using 6mm plate for first time and out of comfort zone

[MoreWellie]

Using Clarke 151 so restricted on amps but most of what we do is 3mm or less but currently have a need to make some replacement axle mount brackets and am not comfortable with the penetration achieved so second (and third) opinions are welcome

Using 6mm plate and right angle butt joints and welding from both sides we used a small V on each side and get decent looking finish but I am not convinced the pentration is adequate

My questions are

1. what amps are really needed to butt weld 6mm plate?
2. should I have root gap and v prep regardless of welder amps?
3. if yes then what size gap and v please?

If you think anything else would be helpful then please feel free

I am happy to grind off the outside welds and cut a root gap with say a 1mm disk but don't want to repeat the same standard

Of course once this is finished then it needs welding to the axle and I really want to get the welds right first time on that

Thanks Mike

 

[piman]

Hello More Wellie,

is the 6mm to replicate the original as I would have thought that 3mm would be more than ample for such a function?

Alec

 

[MoreWellie]

the original was a cast item with approx 6mm thick walls but unfortunately they are not available as a replacement item

In other forum posts where people have done a similar job then they talk about 6mm minimum and others have used 8mm

Other spring mounts on different models of similar vehicles are made out of 5mm

6mm seems an acceptable size

 

[dan.taylor.1]

If you vee'd the joints it should be fine as you've welded both sides.

Dan

 

[MoreWellie]

I was treating it as two lots of 3mm so I only V'eed about 1.5mm on each side

Is that enough or should I have done 3mm from each side so there was only a wedge point in the middle?

 

[awemawson]

Weld up a small test piece. Saw it in half. Polish on wet'n dry. Etch to see penetration. Should use nitric but I suspect a bit of battery acid (sulphuric) would do at a pinch. Infact you can often see the weld metal by just polishing.

 

[MoreWellie]

Thank you for the suggestion, no acid available but will try the polish technique to see what the joint looks like

 

[awemawson]

No old car batteries hanging around?

 

[MoreWellie]

only in my car and not sure that can spare any!

 

[awemawson]

Just dip a cotton bud in one cell, that's all you need!

 

[MoreWellie]

did a quick test and saw pretty much what I expected BUT I don't know what I should expect from a close butt joint so please enlighten me

you can just see the line where the two pieces touch but not sure what to expect when there was no gap and only a little V gap on the outside

If it was done properly would the line have disappeared?

If the answer is yes then what to do differently, more amps? (on max already)

bigger V, how far to cut in?

should I angle in 3mm each side and just leave a point in the middle of the piece?

 

[Mid Wales welder]

I can't really tell from that pic, but if your on max amps then you could always try welding vertical up, this will help with penetration.

 

[MoreWellie]

This is the best I can extract from the photo as the camera is a bit old

You can see the straight line towards the top where the two plates were butted together before welding

 

[dan.taylor.1]

Yeah try another with more vee and see, that horizontal line is where no fusion has occurred.

Dan

 

[MoreWellie]

IF this was welded by somebody experienced with say a portamig 215 or 235 welder would that line have been completely fused or just partly along its length?

Does this answer stand if they only welded from one side?

it looks to me like there has been little penetration along the crack at all which I don't understand as even with a 150amp welder I believe there should be some

how big a V would you normally cut in a 6mm plate? for a 235 or for a 150amp welder?

 

[dan.taylor.1]

If I'd done that with my 250a machine if have just dressed the corners as I do on any piece (I hate cutting myself on burrs etc!) And whacked the power up and welded away. Try a bit with more vee and see what happens, it's all trial and error.

I'm not trained in mig I've just picked it up as I go along, nothing I've welded has ever broken without been clouded with a 2ton skid steer loader, and that weld I was surprised it stuck anyway as the gate was crap from been in a farmyard for 20+years!

Dan

 

[awemawson]

Yes for full penetration that line should disappear, however for proper penetration it shouldn't be a line, you should have 'v' prepared the joint, and left a gap between the pieces equal to the (rod for arc) or wire that you are using. This way you ensure that the weld is right through. On a 6 mm critical plate I'd V it until the edge is about 2 mm wide

 

[MoreWellie]

Thanks for the comments. As I only have a 150 amp mig I obviously need to do a bit more preparation

I shall have a go with a decent V tomorrow and see what happens

When I was learning to work with thin stuff I always thought it was easier to work with thicker metal, now I can see that thicker stuff just brings different problems

I fully expect that there are people on here that think that 6mm is like tinfoil

 

[awemawson]

My big mig welder can blow holes in 6 mm , but actually I'd probably do that job with stick - still needs prepping though.

 

[Drains]

That's a fillet weld, so a non fused section as above is acceptable. For what you're doing, and given the capacity of the welder, I'd suggest though that you vee out the outside of the joint to about one third of the thickness of the joint. Vee to about 60 degrees inclusive, as standard.
You should still see a line, which should be a little shorter, and less reinforcement (lump of weld at the side).
I think your travel speed is a little slow too, hence the very proud weld.

On a butt joint there should be no line. A gap and veeing may be required to get full pen.

For a strength test, prepare a coupon by cutting a slice across the weld, say 10mm wide, and bend it. If it's weak at the joint it'll break.