Dimensional Contraction of 17-4 PH Stainless Steel

This is kind of confusing.

First they say:

In the annealed (solution treated condition- Condition A) the density of this material is 0.280 lb/in^3.

Then:

The contraction factor for the change from Condition A to Condition H 900 ranges from 0.0004 to 0.0006 in/in or (mm/mm).

Hardening from Condition A to Condition H 1150 contracts in the range of approximately 0.0009 to 0.0012 in/ in or (mm/mm).

This makes it sound like it could be unannealed, which makes no sense. Is the Condition A, the treated material or are the H series the treated material? (my paragraph - I can't seem to format all of a sudden).

The solution treated condition is Condition A. It is also called solution annealled.

Regardless, it is untempered martensite as the predominate icrostructure. Tempering to higher temperatures (the numbers after the condition H designator- ie 900 or 1150) followed by cooling in air results in the precipitation of a new copper precipitate phase. I also believe that some tempering of the martensite is going on, as well as the possible formation of reverted austenite. I have seen a paper, though, that claims the tempering of martensite during aging is insignificant in this steel...

The point is that whatever happens, these changes result in a tougher product and one that is more corrosion resistant.

Some suppliers do a double age, but that is beyond the scope of my experience.

I wrote this, thanks for your feedback on readability.

Milo

Your math is wrong. 1.000-(.280/.282)^.3333=.002 not ".0004 to .0006". Similarly, 1.000-(.280/.284)^.3333=.004 not ".0009 to .0012".

Nothing wrong with my math, and by the way these are published figures, credited to Schmolz + Bickenbach in my post.

Your calculations are using density for cubic inch;

The shrinkage factors are in inches per inch.

The density factors were given as experimental correlation to illustrate and support why the contraction.

Have a nice day.

Milo

You will note that I used the third root of the density ratio to calculate linear contraction. The guys you are quoting apparently used the fourteenth root, and no one checked. Technical publications are often copy edited by English majors, because some engineers can't right to good, but some else should check the math.

Nice info, Milo. I used to love working with 17-4PH in the machine shop.

IIRC, shrinkage of 17-4PH is also not necessarily exactly linear. In my machinist days (aerospace) I remember seeing broad thin sectioned parts warp and twist on annealing. On these kinds of parts we always left plenty of material for finish machining and surface grinding to hold high flatness tolerances.

And for trivia addicts; we built lots of wind tunnel model cylindrical "balances" that had high precision machined beams for mounting strain gages. On occasion we would guess the shrinkage from annealing wrong and end up with some undersized feature or another. We found that by selectively chroming the undersized areas we could bring the part back into tolerance without trashing it and throwing it away. I'm talking about undersized by typically < .001" requiring only a minimal application of chrome. And the chrome didn't significantly alter the material/mechanical properties of the piece.

How do you manage to come up with this stuff that brings back memories I thought were long gone?

Hooker

Hi Hooker.

This post found its genesis in a private request from a PMPA member who needed to know how much to allow for shrinkage in this material. I'm their "answer man" for this sort of thing.

I decided to turn it into a knowledge retention post for "them that's doin.'"

Warp and twist is characterized as distortion. I think I have a post on that regarding quenching and tempering on here as well: 8 Reasons

Thanks for your comment.

Milo

Thanks for that link, Milo. I missed that one somehow!

Hooker

We are having problems with some 17-4 parts right now.

they are about 20" long, 3/8" thick and 4" wide.

We have a profile tol of .02 but there are 2 holes, one at each end that have a true pos. of .002 to each other.

the problem is, whenever we take a cut along the profile, the bar warps and twists beyond the tolerance.

I'm not sure of the heat-treat but, I they are for the oilfield industry.

Are there any tips you could give us?

I can get more inforomation on Monday.

Thanks in advance,

Calvin

For that kind of profile, we used to shim them on a mill table, machine one side, turn over and shim, rinse repeat until nearly flat, then repeat the whole process on a surface grinder.

Thank God we weren't a production shop!!

Hooker

Well the facts that we will surely need is the condition of the material that you are cutting. It is probably not condition A. Condition A is difficult to cut and very stringy chip issues. Condition H 900 is probably the better cutting "temper" of the 17-4 tempers available.

So we will need to know condition.

When you get the additional info send me a private message online and we can exchange emails and phone numbers and we'll see if I can help.

Milo