INCLUSIONS

Date 05-21-2012 12:14

Tungsten is really dense.....alot denser than copper. I'm not an expert in RT, but would surmise that that would have two different signatures when viewing the film. Hopefully some of the RT experts can chime in and verify this for you.

By MILLSCALE (*)

Date 05-22-2012 10:54

How about the acceptance criteria for copper and/or tungsten inclusions? Is it similar acceptance as to slag inclusions

By Lawrence (*****)

Date 05-22-2012 13:58

The acceptance criteria will be provided by the code (which you haven't provided us). An inclusion is an inclusion for sure. Size of defects/discontinuity allowed will be provided in the code.

I understand where the source of tungsten inclusions might be... What is your source for copper?

By TimGary (****)

Date 05-22-2012 16:13

Backing Bar?

By Lawrence (*****)

Date 05-22-2012 17:23

Right... Backing bars, and contact tips and nozzles, maybe even fixtures or argon backups...

Just wondering if the origninal poster had any notions about his specific project and where he thought the copper might come from (since copper was a noted suspect in RT defects/discontinuities)...

So far we don't know what code, mateiral or process is involved so it makes it pretty hard to provide much help.

By CWI555

Date 05-22-2012 19:05

Regarding what it would look like, cu's characteristic K radiation is =1.5418Å As I recall copper tends to have a high diffraction ratio..
It's density is considerably off that of iron (Steel ~7.85 gm/cm^3 copper ~8.94 gm/cm^3). http://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html
I would suspect an inclusion if one were possible would contain a diffraction halo around it similar to what thin (.05" or less) titanium welds sometimes have. There would be only a slight difference in density given that by comparison, tungsten is ~19.6 gm/cm^3 which shows up strong on a graph. It would be a shadow at best on the film unless there were a large volume of it.

Thats my WAG on it.

By jwright650 (*****)

Date 05-22-2012 16:32

For Cu....I was thinking GMAW or FCAW and shorted the nozzle or tip out in the puddle....LOL

By CWI555

Date 05-22-2012 16:04

I'd be curious to know how you can have copper inclusions when cu has a melting temp of 1944F and Fe up around 2,800F? I could understand copper contamination, but unless the weld has been slugged with large diameter cu wire, I am at a loss as to how copper inclusions could be formed?

By Lawrence (*****)

Date 05-22-2012 17:27

I have seen thin copper back-ups tear away because they are fused to base metal with both GTAW and GMAW.... But my curiosity is right along your lines too :)

By CWI555

Date 05-22-2012 18:43

I've seen that to. It was the comparison to tungsten inclusions that I am questioning.

By 99205

Date 05-28-2012 06:46

The copper inclusions were probably remnants of a backer bar. Recently I've seen this issue on full penetration welds were copper was the backer. When the welder doesn't grind the " root surface" (A3.0, fig. B24), to clean metal, there will be copper inclusions. D1.8, clause 6.7 does require some form of backgouging though. Proper grinding or backgouging should've removed the copper inclusions.

By WeldinFool (**)

Date 05-23-2012 15:10

When I hear tungsten and copper mentioned in the same sentence, I think of the old wive's tale about the copper coating that comes on the GTAW wire. I have made x-ray pipe welds for nearly thirty years with GTAW and never even once did I sand the copper coating off of the wire, and never even once did I have a problem with the x-rays being good (as far as the GTAW deposited metal anyway, gotta be honest here). But it never failed, you would see some hotshot making a big show of sanding the stuff off (usually a boilermaker) and talking about all of the ill effects you will get if you leave it on there. I say hogwash to that.

By 803056

Date 05-25-2012 21:14 Edited 05-26-2012 03:34

The copper flash is volatized by the heat of the welding arc. OSHA raised the flag back in the later part of the 70's / early 80's and made the manufacturers eliminate the copper flash because the copper was considered a heavy metal. The filler metal would rust so quickly it became clear that the steel wire needed some form of protective coating and OSHA caved.

Copper melts at about 1981 degrees F while steel metals at higher temperatures (2500 - 2800) depending on the carbon content. No carbon/low carbon steel melts at temperatures around 2800 and as the carbon is increased, it melting at temperatures closer to 2500 degrees F. Copper, being a low melting constituent stays liquid in the molten weld pool until the temperature drops below 1981 degrees. It has very low solubility, thus only a small fraction goes into solution with the iron. The copper usually solidifies along the grain boundaries and usually toward the centerline of the weld bead since that is the last region to solidify. That isn't to say it will not segregate toward any grain boundary when the solidification is rapid as is the case with stringer beads.

I use copper to induce cracks for test samples used for NDT training. A very small whisker of copper wire from a welding lead is one of the easiest ways to cause a weld in steel to crack.

As for an inclusion, I don't know. As noted, the copper usually is found along the grain boundaries rather than in a "clump" as is the case of tungsten which has a melting point well above that of steel, i.e., 6100 degrees for tungsten versus 2500 to 2800 for steel. Tungsten usually appears as a rounded indication that appears to be very white compared to the surrounding area.

As for the radiographer calling a less dense indication a copper inclusion, I don't know. I've had that happen when there was spatter on the face of the weld and I've read RT reader sheets reporting slag inclusions when the weld was made with GTAW. Go figure!

Best regards - Al