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Up Topic American Welding Society Services / Certifications / Test Plate Coupons
- - By dlmann (**) Date 02-01-2006 03:05
Hello All: Just exactly how is a plate coupon with backing put together. Is the backing plate just tacked at the corners etc... Much discussion at work on this as we are going to attempt our first inhouse PQR.
Regards, Donnie Mann
Parent - - By MBlaha (***) Date 02-01-2006 11:54
No No NO No. You have to clean the back side of the plates taking care not to round or remove any metal. Also clean the side of the backing plate you are going to use. I like to use 2 extra backing strips the same size as the one to be welded. Lay the 3 backing strips parallel with each other, one in the center of the joint, and the other 2 at the edge of the test coupons. This will keep them flat and easier to line up. Keep the bevel so that your V if you are using one, is up. Set you gap, then tack the 2 plates to the backing strip in the 4 corners, ensuring you have an as tight possible fit to the backing strip. Ensure that the table you are using is flat, with no spatter as this will cause trouble fitting up the coupons. Once you have the 4 tacks in place. turn the coupon over, and use a C-clamp to ensure the center of the coupon is tight to the backing bar, then place a tack (I prefer 1/2") on each side of the coupons to the backing plate. If you do not ensure a nice tight fit, you will have slag lines along the edges.

Hope this helps.

Mike
Parent - - By dlmann (**) Date 02-01-2006 16:58
Thanks, yes this does help. More detail for extra advice. ½-inch Type 316 SS plate, 2G, GMAW, 0.039 wire, 190-210 apms, Ar+30% He shielding gas, ASME IX, 2 tensiles, four side bends, notch testing not required, PWHT not required. What thickness should the backing plate be? Is 1/4-inch thickness of the same material OK? Is 1/2-inch runoff tab on the backing strip enough? Is a 2-inch wide backing strip enough?

(The Ar+30%He sheilding gas is because the WPS will be qualified for RA 253 ma and the AVESTA welding wire literature recommends this gas in the spray-arc mode)

Regards, Donnie Mann
Parent - - By - Date 02-02-2006 01:17
Donnie,
You probably already know this since it seems you've done your homework on the Avesta recommendations about shielding gas and Amperage, but please let me add just one thing. And this also comes from our Avesta Welding Manual. Along with the recommended Amperage, the recommended Voltage, according to our Manual, is between 25-29V. Also, I believe the wire is either 0.035" or 0.045". Maybe you wrote 0.039" by mistake? Either way the paramenters you listed were for the 0.035" diameter GMAW wire. Good luck on your test, you should have no problems.

Chuck
Parent - By dlmann (**) Date 02-02-2006 12:55
Chuck: Thanks for the info. The wire size was actually 1.0 mm. In head conversion changed it a little. We are indeed follwing the recommendations for both the amperage and voltage for the 1.0 mm wire. We have also bought some 1.2 mm wire and have those amperages and volts on the new WPS.

I must tell you, with all the information that AVESTA has readily available the trial and error was eliminated. For the PQR we just had to do one one coupon and it came out alright. The two tensile and four side bend test were jobbed out and they came back as 89,565 and 90,923 ductile and in the base metal, side bends satisfactory.

Welder qualifications are ongoing with little (and I mean little) or no porosity.

Regards, Donnie Mann
Parent - - By aevald (*****) Date 02-02-2006 00:14
Hey Mike, very nicely described, the only real variation that you might see to this description would be dependent on whether there is destructive testing involved, or if it is being tested with radiography. When radiography is used there is no allowance for tackwelds in the weld area, if I have interpreted this correctly that means that the two 1/2" tacks that you described on the back of the plate between the backing strip and the plate halves would have to be left out. Regards, aevald
Parent - By tcoyen Date 02-02-2006 02:29
I would sure like to talk to aevald I was wondering if he might have insight on welding aluminum with millers 350p.......
Parent - By MBlaha (***) Date 02-02-2006 04:59
I respectfully agree with you. I am so used to using destructive testing, that the thougth of radiography never crossed my mind. The only radiography tests of this nature I have ever been involved in, were open root, backgouge, (back grind). I stand corrected.

Mike
Parent - - By thirdeye (***) Date 02-03-2006 03:35
aevald,

If acceptable by Code, a 3' wide backing bar can be used when radiography is required. This not only allows for the 1/2" long tacks to be well beyond the toes of the butt weld (not masking any areas of the butt weld) but it also provides consistant radiographic density across the butt weld.

Adder: Click the link and you will see what I am referring to. The tack below the ID on the penetrameter is beyond the toe of the butt weld.


http://img.photobucket.com/albums/v377/thirdeye2/welding01/1641715a.jpg



~thirdeye~
Parent - By aevald (*****) Date 02-03-2006 04:11
Hello thirdeye, I certainly agree with you there, as long as the edge of the backing is outside of the groove area there shouldn't be a problem with the radiography and the 3" should definitely do the trick. Thanks for pointing that out. Regards, aevald
Up Topic American Welding Society Services / Certifications / Test Plate Coupons

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