welding both sides

[brendan h]

just needed to weld up some stuff and coulnt be bothered buting a V grove on it so i left about a 3-4mm gap. plate was 5mm thick and i used a 3.2 4013 rod on about 135amps. did one side ok. turned it around got the grinder out with a thin cutting wheel and ground out the slag from under. welded it up. welds are fine and for what there being used for should hold up fine.
i had to cut one of the welds i half and when i did i notice in the middle of the weld was a small dot of slag inclusion. i am assuming this was through the whole weld.
just would like to know if it is posible to prevent this other then usning a V grove? i am thinking more gap or maybe more amps?

 

[scarecrow]

If im welding something of from both sides I never leave a gap especially on stuff as thin as that

 

[Drains]

Brendan, i'd turn up the juice for the second run to keep the slag out. I'd definitely leave a prep on 5mm stuff - don't listen to scarecrow, he plays with potatoes for a living.

If the cutting wheel you used to clean her out was too thin, that will have held the weld back too. Whatever, turn up the juice as high as you can get away with without losing control.

 

[scarecrow]

Brendan, i'd turn up the juice for the second run to keep the slag out. I'd definitely leave a prep on 5mm stuff - don't listen to scarecrow, he plays with potatoes for a living. .

Professional potato player £10'000 a week

 

[scarecrow]

I had a few minutes to spare this evening so I thought I'd have a go at proving myself right for once a couple of bits of scrap about 6mm

welded up both sides with no prep just a rub of the grinder to take the rust off and no gap welded with 3.2 6013 at about 135amp


as much as I hate to admit it simondrains but you're right you probably can't see it from the pictures but there is a little spot in the centre between the two welds not much bigger than a needle but still there are all the same
but in my defence I still say that even welded poorley on both sides it would still be stronger than the parent metal

 

[Drains]

Ah, but Scarecrow, i'd have done that exactly the same as you, cos you woz doing a fillet. I was thinking of a butt weld, in which case, prep is required. I never bother with prep on a fillet, and I wouldn't expect full pen either.

 

[snowcat]

Chaps, A double welded butt T fillet is the only fillet that can achieve full pen , It is possible to overlap the weld but only with prep, you are welding a compound fillet scarecrow, which is only a partial penetrated joint you would never expect a complete overlap, more like 2 circles to the edge of each other, this joint is quite strong enough, however a standard fillet only penetrates into the joint, this is why leg lengths become rules, two leg lengths that are equal to 70% of the vertical thickness of the material to be joined will give full strength.........

As the material gets thicker it becomes impractical to weld enormous throats so thats why bevel Ts come into play, Root gaps also have a bearing on overall allowable leg lengths........

Jeusss I'm starting to confuse myself......

 

[brendan h]

i was doing a butt weld

 

[scarecrow]

Sounds like crossed wires then probably should have read brendan h post a bit better I usually leave a gap of about two 2 to 3 for butt joints if im welding both sides as my grinder blades are 3.2mm that way you get everything cleaned out of their
sounds about right snowcat i think

 

[snowcat]

square butt joint, your talking scarecrow, Ok for thiner sections its actually only a static tension joint and not that strong....... but taking the slag out with a grinder and welding would be the best way to do this joint IMHO..... tho as theres no proper root face your always going to struggle with inclusions..... I'm not sure what a 4013 rod characteristics are?????

 

[Drains]

I'm not sure what a 4013 rod characteristics are?????

I think they're characterised by being a missprint

 

[snowcat]

I think they're characterised by being a missprint

40,000 psi????? maybe aluminum????

 

[scarecrow]

It's getting more confusing now to be honest I was I can't even remember the last time I welded up both sides of a butt joint usually just prep and weld seems a lot easier

 

[snowcat]

Single V joint is stronger than a square butt, but is not suitable when bending is concentrated at the root, double V has strength in all positions, as does a Single U joint, however rare to get into U joints under 1/2"