Aluminum GMAW

Date 03-18-2008 15:05

Hello SCweld, this is my take and others may disagree, but if the resulting weld is performing mechanically as it should it doesn't really matter as to the particular motion you are using. Many folks are very set on the aesthetics of aluminum weld beads and feel they should only be done in a particular manner. The bottom line is really whether they have the correct mechanicals and you are satisfied with the appearance. I said correct mechanicals because I believe if beads exhibit excessive undercut or other bead discontinuities they won't meet the mechanicals. Just my $.02. Best regards, aevald

By 803056

Date 03-19-2008 03:25

Based on my limited experience, stringers are preferable to limit the time at temperature if the alloy can be overaged, i.e., if it is a heat treatable aluminum alloy.

Heat input = voltage X amperage / travel speed, so if you decrease the travel speed by weaving, you increase the heat input which can increase the interpass temperature and the potential to overage the alloy.

I usually recommend using a fan to hasten cooling between weld passes to minimize the time at temperature to minimize the interpass temperature and overaging the base metal.

Even the nonheat treatable aluminum alloys can be strengthened by rolling or stretching the metal to cause strain hardening. High interpass temperature can reduce the effects of strain hardening and adversely affect the mechanical properties in the HAZ.

Best regards - Al

By aevald

Date 03-19-2008 03:44

Hello Al, you definitely make valid points referring to time at temperature and how heat affects various types of welds with various AL alloys and their condition, ie. anealed, hardened, etc. I guess I was trying to use a blanket coverage by saying that as long as mechanicals were acceptable the method of bead application wasn't necessarily an issue. I also believe that the interpretation of weaving might qualify whether the time at temperature variable would come into play, one person's weave is sometimes another person's stringer and visa-versa. Appreciate that being pointed out. Best regards, Allan

By DaveBoyer (*****)

Date 03-19-2008 03:18

I have done a weave and it seemed to work OK, I have pulsed the trigger on & off rapidly when things started to get too hot. I don't have any methods for testing welded materials. I do non critical welds for non criticle people. As long as everything stays together everybody is happy.

By 803056

Date 03-19-2008 03:41

Ahh, the old pulse welding trick! ;)

In general, many strengthened aluminum alloys (T4, T5, T6, or H conditions), whether they are heat treatable or stain hardened, lose strength and ductility when they are welded. Some alloys lose strength and ductility more readily than others. From a practical stand point, only the "as wrought" or "in the annealed condition" can be welded without experiencing a degradation of mechanical properties.

Best regards - Al

By DaveBoyer (*****)

Date 03-19-2008 04:51

Al, I agree that if I was doing critical work I would need to establish procedures that gave acceptable performance and adhere to them. As it is, I am the shade tree guy with a shop, and people bring things that need a little "bizzzzz, bizzzzz" here and there. Some of them aren't even familliar with the sound, they just want it stuck together.

By 803056

Date 03-19-2008 21:07

And so we have the "art" of welding.

There's nothing better than a little judicial use of innovation. I've been known to do the same on occasion.;)

I agree that once the procedure has been tested and the mechanical properties meet our requirements, the technique employed while qualifying the procedure has been proven. However, this is one of those occasions where technique is instrumental in determining what those mechanical properties are. The individual responsible for establishing the procedure needs to recognize and implement additional controls when the applicable code does not require controls for heat input, time at temperature, voltage, amperage, etc.

Aluminum is one of the materials where additional controls may be warranted when the applicable code doesn't adequately address our concerns.

Best regards - Al

By SCweld

Date 03-21-2008 01:04

Thank you all for your input. They all make sense. I wasn't completely clear however. I generally stick by a 3/8" rule for weld width sizes which is what my company considers stringers. When I say weave I am not using the term correctly. I simply mean a side to side motion generally a horseshoe pattern. I just prefer the look of the side to side motion rather than the up and down motion others use for aluminum Mig. I just don't see the significance of the up and down kind of circular motion that my coworkers prefer. There is nothing in our procedures as too this and the only time I am asked to change is when I am working with another welder who uses that technique so the welds will look the same which I understand. I quess it is just an aesthetic's thing. When I am on a part myself the inspector does not mind the side to side motion. In fact he said he liked it better because the weld is smooth. He said some of the ones that space their ripples considerably far apart could be considered stress risers. Several have failed visual because the throat dimension in the ripples were low.

Anyway thank you for you comments!

By Kix

Date 03-21-2008 12:29

I reviewed some old aluminum procedures my company had only to find out the mechanical tensile pulls didn't meet the minimum requirement of AWS D1.2. The material was 6061 T6 welded with ER4643 filler. The minimum tensile according to D1.2 was to be 24,000psi and our tensiles pulled at something like 18,000psi. The only thing I can think to be the problem is how the coupon was welded and that they got it too hot. I asked the welder if he was checking the interpass temps and he said no. (I did not do the testing in case some of you are wondering) I'm getting ready to do some pulse procedures on a 6061 T6 3/8" thick test plate to welded in the 3g and 4g positions. You could easily fill this groove with a good weave, but I'm going to have it done with stringers so as to not over age the material by getting it to hot for a long time. I'm afraid that if I weave it, the mechanicals with come out below 24,000psi. So what we are trying to explain here is that most of the time a weave puts more heat into the part which can make the material you are working with not as strong. Hope this helped ya out.

By trlblzr302 (**)

Date 03-21-2008 14:54

Kix,

Nice write-in on the aluminum... Thanks

Happy Easter TO ALL....

trlblzr302

By 803056

Date 03-21-2008 16:29

Hello Kix;

Why are you pulsing on aluminum?

You can use spray transfer in any position when welding aluminum.

I've encountered fusion problems on every project where GMAW pulse transfer was attempted unless the material was less than 3/16 inch in thickness.

Best regards - Al

By Kix

Date 03-21-2008 16:53

Al,
We have a couple guys running those 350P's on pulse for the thinner projects to keep their bead profile consistency up. I had to qualify a procedure for them to use because all we have is spray procedures and pulse is an essential variable in D1.2. The 3/8" plate was readily available and I can write a couple WPS's off of it. They use it for tacking the heavier stuff up as well, but we use spray transfer for all the welding on that stuff. So that is the reasoning behind my madness on this one.;-)

By 803056

Date 03-21-2008 22:17

Just curious.

Al

By Tommyjoking (****)

Date 03-22-2008 10:55 Edited 03-22-2008 11:01

wow

can you guys clarify some things for me, I am nowhere close to using this anymore on the job but, gmaw spray transfer on aluminum....are there not some machines out there that do the spray transfer process whilst utilizing a pulsed (cycling voltage amplitude) for arc control/stabilization. I have welded many of these wire processes "in my former life" but I am trying to develop a deeper understanding of whats actually going on in each and proper application of them. I am weakest in mig and I want to get smarter on it.

As far as vertical technique spraying aluminum....I found I never had to worry about working it ...it seems to just take care of itself..and looked good..as long as the machine is running correctly. Course I never done anything thicker then 1/4 in spray on aluminum either.

BTW. Al

"Aluminum is one of the materials where additional controls may be warranted when the applicable code doesn't adequately address our concerns."

If I quote you on my toolbox, do I have to pay you a royalty?? thats just awesome LOL!!!!

Best regards fellas
Tommy

By 803056

Date 03-22-2008 15:42

Hello Tom;

Please sign on the dotted line.

Aluminum has a very high coefficient of thermal conductivity so that high heat input is required to ensure proper fusion. As such, short circuiting transfer is a loser's gamble and welding in all positions with spray transfer is possible on all thicknesses except very thin sections.

Pulse transfer can provide sufficient heat control to permit welding both thin and thick sections, but welders typically try to minimize the amperage and voltage while welding thick sections to make an uncomfortable job bearable. Unfortunately, lowering the heat input can result in fusion type defects if care isn't exercised.

I've had several clients that purchased machines with pulsing capabilities only to produce welds that were entirely inconsistent from one welder to the next because the machines didn't provide sufficient controls, i.e., meters, to properly control the process from one welder to the next. The simple solution was to use traditional constant voltage power supplies that were easy to set and monitor. Consistent welds and welding parameters were easily achievable because it was easy to monitor the welding parameters and easy to duplicate the welding parameters on each machine provided the meters were checked for accuracy periodically.

The only way to set up or monitor GMAW power supplies with pulsing capabilities is to use an oscilloscope and few shops or inspectors have the equipment or training to use them properly. Added to the fray is that different models (from the same manufacturer) or machines from different manufacturers use different means of delivering the pulsed wave form. Thus those parameters (set using only the meters provided by the manufacturer) do not produce similar results. The dark truth of the matter is that the fabricator needs to qualify the aluminum welding procedures for each model and each manufacturer's pulsing welding machine.

Happy Easter :) I can't wait for the candy hunt tomorrow! :)

Best regards - Al

By DaveBoyer (*****)

Date 03-23-2008 05:27

Tommy, spray transfer occurs at a higher current than short circut and globular transfer, as long as the shielding gas will support spray transfer. The old books say at least 80% argon or helium is needed for spray transfer, with solid wire this is generally true. This is a high energy process. Pulsing is a relatively modern method to tame down spray transfer and get enough controll to use it out of position on materials other than aluminum. WeldReality.com is a great site for more than You thought there was to know about MIG, definatly worth Your time.

By Tommyjoking (****)

Date 03-25-2008 08:54 Edited 03-25-2008 09:00

THX GUYS

Dave I bookmarked the site so I can crack a few open and try to learn something thank you. I know I am going to have more irons in the fire then just my job soon enough ....the more info I got the better prepared I will be.

Al the whole reason I asked is because my experience with spraying aluminum is limited to about two weeks. They had a "very expensive" setup dedicated to a specific job for a customer. I do distinctly remember a toggle switch and two sets of dials on the machine related to pulse capabilities...I cannot remember if it was engaged or not while I was using it....but it was spray (very similar to spray arc on steels) ...and boy could you walk the dog with this thing...fusion was a no brainer...the toes of the welds just laid in their pretty as you please...fillets were way easy...kinda looked like a tig weld purposely trying to avoid laying down laps.......travel speed was phenomenal, you really had to be ready to move...it was very hot and bright (#11 shade for me)...had to use heavy stick gloves. But the material was light .100 to 1/4 ....and pen was very easy to control via machine setup. I really am trying to get my head around just what type of welder that was and official moniker for the process. The machine was so good and laid weld so quickly...penetration profile seemed so easy to control with a thick to thin weldment.......I have friends with boat factories who might benefit greatly from giving this a try. I seen a few guys try this welder during that two weeks that struggled with it but I found it easy to use...you just had to move fast. Sorry but thats about all the clues I can think to give......was it just a fancy spray arc process or perhaps was it a "pulse transfer". BTW the time was about 98-99 when I tried this out.

Best regards (and thx again)
Tommy

Hope you got a lot of candy or gave you share or both!!!! We had a great time and the weather was beautiful!!!!

By DaveBoyer (*****)

Date 03-26-2008 03:54 Edited 03-26-2008 04:50

Tommy, I have usually used 3/64 wire in My aluminum spool gun due to availability at $2/#. Whe I run enough power for a bonafide spray there is an amazing [to Me] ammount of metal coming out, and if it is not an easy straight run, hard to move fast enough.

Really, I was using too big a wire, .047 has a lot more metal per unit length than .035, but My FC2002 method to gain some controll was to back down on wire feed and voltage.