Advice on how to improve my welds

[adam.]

Hi everyone,

Long time lurker and have actually learnt how to do rust repairs with the MIG through this forum's tutorials and now trying to get the hang of the art of TIG welding but I am having a few issues.

Please see attached, picture of my welds, as you can see, not very clean at all.. contamination of some sort.

So a bit of information, I am using a Cigweld transmig 175i inverter using lift TIG, 304 stainless, 2.5" tube. Red tip tungsten, 1.6mm from memory, about 30amps, pure argon gas from Supagas, about 8-10ltrs/min of flow, size 6 cup. No purging was performed.

Welds were all fused, no filler used.

I thought the issue might have been from using a drop saw to make the cuts?

Any help on how to make the welds turn out cleaner would be appreciated.

 

[chevy2]

You appear to have all the machine/torch/gas settings about right,
Bit hard to tell from the pic where you could improve?
Abrasive disc chop saw? Do a few test pieces with and without metal cleanup after the cut to see if thats the problem,
Could be a combination of amps a bit high or travel speed a bit slow, both will overheat the workpiece causing a greyish weld,
keep altering your method till you eventually find the sweet spot.

 

[BrokenBiker]

do you purge the pipe when welding? Apart from that i don't know what to suggest, the welds look good from a technique and settings point of view

 

[SBK]

Are you using a gas lense?
Are you cleaning with acetone first ?
I would say you need no more than 5lpm.
I use an abrasive chop saw without any probs now though I was getting grey welds not long ago and found that dropping my lpm changing to a 2% Lanth Tungsten and going from a size 10 cup to a 6 made a huge difference.
See my post further down "Tig Practice"

 

[Buter]

Google 'weld sugaring'

I think it will get you to an article on the Miller or Lincoln site that might be able to help.

Most filler rod has some sort of deoxidising agent in it as far as I know. Maybe try again with appropriate filler.

The fab looks tidy and heat input looks good, too. I'm sure one of the guys with more ss experience will pop along with some better advice.

Cheers

Buter

 

[wheresmejumper]

You could try doing a pass on uncut pipe, at the same amps.that would rule out contamination from the saw.
if its still there, id reckon its amps/speed.
gas is an unlikely cause, as stainless is very forgiving with purity

 

[Mad Mick]

Hi,it could be a lot of things.My thinking is that contamination is likely to be the cause,probably from the saw.You have to be congratulated for keeping a good line.......not easy. On closer inspection I wonder whether you have been putting too much heat in and have had to keep breaking the arc to stop blowing thro'. Regards,Mick

 

[SBK]

Why not try googling get advice from else where,is that what your saying Buter ?
And Sugaring is on the back side of the weld is it not ? due to not being purged or over heating.
I was not offering advice just advising what I had done to overcome the very same problem.
I will only offer my advice when I have done 20 years service and got me gold watch.

 

[Buter]

Hi SBK

No, I was saying to use that search term in Google to find the article on sugaring. It's got some good info that might help the OP. I was out in the shop when I wrote that reply and didn't have the time to fetch the link myself.

If it was my last sentence about somebody with more ss experience offering better advice that has offended you, you'll be pleased to know that I was referring to myself, not you.

Go get to work on that gold watch.

Buter

 

[hotrodder]

Sugaring (aka coking) is oxidation. It's the 'stainless equivilant' of scaling with mild steel except that chromium is FAR more reactive than iron which is why stainless is welded with a purge when talking full pen butts or thin stuff- not talking light scale that falls off like with mild but a tenacious, thick, hard mess that also ruins the corrosion resistance i.e. you've just 'burnt out' most of the chromium that's needed to make the steel 'stainless'. A little scale/coking on the inside of an exhaust isn't a big deal* BUT if the rootside reaches melting point while welding those oxides can and will end up in the weld pool regardless. That's looks like what happened here to me... a bit too hot/slow or poor argon coverage and the weld is grey instead of all those 'pretty colours' and not a big deal a lot of the time. When there's black bits, cratering and lumps in the weld something else is going on too and it's only gonna come from crud on the material or from the material itself oxidising during welding

Buter was probably talking about Millers top ten TIG -welding-problems-visual-guide-graphic article and/or this one... http://www.millerwelds.com/resources/articles/alloy-pipe-welding-TIG-GTAW-alloyed-/?

A recent (and one of many) threads on the subject of grey/manky/burnt stainless welds... http://www.mig-welding.co.uk/forum/threads/whats-wrong-with-this-weld.44865/#post-496909 covers everything already mentioned in this thread and more plus links to at least one other good thread on the topic

Here's one from a few years ago... http://www.mig-welding.co.uk/forum/threads/any-tips-please.12794/page-2#post-150868 which shows a weld made partly with wire and partly autogenous due to the guy that cut and fitted the tube not listening to me. The settings other people use aren't necessarily helpful because travel speed and arc length make a HUGE difference but FWIW i would have been running around 42 - 45A with wire and the autogenous pulsed at over 80A peak, 35% peak time, low 20s background and around 2 - 3Hz (2 - 3 'freeze lines' a second) which if you average it all out will end up in the ball park of 42 - 45A...


* It's a VERY big deal if talking hygienic work or applications where the corrosion resistance will be properly tested. Not an example of hygienic work but what the rootside of a purged stainless weld on thin wall tube should look like (minus the poor tie in at 12 o'clock)...

 

[SBK]

Buter sorry I took that the wrong way bud Been a long day.
As for my gold watch I will start with a coding assessment next week, just about got 20 years in me !

 

[backpurge]

Hotrodder has just about covered everything in detail, it basically looks as if it is getting far too hot. Either turn your juice down or speed up. Contrary to what has been said above in other postings you don't need filler to get a nice clean weld and gas quality is very important when welding stainless.

As has been suggested practise first on un cut pipe, keep as short an arc as possible and avoid weaving, keep at it you will be surprised at how quickly you get the hang of it

 

[adam.]

I can always count on this forum for help. Thanks for all the responses.

Quite a few ideas and suggestions have been offered and I'll make a start on going through the links provided, thanks, hotrodder.

I will update this thread when I find the solution.


Cheers

 

[adam.]

So I did a few practice welds with filler, adjusted settings and whatnot, but the most interesting observation is this..

The weld on the left is the joint weld where there was the contamination, and the right is where I just laid a weld on a 'fresh' section of stainless (no filler used).

All settings were kept the same, torch technique and speed were all kept as close to how I would have performed if I were to join two pieces together, and the weld has come out looking great.

Would it be safe to rule out amperage being too high?


Edit: Weaving was performed to try and keep technique the same.

Edit 2: Sorry, no gas lenses are used, and I have been using an abrasive drop saw.

 

[BrokenBiker]

does appear to be a contamination issue. Try cutting a piece with the abrasive saw them clean with a flap wheel and acetone and weld on that.

 

[hotrodder]

While it could be contamination it's just as likely (more so IMO) that the bead on tube isn't as dirty because the atmosphere on the inside of the tube has a much easier time oxidising the weldpool on a real joint... top right of pic can see where the edges of the tube have 'pulled away' from each other. with a purge that'd be less likely to happen even if the cut edges are manky. The second Miller link i posted shows the difference a purge makes to both the root side and face of the weld, granted they're playing with heavier wall pipe and therefore have a root gap but the same thing can happen with thin wall tube even with a perfect fitup if you're a tad too hot/slow, dither for a second, arc length is a bit too long, the joint pulls and messes up the fit etc

Running beads on sheet/uncut tube are a good way to practice as said but they don't have much in common with a real joint, just a quick & easy way to get some practice in with regards to carrying a consistant weldpool, maintaining (VERY short) arc length while keeping up with the constantly changing 'angles of attack' that happen when welding tube etc

 

[backpurge]

Your runs are far too wide for the material thickness, the weldpool is getting too hot which as HR says is pulling contamination through the weldpool and causing the heavy oxidation you can see on the surface of the weld. Get some thicker material and practise laying down a much narrower, faster bead

 

[adam.]

Thanks for all the information and tips, I'll give it another crack when it's not 41 degrees celcius outside !

 

[backpurge]

41 degrees, now you're just starting to upset everyone over here, you'll be talking about cricket next!!!!!!!

 

[adam.]

Hi everyone,

Thought I'd give everyone a bit of an update on my welds. In short, they've improved heaps!

The reason for the contaminated looking welds could indeed be due to the drop saw because nothing changed in terms of settings or technique (as far as I know!).

What I did do differently was the preparation and cleaning of the edges which were to be welded. Instead of grinding only the inside and outside of the pipes where the drop saw left it messy, I also grinded the 'face' of the pipe where it would make contact with the second piece (if that makes sense), basically grinding where ever the drop saw would have touched the pipe. And I no longer got the ugly welds.

Thought I'd give everyone an update And thanks for all the suggestions!