Thread: tig questions

Yes Tig is a good choice .

If you have previously oxy welded ,tig is very similiar in postion, speed and manipulation. You are just exchanging a flame heat source for an electric one.

I take it your welder is a DC output version,because will require DC Electrode negative connection, let alone a high frequency start unit attachment ,plus you regulator cylinder of suitable argoshield blend and of course a tig torch.

It may well be far cheaper to have the tank welded by a welding works.

Set up properly, with a 3mm outside corner to corner edge prep the tank be set up and welded with the stick with excellent results.
edit :graphic needs to read "tack at 30mm intervals" -not 3m

Grahame

so it would be alright to use 95% argon 5% co2 gas for tig
when i bought my welder it came with a scratch start tig setup
i want to weld it inside and out and i don't want slag in my oil
i had one quoted at $200 to build
included are pics of my welder and tig torch

You will need pure argon for TIG welding.

Argosheild contains oxygen and will burn up your tungsten.

Quite right,
I was not paying attention there.

Grahame

Originally Posted by welder

so it would be alright to use 95% argon 5% co2 gas for tig
when i bought my welder it came with a scratch start tig setup
i want to weld it inside and out and i don't want slag in my oil
i had one quoted at $200 to build
included are pics of my welder and tig torch

The drift of your first post that you were considering an attachment for your welder.You should have mentioned you have the gear up front.It's really a bit misleading.
With what you have, all you need is a cylinder of argon and the appropriate electrode for steel. By the time you rent /fill your argon cylinder theres the best part your $200 gone.

sorry my mistake when i bought welder they got stolen at the auction place so i never used them i was considering buying more when my neighbor sold me a tig set up for
$ 50 very similar to the one pictured sorry for my mistake

Getting back to your tank set up.If you have the elements of a tig unit,all you need is some argon(yeah! not argoshield god whats wrong with me!!!) and you are good to go.Thoriated tungstens where in use but I think there has been a substitute for them as there is a heath scare on thoria these days.. Taper them like a pencil from a pencil sharper ie 2-3 diameter

Set the plate edges touching cnr to cnr is the preferred joint configuration. Try the following on some scrap sections first.

Use a mild steel filler wire,not the high tensile stuff as one has a different co efficient of expansion/contraction to the other.The reason behind this is that there is big time distortion caused in thin plate by using the wrong wire.
Clean up the wire with steel wool before use if there is any rust on it.
If 3mm plate use at least 2,6mm diameter filler wire.

Frequent tacking say every 30mm and spreading the heat by laying down a shortish bead and moving off to a location on the oppositte side of the tank is the procedure to further minimise distortion.

Make sure your sheet plate is as clean as you can make it,
Tig has no fluxing so any impurities in/on the plate are going to absorbed into the weld bead. I would suggest a buff up with a flap wheel on an angle grinder on the flats and edges at the weld joint.

Finally, its basic stuff like avoiding a breeze that will blow your sheilding gas away. If you have not at least oxy welded before,get some practice up on some scrap.It takes a bt of parcatice to "walk the wire" through your fingers to feed it into the weld pool. Remember to not withdraw the end of the hot wire too far out of the "gas cover cover zone" when dipping it into the molten arc pool. Pull it too far back and you will oxidise the wire end and then introduce oxidisation into the weld pool next time you dip the wire end.



Remember ,the molten weld pool melts & fuses the filler to the parent plate
An old rule of thumb is 1 amp per thou of thickness. That would run out at 120 amps being 40 thou per mm. Start at that figure but be prepared to drop it back a little as the work heats up

Post some pics for some feed back if you want to. I AM BOUND TO HAVE FORGOtTEN SOMETHING, so if anyone notices any ommissions ,please chip in.

Its all I can think of for now , I need to get to work.

Grahame

i have not bought the electrodes yet but i notice they are around 175 mm long do you have to shorten them to fit in the torch

Tig electrodes can be shortened by grinding a circumfrential groove in them at that spot,that you need to shorten them.It is a simple matter to them snap them at that point.They should be covered by a rag to avoid any fragments flying into one's eyes

They are color coded , so it it helps if you can remember to preserve the color code in the length and make your cut where you will re grind them to a point.

Sharpening them can be done chemically or by grinding on a dedicated wheel to prevent contamination.

The chemical paste is cheaper than a good quality wheel in most cases.The method is to heat the tip to red heat and dip into the paste.The electode is plunged repeatedly in and out and self sharpens.

Grahame

one last thing what size electrode do you recommend

Tungsten Electrode Diameter:

1.6 mm

Dinosauars like me used 2% thoriated tungsten (red band) prepared with a pointed end. Today more people are switching to 2% ceriated or 1.5% lanthanum due to their superior performance in most applications

Torch Cup Orifice Diameter:

6.4 - 9.5 mm

Filler Metal Diameter:

2.4 mm

Take your torch with you so the weld shop can match the type of collet which you need for each diameter of tungsten.

Not all torches have the same type of collet.

Lets us all know how you fared.ok!

Good luck.


Grahame

This is an interesting thread. I have a scratch TIG torch exactly like the one pictured previously. I am running it on a CIGWELD 140 Inverter.

The problem I have is getting the thing started. It's infuriating how often i get the elecrode stuck to the metal as I am trying to get the arc started. When it sticks, it really sticks hard, so you're tugging away madly with the elecrode bending and the damn piece you are fabricating getting knocked around.

Most TIG tutorials on the web and Youtube have a footpedal, which my setup doesnt have.

Any tips on how to get a nice arc going with an inverter?

Also, for a relatively low amp setup like an inverter, what shade filter do I need.?

It looks pretty bright through my Speedglas auto helmet, and seems to trick the sensor into not working all the time for some reason. I have a older flip helmet with a darker shade, but that makes it even harder to get the arc going, as you are feeling around in the dark.

I suggest the use of a copper plate to scratch start with. Scratch, as in striking a match.

Bang it on its end and it will likely break off the point and stick.

The footpedal in DIY applications is basically a yank thing. Most Diy units here do not use them.

There's a few out in industry, but I fear we are falling into a mindset when we read on web pages about them used in the US Diy set ups and automatically some of us believe that we can’t do without one.

95% of us do not need a foot pedal. We can manage with out variable amps for stick and mig processes don't we, why not tig?

With some auto darkening shields there are issues with the frequencies generated by the inverter machine. This focuses at around the lower amperages commonly used in tigs.
As far as brightness goes unless you have a variable adjustment helmet, I guess your stuck with it.

Tig on lower amperages emits far less light so it should be less of a problem. Is the problem in the semantics - is the shield lens switching on /off rapidly at that point on striking the arc? The brightness occurs at that point when the shield has not darkened. That’s to do the speed of switching not the brightness control

My much lower quality Techmen does that at 30 amps and less .Once I establish the arc and hold it ,all seems ok.

Here is a link to the Miller WebPages re tig problems.

http://www.millerwelds.com/pdf/gtawbook.pdf

Grahame

Thanks Grahame

Do you mean to use a piece of copper as a scratch plate to warm up the electrode, same as you may do for a arc electrode? Just by scratching it along a few times before moving onto the workpiece?