andrew-theasby
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| posted on 22/2/10 at 08:16 PM |
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Tigging stainless - black corrosion?
Last time i used my tig to do some stainless the weld went black and really rough. Im gona have another go this weekend on something that will be
visible, so what tips can people offer to avoid this. Ill do a bit of experimenting first but few things i want to check are
1 what flow rate for the argon? I have 2 flowmeters set up now one for the back and one for the torch.
2 is the argon heavier than air? ie does it sink to surround certain shapes like welding a blanked off pipe, could you just fill it from one end?
3 which colour tungstens, red or white.
4 ac, dcen or dcep?
5 should i be using the biggest ceramic cup thing around the torch?
Cant think where else i could be going wrong, i can do ally fine, but any tips would be most welcomed. Thanks in advance.
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MikeRJ
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| posted on 22/2/10 at 08:32 PM |
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Sorry I can only answer one of them, Argon is quite a bit denser than air, about 25%.
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mistergrumpy
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| posted on 22/2/10 at 08:33 PM |
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Argon is heavier than air and between the red and white tungsten use the red.
Sorry I can't answer anything else.
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Toltec
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| posted on 22/2/10 at 08:40 PM |
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Not a pro, but from my welding course...
1 what flow rate for the argon? I have 2 flowmeters set up now one for the back and one for the torch. Depends on the cup size, type of weld etc.
Enough to stop oxidation - you can have the flow too high and cause turbulence pulling air onto the weld. About 15 - 20 CFM or 7 - 9 L/m should be
about right for up to 140 amps - I have not tried anything higher than that.
2 is the argon heavier than air? ie does it sink to surround certain shapes like welding a blanked off pipe, could you just fill it from one end?
Argon is heavier than air at same temp, though it will be heated by the arc etc. You are trying to purge the air from the pipe, you want some flow
from the far end to allow the air to be purged, but with some restriction so you do not waste too much gas. You are supposed to use stainless wire
wool for the plugs to prevent contamination - handy for preparing the joint for the same reason.
3 which colour tungstens, red or white. Red, thoriated for stainless.
4 ac, dcen or dcep? Electrode negative.
5 should i be using the biggest ceramic cup thing around the torch? Cup size is mainly determined by the size of the tungsten, i.e the current being
used, though you will need a higher flow with a larger cup.
[Edited on 22/2/10 by Toltec]
[Edited on 22/2/10 by Toltec]
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mark chandler
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| posted on 22/2/10 at 09:33 PM |
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You also need to back gas or it tends to go a little awry.
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madteg
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| posted on 22/2/10 at 09:46 PM |
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Are your using purshield argon or are you using argon light, if you are using light wich is used for mig welding its no good and will go black .
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andrew-theasby
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| posted on 22/2/10 at 09:53 PM |
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quote:
Originally posted by madteg
Are your using purshield argon or are you using argon light, if you are using light wich is used for mig welding its no good and will go black .
Dont know, afaik its pure argon on a contract form energas, think it was £35 last time i got it refilled, how can i tell?
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andrew-theasby
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| posted on 22/2/10 at 09:55 PM |
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Thanks for the quick replies, one other thing, should you just do a little bit at a time, cause once you move past it with the torch, wont it be open
to air?
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madteg
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| posted on 22/2/10 at 09:56 PM |
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Look at the top of bottle and it will say pureshield argon or argon light
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baz-R
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| posted on 22/2/10 at 09:58 PM |
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the black is oxidation of the chrome in the stainless
you should only have a thin black/gray layer that is formed only from the heat left from where you have moved away from (not in your weld pool).
only high purity argon should be used realy
if you have exessive blacking as you weld with fizzing i would say you have air geting into your shield gas or if you are getting a black like crusty
formation say on the back side of the sheet its too much heat making it oxide as its un shielded.
hope this helps
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907
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| posted on 23/2/10 at 07:53 AM |
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Hi.
Excessive oxidation on the outside could be because of one of the following:-
Wrong gas. Use pure argon only.
Ceramic too small. Bigger the better IMHO. The one I use most of the time has a 12mm outlet hole.
Gas flow rate too high or low. I run 9 l/m, but more for an outside corner and less for a fillet as a fillet tends to hold the gas.
Tungsten protruding too far. Keep this to a minimum, but this does depend on the type of joint.
Torch angle too shallow. The nearer the torch is to vertical the better the gas coverage.
When purging the inside as I do for most welds, I run 6 l/m. For a job with several welds this can be turned down as you proceed.
Masking tape is your friend for this.
HTH
Paul G
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wilkingj
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| posted on 23/2/10 at 12:17 PM |
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Just dug out these links..
I cant impress enough on how much these two other bits of info helped me.
The Video got via Bit Torrent... worth the slow download of the 500Mb file. It IS WORTH IT.
http://www.mybittorrent.com/info/633189/
and the Miller site set up info.
At least it points you in the right direction.
http://www.millerwelds.com/education/calculators/tig_amperage_calculator.php
This Miller site helps with getting the Welder settings correct. It helps to have the machine settings correct.
Also have a read:
http://www.locostbuilders.co.uk/viewthread.php?tid=78059&page=1
There are several threads on TIG on this forum.
I am still a novice TIG welder, but its getting better.
The Video was really helpful, even if its a pain to get downloaded.
Hope this helps
Geoff
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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andrew-theasby
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| posted on 26/2/10 at 08:38 PM |
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thanks for the tips, its definitely pure argon ive got, just checked. Ill try all the tips on sunday hopefully and post back my progress (or success
hopefully)
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dave r
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| posted on 26/2/10 at 09:54 PM |
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if you have one of the older tig set ups, check the gas tube....
mine wasnt the coaxial type and it leaked like a sieve
works much better, with the new lead, and all the argon getting to where it should
dave
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JoaoCaldeira
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| posted on 3/3/10 at 10:20 AM |
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quote:
Originally posted by wilkingj
The Video got via Bit Torrent... worth the slow download of the 500Mb file. It IS WORTH IT.
http://www.mybittorrent.com/info/633189/
Hi.
Can you get the name of the video file, as the link does not work?
Thanks in advance,
Joao
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andrew-theasby
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| posted on 3/3/10 at 08:35 PM |
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I found that too, thought it was just me tho! Is it on youtube anywhere?
quote:
Originally posted by JoaoCaldeira
quote:
Originally posted by wilkingj
The Video got via Bit Torrent... worth the slow download of the 500Mb file. It IS WORTH IT.
http://www.mybittorrent.com/info/633189/
Hi.
Can you get the name of the video file, as the link does not work?
Thanks in advance,
Joao
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Peteff
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| posted on 3/3/10 at 11:33 PM |
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quote:
Originally posted by andrew-theasby
I found that too, thought it was just me tho! Is it on youtube anywhere?
Is it the Ron Covell Tig Welding Basics video ? It's a copyright video so will not be available on Youtube 
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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JoaoCaldeira
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| posted on 4/3/10 at 11:55 AM |
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A search on torrentz.com with
"Ron Covell Tig Welding Basics"
Shows no hits, but quite a few near ones... 
Thanks
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