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This temper condition for 17-4PH was referenced from MIL-HBK on Thread330-113147.

What does the M stand for?

The H designations don't seem to be available in the online desk edition, my hdbks are at work, and I am too impatient to wait out the weekend.

congratulations on your persuit.  Are you writing the book, someone else, or multiple authors?

RE: H1150M

I have 3 brochures from ARMCO and none have "M" spelled out.
There is only the aging procedure.  I know H1150D (NACE) is the "Double" overaging

It is one of the overaged, softest, conditions another common one being H1150, 4h + H1150, 4h whereas H1150M is 1400 2h +H1150 4h.  So I’ll have to go with “Modified” or since these heat treatments are used for severe forming it might be “Mechanical”.  Or it could be “Multiple”.

All my contacts with intimate knowledge of PH steels have moved on to better pastures.  I have some more brochures and notes that I’ll look over and see if “M” jumps out.

RE: H1150M

I'm glad you two are members of this site. It's great to have knowledgable people like you here.
  I happened across the H-1150M condition in the "Handbook of Stainless Steel" by Berstein, the best book ever written on stainless but hard to find since it was written in 1977.
This treatment is a double overaged treatment. It consists of a 1400F soak for 2 hours, cooling to room temperature, followed by 1150F for 4 hours. The resulting microstructure is a complex mixture of highly overaged martensite, normal overaged martensite, and highly stable austenite. It is very soft, 85 ksi yield, 32 Rc. The softest condition I can find.

I'm writing the book with a professor from Carnegie Mellon,
Sridhar Seetharaman. We're waiting for a final committment
from our publisher, and then we start.

Unclesyd, there do seem to be better pastures than Armco, sadly. That was quite a collection of minds at one time.

RE: H1150M

Whether it is Mechanical, Multiple,Machining, or Modified is not so important as what process it stands for and you have tied it down for us.  Thanks.

And thanks to mcguire for the interesting explanation of the structure.  I will sleep much better tonight knowing that all these phases are living so happily together!  Moderately strong, corrosion resistant, ductile...  Makes one want to think of an application for it --eh?

I almost wrote, "Makes one want to think up an application."  But then we don't want to nettle jimbo excessively.  See:  What's it with up?  Thread1010-113028

RE: H1150M

One thing I would like to add about the H1150 M heat treatment is that the specified 1400°F temperature is held relatively tight ± 15°F.  In fact all temperatures used for treating should be held a close as practical.
Also always remember that on both the H1150 D and H1150 M  treatments is the material has to cool to below 90°F between treatments.    
In addition there are a few other PH treatments mentioned, mainly for deep drawing applications, but it is best to stay away from them without a long consultation with the mill that produced the material.

I had very many discussions with the ARMCO Research People concerning the continued hardening of 17/4 due to thermal cycling,  the sudden drop in hardness of some parts, and why we had cracking of some parts in molten salt, not all, and many, many  more.  Their technical staff were some of the best with Mr Ed Brandt a standout.  I happened to be talking to Ed about making (10) 36 ft long tapered shafts on their new rotary forge when he found out they were going to close the Baltimore Facility.  

I just wish that the government or some university had the foresight the become a repository of all the papers from  big labs in the metal industry.      

RE: H1150M

Maybe it isn't too late. I'll bring it up with the industry's trade group, SSINA. In the meantime consider calling Allegheny's lab. They have the largest group remaining. I think Jack Shilling runs it.

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