[rahtreelimbs]

I find it interesting when Jody cuts and etches a weld to determine penetration. What I would like to see is a side by side comparison between stick, mig and tig on penetration.

[Otto Nobedder]

Rich, I'm having an excess of free time at work this week, and intend to weld a coupon of 3/8 A36 (or CorTen, depending on what's available) with backing bar, MIG, TIG, 6013 stick, in 1G, just to do a cut-and-etch.

You've piqued my interest to see the nuggets side-by-side.

Steve S

[DLewis0289]

EXCESS OF FREE TIME????? Well head on down to the Sunshine State, have a few columns you can help me build

IMG_3221.JPG (63.76 KiB) Viewed 3064 times

[Otto Nobedder]

EXCESS OF FREE TIME????? Well head on down to the Sunshine State, have a few columns you can help me build

If you were closer to Cape Canaveral, I'd certainly consider it, at least short-term...

We completed our shop setup about a week ahead of the arrival of regular work, and everyone is hunting for PM projects, sweeping floors, organizing work areas, etc.
This gives me time for little projects like this, but only when the boss is there... I've got one sorry-ass tattletale who'll bitch to the boss if he thinks I'm doing personal stuff. Oddly, the guy without enough of his own business to mind can't be bothered to pick up his mess when he finishes a task. He thinks I should be job-scared, but he can only handle one task at a time, while I'm usually working three...

Steve S

[DLewis0289]

Yeah you need those down times. No matter how well we try and stay organized after a big project it looks like a bomb went off in the shop, I have never had an issue with paying for PM and housekeeping, the dividends are worth it.

[Otto Nobedder]

About the time I said I'd have free time, I got real busy... I am working on this, though. I've welded the SMAW and MIG portions of the coupon, and will do the TIG tomorrow. I don't know if the cut, polish, and etch will be done tomorrow or Wed., as I'm now doing this stuff during lunch. Should be interesting, as both the MIG and Stick are 5-pass welds, and I expect the same, or maybe 6, for the TIG.

Steve S

[Otto Nobedder]

All right, I finally have the etches...

DSCF1888 (640x480).jpg (136 KiB) Viewed 2972 times

From top to bottom, Stick (6013), TIG (70s-2), and MIG (70s-6). The coupon was A-36, 37* bevel to knife-edge, 1/4" A-36 backer, 3/16" gap.

My immediate impressions are:

The 6013 showed it's low penetration, as the root (3/32 @ 90A DCEP) has very low forward force into the backer, but cuts fairly broadly into the sides. There's also a slag inclusion obvious. I may re-cut it later to see if I can find a clean surface. This was seven passes, with the last one intentionally wide of the opening to see the penetration on pre-heated metal.

The TIG was the most consistent, with good penetration into the backer, and each of seven passes are clear with their relative penetrations. This was 1/16 70s-2, 3/32 thoriated, 20cfm, #8 on a gas lens, at about 105A all the way out.

The MIG also has good penetration, but betrays my biasing of the arc to one side of the root (perhaps not fully perpendicular to the joint), as shown by the step on the right side at the backer bar. There are also two tiny silicon inclusions, also. These things show me me that, even for this exercise, I should have paid more attention and cleaned better between passes. This was .035 70s-6, 20.8V/350ipm, 70/25 at 35cfh, about 1/2" stick-out.

This is the first time I've done a cut and etch on my carbon work, as I work almost exclusively in stainless, and I've frankly learned a lot. I may have to repeat this exercise. If I do, the stick will be done 6010/7018 (I can hit up the LWS for some samples), for contrast. I may even do spray-arc MIG, to contrast that.

Any and all comments are welcome.

Steve S

[Coldman]

It goes to show that mig solid wire done properly can be a good solid weld with good penetration.
Thanks for the post. Very revealing.

[Coldman]

Nice clear macros Steve. What did you etch with?

[Otto Nobedder]

Nice clear macros Steve. What did you etch with?

Dilute sulfuric acid.

The metal was dressed to 600 grit, then I submerged them in "Alumabrite", diluted to about 25%, for maybe five minutes.

It was that, or try an even more dilute solution of phosphoric acid in a rust-blck primer that would have had other impurities to deal with, so I tried this first and it worked.

Steve S

[LtBadd]

Nice clear macros Steve. What did you etch with?

Dilute sulfuric acid.

The metal was dressed to 600 grit, then I submerged them in "Alumabrite", diluted to about 25%, for maybe five minutes.

It was that, or try an even more dilute solution of phosphoric acid in a rust-blck primer that would have had other impurities to deal with, so I tried this first and it worked.

Steve S

Steve, would this solution be okay to etch any alloy?

[Otto Nobedder]

This solution work a treat on stainless, as well. I've used it full-strength on SS, seeing results in less than a minute.

GEDC1588.JPG (136.28 KiB) Viewed 2583 times

On carbon, it's important to rinse thoroughly as soon as you've achieved the desired contrast, then wipe it dry and give it a quick shot of WD-40 or similar to prevent rusting of the now very vulnerable surface.

I've not tried it on aluminum yet.

Steve S

[LtBadd]

This solution work a treat on stainless, as well. I've used it full-strength on SS, seeing results in less than a minute.

GEDC1588.JPG

On carbon, it's important to rinse thoroughly as soon as you've achieved the desired contrast, then wipe it dry and give it a quick shot of WD-40 or similar to prevent rusting of the now very vulnerable surface.

I've not tried it on aluminum yet.

Steve S

very cool, thanks