Welcome to the forum Kneal
Rail Cracks?
I've spent many cold blustry nights out on the line repairing Greek Ascoloy rails on compressor cases on JT9D's.
They should weld with relative ease.
First the process questions.
1. Are you using the class 1 repair doccument the FAA requires you to use?
2. Perfect surface prep is required...Abrasive (not wire brush) removal of all oxides near the weld and HAZ
3. Argon backup behind weld and heat affected zone?
4. Are post weld stress relief treatments being employed immedatly after welding operations as required by your class 1 repair doccument and the general material behavior of Greek Ascoloy?
Back to surface prep... If you are repairing rails... 100% of the crack must be removed, (it is a good idea to dye check to verify)... In a web area this may mean a thin cutting disc or dental burr to slice through the crack completely... It will not work to route half way and try to penetrate through. Also.. This stuff work hardens like nothing else..... Do not push hard on your ball burrs or they will last about 10 seconds each.
After routing the crack fully.. a smooth stone on a pencil grinder is a good choice to remove oxides from the weld and heat affected zone (some folks like 1 inch 80 grit discs)... A full flat argon backup/heat sink must be attached to the backside of the repair, we made our own custom backups for this repair. (poney clamps do a pretty good job holding them tight).
The weld should go in pretty easily.... I liked to run two passes, a hot root and a cooler cover to avoid undercut, rather than one big one.
If it is in the rail itself and not the web.. The crack still will most likely need to be sliced out fully, the edges beveled and several fill passes used to reshape the repair. If removal is of reinforcement is not required by your repair doccument, do not remove it.
If you are talking about cracks in the pressure vessel, this again requires full argon backup and complete routing of the original defect. If the engine is still on wing, how will you supply argon to the back side of the weld and how will you remove all oxides from the back side of the repair and HAZ? If you have no answer to this question, you cannot be in compliance with your repair doccumentation,, Stop.. Do not proceed without an engineering variation authority doccument (EVA).
That ought to get you started.
Thank you Lawrence, this was indeed a great help, I have a couple more quick questions if I may trouble you? the FAA repair says to use a AMS 5817 filler rod, however all the INTERNET resources I have questioned say to use 310, what is your opinion? also do you feel that setting my welder on a pulse setting would be beneficial? and what about pre-heating the material to 400 degrees prior to welding, as well as post heating, this method contradicts the use of argon back-up, but again all resources I referred to says to pre & post heat. the case seems to want to crack after the weld before I can even get to post heat. Again thank you for all your help!
Best regards: Ken
Hey Ken,
Stay with the 5817 filler is not the problem.
Preheat on 0.050 material won't be effective in the shop or on the wing for a long list of reasons... so forget about that. (besides if Pratt does not call out for preheat you just can't do it)
This stuff is pretty robust and I'm suspicious about the cracking before before the stress relief, unless the stress relief is being delayed more than an hour after the welding is complete.. Your repair doccumentation should stipulate that the stress relief is immediate following the weld and impose an actual time limit.
Are you doing a dye check after removing the original crack and before your first weld? You cannot weld over even a tiny bit of crack, porosity, contamination or discontinuity with this stuff. Much like Hastelloy X, welding over a crack in even the thinnnest Greek Ascoloy will just cause that crack to float right back to the top.... Its funny how it works, but trust me on this one. The metal won't lie and any shortcut will rise from the grave and cry aloud.
Pulsation is also not the answer on this type of repair.. The only time pulsation provides a heat input reduction benefit with GTAW is when the travel speed is constant... A manual repair of this nature is going to require the craftsman to change speeds, torch angles and heat input as every weld progresses eh? The pulser will only trigger migranes in yourself and everybody nearby.
Keep us posted
PS: Pratt Whitney has one of the best and most comprehensive Standard Practice welding manuals ever published. Your engineering staff should have this on file... Get access to it and read read read... You will be a much better craftsman when you have their data at your disposal.
thanks again Lawrence! this was just the information I was hoping to recieve. you have been a huge help and I greatly appreciate your input.
best regards: Ken
I also work for a repair station,and we just got a contract to repair PW600's.We haven't repaired any yet,as we are just tooling up.We got the first one in and the exhaust nozzle was cracked like crazy.
Do either one of you guys know if this Greek ascoloy is a major player on these engines?
By kneal
Date 03-05-2008 14:38
hey Ringo,
first off I would like to apologize for taking so long in my response, we have not done any repairs in the PW600,
the company I work for is very young (5 years), should I come across any of this information I will be glad to post it here. Good luck!
best regards: Ken
