Welding Tips and Tricks

Hey guys. I'm a brewer by trade and am currently teaching myself - albeit with varied success - to TIG weld. I'm not looking for a career change, just some skills to help me with the constant upgrades of a growing brewery. I'm new to this sort of thing, although I have a basic understanding of whats required for the welding of essential components. I'm hoping you can help me out with a few finer details.

Up until now i've been welding non-sanitary/critical parts that won't come into contact with beer/wort etc. But still always in SS - mostly 316.

Now I want to be able to confidently weld sanitary parts (always in 316) for beer/wort transfer and other food grade applications. The problem I'm having is with the backpurge.

My pipe/tube and RJT fittings are 1.6mm wall, with 1" pipe. 1.6mm 2% lanthanated tungsten is ground to a point with just under 1/4" stick out with number 8 cup, gas flow to torch is 15L/m, and running from 30-45 amps depending on the ease of weld - travel speed. Most welds seem to be fine with good penetration.

When backpurging though, I still tend to get huge discolouration on the backside of the weld - inside the pipe/tube - and with limited penetration. I've played around with pulsing at 1 pulse a second, 25-45% down, but again with no success, so have left that well alone. The backpurge i've tried at 4 right up to 20 L/m, but nowhere seems to work. At the higher end of the scale the gas pressure seems to blow holes in the weld and shoot the arc off all over the place (usually when nearing the end of the weld) and still discolours the inside of the pipe/fitting, at the lower end of the scale I still get discolouration. Nothing I seem to do works. Even parts of the weld that does penetrate, finishes with colours typical of an external weld - blues and golds - Most frustrating.

Needless to say, the argon flow from my gas is sealed to one side of the tube/pipe with no holes, and the other end is also sealed with tape, but with half a dozen tungsten holes in for the gas to escape.

I'm not using filler wire for these welds, although I do have plenty of 316 filler available in various sizes of diameter.

I''ve attached 2 shameful pictures of one of the messed up parts I welded today. Granted, I could get in and grind away aforementioned discolouration, but most of the other parts I'll weld will be obscured for this - Hence the reason I started with this weld first. I want to be confident that the welds are successful.

As with the nature of the welds, I'm guessing penetration here is vital, so what can I do to improve this and avoid further discolouration?

I'd be grateful for any help/suggestions on this. I have plenty of 'scrap' 1" pipe to practice with left over from the old brewery.

Apologies for the quality of photos, lighting along with a royally buggered phone hinders my photography skills.

Hey,

Welcome to the show. Jody has a video on sanitary tube welding, where he cuts a cross into the tape. This helps the gas escape better as everything gets hot.

Also I know a few ss pipe welders who swear by volume of gas, and some even use a oxygen regulator to allow the the extra flow the require.

Mick

You may not be filling the pipe with argon. And I agree, look up some of Jody's videos on ss and I'm sure it will help alot.

Small diameter pipe like that need only 3-5 l/min minute in root. Otherwise you get too much pressure. Also stag only 3 or 4 holes at the other end with tungsten for example. Theres is no need for more.

Check your root gas hose and regulators fittings for leaks. Also make sure you are using gas hose and not just anykind of hose. Inpurities will go through even a decent gas hose. Air pressure hose is not acceptable for example!

Wait long enough before welding. Usually it takes several minutes to purge 51 mm pipe. It's also good to keep in mind that argon is heavier than air. So you want to keep argon in the bottom of the pipe and fill the pipe like you would fill glass with water.

Never use tape near welded area! Heat will boil tape's glue and all that smoke will end up inside your pipe and ruin your root. Aluminium foil help alot when tape can't be used.

On austenitic stainless small amount of hydrogen helps a lot to burn the last oxygen away. Plain argon is quite poor root gas to be honest.

I strongly recommend you to first check gas leaks and change your hose, if it's not decent gas hose. Too many welds have been ruined because wrong hoses and or leaks.

Almost forget. Clean welded area with IPA or acetone. If pipe is in bad condition it needs to cleaned with flap wheel too and then with ipa....

Cheers guys for the tips.

Yeah I have seen the videos on this site. Only it seems to be on my wider OD pipe. I'm only using 1" where using tape has been of limited use.

Markus wrote:Almost forget. Clean welded area with IPA or acetone. If pipe is in bad condition it needs to cleaned with flap wheel too and then with ipa....

Great idea.. am going to grab some foil and take that in to work. Will try this today and report back.

Thanks again.

..Forgot to ask.. is everything else OK though in terms of parameters - amperage etc?

I think your amps are fine. Honestly there is no right parameters, it all depends travel speed, angle, height of tungsten and even batch of the alloy. I would use a bit faster pulse. My personal favorite at the moment on thin walled stainless pipes:

50 amps / 0.10 sec (upper)
25 amps / 0.30sec (lower)

Does work great with orbital too

Btw make sure you have a tight fit. Otherwise oxygen slips through the gap between pipes.

With 1.6mm wall I'd run about 45-48amps making nice small circles as you run the bead. (Depends on your travel speed however) The fit has to be very tight, flat and free of all debris. No filler should be used...

I agree with others as it seems your purge gas or purge setup is letting you down to have issues like your seeing.

Do you have a picture of your purge setup?

Also try to avoid "misalingment". What you guys call that btw?
Those cause easily penetration problems when difference between pipes are more than 0.20 mm.