Welding test HELP please.

By Lawrence (*****)

Date 07-16-2003 16:03

If you must keep the above mentioned dimensions for your test (land, gap, bevel) I can suggest a couple of things.

Go to a full length 3/32 electrode minimally (preferably a water cooled torch)

Create a pointed tip, blunted at the end.

Assuming you have a foot pedal control, set the amperage at 150, you may need even more. Keep in mind you may also find it necessary to decrease your heat input and increase your travel speed as you proceed along your coupon, once your test piece gets good and hot the welding becomes easier.

Remove all oxides from front and back of weld zone (I prefer 1.5 inch 80 grit aluminum oxide discs on a 18,000 rpm. 90 degree pnumatic angle die grinder.)

Assuming your powersource is squarewave, and your material is well preped, set your balence control to 7or 8 on a scale of 10. (max penetration 10 vs. max cleaning 1)

Try keeping your torch angle close to 90 degrees rather than a more push style angle, with aluminum the heat goes right where the electrode is pointed, and if your having penetration problems than it should be down where you wish the melt to occur.

If however, you can change your land and gap conditions than you can do even more to gain your penetration, but I won't get into that unless those conditions are variable.

tell us how it goes

Lawrence

By UKmxer

Date 07-16-2003 19:48

Thanks Lawerence,

Its now 9pm here so I will have a go tomorrow. I have a job interview in the next 2 days and I think this will be what they give me.

Could you please give me the other advice you have held back on, as I might be able to set the plates up as I prefer( within reason) which hopefully will lead to a better chance of getting it right.

By Lawrence (*****)

Date 07-16-2003 20:28

Okee dokee UK;

Much will depend on how your cupon will be restrained/fixtured.

For even consistant penetration at the root, I prefer to have a standoff distance at the bottom of the work and the fixture/table. This provides space for the penetration (melt thru). If your coupons are clamped directly down to a table it will be hard to have good fusion at the root. Just a little shim under each half will do, make sure the shims are 1/4 inch distance from your Heat affected zone.

I have not GTA welded heavy sections of aluminum with backing strips, so if that is your case somebody else must give the tips for that.

You could also minimize your land, if you take it down to near knife edge <0.060 they can even be butted.

The problem inherent with the above *tricks* will be that trials (practice) are necessary to discover the best way to go.

Thinner sections of aluminum prefer to be tightly butted for groove welds. A nice round puddle results and the depression due to penetration is simply filled with filler to make the weld complete. This eliminates the more difficult Keyhole technique. However, your tester may wish you to demonstrate the more difficult method. In this case the tips in first post will be most effective.

Do not be too worried if your penetration looks beefy, Aluminum has a tendency to have a larger profile in both the bead and the root reinforcement (penetration). If the tester is interested in cosmetics at all, he will most likely be conserned with the consistancy of your heat input and filler deposit/bead profile.

If your test coupon is to be X-rayed, make sure that you stop at once if your tungsten touches the work and that you grind out the contamination in the puddle and re-dress your tungsten. always make sure your tungsten is in perfect condition throuout.

By UKmxer

Date 07-17-2003 12:50

Lawrence, I have emailed you some pics of what is happening.

I dont know how to post them on the site but you are welcome to post them if you know how.

Do you know the proper values for the plates and distances on a weld test. and am I allowed to tack the plates from underneath before I begin.