Tips Tack weld with TIG DC

[zaraomega]

Hello to all!

I'm a student, beginners with the welding techniques.

I'm using a TIG DC welding gun on which you can set amperage and time parameters.

I need to link two plates 3mm thick of inconel (austenitic nickel-chromium-based superalloys) in flat position with tips tack weld without filler metal.

Can you give me an advice on how to get started and which are the parameters recommended for this problem?

Thank you in advance, I really need your help!

Zara

 

[zaraomega]

up

 

[Boss]

Wouldn't need a pulse to tack something would you?

 

[BrokenBiker]

Just set around 120 amps, light up where want the tack, wait for it to puddle and back off

 

[Liquid Metal]

I would be careful doing anything autogenous with Inconel or any other nickel/chromium alloys, as you can destroy the properties of them through heat input. Your better of using a tiny dab of filler I would always say.

 

[Lawnmowerboy]

Liquid metal is right. You are quite prone to shrinking and cracking welding inconel without filler.

 

[zaraomega]

Thank you all for the answers!

I would have more questions:

1. How many degrees I have to tilt the tourch respect the plan?
2. How many millimeters have to carry out the tungsten electrode?
3. How far should I place the electrode tip from the panel to be welded?

Thank you very much again!

 

[BrokenBiker]

Thank you all for the answers!

I would have more questions:

1. How many degrees I have to tilt the tourch respect the plan?
2. How many millimeters have to carry out the tungsten electrode?
3. How far should I place the electrode tip from the panel to be welded?

Thank you very much again!

to be honest if you don't know these things i would suggest you practice first on a less important price of work or scrap

 

[whm_fab]

Thank you all for the answers!

I would have more questions:

1. How many degrees I have to tilt the tourch respect the plan? as close to 90deg as you can realistically get it
2. How many millimeters have to carry out the tungsten electrode? depends on the gas lens/cup you are using ?
3. How far should I place the electrode tip from the panel to be welded? for inconel, try to be as close as possible to prevent excess voltage/heat, around 2mm

Thank you very much again!

make sure for tacking your tungsten is newly ground and perfectly prepped - tacking with a used tungsten is alot harder.

ps, what are you making as a beginner student with 3mm inconel!? that college obviously has alot more $$$ than the one i went to

 

[whm_fab]

to be honest if you don't know these things i would suggest you practice first on a less important price of work or scrap

i was thinking the same, id like to take home his scrap bin

 

[BrokenBiker]

inconel isn't cheap, i cant see why a college would require him to weld it without any knowledge of the process or technique

 

[Liquid Metal]

But then again he may not be at a college, might be an apprenticeship or worked based training scheme?? Anyhow like said, tacking or welding inconel without filler is asking for trouble, it will screw up the metal composition and have a very good chance of cracking.
As far as physically tacking it goes, then follow what WHM FAB has said, although for actually running weld beads I would use a slight push with the torch but still the same re stickout and arclength. Stickout is quite important with inconel due to needing very good gas coverage like with all alloys

 

[zaraomega]

I would have more questions:

1. How many degrees I have to tilt the tourch respect the plan? as close to 90deg as you can realistically get it
2. How many millimeters have to carry out the tungsten electrode? depends on the gas lens/cup you are using ?
3. How far should I place the electrode tip from the panel to be welded? for inconel, try to be as close as possible to prevent excess voltage/heat, around 2mm

make sure for tacking your tungsten is newly ground and perfectly prepped - tacking with a used tungsten is alot harder.

ps, what are you making as a beginner student with 3mm inconel!? that college obviously has alot more $$$ than the one i went to

I've a shielded tig torch like this and the tungsten is ~ 2mm
So, ideally, could I push inside the electrode and use the cup as a support to get the 90 degrees?
In many videos on the internet I saw tilt the torch to make the tack even when there is no filler... maybe I'll be wrong!
Can you explain me the "excess voltage/heat" question?

Thank you so much for the help!

 

[whm_fab]

what you have there by the looks of that photo is pretty much perfect, you could get away with a little bit more stick out perhaps, but not much more without a gas lens (i would HIGHLY recommend you use a gas lens on inconel)

the 90desgrees is just the ideal, in the real wold this never happens, anything up to roughly 25-30deg tilt would be ok, after that you'll get arc wander and undercut.
on the videos you have seen, that was probably stainless, which is perfectly fine to tack with no filler - not with inconel, you will need a small dab of filler as the guys said previously to prevent cracking when cooling

the further you move the tungsten tip away from the workpiece, the voltage increases, the heat increases and again you'll loose control and get undercut. (this is very normal for a beginner to get the distance wander, dont worry!!)

 

[zaraomega]

Unfortunately the photo doesn't help me a lot because in my case I have a butt joint.

Oh! So for the ideal 90° you mean the tourch parallel to the plan right? I understood orthogonal (as in the photo on the left (1))

I need temporary tack, before the weld bead, therefore I do not require a perfect tack!

 

[Liquid Metal]

If you want the material to stay where it is you do want a very good tack. Inconel warps pretty well when welded, plus you will screw the properties.
As WHM Fab has said, the videos you refer to, were they deffinately videos of how to weld inconel??
All the time you are running a bead of weld, the filler wire not only fills any gaps between materials and provides the meatl required to build up the profile of the weld, it also acts as a heat sink. Without this heat sink effect you are requiring that the base metals absorb all of the heat from the molten pool, not just a percentage of it. When welding any nickel alloys such as inconel, monel etc, or duplex, this will screw the properties of the metals within the Heat affected zone and therefore the job may as well have been made with much cheaper materials. Any customer or employer is not going to be happy about that. Also with stainless steels it sometimes screws the corrosion resistance.
Due to the material cooling down to quickly it will more than likely leave a tiny star shaped crack in the centre of the tack if not all the way across the tack, which over time may well spread all the way along the weld.
These materials are a bit more expensive than 304 or 316 to say the least, and any employer or customer is not going to be happy if you are often having welds in Inconel with cracks starting to form or failing NDT and needing reworks. Therefore you are better of getting into the habit of tacking using filler wire.