I'd like to get some opinions on a good technique for welding an open butt coupon for a welding test. The spec is Mil Std 1595A, For the aerospace industry. The coupon is .040 inco 718, With a backing gas of argon. We have a purge fixture that the thin plate is mounted into. What I want to get an opinion on is, Coupon Preperation, Filler wire size, and what amount of gap would you run on the open but? We use Inco 82 wire in .045 size. I bevel the edge to a sharp, No land edge and I run a gap the size of the filler wire.We also run the weld in one pass, as it is such a thin coupon. In the past, We have had problems with the welds having a line that shows up as lack of fusion on the X-ray. This is really hard to understand, Because the weld will look visually perfect on both the front and back sides. I was told once that this is called core freeze. I am hoping someone with some experience with this procedure, Can shed some light on what we can do to prevent this problem. I would appreciate any tips on prepping the wire and coupons prior to welding , And a good procedure to use for welding. The test requires the same welds to be performed on several different alloys, But the Inco 718 is the only one we ever have a problem with. Thanks!
For a 1595A (generally now superseeded by AWS D17.1) flat butt cert/qual exam. I would advise no gap. Butt the cupons. With the cupons butted and sound technique, heat input can be more consistant and overall lower than with the gap. Plus with an open root gap you risk back up argon causing a disturbance and prompting oxygen/nitrogen pickup when it converges with your cover gas.
Edit** In fact D17.1 Annex I Guidelines for Design, analysis, and Fabrication, Figure I-1(a) states that max root openings are 1/2t or 0.045., Which ever is less
120 Grit 1.5 inch alum oxide disk, mounted on an 12-18k rpm angle die grinder to prep both sides of the cupon up to 1/2 inch from weld zone plus oxide removal of root faces (shear contamination and dull cuts make for alot of rejects.) A wire brush won't cut it with inco 718 the oxide on this stuff is tenatious, and unremoved,unmelted oxide layers may indeed appear to be a lack of fusion.
1/16 inch or 0.040 electrodes
Torch angle perpendicular, no leading or push angle.
Keep wire under argon at every instant. Clip ends on restarts.
0.035/0.045 MC Grade AMS 5832 weld wire. My prefrence is http://www.usweldingcorp.com/tds/tds5832.htm
Make sure your backup fixture is making no contact with your weld melt thru.
D17.1 while by no means a big doccument, is more comprehensive than 1595 and it's my understanding that the DOD aviation agencies are moving to adopt D17 (which is why it was created in the first place) My copy of 1595 has hand drawings. It might be wise to make sure the folks to whom your contracting havent already superseeded 1595. There are some significant differences between the two.
TWI provides a few free tips for precipitation hardenable alloys like inco 718,
http://www.twi.co.uk/j32k/protected/band_3/jk22.html
Thanks you very much Lawrence.There is a lot of good info in the link you posted. I will bring this info about the AWS D17.1 replacing Mil STD . 1595A to the engineer over the welding dept.. He may be aware of it, But changes in specs around my company aren't something they like to deal with if it isn't mandatory. Is there a website where I could view both specs?Could you elaborate on the significant differences between the two? It would be great if the new spec allowed a cost reduction in the up coming test. We have to re-certify every 5 years, and there are around 12 different welds involved with different alloys and thickness ranges.By the time a few welders take this test, the material cost and radiology tests, along with the destructive tests and labor costs involved is very expensive. Thanks again for the info.
Seaplane:
1.) Why are you applying a bevel or V groove to such thin material?
2.) I typically to not use a gap >0.030" for material this thin and pass radiography without problems.
3.) The line present in Inconel (and other nickle based alloys) is typically an oxide present within the weld. There is an extensive discussion on this subject in previous posts in this forum. Use the search engine.
4.) I don't know that AWS, IHS Global or SAE will let you "view both specs" (or any spec. for that matter) without shelling out some $$.
5.) I am currently certifying welding personnel in accordance with D17.1 which the Engineering Authority is using in lieu of the superceeded AMS-STD 1595. Your employer will have to pay for those tests if you want to perform welds in accordance with either the AWS or AMS docs.
Hey DGXL
Do you fabricate your own butt joint thin coupon fixtures or can they be purchased? If yes, from whom?
I couldn't take my test fixtures with me and now could use new ones... It might be nice to just buy some rather than bribe the folks in the machine shop.... Any ideas would be welcome.
Seplane:
DGXL is right about the bevel... forget that idea.
Global Engineering Doccuments are the folks who sell the specs, both DOD and AWS. They don't give anything away. I guess life is good when you have a monopoly......Cossacks!
Lawrence,
In reality these specs were never previously "given away", so IHS/Global is not to blame for being a reseller. They provide a service that is difficult to find elsewhere and that AWS was not providing on their own. I believe the retail price is still controlled by AWS, so they are the ones responsible for high prices. If you're shopping around, try:
http://www.techstreet.com/
Lawrence:
Most all of my clients have machining capabilities or access to a mchine shop. It just so happens the one who is currently doing the D17.1 qualifications is a tool & die shop. So, as you can imagine it took basically a few minutes to manufacture a fixture. It also is set-up to accommodate ceramic backing that slides right in and out when it needs replacement. Very slick.
Have a good T-day.
MB,
Hey I never suggested anything was given away. Being a free marketer and a tightwad are not a contradiction in terms. Ive made many purchases from Global and all have been more than $1 per page... I just wish there was competition, because in my opinion the prices are unreasonable and prohibitive. Every year I get a FREE MSC catalog containing over 4,000 pages, so I guess some printing presses are more expensive to operate than others :)
Inconel shminkonel
I agree that the prices are steep. I compared Techstreet to Global and found that Techstreet charges USD$121 for D17.1 vs. USD$112 for Global. The AWS website lists D17.1 at USD$112 for nonmembers, USD$84 for members. You can get the AWS member price through Global by providing your membership number and that helps a little. My point was that retail price is pretty much controlled by AWS, not the resellers, and perhaps your comments should be directed to AWS. I would have thought a "not-for-profit" society could do a little better on pricing of standards.
Forum
