Manufacturing procedures of a 17-4 PH part 8

[cys150858]

Hi friends,
I have a part which it's material is 17-4PH ss and H1025 condition is requested. I know after H1025 the hardness might up to 38HRc. So I have to leave it the last step. I have 2 questions below :

1. Is it a necessary step to apply solution condition A before H1025? What might happen if the material I bought has no condition A and I send it to H1025 directly?


2. I have manufacturing procedure options I and II listed below. Could someone kindly give me some suggestion about which one is correct?

Option I :
17-4 plate -> Condition A (1900°F, air cool below 90°F) -> Machining -> H1025

Option II :
17-4 plate -> Machining -> Condition A (1900°F, air cool below 90°F) -> H1025



Thank you for your kindly help.

 

[redpicker]

1. Is it a necessary step to apply solution condition A before H1025? What might happen if the material I bought has no condition A and I send it to H1025 directly?

Yes, solution treatment is a required step. Often, however, the material is supplied in Condition A by the material supplier. If you are unsure, contact your supplier for clarification

2. I have manufacturing procedure options I and II listed below. Could someone kindly give me some suggestion about which one is correct?

Option I :
17-4 plate -> Condition A (1900°F, air cool below 90°F) -> Machining -> H1025

Option II :
17-4 plate -> Machining -> Condition A (1900°F, air cool below 90°F) -> H1025

You forgot Option III, treat to H1025 before machining. While 38 HRC is hard, it can be machined with carbide tools just fine. Unless you have some very exotic machining operations, Just machine the part already heat treated.

Opiton II would be the least desireable. You would get distortion and scaling of the surface with the Solution treatment. Option I is also undesireable as you will also get some distortion and scaling, although not as much.

rp

 

[EdStainless]

Option 1 is how it is done.
Remember that there is a little size change when you age the parts, they will grow.

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Plymouth Tube

 

[daschell]

With decades of experience machining 17-4 I will say from a machining stand point either option 1 (purchase material in the "A" condition and age to 1025 after machining) will work. Heat Treating after machining must be done in an inert atmosphere and the part will grow some .0002 0r .0003 per inch at the most. I have machined many parts net prior to heat treat and slight compensations produce fine parts.

Option 3 (Machining after heat treat) is in my opinion the best option as the 1025 condition is only 38 R/C and with carbide tools and even High Speed taps, drill produce beautiful parts with great finishes

 

[israelkk]

I agree with redpicker that option III is bast. We use option III for many years after lot of bad experience with option I or II. There is a problem of removing the heat tint before passivation without affecting precise dimensions. There is also a problem of hydrogen embrittlement when using chemical removal of the heat tint prior to passivation.

 

[EdStainless]

I presumed that the only finishing was machining. If you are going to bend, form, weld, swedge, or draw you would be better off working with material in the H1150M (overaged condition). This condition had much more ductility (even though it has higher strength) than the annealed material.
This does cause more HT work since you have to re-anneal before aging.
The heat tint can be removed with a light pickle treatment (30% nitric acid 0.5% HF).

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Plymouth Tube

 

[cys150858]

Dear Friends,
First to all I would apologize for the late response.

I am sorry for asking this simple question... I did try to study this by reading some heat treatment texts and data sheets from material manufacturing companies. But all of them simply describing solution and/or aging respectively without discussing the sequence/procedures of part manufacturing... It's really helpful for me to get opinions from your precious experiences.


Thank redpicker for reminding me option III and the surface problems. I might think of option III but did not realize it could be practical (I think was fooled by my shop lol)

Thank EdStainless. The additional information about H1105M and it's after treatment is very valuable for me. I am lucky the finishing this time is machining only as you mentioned it.

Thank daschell for your experience about the dimension growing. The biggest dimension on my part is about .7 inch. It looks the distortion could be under control. I might have no choice to choose option I due to my shop is not willing to machine part harder than 30 HRc..... Orz.....

Thank israelkk for your opinion. Upon all the information I am quite sure option III is the best solution. I hope I can convince my shop to go this way...

Again thank all the friends.



cys

 

[cys150858]

Dear Friends,
Sorry I have to again bother you about the 17-4PH.

1. I have found a supplier of 17-4PH (actually SUS630 instead) with solution treated. However the supplier told me that it's hardness is about 380 HB? It's almost 41HRc and actually harder than H1025 aging... I read from the text that there will be precipitation soluted in the austenite base after aging to cause the material hardened. But at this case it looks that it's actually "softened"? If the hardness of condition A is correct, upon the machining stand point, it looks option III and I are not much different? May I ask is my understanding correct?

2. I saw 2 values of holding time of H1025 on different texts. Some says 1 hour and some 4 hours. Is there a "standard" value? Or simply get different hardness?

Sorry it's my first time therefore those questions are quite simple... Thank you for your help.


cys

 

[btrueblood]

The material is a bit more ductile in the aged condition than in condition A, which is why some(many?) prefer the former. Can't help on hold time, I'd consult the data sheet from AK steel at the link below as a starting point, then increase or decrease based on the part size/thickness and your heat treater's experience:

http://www.aksteel.com/pdf/markets_products/stainless/precipitation/17-4_PH_Data_Sheet.pdf

 

[cys150858]

Thanks btrueblood for the response. Actually it's AK steel's data sheet to give me the idea of 4 hours. With your suggestion I am more confident about this number.

Thank you.


cys

 

[redpicker]

The different holding times are a bit of confusion.

For maximum ductility, the 4 hour time is recommended. I have only seen the 1 hour time used when maximum hardness is required (that is, for H900 or H925), and 4 used for other conditions.

cys,
In reply to you previous post,

I have found a supplier of 17-4PH (actually SUS630 instead) with solution treated. However the supplier told me that it's hardness is about 380 HB? It's almost 41HRc and actually harder than H1025 aging... I read from the text that there will be precipitation soluted in the austenite base after aging to cause the material hardened. But at this case it looks that it's actually "softened"? If the hardness of condition A is correct, upon the machining stand point, it looks option III and I are not much different? May I ask is my understanding correct?

Your understanding is mostly correct. Machinability is dependent on hardness, as well as other factors. The machinability in Conditon A may be slightly better, even though the hardness my be slightly higher than H1025, because the toughness is much lower and the chips will break easier (this really starts to depend on exactly what machining operations are being considered). With HSS or carbide tools, however, the difference isn't much and most people will age the material prior to machining.


Alloy 630 is sometimes used for 17-4PH. 17-4PH used to be a tradename for a patented alloy (Owned by Teledyne? I am not sure). 630 had slightly different chemical ranges (inconsequential) to avoid the patent (also showing the problems in trying to patent an alloy). I believe the patent has expired, though, and it is obvious nobody is trying to protect the trademark, so even that difference isn't there anymore.

rp

 

[EdStainless]

Typically at higher aging temps (lower strength) longer aging times are used.
The problem with the annealed material is that the properties are highly variable. If you are working in H1025 then I would HT and then machine. If there is concern about the stresses from machining you could always age at 1000, machine and then re-age at 1025. The aging is an effective stress relief.
The alloy is S17400, commonly called 17-4PH and 630 in various specifications. This does date from when 17-4PH was a tradename.

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Plymouth Tube

 

[mfgenggear]

cys

a lot of good advice.

with me it depends on the configuration & the hardness required of the parts.and the application
the stresses that can be predicted by the amount of stock removal & the aggressiveness of the shop doing the machining.
sometime I like to rough out parts and then do the heat treat, then finish after heat treat.

I like to machine after heat treat if it is permissible & the hardness or manufacturing allows for it. I only machine before
when I have too. some tolerances have to be ground, due to the tolerancing, or machined to a very very close tolerance.
then these attributes have to be machine after heat treat.
It is very hard to give advice on your question because there are numerous question that need to be addressed on the print & the complexity of the part. Is a pin or a very complex part with thin walls, & very close tolerance bores or holes.

a lot of good advice has been given this is to add to it.

Take Care
Mfgenggear

 

[israelkk]

Hardness for PH steels is not guarantied. Only minimum and maximum yield and tensile are guarantied. For the same heat treatment (such as H1025) the hardness deviation range can go up to 10RC. Therefore, if you stick to the standard guarantied heat treatments (according to MIL-HDBK5J or AR-MMPDS-01) such as H900, H925, H1025, H1075, H1100, H1150, only minimum and maximum yield and tensile are guarantied.

 

[cys150858]

Hi redpicker,
Yes, most texts I read indicate 4h hold time for H1025. Probably only one says 1 hour. I believe 4 is correct. Thanks for explaining the difference before and after aging. Combining those advices I believe to machine parts after aging is preferable choice.

I recall a similar situation (sorry it's not about 17-4PH we are discussing). Once in a meeting for discussing a part from customer. It's a S45C motor shaft (3/4 Dia. I think), quenching and tempering to 26+/-2 HRc. One really senior engineer said that we should use SCM440 without HT instead cause it's hardness of the bar stock we purchased is generally 22~24 HRc and it has Chrome and Nickel... Then we can save HT and get even better property.

However I doubt if it's correct... Our bar stocks from supplier were shipped from the mill directly. If it's not officially Q&T, I suppose the hardness is very possibly comes from the drawing process and the mechanical properties are not stable/uniform each patch. But eventually we followed this suggestion and continuously deliver SCM440 shaft without HT... I never feel comfortable about this...

The relation between 17-4PH and 630 is new to me! Thank you.


cys

 

[cys150858]

Hi EdStainless,
Thank you for the response. I did see the hold time are all 4 hours above H1025 and there are even H1150+1150 or H1150-M above H1150 only. Thanks for the H1000/H1025 suggestion. That's really what I never read on HT texts or handbooks...


cys

 

[cys150858]

Hi mfgenggear,
Yes, I did appreciate to get a lot of good and practical knowledge in this forum .

To work with 17-4PH is not that popular in the location I live. Especially to obtain the material (maybe cause I only need few kilos). I also agree with you it's about if the shops are aggressive or not... The shops here used to play with steel below 24 HRc. If there are some hardness (say 36 or 40 above) needed, we have to remove most of the material and leave .01 inch of final dimension for grinding after Q&T. However my part is actually not complex at all.

Again thank you for the suggestions. I think I will send the solution treated material to H1025 aging and then machine it. I will try to convince my shops...


cys

 

[cys150858]

Hi israelkk,
Sorry for the late response duo to I tried to find AR-MMPDS-01. I did check the values you mentioned (like Ftu, Fty..). It contains much information about 17-4PH (also other materials). Thank you for giving this instruction.


cys