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]

Here is an update to my current project.
The casting is ASTM A216 Gr WCA.
Here in St. Louis the shop isn't getting much above 40 deg F so I want to preheat and maintain the casting at something around 100-200 deg unless someone knows of a better choice while we air arc to remove the offending indications found by RT.
PWHT will also be required mainly due to the amount of surface area involved.
Would it required or advisable to PWHT after air arc and can I process one are at a time then move to the next?
I have a couple of Weld Engineers here that I can work with but I'll take all the advise I can get.
Best regards, David

 

[Tmoose]

I have nothing to offer about preheat for air arc .

You probably already have also read this in A216 -

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10. Repair by Welding
...........

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10.3 Castings containing any repair weld that exceeds 20 %
of the wall thickness or 1 in. [25 mm], whichever is smaller, or
that exceeds approximately 10 in.2[65 cm2] in area, or that was

​

made to correct hydrostatic test defects, shall be stress relieved

​

or heat treated after welding.

 

I am dubious about how induction heating could work on such a large, non-cylindrical part. This looks like a job for natural gas fired radiant heaters; the second choice would be electric resistance heating pads (slower and more costly).
For purposes of preheat I treat thermal gouging operations the same way as welding operations; in other words, I generally require the same preheat for the material and thickness as I would for welding.
If you have a couple of Weld Engineers, why can they not help you?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[DAVIDSTECKER]

Tmoose, We are on the same page regarding the ASTM spec.

im, the induction coils can be used in a flat pattern although most applications are for cylindrical parts which is the basis of my post.
I would like to see more examples of these odd applications and see what I might be able to incorporate in to my projects.
Most of the wall thickness's are only 2" so they are well within the range of system.
It is going to require a lot of special insulating materials to keep the heat where I need it.
I have found some examples of non-cylindrical applications but they are typically for some sort of production process while most of what I need to do is a one time shot.
While the Welding Engineers I know are very knowledgeable and helpful their experience with large castings and induction heating is not that great so to me it makes sense to go farther a field to find people with first hand experience.
While this project is WCA, we also have current projects made from ASTM A757 Gr C1Q and A1Q which present similar challenges.

We have used the induction system in slightly different ways such as pre-heating this casting for hard surfacing.
While we were able to wrap the cable around the part we could have done it with two flat coils draped over the curved surfaces.

Thanks to both of you for your input.

 

[arunmrao]

I have used induction or electric resistance heater pads for CA6NM grade castings. But for 216 grades,, I just followed the ASTM recommendation even for large odd shaped castings.

The castings looks nice ,what was the sand system used?

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[DAVIDSTECKER]

Arunmrao,
The foundries web site states that they use a sodium silicate no-bake sand system.
I'll pass along you comments although they've sent me some that look like death warmed over.
Sand inclusions do seem to be one of the most common defects we have to deal with.
To their credit, we do make a lot of large items with some expansive thin sections so that leads to some higher flow rates of the metal and erosion.
This anchor crown and flutes is a good example.

 

[arunmrao]

If they can change to Furan resin sand,, sand inclusions would be reduced drastically.This looks like a ship anchor casting. what class? Its is not a simple job that every foundry can attempt.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[DAVIDSTECKER]

Did a quick Google on the Furan resign, very interesting.
My first impression as to why the foundry may not use it on the whole may be the working time once the mix is made, sort of like a two part epoxy.
I will ask them about though when I get a chance.
The last photo is for a Navy Light Weight type anchor, full MIL spec.
Some times we make this style out of Hadfield Manganese so they are non-magnetic.
Big pain in the A**.
I think the assembled mold for the part I'm working with came in at around 35K.
With this being a one off there is a lot of manual labor and a lot of territory to cover so trying to beat the clock could be a problem.

 

[EdStainless]

If you are thinking of holding your coils in place with SS braces please check and make sure that they are really nonmagnetic.
They will still heat because they are conductive, but a lot less.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[arunmrao]

David a candidate casting for 3D sand printing. You could get them printed in less than a week and have them cast. Well,the mould and core material is Furan. I make these castings and I know the exact spot where it pains.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[DAVIDSTECKER]

EdStainless,
I'm probably going to go with 6061 aluminum since we also fabricate with a lot of it here, I was thinking about 316 SSTL wire but might switch to aluminum as well even though we do have a gage for magnetic permeability.
I ran across a sheet product called Isoplan that I am thinking about as a backing material to hold the coil shape in position.
I've seen wood and plywood in some fixtures but I think they were mainly preheat and not PWHT.
I have lots of nooks and crannies in less than ideal positions to deal with.

arunmrao,
Have you done much with WCA with regards to repairs that require PWHT?
I've been communicating with the foundry and I am getting the impression that I don't need to PWHT until all of the repairs are complete, and not while the area is still at weld temp.
What are your thoughts?
We just had a C1Q casting eat our lunch the other day.
I'm not 100% sure what the main issue was but it has me concerned about proper heat management.

 

[DAVIDSTECKER]

arunmrao,
How are you with?

 

[DAVIDSTECKER]

WHO are you with?

 

[EdStainless]

Be careful with using Al, it starts getting very soft at fairly low temperatures.
SS wire is a good option.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[DAVIDSTECKER]

Esdtainless,
The temperature outside of the 1" thick thermal blankets where the coil and fixturing shouldn't get that hot.
While it does get pretty warm outside with the inside at 1,100 deg I don't think that it gets too much over 200 deg if I recall.

 

[CWEng]

Having formerly worked at a foundry, we repaired millions of pounds worth of WCA/WCB castings and allowed the welds to cool to room temperature before PWHT. And as your foundry implied, only PWHT-ing once all the repairs are done is adequate. Never had a problem doing it that way that I recall.

 

[DAVIDSTECKER]

CWEng,
Thank you for the input.
As I mentioned earlier we just had a C1Q casting eat our lunch so I'm look for all the information I can get.
Normally we have all of these repairs done at he foundry but this job requires NAVSEA welder qualifications which the foundry has not done.
Although for some reason I seem to recall somewhere in some ASTM spec that some how a foundry is sort of automatically qualified to may any repairs to castings.
Do you know anything about that or is this wishful thinking?
Best regards, David

 

[CWEng]

What process are you using to weld, and what do you mean by "eat our lunch"? That could be a lot of issues- cracking, distortion, foundry defects??? We didn't do a whole lot of A757 C1Q, but did have one PQR spefically qualified on this grade using a 3" thick test plate (which gets you go ulimited thickness in TP-248). We preheated to 150F, used MIL-81T1-Ni1C filler metal (Select Arc 820 Ni1) and didn't have any issues qualifying including impacts at -50F. PWHT was at 1125F.

One thing you may look into is the foundry's melt process. Most of our high strength low alloy steels were put through the AOD refining process. If you are getting arc melted or induction melted castings, they may not be as good quality and have higher S and P...but that also depends on your starting material.

There is no magic bullet to qualify foundry welding being automatically qualified, but there is an ASTM specification for qualification of repair welding- ASTM A488. It has qualificaiton rules similar to ASME IX, but with some casting specific rules as well, such as bend testing less ductile material.

 

An impressive lack of PPE on display by the personnel ...

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."