Glen-L.com

I've started a new thread to avoid hijacking others' about welding aluminum. This post is about the various aspects of welding aluminum using the pulsed TIG power supplies now on the market. I only have one of these, the Miller Dynasty so I can't do a comparison with other types of welders. This power supply is expensive and requires more than a little experimentation to make full use of the features, however the post is intended to show the possibilities of these new power supplies using semi-automated TIG equipment.

AC TIG welding of aluminum can be done with power supplies built with different levels of technology some of the older 60Hz pure transformer power supplies are still in use and provide a stable reliable weld. Newer power supplies work as inverters where the power is transformed up from 60Hz to hundreds or thousands of Hz then rectified into DC and BACK to AC, instead of just making modifications to the original 60cycle 'wall current'.

These power supplies are usually newer and they have digital control circuits allowing arc control characteristics that were not really available when the previous generations of TIG welding power supplies were made.

For this reason the newer power supplies have controls that allow the welder to adjust the arc cone from the tungsten to the aluminum in ways not formerly possible. Also these newer welders allow the amperage to be surged up and down in a very consistent and preplanned pattern. The result is a 'square wave' where the welding power surges up to some set amperage for a given period of time the drops back to a lower value for a time.

Both the amount of the surge, peak power, and the time of that peak can be set exactly. When the peak time is done the power supplies digital controls will reduce amperage to a lower 'background' amperage which keeps the arc 'lit' but allows the aluminum to cool for a small period of time.

By delivering this cycle of high amperage then low amperage TIG welds can be performed that were formerly not possible for most welders. (me included)



here is a tank of 3/6" material welded using a relatively slow pulse where the surge and travel of the torch are combined to leave a 'row of dimes' type of weld. The square wave timing and the step, pause movement of the torch combine to create distinct puddles or bulges of weld metal in the final weld.

One advantage of the high surge amperage in this type of one sided weld is to allow the weld to keyhole or fuse through the joint for a brief time, then the weld fills in an covers the 'hole' while the low cycle amperage is present.


this weld, while not in the best focus shows the keyhole of a correctly fused set of plate edges. The key hole was left for the photo by stopping the weld before the high peak amperage was dropped to the low and by stopping the wire feed to insure the keyhole was visible.


here to pipe end caps have been welded using a variety of pulse settings to illustrate the effects of the timing of the square wave on the weld's appearance.

the 3" on the right has a series of puddles created with a 1.4 pulses/per/second pps while the side of the left hand 2-1/2" pipe shows a weld done at 80 pps. As the pulse rate increases the welds become more smooth and have less puddle definition between pulses as the time of the pulses is very near the freeze time for each distance of weld travel.

At some settings the welds become smooth without puddle definition

here is another side of the 3" end cap plate weld showing a 156 pps and the resulting finished weld.

However, the gains to the weld integrity have still been realized; that is the high pulse allows a peak surge of power that melts the parent metal but at nearly the same time that high amperage is lowered to chill the metal. The result is the reason these power supplies command such high costs the resulting welds are more controllable as they deliver an 'average' of the high and low amperage.

So, you might say, why bother with the high and low if the average is what is actually deposited? The missing 90% factor in that question is; the way aluminum reacts to amperage surge. Aluminum 'wets' or becomes molten and the oxide is floated to the top, blown away by the hot argon (or mix) and the molten metal's puddle edges fuse during the upsweep in current far better than during the down swing.

This is so critically important that is seems obvious to all AC TIG welders but is not obvious to steel welders or those who only use DC MIG on aluminum. By surging the power in a square wave the weld is performed deeper, at lower net amperage and with more 'control' ( the puddle doesn't fall through) of the shape and final appearance.


here is a coin for scale of this smaller weld between 1/8" and 1/4" bar using these techniques. Even with a relatively heavy section like 1/4" the full fusion weld is in proportion to the metal, not oversized and yet has full fusion in the back weld inside this fillet.

continued

Cheers,

_________________
Kevin Morin

continuing the discussion of why the newer digitally controlled TIG power supplies are so popular with welders.


this outside corner weld between two pieces of 1/8" sheet- is a single pass at a travel speed of about 1.5 to 2.25" per second and the pattern is not caused by the pulse. This weld is pulsed at 126 pps and the pattern is done by a small step pattern with the torch to help with movement uniformity and weld consistency. The finished weld is just over 5/32" wide and varies up to about 3/16". The coin for scale is just to help visualize the small size of this high pulsed weld.


Another weld- this one an inside corner- and the additional arc controls are used to reduce weld width. Miller's Dynasty has a high frequency control that allows up to 250 cycle of AC to be used in the weld, the effect on the weld is to narrow the weld.

here the weld is about 1/8" to 5/32" wide and the travel speed is higher than the outside corner in order to reduce net heat and puddle size. These welds have a very tight tolerance for tungsten to metal in order to further reduce the arc cone and allow the weld to be applied as small as possible.



last look at another inside fillet between two 90 degree adjoining 1/8" sheet on a boat cabin build.

Of course, if you're not welding for work or selling your welding time its not likely anyone is going to spend the cost of these digitally controlled power supplies. What I'm illustrating here is the reason for the costs asked (and paid) for these power supplies. With the controls now incorporated in this generation of power supply for AC TIG welding, welds can be applied that were not possible in the past.

Higher speed travel, due to puddle control and arc controls not formerly offered make for smaller welds, less distortion and therefore more use of TIG welding in the overall metal boat building process.

Cheers,

_________________
Kevin Morin

i have to admit this is the best i have seen on welding aluminum. i learned this as an apprentice and we were doing some rather thick material up to two inches thick. the explinations here are very good. when i taught welding for los angles unified school distric we didn't have the equipment there is today, also when i learned i used a P&H tig machine that was older than dirt to start with, but it sure was a smooth running machine. there are also a few tricks when doing aluminum, in as much as adding a small amount of helium in the mix to increase the arc temperature when doing thicker material so as to reduce the amount of heat being generated by the welder and it increases the working time for the duty cycle.

Kevin,
Nice welds but I really think you need to re check your travel speeds. 2" /min equate to being able to weld a 5' joint in 30 secs. Even 1.5"/min would be a 45sec 5' weld. Not sure that could even be done with mig pulse or spray. The welds are very nice. I perfer the Lincoln machines, but neither one of them are junk. I don't use pulse on aluminum as much as I do on SS, although I do use it if I am welding <.100 material.

Being looking at your welds and I have say top class. I am only learning and you just raised the bar quite a bit. Thanks a lot! Joking aside we are making a ferry fuel tank and you have raised my standards.

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FergusM

Nice work, Kevin. I've found that TIG welding is as relaxing as most other hand-memory tasks, like wood turning. I do a lot of steel TIG but very little Aluminum; therefore I am interested in your postings. Keep them coming. For other, who may be interested, here is a website that has lots of video examples and explanation of the various welding processes.

http://www.weldingtipsandtricks.com/

Have fun.

_________________
Paul Miller in Memphis, TN
"Yeah, I had lunch with him last week at the Cracker Barrel out on I-40."

Gentlemen, I've already posted these image links, I believe but I should add them again to make sure no one thinks I've welded the beads above with a hand torch and dip rod!

That is not really possible. As mcmbuilder notes the travel speeds seem unrealistic but not when you recall the fact I weld with a cold wire feed TIG Gun.



this torch and wire feed system allow aluminum TIG at rates that are 'super human' ; that is -- it would be very hard to dip by hand the speeds I can weld with this wire feed TIG gun.



here the gun is rigged for mild steel but the same gun and tungsten will do aluminum -just change wire- maybe add some helium gas mix if you'd like but in this set up, the gun does the work, I just hold on with both hands.

mcm, the reason I can travel so fast on the smaller beads is that a 3/32 tungsten (pure even with an inverter) and the high pulse and high frequency creates a wetting not possible with a hand torch. I do mean 1.5to 2.25 " per second and I've timed it plenty. I can't move and position for a long weld, I usually stop every 4-6" on the seams shown, but its all I can do to get that puddle to tungsten tolerance and go......

I did mention this is a bit tedious, and I should say that in in context. The context is more than 5k hours looking at an aluminum arc, in other words, "this isn't my first rodeo".
But..... EVEN WITH THE TIG GUN........ without the Dynasty's arc control features this is not possible.

And if anyone wants to consider why Miller would make a power supply with these features? That is; features that won't add considerably to hand TIG? Look at the number of power supplies they sell to robotic welding cells? I will estimate that number is higher, by far, than the number of TIG welding power supplies sold to hand TIG welding shops?

so, the beads, shown above, are possible only by wire fed TIG, they come from arc control(s) that are not obvious to the hand TIG torch method of welding and the features are driven by the need to provide these types of welds to the robotic welding methods.

I provided them to explain to this Forum why so much cost is associated with the newer Miller inverter and digital controlled power supplies and as an example of the types of weld possible by this technology. The welds are so fast and require so much precision that I can only do them for a few seconds at a time and I can only do them because I'm using the wire fed TIG gun shown.

hope this added perspective helps to make sense of my earlier posts?

Cheers,
Kevin Morin

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Kevin Morin

Kevin. I have been welding for 35 yrs, doing so to the some of the highest standards you can imagine. Lots of work in the nukes, hyperbaric work for military applications and the petroleum industry. I have also done considerable work with marine aluminum applications. Been working as a welding instructor and doing consultant work for the last 17yrs. Yet I have never ran across a hand held auto tig gun such as that. That is truely awesome. I did not realize you were using such when I questioned the travel speeds. Very impressive work, even with the auto rig you still have to be able to keep it steady. I have got to find one of those to try!!!!

I am a big fan of pulse weld procedures, but I favor the Lincoln lineup although neither one is junk. Even with traditional tig torch it is amazing the increase qaulity you can acheive with the rigs. I use a Power Mig a lot in the pulse and pulse on pulse modes and acheive near tig quality results with the mig. I understand Miller now has a machine which compares very well to the Lincoln. I build a lot of replacement fuel tanks using 5086 alloys. I use a pulse tig alot especially on .090 and .100 thicknesses. I like the fact I can get a nice "keyhole" going and not really have to worry about the puddle falling out.

Keep posting, I always enjoy your post.

mcm, I use the blue power supply to get the arc control features not offered on the Lincolns but use the Lincoln 350MP for all MIG both steel and aluminum.



here are some pipe caps made into concentric reducers with drains using the TIG gun and 308 wire, very high pulsed DC to get a very fast wetting action and allow the puddle to flow so the positioner welds can be done at higher speeds and completely exclude distortion.



works small too, the drill is 0.065" dia. weld is two pc of 18ga with 0.023" wire 'laid' in the fillet and pulsed over at about 250pps DC and 60% hi, 50% background and 38-40 amps of current. I can't hold wire that small without a TIG pencil and am too slow with one to make this weld without wirefeed.



Mild steel V fillet on rolling base for larger band saw, the flange is an extension for the wheels to bolt on the angle frame base.



closer look at the fillet's resolution at the edges of the mild steel angle and flat bar extension.

I don't expect that most welders will take time to find (one of these out of manufacture) TIG guns, and spend the big $ on a feature laden blue TIG power supply to do welds like this. BUT.... I cannot weld like this without the technology, that includes the gun, the programmable power supply's many arc control features.

What we're exploring is the potential that we all have to weld better, to weld more exactly and to weld with the most appropriate welds possible- by using the newer digitally controlled power supplies. If you happen to have access to a TIG gun, the programmable features of the TIG arc control will allow more precision welds, even to old shaky welders like me.

cheers,

_________________
Kevin Morin

I don't know how much heavier steel you weld but you may be interested in this. Lincoln has developed a pulse mode for doing vertical welds which can be downloaded on the PM350. I sometimes do some contract fab work for a local industry using 3/8 and 1/2" plate. Rather than going to a flux cored wire I use .035 hard wire and the pulse mode with a 90/10 ar/co2 mix I have conducted test to make sure the results are comparable to FCAW and they do meet all the necessary specs. It really simplifies out of position welding a makes great looking totally splatter free welds. If you have a good local Lincoln Rep contact him and see if you will come by and down load it for you.

Kevin; I have to admit that when I first saw these welds , I too was doubtfull . I was certain they were machine welded and wondered why you were posting them, as I couldn't see any relevance to the amateur builder.
Thanks for clearing it up.
I've always felt spending money on good tools when you are tackling a BIG job is always the wise approach and usually the most economical in the long run.
I do know if I tried this the weld would not be straight , but quite wiggly indeed
Fantastic welds indeed.
Doug

Doug, mcm, and other readers,

I use steady rests, hand bases, guides, a wire feed gun, and a programmable power supply to get as good a quality weld as I can. All I care about is the final weld, so whatever I can find to make my steady rest more useful, I use. Whatever I can find to improve the welds, (if I can afford it) I do and everyone who welds can follow the same ideas to get better welds than they might put down if they tried to everything with the older transformer power supplies and pure free cup, free elbow welds.

I didn't just buy the Miller Dynasty 300DX and get these welds. I have spent dozens upon dozens of hours making small adjustments to the various arc controls then making welds in all four positions (flat down, vertical up, overhead and vertical down, and some odd angled or sloped runs too) to see what each control did to the arc in AC or DC and in Aluminum, carbon and Stainless Steel. So I'm also advocating that if you buy an inverter you will only get it to perform at the highest level if you 'know that machine' and that has to come from personal experimentation and practice.....

....but if anyone will take some time to 'tune' their bead, they can get fine, uniform, well formed and strong weld beads from the new inverter type power supplies that are digitally controlled.

When I run the TIG gun I use the back of my left hand -on the gun- as a general guide, that is I'm holding with BOTH hands so steadying is much more easily done. One hand (right) has the pistol grip and trigger and wire speed and amperage controls, the other (left) cups the gun along the front edge of the case and hoses.

Next, if the back of the left hand or forearm is on the work (assuming the work is large enough) then the torch is guided along the work, not being steadied by my arms, but by the guide of the arm/hand/wrist on the work.

So I'm two handed welding, and not 'free hand' or 'free elbow'!

Last, if I can't find a way to 'lock up' on the work, then I rig some sort of steady rest.



Here is an example of the type of temporary steady rest clamping I use made from furniture clamps.



same set up from a different point of view but showing how to set up arm and hand rests to improve weld quality without having to take all day to adjust or assemble a rest.

I also use pipe jacks with pipe or angle between them to work long seams, and I use an electric roll out wheel or positioner to do work that is round if possible.

I realize that many welds are only a few seconds long, maybe a minute at most. BUT... I contend that the weld is going to last a long time, may be the key to safety and reliability and is therefore something that could be called a 'critical path' or weak link in the chain of sound metal fabrication. My experience is that it is worth it to take time to get good equipment, to have prepared yourself to do the weld and that includes steady rests, good position of the body and some practice welds to insure you're as ready as you're going to be to do that weld.

Getting familiar with a power supplies controls, adjusting them to the best they will perform for a given weld and using the most effective means of putting down a 'straight' bead is also critical to good welding.

Shaft struts, engine mounts, tanks, deck hard ware including cleats and all the other metal parts that might be involved in a wooden or composite boat can be made by the home builder. If these parts aren't well made it would be safer for the builder to buy or have others make these parts. But, with the newer digital controlled welding power supplies, just like modern glues and higher grade leveling lasers and other building aides; more and more of the formerly higher end metal fabrication is now within reach of a home builder if they are inclined to buy the equipment and work to learn how to use these power supplies.

cheers,

_________________
Kevin Morin