Al-GMAW summary is correct?

MIG Spray arc aluminum with DC pulse? Is this correct?

I have only done a hundred feet or so of this type of bead. Maybe 200 feet at most. My experience is lacking. I have no broad breadth of experience to draw from. I have a single phase DC MIG welder with a spool gun I have used for this. It does not have pulse capability, but I think some of what I have to add might help. My experience was that I got a fair amount of burn back and tip slagging. I buy bulk import tips for this reason. I just remove them and throw them away.

When trying to dial in the weld I would use all the factory suggested settings and then I would have to increase the wire speed to get decent continuous spray transfer. (nice smooth frying bacon sound) It worked ok, but I overheated the metal and could only make short welds before letting the base metal cool. I could get the job done, but I would have to stitch and fill stacking my starts and stops.

I struggled with correct tip to work piece distance. I always wanted to be closer than I should have been and I often started the arc to close to the work piece. I did two things that helped a little bit. I pulled the hood on my spool gun and shortened the tip holder so it was deeper inside the hood, and rethreaded it so the tip would screw all the way in. I clip the little ball off the end of the wire before EVERY restart. The tip holder mod helped, but it may have contributed to another problem. Even with fairly high (30-35 CFH) recommended flow rate of argon I think I may not have been fully covering the HAZ when welding because the hood was now closer to the weld. I dropped my spool gun some time back and broke the internal tip holder. I have not shortened it again since replacing that part. Instead I try to school myself to maintain the recommended 3/4 inch (19mm) wire stick out. Welds went ok, but I very recently learned two things that may help.

I need to be even further away from the weld on starts. This reduces burn back. About 1 inch (25mm). As soon as the arc is established then move up to 3/5 inch (19mm). The other thing is instead of increasing wire speed I should turn down voltage low enough that the arc cuts out and then slowly increase it until I get a decent continuous spray. This latter should help with heat buildup in the work piece. I will probably still have to stitch and fill. Its not a substitute for pulse for heat management, but it should reduce the heat input a little.

I found no matter what I did when welding 5052 with 5356 I seemed to get a lot of soot. Atleast when I was starting. Two things helped. Getting the stick out distance correct, and adding a mesh inside the hood to make the gas flow more homogenized. I still got soot, but not as bad When welding 6061 with 4043 I was able to get almost, but not quite zero soot.

I feel a little embarrassed sharing my experience with aluminum MIG welding with an experienced pro such as yourself, but you have been helpful to me in the past. I'll risk a little embarrassment if something I can share will be helpful to you.

Yes. Exactly so. You instinctively do this. Even with a good setup, you get to like the smooth seems-easy work, so you still do it to reduce the chance of annoying intrusions in your work flow ever happening.

In that vein... They say have a pocket full of Al contactor-tips (bigger wire hole dia. than for steel) because you'll get through them at some rate. Commercially welding, I've gone like 2 or 3 days on the same contactor-tip. Frequently stopping and "cleaning-out" the tip with oxy-acetylene torch cleaning wires makes that happen. Filing the outer end smooth. On steel contactor tips wear out. On Al they clog in. (?) So you are opening up the orifice in the tip for Al.

You'd have to intervene anyway, changing tips. You like trouble-free welding, so cleaning the shroud and tip frequently is an extra task yes, but you run trouble-free in-between. Valuable if for no other reason that avoiding welder-the-person fatigue. Smoothly working from break to break, pacing the work.

As seems to me...

There is a pulse-on-pulse as I've heard about which gives the "stack-of-dimes" appearance when MIG/GMAW of Ali. TIG appearance with MIG. Never seen in - never met one. Cannot make any comment about

- how it works

- how it's set-up

- the pro's and con's.

- etc.

Both my spray and pulse welds are smooth beads from unmanipulated straight stringer bead progression.

Seen push-pull guns in British Columbia, Canada. Lot of Ali boats and other Ali applications. Some locations had and continued to use spool-guns. Others had taken to push-pull guns. Colleges provided which one was the local practice. Apparently push-pull guns have this "holy grail" of unconditional effortless Ali MIG welding. Friends who are long retired say push-pull for Ali used to be achieved by having an air-motor driving rolls in the torch. Long before electronics. Makes sense - presumably they pulled on the wire in proportion to the air pressure supplied. Air motors tend to be constant-torque. Power electronics and data electronics make for "modern" push-pull guns having electically powered rolls in the torch. As you'll know...

Another I can't comment on further though.

My spray aluminum welds look like somebody laid down a series of soft turds. I'm just happy if I can see visible fusion in both toes.

As far as my experience goes; you can with Al-GMAW in spray get fillets with a 45deg triangular shape and flat fillet face.

I'm warned from Canada that "good fusion" as you'd look for with steel

- what is really meant is plenty of weld-pool fluidity let us make that clear - can be a liablity with costs on Al.

That fractures are more likely on Al welds which look very "fluid" and smooth. As warned by breaking tack-welds and temporary welds for dogging-together plates, etc. Likely also being there in the "production" welds. Keeping heat levels down in Al is a good thing. Else strength drops.

Al is "Face-Centred-Cubic" (FCC) crystal structure so never shows brittleness. My assumption stated here without consulting with anyone else is that weld flaws and defects cannot kick-off brittle fractures like they can with steel. Genuinely - ??? Obviously (?) though, in a highly cyclically stressed structure they could be the immediate initiation location for fatigue cracks? But if you grain-grow the Al and lose strength, you could get cracks anyway. So nett - apparently keep heat down in Al.

I find with my fillets that if I turn down the heat at all by a tiny fraction, you immediately fall out of "smooth fillet" and get something lumpy. Implying the conditions used are very very close to the lower limit, and the inference is the Al cannot be dwelling at temperature.

I wish I could strength-test my welds. Make samples and do one of my strength measurement tests. My welds are considered to look as solid. I wish I could know that by measurement.

Your welds... You mean they are smooth but highly convex? That would to an extent mean more heat input as you have melted more metal into place. More metal melted must mean more kJ/mm, (heat per unit length). If you turned up the power - more Amps and Volts - and got a flat fillet surface in a faster weld run, you could have no more heat input?

BTW - Al welds run fast, that's for sure. When your reference is working with steel.

No. I mean my aluminum welds look like crap.

Ahhh - OK... I tend to be a bit of an optimist.

That should not be the case. Could you manage an photos?

My impression is the welds go in just right, but that that "good envelope" is very narrow. That the "easy" is a bit illusory...

LOL. Yep. Forever the optimist. I've actually found I get my best aluminum welds by doing some research on feed. Making some practice cold runs on coupons, then hot runs. Then adjusting and more practice hot runs. Then cold runs on the part and finally welding my parts. I actually weld so infrequently that muscle memory is totally forgotten by the next time I need to weld a part.

Given that one of my wishful plans is to make a couple aluminum boats I guess I am an optimist too.

Now I just need a 24 foot (~7-8 meter) sheet metal brake. LOL.

LOL. Thumbs-up

What about thinking along the line of the people who instal continuous eaves troughs? A coil of flat stock feeding through rollers to produce the required profile.

It looks like they extrude ships by the metre and stick on a bluntly pointy bit at the front and a chuggy bit with the bridge at the back - but to make a small boat?

I've worked on boats, but never seen how you'd form-up an aluminium boat. Any good links anyone can offer?

I would guess it would be manufacturer specific. Most I've noted are welded at the chines and keel. In some cases like inexpensive flat bottoms the stringers and hulls stiffeners appear to be rolled or stamped in. I expect using a rolling operation like corrugated sheet metal used in metal building construction. Most backyard builders usually weld in stiffeners and stringers (or on the outside in some cases). Some purpose extruded, and some shop made. Some just a generic piece of aluminum angle. The actual curved shape of a hull is usually formed by flexing a flat sheet to fit up to strength members or other sheets. They often employ more geometric sections than you might see in a laid or sprayed glass boat for practical reasons of fit.

Since 5052 seems to be the preferred hull material work hardening IS an issue when doing more complex forming. If for instance you want to make a tight radius relatively sharp angle brake you may need to stop half way and anneal the material before finishing the bend. The answer is often either to cut and weld or to create a larger radius on the bend.

I've done a little aluminum boat repair (90% of my aluminum welding) and spent a bit of time researching methods and looking at other builders methods. One boat made by Tracker Was "formed" out of aluminum with such nice lines that at a glance it looked like a glass boat sprayed into a mold. Then you look closer and see they did do more welding than just to fit trim, stiffeners, and gunnels. The keel (relatively sharp bend) is welded right down the length of the boat.

The comment about a 24 foot brake is more a joke than any real need. A rolling press of some kind would do a far better job, but for one or two boats would be far to time consuming and expensive to build or have built. If I ever get to that point I'll probably use purpose extruded stiffeners and some form of ring roller to form them into shapes where needed. I've got a lathe. I can make my own rolling dies. In fact I madified some for a buddy of mine for his cheap Harbor Freight Roller.

I once saw a small boat/dinghy that was made from corrugated steel sheet rolled up at each end with wooden sides. The ribs ran along the length of the boat. I thought it was a clever solution if you have access to kit to roll corrugated sheet.

There are some pretty interesting "economy" poor man boat builds on YouTube . From reshaped plastic barrels used as panels to boats that seem no bigger than a surfboard screaming up channels with a modified weed eater being used as a surface drive.

Not quite the same, but love the structured madness of the Thai longtail boat racing.

One of my buddies is a hard corps mud boat / surface drive guy. I'm pretty familiar with his weed eaters. He runs a log tail on his little boat and a short tail on his slightly larger little boat. I'm an outboard or outboard-jet guy myself, but I've got one rig I've been thinking about putting a Twister XL4 "short long tail" on with a souped up Predator 670 for a power plant.

My dream shallow water boat is actually a bit bigger. Something with low dead rise (just enough to shed air bubbles), pocket tunnel, and extra rear flotation boxes setup to use the 250ProXS, I've got hanging off a stand in the back shop. After I fit it with a jet pump from Outboard Jet Co of course. It should jump sandbars just as easily as the smaller boats, but if it does get hung up I will need some help getting it off. LOL.