Weld procedures for Inconel alloys?? 2

[LongCarbine]

Hello this is my first time on this forum, and I have a question..How do you weld inconel? I am a welder but have never worked with inconel, so the first time was a miserable dissapointment and it cost me a good job..I was unable to figure out this alloy's secrets in the little time I had to work with it, so any information which could bring me up to speed would be appreciated greatly..I have a good tig welding background with stainless steel, so if compared to SS it is ??how?? Thanks Matt

 

[CWIC]

It takes practice.

I do not consider inconel as similar to SS. SS's are typically Cr based. Inconels are Ni based materials.

GTAW or PAW are the commonly used processes of choice in the marine, aircraft and aerospace industries for joining this material. Other processes may be used to join this material, but these are the most common.

You'll notice a black line down the weld and the surrounding weld pool (a green hue is also present at the weld pool) during [GTAW] welding. I have welded miles of Inco tubing and sheet back in my aerospace days. Many marine mufflers are comprised of this material as well, but are more difficult to weld if they have been in service and exposed to the elements.

The exact base metal specification must be obtained prior to selection of a filler metal. There are many inconel alloys out there so I will not recommend a specific filler material. I believe INCO Alloys has been aquired by another corp. Use your search engine and do some research before taking on another Inco project. Once you've performed welds correctly, it is not that difficult.

It takes practice.

 

[LongCarbine]

Hey thanks for the info..It was for a job interview/weld test in aerospace shop..The alloy was 718 (5362??) and I had to do a standard butt weld with .030 and .060 plates and a thick/thin tee joint with the .030 on the bottom..The butt welds went okay, I noticed it really moves( shrinks) and I had to move quicker than I was used to..The problem was the tee joint, I couldn't get it to flow into the joint well and then it blew thru..I know practice practice, but I have no access to equipment or this material to play with, just 2 weeks to figure it out on paper before I take another test, I really want this job it would be a big break for me..I am self taught and have been into welding and fabrication since @86..Never had an opertunity to play with Inconel, what are the tricks??Is it in set-up? I was using a miller Syncro350 standard/straight polarity , 1/16th 2% thoriated w/gas lense the .030 I was welding @ 30 amps with .035 and the .060 @ 50 amps with .045 filler. I was jsut very dumbfounded with how this stuff reacted..I was wondering if I should have used the pulser, but I was unsure of the set-up on that so I jsut rocked the peddle..If someone could jsut give me the setup for the pulser (background/pps/% on time) with current peak for those two thicknesses, it would be greatly appreciated..Thanks for the input..Matt

 

[CWIC]

LC:
That is a standard Mil. 1595 welder performance qualification test used by most companies. 718 is very common in the aerospace industry, but have welded many other Inconel alloys. Usually companies have you run SS, Inco and aluminum - T, lap and butt joints on thick to thin materials.

My suggestions:
TECHNIQUE
1.) Use .035 filler rod. (The .045 can cool down or "chill" the weld when adding relatively large diameter filler metal on relatively thin material typically resulting in incomplete fusion. Think about it, the .045 is thicker than the thinner part joined...)

2.) I would not use the pulser on the Syncrowave. (I have taken this test everytime I started at a new company, and also had to retest every 6 months. Never had to pulse the thin Inco. Could be the reason for failing unless the company or WPS required pulsing the current.)

3.) Do NOT pump the pedal. (For the same reason I would not pulse the current.)

4.) Try fusing the joint first (yes the T) and then run a second pass with filler metal. You can use small tack welds at the start/stop points and they help initiate and terminate the initial autogenuos weld pass. (I have used this technique often on all 3 of the materials mentioned previously and never had any problems passing tests. A very steady travel speed is required and set the machine where the pedal is almost hits the stop. This will help to prevent blowing through the thin piece.)

5.) Direct the arc at the thicker piece washing the molten metal down onto the thinner part. (This action minimizes heat at the thinner part. This is performed with minimal torch oscillation as possible. Large weaving action will typically result in overheating the thinner part and the entire joint.)

6.) Joint fit-up is critical. 0 root opening. (Keep root opening as tight as possible during tack welding. This can make or break the test.)

7.) Slow arc travel speeds will overheat the entire test coupon. (Maintain a steady, continuous travel speed. This is completely dependant on your skill level. 4 -6 ipm should be about right depending on amperage.)

PREPARATION
8.) Wire brush weld areas just before the test and wipe with a clean, dry rag. (Do not use any chemical cleaning unless the parts have oil present. Clean the ink with the material spec. from the weld areas, front and back side of the joint. Also, wire brush the joint after tack welding and blow off the black soot. If you have to use solvents, make the dry rag the final cleaning process. Don't forget to wipe down the filler rod as well. Use a clean pair of gloves.)

9.) I usually use a #9 lense for materials that thin. Always show up for a test with a clean filter and protective plates in your hood. (This will increase your visibility, particularly on this type and thickness of material. I also use the "gold" lenses.)

10.) Clamp the parts to the bench, use chill bars if you have them. (This will help maintain root opening, keep the joint cool and minimize warpage during welding.)

COMMENTS
a.) I have taken this test without the "newer" generation of power supplies like the old Miller AB/BP's, Lincoln Idealarc Tig 300's, etc. without any problems. On the other hand have done it with an Aerowave or Squarewave Tig. It's the driver, not the car that wins the race (or in your case - who passes the test.)
b.) You probably need some practice, try to find a shop, school, tech. or vocational center where you can get some trigger time. Check around local precision sheet metal shops for scrap materials.
c.) Good Luck.

 

[LongCarbine]

CW thanks sooo much for the pointers, that was exactly what I needed to know..Now I just need to find a test machine and some material to play with and I should nail this test and hopefully get this job. Thanks again for the tips, I was having trouble finding stuff that was pertinent to my needs..Thanks Matt

 

[arto]

Lotsa info on welding nickel alloys in here:

http://www.nidi.org/multimedia/tech...re_pdfs/11000_reference_book_series/11012.pdf

 

[TVP]

CWIC referred to it earlier-- Special Metals is the company that now owns the trademark for Inconel, Incoloy, etc. Inco still mines nickel ore, but Special Metals is the company that does melting, casting, alloying, rolling, etc. More information on welding is available using the following link:

http://www.specialmetals.com/publication/Joining.pdf

 

[tigcast]

Your setup for the job sounded ok, if it were me taking the test I would use the pulser, set at 90 to 100 pps. 65 peak and 40 background. I would also recomend using a gas backup box for the test..

 

[tigcast]

LC;
I have read some of the info that has been put out for you and I have to say that what I wrote the first time was not quite so much into detail as what I have read, and I must say that I was most impressed with what I had to read, on the other hand there are some points of interest that I have to say I do not agree with, for example: I read one post of telling you about cleaning; I can tell you this about what I know about that part of the process, Inconel has a lot of oxidation on the surface and by wire brushing it all you are doing is shinning the surface, you are not removing the oxidation, I weld inconel every day and I use a roto file to remove this from the surface, it does not say whether your test is to be x-rayed, but I can tell you this as well, if it is I would not tell you to make 2 passes, you will fail, judging by what I have read you say you need practice and 2 passes + x-ray = fail, unless you are good, even if you do go with the 2 passes anyway I would reclean the first bead with the roto tool again, and for a filler wire, I would also go with the .045 you want the weld pool to cool, thick to thin, this tech. is called staling. if you go with the .035 you may wind up with cracks in the thiner wall.
Just some thoughts...
Good luck