Portable Induction Coil fixturing

[DAVIDSTECKER]

We have a Miller Pro heat 35 with the liquid cooling for PWHT and so far we love it.
Most of the time we can warp the induction cable around the part even if it's not a true pipe or can wrap it in a flat coil as long as it is on a horizontal surface or we can drape it over the part.
We are getting into projects where we may need to a place flat coil on a vertical surface or ID of a large horizontal tube at the 9; 12; and 3 O'clock positions for spot pre and post weld heating.
I have been searching the internet for photos and videos of induction heaters in use but it seems that 99.9% of them are of welding pipe; a few fixtured flat panels but nothing really out of position; 2D or 3D.
I recently confirmed that aluminum and stainless steel are not effected by the induction field so that has opened quite a few possibilities.
Does anyone know where I can find more examples of fixturing coils or users groups or can share their own experiences?
My current work is gong to involve PWHT to 1,100 deg F although I believe our unit is capable of 1,450.
Thank you in advance.
Best regards, David

 

[DAVIDSTECKER]

CWEng,
The issues started with some defects in the casting which were only discovered when it was being rough bored.
I'll see about posting a photo of the part later to give a better picture of the project.
Part of the casting had a limited area that required RT and then the rest was MT which all pasted.
Things got worse when the guys air-arced the casting cold, they introduced all sorts of stress cracks.
Upon realizing the error the casting was stress relived then the areas were machined out with a ball mill until MT came out clean.
The troubles continued most likely due to a combination of the welding technic and heat management.
The areas were welded up, some around 3" deep in a 5-1/2" thick wall and maybe 10" x 15" in area in one case, with just pass after pass.
I'm unclear about all of the details regarding when PWHT was done in the gas oven but as they were grinding the welds flush they started hearing a series of very loud pings.
They ended up digging out cracks which pretty much remove all the weld seems and then expanded well into the base metal and we just couldn't get any clean metal after that.
All of the above and 13,000# of scrap is what I mean by "ate our lunch".
Which is again the basis of my original post.
We have at least learned our lesson regarding the welding technic hopefully, we didn't get a change to implement our new plan.
I want to learn more about how other people use their induction system on parts other than pipe.
I believe the foundry has welders qualified to AWS and others but NAVSEA is very intense, requiring something like 24 different test coupons for starters.
They also have very different metal groups compared to AWS and ASTM.
Our welding procedure is very similar to what you described with one notable exception that we pre-heat to 300 and inter-pass 300-500.
The funny thing is that we have another product made from C1Q and I don't were the weld procedure we use came from, but we barely per-heat it and then just slow cool it under a blanket.
At it's largest it is about 8" cross section,tapering to a bull nose, 100% weld, never a problem.
Best regards, David

 

[CWEng]

The MIL standards (now technical publications) do have a lot of rules that don't fit other industry standards, but once you get used to it, and get a system down, that aren't that bad. Not sure why you would need so many coupons unless you are talking about qualifying a lot of welders.

The cavity you desribe is not unusually big for large casting repairs. Some thing you could try is an intermediate stress relief after partial weld completion to help relieve some of the built up stresses before they become problematic. Another thing that caused problems like what you describe was having other internal casing defects near the weld repair that were undetected, or were detected but deemed acceptable. They can cause stress risers and lead to eventual failure.

We also always used fairly tough weld metal whenever possible, and difinately low hydrogen. We would use E71T-12MJH8 (or H4) for instance, instead of regular E71T-1. Or E7018-1H4R instead of E7018.

And one more odd one, but you didn't say which welding process you used (unless you were saying that your welding was similar in that it was FCAW as well). But if you are using GMAW (or metal core), we used to have cracking problems with that process that we never had with FCAW on thick repairs. No real explanation other than that the weld metal may not have been as tough, or possible build up of Mn and Si to make it harder when you are doing pass after pass.

It's an unlikely source, but do you know the heat treat condition of your casting? Some alloys/foundries do weld repairs before heat treatment for properties, (like normalize or quench and temper). Is there any chance the foundry was planning on that and sent you a "green" un-heat treated casting. It could be brittle and segregated in that state. Normalizing also helps reduce the segregation that happens during the solidification process in castings.

 

[DAVIDSTECKER]

The high number of coupons were for the PQR which the foundry would have to do even if the they copied ours.
It's typical of a lot of folks I talk with in that they are running at capacity and can not fill open positions little lone add more.
I once joked with the main guy at the foundry that he should hangout at the prison and get guys as the were let out and offer them jobs.
His reply was that they were his best workers.
I far as I know every thing the foundry did was done as required.
The weld technique we were going to implement was to lay down beads up the sides of the excavated areas, grind about half of that off then peen and repeat 3 times.
I concept is that this would stabilize the base metal and keep stress contained.

 

[DAVIDSTECKER]

While I have the photo of my casting in this thread, does anyone know of a tool that I can use to transfer the areas marked on the out side of the casting to the inside?
I'm thinking of something like a pair of outside calipers with a pencil or marker holder on one of the tips.
Curved leg dividers.