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17-4 stainless heat treating

RJT

Titanium
Joined
Aug 24, 2006
Location
greensboro,northcarolina
I'm used to giving instructions to my heat treater for tool steel, carbon steel, 400 series stainless etc. but we do very little with 17-4. If I give a spec for the Rockwell hardness , what difference will the condition make? For example R/c 40 -45 condition H0900 versus H1100?? My customer doesn't specify, and if I know what properties the different conditions would affect, I could make a recommendation based on how the part is used. I know the condition refers to the temperature it is heat treated at, but how does that affect the characteristics of the steel?
 
H900 will be the maximum attainable hardness for 17-4PH. As you increase the temperature the ultimate strength and hardness will drop.

I am not sure if the H values will affect the materials properties in other facets such as chemical resistance, corrosion, etc.
 
Usually on 17-4, you don't specify a hardness for HT, you specify a condition. H900 is machinable and we purchase a lot of our 17-4 in that condition. H900 gives you the highest strength and hardness. If you have a CNC with decent tooling, machining is no problem.
JR
 
From what I recall, and from what the PDF up above also says.. 17-4 ends up all over the
map on hardness..

H900 40-47C, and I've seen it as high as 51C
H1025 33-39C
H1150 28-37C.

I've never seen a hardness call out on a 17-4 part... Its always a CONDITION, which gives
you a strength, and nobody has ever cared about the hardness.
 
and nobody has ever cared about the hardness.

It's worth knowing the range of hardness for a particular H condition, so if the Heat treater does a hardness test on the parts, you know whether it's in the correct range or not.
 
I am not sure if the H values will affect the materials properties in other facets such as chemical resistance, corrosion, etc.

From Mil-handbook 5

Design and Environmental Considerations — For tensile applications where stress corrosion is a
possibility, 17-4PH should be aged at the highest temperature compatible with strength requirements and at
a temperature not lower than 1025EF for 4 hours minimum.
The impact strength of 17-4PH, especially large size bar in the H900 and H925 conditions, may be very
low at subzero temperatures; consequently, the use of 17-4PH for critical applications at low temperatures
should be avoided. For non-impact applications, such as valve seats, parts in the H925 condition have
performed satisfactorily down to -320EF. The H1100 and H1150 conditions have improved impact strength
so that parts made from small diameter bar can be used down to -100EF with low risk. For critical low
temperature applications, a similar alloy, 15-5PH (consumable electrode vacuum melted), should be used
instead of 17-4PH because of its superior impact strength at low temperature..
 
I used some 17-4 materilal on my shelf (unknown condition) and sent it to my heat treater asking for 40 - 43 R/C. They asked what condition it needed to be, I responded H900 after reading response #3. Heat treater now says results are 30 -31 R/C that the material must not have been solution annealed. I told them go ahead and solution anneal and re age it. Is that how it normally would have to be processed?
 
If you start in the solution treated condition, you can simply perform aging to the desired condition. You can also re-age already aged material as long as you are doing a higher temperature age. You cannot, however, go to a lower temperature. For example, if you have H900 material, you could age it further to H1050. But if you had H1050, you cannot perform the aging treatment and get to H900. You would have to solution treat it and then perform the 900 degree age.
 








 
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