Certify on aluminum buss bar

Date 12-29-2008 17:21

Clean, clean, and reclean.

Use a U-groove with about a 1/16 to 3/32 inch root face, no root opening, no root purge. Make sure you are in the spray mode, don't try to use low volts/low amps. Use upward progression, and point the nozzle upward slightly. Move fast, but steady with no side to side weave. Stringer only.

Practice and more practice. The contact to work distance is important. If you hear a crackle sound, stop and clean up your crater. You will most likely detect some porosity where the crackling was heard. You want to hear the steady "whoosh" of spray transfer to get the best fusion, joint penetration, and least porosity.

Check other threads for details on cleaning the aluminum. It has been discussed several times.

DO NOT PREHEAT the aluminum!

Best regards - Al

By bardco Date 12-30-2008 23:33

Al, Thank you for your very helpful responce. I have welded buss bar in the spray mode before and had great results. the U-groove
with no root opening is the suggestion I needed . I am excited to get back in the shop to try this set up.

Thanks again Bardco

By bozaktwo1 (***)

Date 12-29-2008 17:30 Edited 12-29-2008 17:33

What type of joint? Is it a groove? CJP? Backing? What diameter/wall thickness is the pipe? What voltage, wire feed and gas settings are you starting with, and have you adjusted them within the allowance of your WPS? Is this a PQR or a Performance qualification?

Aluminum is a tricky critter, especially when it comes to thin materials; these are better off being welded with GTAW, in my opinion, because you have much better control over heat input than with GMAW. GMAW with 100% argon is probably your best bet here, with the 4043 wire. I would guess you're using 4043 for a reason? If you are making a CJP with no metallic backing, you're going to have a tough time, unless your pipe is something with a heavy wall. 4043 doesn't like to run too cool, so your welds look better if you run them hotter; hotter or cooler in this case is wholly dependent on what settings you're starting off with. For example, a 3/16" plate CJP v-groove, 1/16" root opening, no backing might require 22v, 180ipm and 30cfh. A tube might require less voltage, since the heat will not be given the same chance to dissipate in the circular weld. However, in this case you might consider a preheat, again if it's within the allowance of the WPS.

While I'm at it, I may as well remind you to clean, clean, clean the base metal. When you think it's clean, clean it again! Good luck!

EDIT: right as I post this, I see Al said not to preheat the aluminum. I will amplify my reasons for preheat. If you're using lower voltages, the first 'x' number of inches of weld (depending on material thickness and voltage) will have a tendency to resist proper fusion. A light preheat will assist in bringing the material up to a temperature which is more conducive to welding. By light I mean no more than 150 deg. F. It's not necessary, but if done right can help out a lot.

By bardco Date 12-31-2008 00:30

Bozaktwo1, It is a butt joint,3"diameter 7/32" wall thickness.I have to document my own WPS and come up with my own PQR.I have a
welding inspecter that is going to help me with that,but I have to come up with a passing sample first.I am using the GMAW process
because that's what i am going to use in the field.When i was trying to weld it as a V-groove with a 1/8" root opening I was having problems
with a cold start so your suggestion was right on with preheating. I really appricate the great suggestions, I am going to try AL's U-groove
idea first I think I can make that work.So for now I am going to clean clean and more clean my way to certification.

Thanks for all your help BARDCO

By 803056

Date 12-31-2008 05:10 Edited 12-31-2008 05:23

I forgot to mention that if you are running small diameter aluminum electrode, the wire feed speeds are very high and some wire feeders do not have the ability to feed at the speeds required. You may be up 500 ipm or higher for 0.035 inch diameter electrode while maintaining spray mode transfer.

The mechanical properties of the heat treatable aluminum alloys are adversely affected by high interpass temperatures. Likewise, nonheat treatable alloys that are strengthened by cold work are also adversely affected. It is best to weld the aluminum as fast as possible and maintain a low interpass temperature between passes. You may want to consider cooling the weld with blowers. If you are qualifying the procedure, you need to maintain the mechanical properties by monitoring your interpass temperature.

I haven't seen a short circuiting transfer procedure for aluminum yet. Someone might have one or they may have used one, but I haven't seen one that passes all the mechanicals and NDT. This is no easy undertaking if you are welding in all position.

If you are using the spray mode of transfer, there should be no need to preheat the base metal. If you are having problems with proper fusion, you need more wire feed speed and possibly voltage. I hope your machine can handle it.

You should also be using a spool gun or preferably a push-pull gun if you have more than a couple of pieces to weld. Use a slight push angle when welding aluminum. Remove any cracked craters.

There is no need to use a backing gas with aluminum. There will be a tenacious oxide layer that forms as you weld that protects the aluminum from further oxidation. You will see a crease or line right down the center line of the root bead when you turn the buss bar over. This is normal. If you blow through the root face, simply increase it to a thickness that is sufficient to prevent blow through, yet provides penetration through the cross section. Your travel speed will be "high", any hesitation and your arc will blow a nice hole through the root face. As you terminate the arc near the top of the buss, roll your wrist to change the angle of the electrode to almost parallel to the surface of the buss.

A four inch side grinder with a concave milling cutter blade will make preparation quick and easy. Be careful not to try to remove any "oxide" from a "screw-up" with the cutter. It will round the teeth instantly. Remember, most grinding disks used on steel are made of aluminum oxide. You do not want to use aluminum oxide abrasives on aluminum.

As is always the case when welding, "there's more than one way to skin a cat and there is more than one way to weld successfully". What works for one person may not always work for the next without the experience and the training required to do it properly. That's when its nice to have the experienced welder beside you as a coach to walk you through the process.

Good luck.

Best regards - Al

By bardco Date 01-02-2009 16:35

Al,thanks again for the information, its great having an experienced welder at my finger tips to ansewer my questions.I have a 30amp
spool gun that I run off a miller trailblazer or a miller shopmaster they both work very well for welding aluminum.I use aluminum grinding
wheels for aluminum if they don't work i'll have to look for a mill cutter for my grinder.I have seen the crease down the middle of my
root I did not think that would pass a bend test.Thats why I need your expertise. I have not had the time to try your suggestions
yet but I am hoping to do it soon. I will let you know how it goes.Thanks again for your help, i wish I could find someone local who
had your knowledge to help. I hope you don't mind me asking for your help.

Have a great new year ,Bardco

By 803056

Date 01-02-2009 17:51

Not a problem. That's why we're here, to lend each other a hand.

Best regards - Al