Heat treating 15-5 after HIP

[bigsmacgofast]

Thanks for reading. I have a product I manufacture that is made of 15-5 stainless. Up until just recently the process was; casting, heat treat H1950, heat treat H900, then machine.

Due to casting issues we have deceided to have our product HIP'ed (hot isostatic pressure). I am wondering what process to put the product through after HIP. They will go to the HIP facility after the H900 treatment. The HIP process is 2075 degrees, 15k psi, 3 hour min. After HIP I will do the machine work.

My question is will I be able to just do the H900 process after machining or will I have to also do the H1950 solution treatment? I have not been able to get an answer on this and thought I would throw it out here as there seems to be a lot of knowledge here.
Thanks

 

[kenvlach]

HIP will totally undo the H900 treatment.

Do the HIP process at 2075 degrees (^oF I presume) right after casting. It will do most of the homogenization-solutionizing. Probably imposssible to do accelerated cooling from HIP or else it could entirely save you the solutionizing step.
Then solutionize at 1900 ^oF for 1/2 hour, quench, rough machine, H900, machine or grind to fit.

 

[bigsmacgofast]

Thanks for the input.
The parts that are going through HIP now have already been through the solution treatment. I assume the HIP, since it is not a rapid cool down, will undo that?

Then do the 1900 for 1/2 hour, rough machine and then H900?

I was hoping to avoid the h1950 treatment but it looks like I will have to redo that, right?

Matt

 

[kenvlach]

My opinion is yes, yes, yes.
However, I lack experience with this particular operation.
Suggest that you find out the maximum cooling rate within the HIP machine (they always have T-t profiles). Also, is this alloy UNS 92110 (cast version of 15-5)?

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=NMETEK066

and is this to meet some spec. such as ASTM A747?

Probably, less costly in the long run to solve the casting feed/solidification problem to eliminate forming porosity.

 

[arunmrao]

Has the process capabilities of Hipping for your 15/5 SS castings been evaluated? What kind of advantages were obtained. Can the same not be achieved by better feeding and solidification process. Perhaps a talk with local Foseco engineer might help as they have numerous products. Also now they are offering solutions to customer's need rather than sell their consumables as stand alones.

I entirely agree with kenvlach's suggestions.

 

[bigsmacgofast]

These are boat propellers. 16.5" diameter. Since we machine them the blades are very thick, about 10 times thicker than a typical cast propeller. The foundry has made great advances with the casting process. We used to have holes about .25" diameter throughout the joint of the blade and the barrel. The base of the blade is almost an inch think and the barrel is only .100" thick. This is where the bieggeest problem is.

The other advantage of HIP is the strength increase. We need all the strength we can get so the props stay together. Otherwise blades have a tendency to fly off.

There is no spec to which we need to HT these to. Just whatever we find that works the best. There has to be a balance between ductility and hardness. Too hard and the blades fly off, too soft and they bend. It's a balance act.

The minor cast voids are also a cosmetic issue. If HIP removes the voids, like I hope, it will eliminate a great deal of finish time.

So from what I gather here I should treat these parts after HIP as if they just came out of the mold?

Thanks for all the input.
Matt

 

[arunmrao]

your application is an interesting one.If Hipping is an econmical solution please proceed. However, I will be thankful if you could provide the costs differences for a hipped casting and and a component machined from solid block.

As an aside can you not consider a 2 piece construction,i.e the barrell can be solid/pipe which can be inserted during casting or can be welded separately. This might reduce your problems and eliminate the need to Hip.

 

[bigsmacgofast]

A billet prop is much more expensive than cast. A casting is about $300. A block of 15-5 billet, 16" x 16" x 10" would weigh about 720 lbs (it's been a while since I did the math) @ $5 per pound would cost about $3600. The casting is $300 + $140 for HIP.This is substantially less than billet. Not mention the additional machine time.

When I was looking for billet I given wait times of about a year. I can have a casting made in 10 days.

I have considered billet and I would offer it to my customers but the cost would be about much more than that of cast.

You are correct in that a two piece or weld on blades are not an option. The blades fly off!

 

[arunmrao]

Thanks for the info. I just needed a comparative cost to understand the economics.

 

[EdStainless]

How many of these do you make? I am thinking of some other options, but volume would be critical.

There are ways to make these as welded structures that would be stronger than castings. Think of splitting the hub, so that each blade and its transition to the hub would be a single machined piece. Then weld the hub sections together. This way the welds are in lower stress locations.

Remember with HIP that it will only help with closed (internal) defects. Any that are open to the surface will be unaffected.

I doubt that the cooling rate from HIP will be fast enough. You will probably have to follow it with the 1905H step.

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[bigsmacgofast]

Edstainless,

Thanks for the input, well thought out! I make several hundred a year of these.

The holes are deep in the casting and yes the HIP facility said the cooling rate is quite slow.

With the exception of the holes this program is going very well. I like your idea about welding the hub but I have soooooo much time and money in the current project I need to get it rolling before I get into another idea.

Thanks for your input!

 

[EdStainless]

It sounds like you are on the right track.
Do you take samples from each heat of castings and heat treat them to come up with an optimum aging temp?

I have seen this done with forged blade/hub segments. The process was; forge, rough machine hub, welded together, rough machined, annealed, bulk machined, heat treated and aged, then finish machined and polished.
This could be done with castings, forgings, or machined from plate sections. If I was going to weld thick sections I would look to an alloy like 17-7PH.

The real reason that I asked about volume was that I was thinking about powder metallurgy. You could even do individual segments, sinter, assemble and then HIP.

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Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[bigsmacgofast]

The biggest problem is cost. There other processes that are better than what we are using but the cost goes up quite a bit.

The HIP and HT (after HIP) are 2 expenses we didn't expect to have. Of course they will reduce the profit margin. Down the road after we establish the improved durability of our product we can get away with charging more for our product.

From input here and other sources I think the process is going to be;
cast
HIP
H1950
machine
age to H1025 or H1075
final hand finish

Unless anyone finds any problems with this process.

Matt

 

[EdStainless]

You know that the parts will grow when you age them. I don't know how much to expect with cast 15-5. In 17-7 it is 0.004"/inch.
My only other question, and I hope that some one knows, Does 15-5 care how long it sits between the 1950 and aging? It does matter with some grades, but not others.

Looks good.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[bigsmacgofast]

That's a good question about how long it has to wait between the two heat treat processes. There will be days or even weeks between the fitst cycle and the second.

Tolerance is not that critical. As long as we are within .005" we will have a superior product.

Thanks for the input.