NEED help from the experts? Trying to pass a weld cert with Inconnel 939 castings" I have tried everything i can think of to pass this cert but having trouble with cracks found in x-ray; I`am using c263 tig rod and the sample piece is preheated and then heat treated after welding' aparently no one here has had any success either, could we be using the wrong filler rod? any tips or sugestions would be apreciated thanks!
I'm no expert with nickel, but my experience has been that preheat isn't necessary as long as theere is no surface moisture. Keep interpass temperature as low as practical. Grind to remove surface oxides between passes. Wire brushing alone isn't aggressive enough to remove surface oxides between weld passes. No weaving, use stringers.
Check for contamination by low melting point constituents like sulfur, lead, etc. Contamination from markers, paint, cutting fluids, etc.
You mentioned this is a casting. Did you grind the surfaces to be welded to remove surface contamination associated with the casting process?
Good luck - Al
Al' thanks for your reply! I have certified for In 718 before along with numerous other exotic materials so i assure you all the prep work was done (grinding with a carbide cutter) not just wire brushing ,and then some to assure a sqeaky clean surface, yes a mild pre heat was done to remove moisture. Ronb
Exactly what type test are you taking and what kind of "cracks" are being found.
I don't have experience with your specific type of inco..... However do have plenty experience with it's cousins.
Hipped inco castings often will fail outside of the weld zone with liquaqtion cracks in the HAZ.
Is your test simple argon purged plates or is it a solid lug with scallops that you must fill?
I have also seen cast test coupons delivered with flaws already in them..... We thought we all lost our touch until we did a few independent x-rays prior to the tests. Test lugs or pads are sometimes just extracted from scrap cases.
We refined our in-house wps by keeping a 50 amp maximum heat input control and managed this by moving down to a 0.040 electrode and a 500 degree interpass temp to be sure to keep the overall heat input low. Our procedures also included a 2.5% hydrogen shield gas
Lawrence" the test specimen consists of a (1) thru-hole fill 3/8 x 1/4 thickness, (2) slot fill about 1-1/2 long x 3/8w, and a corner fill about 1-1/2 in long. the hole thru is the biggest problem,as cracks apear in the center and are found by x-ray and sometimes FPI, we are using liquide argon as both backup and shielding gas, the welds look great and the drop through is perfect which leads me to believe the right amount of gas is good' I have been paying alot of attention to the degree of heat aplied and diferent types of bead placement. do you think a different type of shielding gas would help? Ron
Ron,
I'm not qualified to suggest that you actually employ such a change. The mix is more common with the Euros but the Hy provides a little more heat per amp and the edge wetting is superior as well. However the addition of Hy to shield gas must be determined by engineering experts.
Minimizing the heat input throughout the operation will be key. But you might ask extra question of the folks who did pass the thru-hole portion and see if they had a bit different bead sequence or technique when all edges came together.
It takes a bit of patients to keep your heat under 50 Amps on a comparitively thick casting but that was key for us and it can be done. We took the WPS from Pratt Whitney and really tightened things up. It worked so well over a several year span that Pratt eventually adopted our methods.
here`s the latest" I tried welding the sample using no more than 50 amps as sugested and seemed to work well" I was able to weld and pass the IN939 casting sample through X-Ray, Unaffically that is" I was told it was good so i submited it as a known good sample to be processed normally witch follows a visual then heat treated, FPI, X-Ray, and if it is o;K then to the lab to be cut up, polished and inspected under microscope" Problem is when it came out of heat treat it fell apart" i mean this in a sense it had suface cracks all over and the area`s x-rayed before now show cracks" I really do not know how to contend with this problem? my first thought is the heat treat process could be wrong but since i`am not a metalurgist i cannot dispute that? I should also state that i `am also having a similar problem with st-31 (stellite casting) RonB
As of this day I have no success with this materiel" I just found out the company i work for is bringing some guy in from texas next week to show me how this materiel is to be welded, I can`t wait" My predictions? I think the company this guy is coming from has a different production process than we use? (not heat treating parts) since i have heard that they primarily do repair work on parts that have already been in service" but we shall see???? anyway i will post the findings and end the mistery as soon as i know somthing"
Ron,
Keep an open mind :)
But DO LET US KNOW !!
I'm interested in your project... and even more interested in what your "hired gun" has to say.
Yes Lawrence" I will keep an open mind! how else can one learn??? well as of yesterday i was told the hired gun will not be here till next week now"
the hired gun arived on Tuesday! aparently the info i received about his shop not heat treating their repairs was false! they do heat treat! next the c263 filler wire is the correct wire to use! so both of those questions i had have been answered" however" much to my surprize the hired gun did not use backup gas for the through hole fill! what he did do was use copper chill plates for all of the welds and had several going at one time and just juggled them around after making a bead or two on each peice, the 50 amp stringer bead process IS the way to go! so the key seems to be NOT to get the sample too hot" I however have not yet had the chance to submit a sample myself as of this writing but i have started a couple and should finish them next week and will post the results when i do!
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