 as shielding gas.

 

[dannyp]

as the weld cools it contracts, outside cools faster and as it shrinks draws the hotter more mauable metal in the center, resulting in a crater

 

[biffa]

I know it held but you might not have complete fusion between the two parts, if I was you I would counter sink the hole that way you can watch the edge at it fuses

 

[fizzy]

I will also be welding the crossmembers on the edges and everywhere else so probably overkill.
I was going to countersink quite a bit so the plug will resemble a bolt with a head.
The crater is quite pronounced hope it will cure it.

 

[dan.taylor.1]

that looks like you havent gone over the edge of your hole with the weld? i always make it so the plug sits proud and overlaps the edge and then flat it back with a grinder.

dan

 

[mfletch]

To me it looks like it's just welded in the centre I. Start in the centre then swirl round to melt the edge in plus counter sink

 

[fizzy]

Well I did swirl to start with but not at the end.

I think I will just drill a hole through the crossmember from underneath and weld a plug on the underside - will flip it with a forklift. Will save me a lot of grinding as well. Although penetration wont be so good into 10mm.

 

[madkayaker]

it might not pull apart by hand but under load that will fail there is very little weld strength in that. try taking a big hammer to it and see how it fails

 

[Welderpaul]

Not strong enough. I would drill out a 50mm dia hole and weld around the perimeter of the hole, pointing the wire at the part underneath. I wouldnt necessarily worry about filling the entire hole up. Have a look on excavator diper arms, this is regularly done on the joint between booms, albeit a large profiled, round ended slot.
With such a small hole there is danger that you just fill the hole up with not enough time for it to melt into the metal below.

 

[fizzy]

As I said earlier

"I hit the piece of channel a few times with a big sledge hammer and it held" That piece was tight up under the girder and was flat before I whacked it!

The channel has bent and twisted and the plug held. Also it will be welded along the edges and sides!

 

[Welderpaul]

As I said earlier

"I hit the piece of channel a few times with a big sledge hammer and it held" That piece was tight up under the girder and was flat before I whacked it!

The channel has bent and twisted and the plug held. Also it will be welded along the edges and sides!

Trust me, what i am saying is correct.....

 

[dannyp]

it'll be weaker than it looks, 16mm hole really isn't that big be ucky if a 10mm spot is actualy welded.

if dong simalar i tend to go for as big holes as i can easly do without weackening things 25 mm on say 6mm 32 - 50 on 10 ish mm and just weld round the outside as welderpaul said. filling the hole is probaly counter productive lay weld onto of weld isn't going to give any more penetration and just add more heat (distortion) for no benifit as well as taking up time and wire. whene you fill them the center shrinks fairish leaving a crater and that can't do any favors

 

[fizzy]

And there was me always thinking the smaller the hole the better................

I see what you are getting at - i think! Instead of basically creating a solid rivet make a bigger hole and just run a bead around the circumference is that correct?

 

[fizzy]

Ok I love a challenge.

Not strong enough? Have just whacked hell out of it with a big sledge hammer and a 5' length of RSJ used like a pile driver. This is the result. The 100mm channel has bent and twisted - the weld still holds!

 

[dannyp]

And there was me always thinking the smaller the hole the better................

I see what you are getting at - i think! Instead of basically creating a solid rivet make a bigger hole and just run a bead around the circumference is that correct?

yes

fair play for it holding, think the thing we are trying to get at is even tho that one may hold well, the next one chould very easly not hold so well, it's very difficult to see whats happening whilst your welding, so difficult to know how good the weld is and thats bringing luck into the equation, usally best avoided. with the bigger hole and a good bead round it you can see the weld go down better and much better chance of the next being the same as the last.

 

[Lawnmowerboy]

Belting it on the back face as you have makes full use of the springiness of the steel and the steel deflects rather than loading the weld up. Belt it on the side and I bet it'll break. Some think like this needs to be able to withstand shock and constant loads repeatedly on all axes.

 

[fizzy]

Belting it on the back face as you have makes full use of the springiness of the steel and the steel deflects rather than loading the weld up. Belt it on the side and I bet it'll break. Some think like this needs to be able to withstand shock and constant loads repeatedly on all axes.

Initially the springiness of the steel would have been a factor. But after it had bent down the edges of the channel were tight up against the web in the centre of the column so all the force was pulling the weld downwards. I agree it needed more whacking from different angles - so I hit it all shapes - still hasnt gone. I give up!

Ok it is far from perfect - awful in fact but it was my first attempt. I dont think I need worry about the strength though................

 

[Mr shiney]

If you knew best already, why did you ask the question?

 

[PhillipM]

Belting it on the back face as you have makes full use of the springiness of the steel and the steel deflects rather than loading the weld up. Belt it on the side and I bet it'll break. Some think like this needs to be able to withstand shock and constant loads repeatedly on all axes.

Or just apply some torque, it'll spin on the weld.