What's the specialty of TIG welding

Thread Starter

Autobike

Joined Feb 23, 2018
54
Hello. recently i had to take an aluminum alloy motorcycle part to a welding shop. that part was cracked and i needed to get it repaired. the shop where i brought it said that they can't weld it since they have only an arc welding facility. if they do, it would melt the workpiece. so i brought it to another place and they did a perfect job. they used TIG welding for that. i have a very basic knowledge in Arc, TIG and MIG welding methods. i have a few questions,

1) What is the main reason behind using TIG welding to weld aluminum alloys? is that the heat where it generates very low heat (just a guess) so the aluminum won't melt ? as we know an aluminum alloy has a low melting point compared to steel. did a bit of research and it seems that it needs more heat to cope with the aluminum oxide. but how TIG manages it without melting the workpiece?

2) the welder took one thick wire from the welding machine which had a big crocodile clip at the end and connected it to the workpiece before the welding process begins. so i guess it was the negative or positive side of the circuit. got to know that they use a low voltage and high current for welding. he was wearing rubber gloves and rubber shoes. do they do it for safety ? i mean can the arc goes through our body and harm us. apparently the welder was not a part of that circuit.

thank you very much :)
 

MaxHeadRoom

Joined Jul 18, 2013
19,014
TIG uses a non-disposable tungsten electrode to strike the arc, initially about 70v, dropping when the arc is struck to around half, then a filler rod is used. The Helium-Argon shield gas is one of the secrets to weld aluminum.
Max.
 

Tonyr1084

Joined Sep 24, 2015
3,577
WARNING - NOT AN EXPERT ON THIS SUBJECT: However, I do know that TIG (Tungsten Inert Gas) welding temperature is controlled with a foot pedal. The gas is there to replace oxygen and thus prevent oxidation of the weld. When welding steel the welder works with a bright molten puddle of steel. The eddy currents mix the metals together and thus "Weld" the joint. With Aluminum, since it has a lower melting point AND you don't work with a bright molten puddle, TIG welding allows the welder to create a small puddle and work it around using the eddy currents to bond the metals. TIG is a little slower but much more controllable than MIG or Stick welding. With MIG and Stick, you pre-set the machine to produce a certain amount of heat. With MIG you set the feed rate as well. MIG uses an Inert Gas as well as does TIG but Stick uses the flux that is on the wire itself. All these methods are intended to remove oxygen from the molten puddle. But temperature control is in part a function of how far you draw the arc ("Stick-out") and how fast you move.

Because of aluminum's low melting temperature TIG is the best way to go because it's way too easy to blow through the metal with MIG or Stick.

As for the rubber gloves and boots - I can't answer that. I can only offer conjecture: It may be the welder power supply doesn't use a transformer. If using Pulsed MIG or TIG, pulsed directly from mains then perhaps rubber gloves and boots is a precaution against an inadvertent failure of the machine and thus protect the welder from being exposed to potentially lethal voltages. Again, this is conjecture.
 

MaxHeadRoom

Joined Jul 18, 2013
19,014
One of the main differences between MIG and TIG is the former uses a disposable electrode, usually shielded by CO2.
The latter as previously explained.
Gloves and work boots are mainly as heat/spark protection etc.
Max.
 

jpanhalt

Joined Jan 18, 2008
7,876
Aluminum can be welded by more than just TIG. In fact, MIG is probably more common for heavy duty welding, like truck trailer bodies. Aluminum filler wire is softer than steel, so it does not push easily though a MIG cable like steel does. Spool on gun MIG avoids that problem.

As for TIG (my favorite welding mode), with foot or hand control, you have excellent control of heat. I find TIG welding very relaxing as you can work the puddle to get full thickness easily, and weld visibility is better than with MIG. I repaired a battery box made with 0.016/0.020 aluminum using TIG, and I am far from being good at it.
 

Thread Starter

Autobike

Joined Feb 23, 2018
54
thank you. read both articles. specially the 2nd one is very informative and clear.

TIG uses a non-disposable tungsten electrode to strike the arc, initially about 70v, dropping when the arc is struck to around half, then a filler rod is used. The Helium-Argon shield gas is one of the secrets to weld aluminum.
Max.
thank you.

WARNING - NOT AN EXPERT ON THIS SUBJECT: However, I do know that TIG (Tungsten Inert Gas) welding temperature is controlled with a foot pedal. The gas is there to replace oxygen and thus prevent oxidation of the weld. When welding steel the welder works with a bright molten puddle of steel. The eddy currents mix the metals together and thus "Weld" the joint. With Aluminum, since it has a lower melting point AND you don't work with a bright molten puddle, TIG welding allows the welder to create a small puddle and work it around using the eddy currents to bond the metals. TIG is a little slower but much more controllable than MIG or Stick welding. With MIG and Stick, you pre-set the machine to produce a certain amount of heat. With MIG you set the feed rate as well. MIG uses an Inert Gas as well as does TIG but Stick uses the flux that is on the wire itself. All these methods are intended to remove oxygen from the molten puddle. But temperature control is in part a function of how far you draw the arc ("Stick-out") and how fast you move.
Because of aluminum's low melting temperature TIG is the best way to go because it's way too easy to blow through the metal with MIG or Stick.
As for the rubber gloves and boots - I can't answer that. I can only offer conjecture: It may be the welder power supply doesn't use a transformer. If using Pulsed MIG or TIG, pulsed directly from mains then perhaps rubber gloves and boots is a precaution against an inadvertent failure of the machine and thus protect the welder from being exposed to potentially lethal voltages. Again, this is conjecture.
thank you. as you said they don't use stick to weld motorcycle gas tanks. i think it would blow through the metal surface since tank metal is very thin. i've seen that they used kind of gas welding method for that. so it seems that the secret is the foot pedal which controls the heat. the welder i was talking about used the foot pedal too. what i noticed was when he pressed it, it gave a thud sound and simultaneously created the arc. saw this video and got the idea. thx again

One of the main differences between MIG and TIG is the former uses a disposable electrode, usually shielded by CO2.
The latter as previously explained.
Gloves and work boots are mainly as heat/spark protection etc.
Max.
thank you. got it :)

Hello,
Here I found some books on welding:
https://the-eye.eu/public/murdercube.com/Workshop/Welding/
Bertus
thx a lot.

Aluminum can be welded by more than just TIG. In fact, MIG is probably more common for heavy duty welding, like truck trailer bodies. Aluminum filler wire is softer than steel, so it does not push easily though a MIG cable like steel does. Spool on gun MIG avoids that problem.
As for TIG (my favorite welding mode), with foot or hand control, you have excellent control of heat. I find TIG welding very relaxing as you can work the puddle to get full thickness easily, and weld visibility is better than with MIG. I repaired a battery box made with 0.016/0.020 aluminum using TIG, and I am far from being good at it.
thx a lot. the welder i was talking about used the foot pedal too. does it control the current which creates heat ? does it work like the gas pedal of a car. like when we press it gradually the heat increases gradually ? or is it like a regular ON/OFF switch ?
so i think TIG is good for aluminum since it uses an inert gas which easily prevents the oxidation. other thing is the welder has more control over the heat. so he can weld something thin or something which has a low melting point. thx again.
 

Thread Starter

Autobike

Joined Feb 23, 2018
54
@Autobike
Yes, the foot control allows one to vary the current. It is not just on/off . My welder happens to be a Miller from about 1983. Here's a link to the Miller site (https://www.millerwelds.com/equipment/welders/tig-gtaw ).
thank you now i got it. miller seems to be making some robust welding machines :rolleyes: actually i thought that this TIG method is a new method invented recently. but according to the haynes manual posted by @bertus it was invented in 1940s. that's interesting :)
 

oz93666

Joined Sep 7, 2010
668
One big advantage of TIG , particularly for the job you had , is that it's an electrical welding system that does not have to add more metal .

With stick of MIG welding you have to add more metal , otherwise you cannot weld .. If you have a fine crack you do not want to add more material , and TIG can just heat and melt the cracked region.
 

Thread Starter

Autobike

Joined Feb 23, 2018
54
One big advantage of TIG , particularly for the job you had , is that it's an electrical welding system that does not have to add more metal .
With stick of MIG welding you have to add more metal , otherwise you cannot weld .. If you have a fine crack you do not want to add more material , and TIG can just heat and melt the cracked region.
thank you. yea actually in my particularly job the crack was very bad. so the welder had to break that part and then fill it with the metal. then he used the grinder and made it identical to the original part. he used a filler wire/rod to fill it. it was a shiny silver color one. just like aluminum.
he said that he can weld it without filling but it wouldn't make a convincing weld. so he recommended the filling method. for a fine crack it will definitely work :)
 
I think the foot pedal is mandatory for TIG aluminum welding, but not all TIG machines have it. I had a stick in my hand once, a TIG welder once and a MIG welder once. Since everything was set up to weld, I did an excellent job on my first try. The auto-darkening helmets made a big difference.

What I did with the stick welder, I can't remember. it was like 40 years ago in my teens. The MIG and TIG weld were butt joints in steel. One was 1/4" flat stock and the other was 1/8" angle.
 

Thread Starter

Autobike

Joined Feb 23, 2018
54
I think the foot pedal is mandatory for TIG aluminum welding, but not all TIG machines have it. I had a stick in my hand once, a TIG welder once and a MIG welder once. Since everything was set up to weld, I did an excellent job on my first try. The auto-darkening helmets made a big difference.

What I did with the stick welder, I can't remember. it was like 40 years ago in my teens. The MIG and TIG weld were butt joints in steel. One was 1/4" flat stock and the other was 1/8" angle.
thank you.
 

Wolframore

Joined Jan 21, 2019
1,253
I’m am not an expert but have been MIG welding for year and have been wanting an AC TIG for a while. For aluminum welding a TIG welder is recommended but it is possible to use MIG using a spool gun. A spool gun is used to bypass the normal wire through the lines which gets kinked up. TIG welders designed for aluminum also has an AC output because the positive cycles has a cleaning effect. Aluminum will have oxides and the positive cycle breaks this up while the negative cycles provides heat and penetration. This was first introduced in the Miller Syncrowave. The adjustment between the negative and positive cycles provides a balance between heat and electrode life as the positive cycles can damage the electrode.
 

Thread Starter

Autobike

Joined Feb 23, 2018
54
I’m am not an expert but have been MIG welding for year and have been wanting an AC TIG for a while. For aluminum welding a TIG welder is recommended but it is possible to use MIG using a spool gun. A spool gun is used to bypass the normal wire through the lines which gets kinked up. TIG welders designed for aluminum also has an AC output because the positive cycles has a cleaning effect. Aluminum will have oxides and the positive cycle breaks this up while the negative cycles provides heat and penetration. This was first introduced in the Miller Syncrowave. The adjustment between the negative and positive cycles provides a balance between heat and electrode life as the positive cycles can damage the electrode.
thank you for the information :)
 

shortbus

Joined Sep 30, 2009
6,976
what i noticed was when he pressed it, it gave a thud sound and simultaneously created the arc. saw
The "thunk" was probably the solenoids and relays. It uses a solenoid valve to control the gas flow and a relay to turn on the electric to the electrode. At least in the older models the used relays probably a solid state relay in newer machines. Some of the older machines I welded with also made a "thunk" in the transformer core, when the high amperage of the electrode started over the years of use the lamination's start to vibrate..
 

Thread Starter

Autobike

Joined Feb 23, 2018
54
The "thunk" was probably the solenoids and relays. It uses a solenoid valve to control the gas flow and a relay to turn on the electric to the electrode. At least in the older models the used relays probably a solid state relay in newer machines. Some of the older machines I welded with also made a "thunk" in the transformer core, when the high amperage of the electrode started over the years of use the lamination's start to vibrate..
thank you. yea the sound came from the welding machine.
 
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