|How it works
- Machine strikes arc between the work and a non-consumable tungsten electrode, melting a pool of metal
- Filler wire is added manually while moving the torch forming a weld bead that joins the metals
- Gas shields the weld pool and the tungsten from air exposure
- Earth clamp provides return path
|Basic process details
- Gas shroud
- Back cap
- Power control
- Base unit
- Power source (we'll get into settings later)
- Power, Control and Gas lines
- Gas connection
- Power feed on the back, mention the limits imposed by 13A connection
- Gas bottle
- Type of gas and why
- Basic safety for the Albee bottles
|Covering what all the parts are called and do
|Preparing to weld (continued)
- Clean up weld area
- The complete lack of fluxing action from Argon means TIG is a lot pickier about cleanliness than any other welding technique
- The weld zone must be immaculately clean
- Cleaning the weld with solvents
- Acetone is recommended, pure alcohols like IsoPropanol or Methanol will generally work, Meths or white spirit will not.
- NEVER Chlorinated solvents like brake cleaner (Phosgene risk)
- Remove all solvents and cloths when done because of fire risk
- Avoid even touching the weld zone once it's clean
- Clean area for earth clamp
|Proper preparation is necessary for good welds
|Setting up the welder
Start at the tip of the torch and work back....
- Types and their suitability
- 2% Thoriated (Red Tip) - DC Welding on steels only, radiation danger
- 1.5% Lanthanated (Gold Tip) - DC Welding, Good on copper/brass/nickle/titanium/high-alloy stainless
- 2% Lanthanated (Blue Tip) - Universal, can be used on all metals and polarities, recommended for normal use
- 2% Ceriated (Grey Tip) - DC use on thin materials, excellent arc stability at low powers
- Others are available for special job but these should cover 99.9% of welds
- Selecting a suitable diameter (diameter 50%-100% of work-piece thickness, checking chart on welder)
- Grinding a suitable point, 30 degree point, blunted tip if running higher currents
- Picking a suitable collet and collet body and fitting them
- All fittings on the torch are hand-tight only, no tools allowed
- Picking a gas cup from the table on the welder and fitting it, what the cup numbers mean
- Using a suitable back cap, access and clearance issues, silicone grease is needed
- Setting stick-out
- Power button on torch
- Option of using pedal control later but for now stick to the button
- Set power dial to 10 and don't try to adjust while welding
- Checking correct polarity, making sure earth lead is connected to work
- Check tightness of connectors
- Plug in welder but don't turn on yet. Directly plug in, never use extension leads
- Connecting cylinder
- Setting suitable gas flow rate using both bottles using the table on the welder, but consider situation of weld
Suitable setup and settings for executing the weld
|Configuring the welder
- Mode Settings around the outside
- AC or DC
- Steel and stainless steel are done DC electrode negative (Straight polarity)
- Aluminium and other metals with refractory oxides are done AC, that is not covered in level-1 induction
- DC electrode positive is a thing, but only very rare situations call for it
- Pulse mode
- Useful sometimes but details not covered in level-1, leave this turned off
- Purge - Used to clear air from the lines
- Power and overheat lights - Duty cycle, 100%@90A, 60%@115A, 20%@200A but max is about 120A on 13A plug
- Lift-TIG - Hard to use, not covered at level-1, only useful if sensitive electronics are nearby
- HF-TIG - Standard mode, use this
- Stick - See TIG Welder (Stick mode) Induction, beware that going into stick mode - even momentarily - will cause the electrode to become live at up to 90V with no control from the trigger
- 2T - Press and hold to weld, we'll be using this mode
- 4T - Press and release to start, press and release to stop, good for long welds but has more parameters to set and harder to use, not covered in level-1
- Parameters set using the middle section. We're using DC (Electrode negative), no pulse, HF-TIG in 2T mode. Back and Forward controls step through the parameters that are relevant to the selected mode
- Using the chart on top of the welder to pick settings
- Do not attempt to reduce settings very much to make things easier. Small current reductions may sometimes be needed but if you try to slow down too much the weld will turn to shit and heat affected zone will be huge because you'll be going so slow. You just have to learn to keep up with proper settings.
- If the chart isn't helping then use the following guidelines. Use all the %age changes that apply to your work, e.g. if you're doing an outside corner on stainless steel then apply both -%10 current for Stainless and -10% current for outside corner for a total of -20% change to current and +45% gas
|Basic Current & Gas
||40A/mm of material thickness
||1L/min per cup number
||-20% Gas flow
||+25% Gas flow
||+20% Gas flow
- Preflow - Time in seconds, is used to establish coverage of shield gas before the arc is ignited. How much to use will depend a little on what you're doing but 0.5-1.0 seconds is usually reasonable for steel
- Hot Start - This is an extra very short pulse of current used to help establish the arc, this is IN ADDITION to the base current, so you don't need very much, 5A-20A is normal
- Base Current - This is the normal weld current that will be used for the entire weld, check the chart for an initial reasonable setting for your job. Think carefully about this one, it's your biggest factor controlling heat buildup in the weld. If you go too high the weld will overheat, but it'll ALSO overheat if you go too low because you'll have to slow down too much.
- Downslope - This is how long the welder spends backing the current own gently at the end of the weld, values around 0.5-0.7 seconds are typical for steel but if you're getting "crater" at the end of the weld then a longer period may help. Note that this gentle back-down occurring AFTER the trigger is released means you can't pull away from the weld right away, you have to stay close and let it happen.
- Post-Flow - This is how long the gas stays running after the arc has stopped in order to keep the weld and especially the tungsten shielded as they cool down. It will depend on how large your weld is, huge welds might need as much as 15 seconds, a small weld with a small electrode might only need 3 seconds. We'll be using 5 seconds as a middle-of-the-road setting but you might need considerably longer on stainless steel. You must keep the torch pointed at the weld throughout the post-flow period and also note that if you press the trigger again during post-flow the arc will re-ignite instantly!
|How to set the arc parameters
- Overalls are required for UV protection
- We have special TIG gloves that are much lighter and less stiff than normal welding gloves which can be used because TIG doesn't generate very much radiant heat or spatter. These gloves are made of goatskin or pigskin and are specifically reserved for TIG welding and must not be used for anything else
- Depending on the welding current you may want to use shade 9-12 on the welding helmet. All settings will save your vision, you're just adjusting for best visibility. If you're used to MIG/MMA then go one setting darker than you normally would for this current. Make sure the mask is clean, dirty lenses will make this a lot harder than it needs to be.
- You may see people online welding without overalls or even without gloves. They can get away with this because of the low-spatter nature of TIG welding. DO NOT DO THIS - They are probably wearing SPF-1000 sunblock and have developed a tolerance over years, they'll still probably wind up getting skin cancer from it! Cover all exposed skin at all times while welding.
|Using the right PPE for TIG welding
|How to actually execute a weld
- Proper position of self
- TIG can be used in all standard positions, but over-head is rare and difficult as there's a tendency for the puddle to fall out onto you.
- Holding TIG torch in your dominant hand and the filler rod in the other hand
- Getting a comfortable position, sitting down if possible
- Lead can be draped over your shoulder if you find that helps to keep the load off the torch
- Checking the position remains comfortable throughout the range of motion needed for the weld you're about to do
- TIG requires precise, steady movement, so it's very important to be comfortable and able to move freely while doing it.
- Proper position of torch, direction of motion
- Ideally we'd hold the torch perfectly vertical but if we did that we wouldn't be able to see what we were doing or feed in filler rod, so we normally use a push angle of 10-30 degrees. More perpendicular torch position will usually result in a better weld but consider your movement, access, and vision, angles 45 degrees or more WILL NOT WORK PROPERLY.
- Pull welding with TIG is not a thing, don't try it, but it is sometimes possible to back-track a very short distance (no more than the puddle width) in order to move the puddle around and get full fusion.
- Correct distance of the tip is only 1x-2x the diameter of the electrode you're using, and needs to be maintained very steadily. Maintaining this distance properly is the single most challenging thing about learning to TIG weld and will have the biggest effect on your weld quality
- The tip must never touch the weld or the filler rod, in fact it should never touch anything if you can help it! Even the slightest contact will require you to re-grind the electrode. With Steel this isn't too bad as you'll only loose the small section that touched, with other metals you may wind up having to grind away as much as 10mm of the electrode to restore proper operation.
- How the pool forms under the electrode, angle of the arc and how it directs the pool
- Taking the pool "for a walk"
- Moving patterns, circles, arc, steady, stepped
- TIG welding is nearly silent when done correctly, the proper sound is a very faint hiss or buzz when using DC, and a slightly louder humm or whine when using AC or pulse mode, there should be none of the popping or crackling sound associated with other welding techniques. There should be practically no sparks or spatter, if you're seeing any of them at all, you've not cleaned the work well enough.
- What I'm going to do now is to demonstrate how the TIG welder forms and moves a weld puddle, I won't be adding in any filler rod at all to keep things simple. This is usually called "reflow" welding and is the easiest TIG technique.
- [Demonstrate walking a puddle along a bit of thick material]
|Cover the basic technique of establishing and moving a weld bead
These are some of the problems you might find when welding [Deliberately set up and demonstrate each of these faults]
|Bad gas coverage
||Weld shows porosity or brown discolouration, maybe spatter if extremely bad
||Gas flow too low won't shield the weld well enough, gas flow much too high will entrain air.
||Puddle takes a very long time to form if at all, penetration very poor
||Current too low is inputting insufficient heat into the base metal to form a proper weld pool
||Puddle is over-sized, heat affected zone very large, electrode starts to ball up at the tip, penetration excessive
||Too much current is resulting in excessive heat input into the work and over-heating the electrode causing the tip to melt.
|Arc too long
||Puddle is slow forming, arc sounds/looks like a flame, heat zone very large
||Having the arc too far away is causing the voltage to go too high and meaning the heat is spread over too wide an area
|Arc too short
||Puddle is tiny, pool rises up to touch electrode
||Having the arc too short focuses the heat onto too small an area which will make it hard to join workpeices, the short arc causes the pool to actually dome upwards and move towards the electrode. When the tip touches if it gets stick don't try to break it free, stop, let it cool, take the tungsten out of the torch then snap it off the work
|Angle too steep
||Large flame-like arc, elongated puddle, difficulty controlling filler rod
||The steep angle causes the arc to spread out sideways and fail to remain directly under the point of the electrode, the heat spreads too far down-weld of the torch changing the puddle shape and the plasma jet tends to melt filler rods before they can get to the pool.
||Weld surface is grainy/porous, pool moves erratically
||Contaminants that were not removed from the weld area prior to welding have got into the weld and disrupted the chemistry of the pool which messes up fusion into the base material.
|Travel too slow
||Heat affected zone very large, penetration excessive
||Slow movement allows excessive heat build-up within the material which causes the weld puddle to sink into the material and "overcooks" the metal giving a poor surface finish
|Travel too fast
||Gaps/thin spots in bead
||Fast movement has pulled the bead forward faster than the welder could melt the material
||Recognising faults and knowing how to fix them
|Practising a steady bead
||Inductee practices moving the puddle on flat stock till competent (may take a lot of time and re-grinding)
||Getting the basics right
|Laying a bead using filler
- Next step is laying down a bead but adding filler
- Selecting a suitable filler rod.
- Material must be compatible with the base material(s) - Note that this does not mean it always needs to be the same as the base material, just compatible
- Rod size is usually the closest size available to the electrode diameter
- Too small will result in stupidly high feed in rates and hard to control
- Too large may tend to "freeze" the puddle when introduced
- Taking care of who might get hit with the filler rod, turning over the end
- Holding the filler rod properly
- Technique for feeding the filler rod through your hand
- Holding the tip of the filler rod near the puddle so that it's shielded, but not so close it melts
- Dipping the tip of the filler rod into the nose of the puddle and quickly back out again
- The puddle will rise every time you dip the rod so be careful it doesn't touch the electrode
- May be helpful to use stepped movements on the electrode
[Demonstrate laying a bead along a bit of thick material]
[Demonstrate too little and too much filler]
[Inductee practices laying a filler bead]
|Laying a bead while using filler
[Coupons used must be 2mm thick steel, thinner makes this too hard for inductions]
- Can be done with (conventional) or without (re-flow) filler
- Proper grinding and prep
- Bevels right way up and properly spaced
- No bevels if re-flow welding
- Proper fit-up between parts
- Option of using backing blocks (temporary and permanent)
- Using holding magnets and clamps
- Do NOT tack work to the table
- Tacking to limit distortion, you are GOING to get distortion
- Straight, back-tack and half-split tack welding
- TIG welding doesn't normally use multi-pass approaches
[Demonstration and practice till successful]
|Executing the most basic weld
[Coupons used must be 2mm thick steel, thinner makes this too hard for inductions]
- Don't need to grind, but parts need to be clean
- Good fit-up essential
- Less gas needed for internal fillets, more than usual gas needed for external
- Proper torch position and angles
- Biased towards the vertical plate
- Weaving pattern, spending more time on upper plate
- Option to "walk the cup"
- Watching our for under-cutting and how to deal with it.
- Stitch and alternating stitch to control distortion
- Pre-compensation for distortion
[Demonstration and practice till successful]
|Second most common weld type
[Talk about but don't demonstrate this type]
- Lack of need for grinding but must still be cleaned
- Treat it as two fillet joints
- But watch out for heat buildup in the edges and undercutting
- Extra care if the sheet is thin to watch for balling up
- Alternating stitch welds to control distortion
|Next joint type
|Shutting down and cleaning up
- TIG welds often don't need grinding back, just a wire brushing may be enough
- Shutting off and purging the gas before un-hooking the couplings
- When you're done shut off the power to the welder
- Put any half-used filler rods back, they can be re-used
- Leave the tungsten in the torch if it's condition is still good
- Sweeping up and putting everything back where it belongs
- Working out your total weld length and paying for it
|Clean up after yourself and pay what you owe!
- This has only been an extremely brief over-view of TIG welding
- Do not expect your joints to be structurally sound until you have practiced a lot
- If you want to weld aluminium or magnesium alloys, TIG-Braze or other techniques then you're welcome to come back for level-2 induction although it's not at all compulsory if you think you can manage these techniques without
- If you want further tuition then some members of rLab are willing to provide this, but they may charge for it.