D1.2 PQR bend test acceptance criteria question.

Date 04-28-2008 13:42

Kix;

You said there is no post weld heattreatment, but you then say you annealed the bend straps? Which is it? PWHT, i.e., anneal after welding or no PWHT and bend the straps in the as welded condition?

What welding standard are you working with?

Did you machine the straps to 1/8 inch thick before bending?

Does the open defect exceed the acceptance criteria? Yes - it fails, no - it passes. The HAZ is considered to be part of the weld.

Best regards - Al

By Kix

Date 04-28-2008 15:37

Al you answered my question by telling me the HAZ is considered part of the weld. Now to answer your questions. The actual pipe coupon was not PWHT, but the bend straps where which is leagal by D1.2 when using 6061-T6 and a 4643 filler. Yes the straps where machined down to an 1/8". Yes the crack in the HAZ exceeds the acceptance criteria per D1.2.

Thanks, Ray C.

By bozaktwo1 (***)

Date 04-28-2008 17:06

What process did you use for annealing the straps? Did you try to bend without annealing? T6 is a CIB to get right on the best of days; if you exceed heat input values, it wants to "overage," making the base metal in the HAZ somewhat brittle. My line of thought here (such as it is) is that you could actually be hardening the base metal while trying to anneal it. Maybe.

By Kix

Date 04-28-2008 18:08

He said he used an oven and I don't know what temps and for how long he held them at those temps. Do you suggest bending them in the as welded condition and chance it that way? I think I remember him saying he left a set in the oven for a little longer then normal while he was teaching a class. mmmmm

By 803056

Date 04-29-2008 02:09

I have a client in the aerospace race that performs a PWHT on the 6061 after welding, but it involves heat / quench / artificial aging to regain some of the properties lost by welding. The PWHT of aluminum differs from what is typically done to carbon steels. The PWHT was also included in the qualification of the WPS, not just the welder qualification.

You may find it worthwhile to check into the exact conditions of the PWHT.

Best regards - Al

By Kix

Date 04-29-2008 12:07 Edited 04-29-2008 17:21

Here is how the code says to anneal the bend straps before bending. It says to hold them at 775 deg F for 2 or 3 hours and cool at 50 deg F per hour till you get down to 500 deg F. Below 500 is not important. He told me this is how he did the annealing process, except for when he got stuck in class at one point and they held at an unknown temp for to long.

By bozaktwo1 (***)

Date 04-29-2008 16:49

Yea, sounds like he deviated from process and FUBAR'd the straps. Fun. I love aluminum, as long as there's no heat treat involved.

By 803056

Date 04-29-2008 20:40 Edited 04-29-2008 20:47

OK, now you are forcing me to go back to the good book to see what's required.

I see the filler metal 4643 is an alternate to 4043 and suggested when PWHT (solution HT and PH) is necessary for materials are 1/2 inch or thicker: table 4.2

4643 is an F23 filler metal.

6061 is a M23 base metal.

No PWHT parameters are provided for production welds.

Clause 3.8.1.7 permits the bends to be performed in the as welded or annealed condition. Since you annealed the samples, what bend radius did you use?

Your original question about the HAZ is found in clause 3.8.3.1.

Most of the bend testing of 6061 welded materials I've worked with have been bent in the as welded condition. As I stated before, only one client performs a PWHT on the PQR sample and that is a full PWHT and PH operation. The welder's quals are bent in the as welded condition.

Good luck Kix and let us know if you find out any additional information.

Beswt regards - Al

By Kix

Date 04-30-2008 12:25

Al,
I've been doing some more digging and was able to put the crack in the weld by etching the coupon. I've got another thread going in shop talk about why I believe the bend strap cracked. I will also have pictures posted here in a bit. I believe on this next try I'm going to purge the coupon and bend the straps at 2-1/16" in the as welded condition. When annealing the bend straps they want you to bend them at 6-2/3t which would put my 3" sched 40 pipe straps at a 1.4" bend radius. That's pretty tight in my book even if they are annealed.
About clause 3.8.3.1, I would have to disagree with you and how that answers my question about the HAZ. All it states is that the HAZ must be in the bend radius for the strap to count as a good bend. I've seen wrap around testers almost miss putting the weld and HAZ in the radius and I've seen plunger style hang up on one side while pushing down throwing the weld almost out of radius. This is how I interpret clause 3.8.3.1 and would like to know your thoughts on my thoughts.;-)

By 803056

Date 04-30-2008 15:52

You're are correct that clause 3.8.3.1 says the weld and HAZ must be "completely" within the bent portion of the specimen after bending. You need to continue to the next clause, 3.8.3.2, and read that "the convex surface of the bend specimen shall be visually examined for surface discontinuities." The convex surface includes the weld, HAZ to either side of the weld, and any base metal within the convex surface. All of the material within the convex surface has to be evaluated and compared to the acceptance criteria.

As for the situation where the specimen shifts to one side while bending, it can mean the bent sample is not acceptable for evaluation. If the sample shifts such that the entire HAZ is not within the bent portion of the sample, it must be discarded and a new sample made. It is for that reason longitudinal bends are used or a wrap around type fixture is used when dissimilar materials are welded and evaluated. Even the wrap around type fixtures are not fail safe unless the technician takes sufficient care in placement and securing the test sample. My wrap around testing machine has a bolt passing through the secured end so that the bend sample can not shift from the proper location. I have to locate the drilled hole so that the weld is properly centered on the bend radius. I always cut one extra sample that is used to verify the proper location of the drilled hole. The first sample is not evaluated, it is used to simply verify the proper location of the drilled hole or let's me know that it has to be shifted closer to the weld or further away so that the weld is properly centered. The hole location can vary from one alloy combination to the next due to differences in ductility.

I have passed many aluminum bend tests to D1.2, D17.1, MIL-STD-1595, MIL-W-8604, as well as MIL-STD-2219 without a root side purge and without porosity problems.

Good luck. It appears you are on the right track.

Best regards - Al

By Kix

Date 04-30-2008 16:37

I knew you could get good results without a purge for that's why I tried it again. This is not the first time I'ce seen this and I never found out how to fix the prob. Al, Check out the thread in shop talk again. I'm posting pictures up in there right now.