Subject: Re: TIG welding stainless - any tips for a novice

From: [email-masked] (William Reid)
Date: 4 Jun 1995 23:35:24 GMT

In <[email-masked]> [email-masked] (Peter
Northway) writes: 
>
>Firstly let me say that I am an experienced gas & arc welder but I
have never 
>tried TIG until last week.
>
>Are there any special tips or techniques for welding thin (20 guage)
stainless 
>steel tubes. I found it reasonably easy to butt weld, but difficult to
localise 
>the heat when doing a tee joint. Consequently the practice pieces had
either 
>large fillets or holes.
>
>
>         BIG     |    |   Holes
>         Fillet /|    | 
>       --------/-|      --------
>
>
>
>       -------------------------
>
>The TIG machine I am using is a large industrial machine with a
variable 
>current foot control so I am sure it is not the machine but my poor
technique. 
>Any tips would be much appreciated.
>
>Cheers.
>
>--
>     Peter Northway         | Out the serial port, through the modem,
>  Wanganui New Zealand      | down the leased line, over the bridge,
>[email-masked] | off the wall - nothing but net!
>
Are You Using a gas lens?  If not try it.  Theres a world of difference
in control.  For thin stainless tubing I'll normally sharpen the
tungsten(2 1/2%thoriated...always)to a pretty long point say about a
1/2" taper. Keep the amperage down to the minimum.
If your fillets are too big where's the metal coming from to make them
too big? Indications probably are that you are using too big a rod try
using .035" or .045 mig wire.  Cut off about a foot of it and hold it
in a pin vise(starrett type) this is the way I do really fine stuff
because mig wire is hard to control in a big old burn scared hand. 
Another reason for too big fillets is a crappy fit, remember the better
the fit the better the weld.  The number one rule of any pipe or tube
weld is that if you spend 90% of your time making the fit exact the 10%
that you spend on welding will make the job look easy.
Another consideration you should ponder with stainless is carbide
precipitation, that's the black shit sticking out on the inside of the
pipe when you are done.  What that is is the chromium that used to make
the stainless what is was, it's what happens when melted stainless
comes in contact with oxygen.  If you set up an argon purge running
through the pipe while you weld it the problem goes away.  Run your
purge line at around 5cfh.  Dont try to pressurize the line, you're
just trying to eliminate oxygen.
Last pointer...use good fixtures they are worth the extra effort to
build them and it's better than having them hard black fingers on your
gloves, or on your hands for that matter.
            
                                    have fun
                                            Bill Reid

---

From: [email-masked] (William Reid)
Date: 4 Jun 1995 23:35:24 GMT

have never 
stainless 
localise 
either 
variable 
technique. 
            
                                    have fun
                                            Bill Reid