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  #1  
Old 7th April 2011, 06:04 PM
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Bonzo Bonzo is offline
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Smile Testing your welds !!

I have been meaning to make a post on this topic for a very long time.

Been a nice day today and having nothing pressing to do, I thought it was time that I did.

This post is very relevant to a recent thread elsewhere but I guess this is the correct place for this post as it is mostly relevant to building the chassis.

Spent an hour or two this afternoon making a few welding test pieces.

The test pices were 25mm X 25mm, 16 gauge ( 1.6mm ) ERW square tube off cuts.

The welder used was a Lincoln Powertech 191C ( 180 amp ) .8mm wire & sheilding gas was, BOC Argoshield Universal

All of the test welds were un-prepped & but welded with no weld gap.
None of the material had been subjected to heat & all welds were started from cold.

Once the test sections were welded, the welds were cut out from the square tubes to produce, flat test strips.

Here is a sequence of photographs.



For ease of identification the test pieces are marked A, B & C

Looking at weld A you may think it looks reasonable.
Nice narrow weld bead that will not take too much work to fettle & make flat.
However, looking at it with a trained eye, allarm bells start to ring & the weld looks cold.

Weld A used a low current & wire speed setting.


Weld B looks fine & used a sligtly higer current setting with increased wire spped

Weld C looks fine with exception of visual evidence of being a tiny bit on the hot side !!??
This was performed with another increase in current & wire speed.

Now we flip the samples over to reveal the truth.



Instantly it is evident that weld A lacks any form of root penetration.

Weld B has a full root penetration ( A tad shallow )

Weld C has a good root penetration ( A tad too much )

To be ideal, a weld setting in between B & C would produce an ideal weld, one that I would be happy to submit to any form of testing.

That said, in my humble view, either weld B or C is more than suitable for the Roadster chassis & would easily pass BS standards testing.

More to follow in part 2 , just as soon as it is typed in a few moments from now
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Old 7th April 2011, 06:37 PM
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Smile Testing your welds part 2

Here we go for part 2 of this post.

Here is a picture of welds A, B & C after the weld cap has been removed ( Fettled flat )



On close visual inspection of all 3 welds, from the outside face of each joint there is nothing visualy to distinguish any one from another.
No porosity evident, no inclusions evident.

Without polishing & etching, all welds appear to look as they should do when making a simple visual inspection of a weld.

Now here is a picture of wels A, B & C after they have been subjected to a very mild bend test of about 100 - 120 degrees
A true test would be made by bending the sample through a full 180 degrees, with a radius appropiate to the thickness of the material being tested !!



It is self evident that sample A has failed the bend test miserably & is a totally unsuitable weld joint for the Roadster

As there was really nothing to choose from between the next 2 samples, I chose to test the strength of the root weld sample B ( Could be argued that it looked the weaker of the 2 remaining samples )

Tested sample B buy bending pressing the dressed face to put maximum stress on the welds root.
The root held firm & I am confident that it would bend to 180 degrees without showing any signs of stress fractures.

Sample B was tested in the other direction to test the front face of the weld.
Nothing undue was observed.

In sumary, if you are unsure of your welds, keep practicing & don't be afraid to test your welds frequently .... It won't take long & will give you peace of mind, knowing that you will be building a safe, sturdy chassis

I hope this helps some of the novice welders on the forum.
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Old 7th April 2011, 07:12 PM
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Nice work Bonzo, thanks for putting in the effort and posting it up
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Old 7th April 2011, 07:53 PM
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Ronnie,

Thats a really useful thread , very informative & with pictures that actually shows what we,re looking for in a good weld ( a picture tells a thousand words so to speak ).

Nice work Ronnie

cheers
andy
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Old 7th April 2011, 08:04 PM
Enoch Enoch is offline
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What a useful and informative thread. very well put together and very well executed. I salute you, sir
Enoch
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Old 7th April 2011, 08:55 PM
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Very nice work there Ronnie, perhaps you could put what rough amps you used to weld A,B and C.
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Old 7th April 2011, 09:19 PM
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Red face Just to tidy up a few loose ends

I thought it best that I completed a full bend of the test pieces

Here is a picture of the fully bent pieces.



Test piece A folded in half by hand !!, if I were to try & straighten it again, one piece will become two again.

The other two samples exhibit absolutely no signs of stress fracture, if test piece B looks a bit iffy, I can assure you that it is only a bit of mill scale as the test pieces have not been cleaned/polished

Basic testing of a weld sample is quite simple to do at home, well for thin material anyways.

If you do not have a press, a simple vice and an appropiate piece of round bar will do the job fine.

Open the vice a little, place the piece of bar directly over the centre of the weld on the test piece & strike with a suitable hammer.
This will allow you to bend the test piece a fair way.
To complete the bend, just pinch the piece in the vice until fully bent, when I say fully bent, I don't mean squished flat

Once bent, examine the surface of the welded area for signs of stress fracture.
If you want to examine in more detail, fettle & polish the weld with emmery paper, this will help to highlight any imperfections in the test piece

I have not gone into fine detail of the weld settings used for the test pieces because.

A: My welder does not have any digital read out of the weld current.

B: The settings will vary between welders, even identical machines !!

Hopefuly I have a least covered the basics of testing your welds.

Setting up the welder & weld prep is another story waiting to be told.
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Old 7th April 2011, 09:43 PM
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Quote:
Originally Posted by Talonmotorsport View Post
Very nice work there Ronnie, perhaps you could put what rough amps you used to weld A,B and C.
Hi Phil

To be honest, the settings I chose for the test pieces were deliberately askew in order to produce test pieces best suited to ilustrate this particular thread .... Came out quite well considering that the 3 pieces done were the only ones I did

My welder is a 180 amp set with power settings of 1-8 & a wire speed range of 0-10

Sample A was using power setting 2 with a wire speed of 1.5 ish ( Blatantly too low a setting for the material thickness )

Sample B was using power setting of 3 & a wire speed of about 2 1/4 ( not that far off the mark for 1.6mm, I would say )

Sample C was using a power setting 4 & a wire speed of just over 2.5 .... A tad on the hot side for a down hand butt weld.

My personal preference is to weld a tad on the hot side, in my view, there is no worse sin than a cold MIG weld

I also hold the view that a properly set up weld job will do more to aid the war on distorton than trying to reduce the heat put into the job .... The propper weld procedure/sequence will help greatly in the fight against heat build up
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Old 7th April 2011, 10:06 PM
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Thanks for that, very informative and great pictures. Although I bought my chassis complete I still need to weld a lot of brackets and such like. At least now I know what my welds should look like, even if I cant achieve it !
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Old 7th April 2011, 10:42 PM
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Well done ronnie im sure this will help lots of people with their welding.

its hard to make the welder misbehave once you know what your doing isnt it ronnie

i remember writing the welding articles for ckc and i found it really hard to do bad welds on purpose.
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