Allowable Stress Values for 17-4 PH stainless steel (H1150 vs. H1150M)

[auzie5]

I am currently designing a line blank component using SA-564 Type 630 (a 17-4 PH stainless steel) in the H1150M age hardened condition. However, ASME Section II, Part D, Table 1A only lists maximum allowable stress values (S) for SA-564 Type 630 in the H1150 age hardened condition. No allowable stress values are listed for H1150M!

My question is:

Can I use the H1150 maximum allowable stress values (S) listed in ASME Section II, Part D, Table 1A when designing a component made from H1150M?

Note: SA-564 Type 630 H1150 appears as line 22 on page 46 of ASME Section II, Part D, Table 1A (2011 verision).

I realize that the elevated UTS and YS of H1150M is less than H1150, however there are no mechanical properties for H1150M or H1150D in ASME Section II, Part D. I’ve always considered H1150M and H1150D as sub-conditions of H1150 but I’m not 100% positive that the values listed for H1150 in Table 1A are intended to apply to both H1150M and H1150D as well.

Thanks in advance for any light you can shed on this request for clarification.

 

[metengr]

I think using the higher allowable stress values would not be prudent for the 1150M material. What you might want to consider is to review the mechanical property values of the 1150M and compare to condition 1150 at RT. Using the allowable stress values for 1150 material in Section II, you could ratio the value for 1150M at RT and higher service temperatures. This way you have allowable stress values which have a knockdown factor rather than using the higher allowable stress values.

 

[auzie5]

Thanks for the suggestion metengr!

I agree that taking the ratio of room temp TS between SA-564 Type 630 H1150M to H1150 would give me a ratio I could then apply to the elevated temperature values listed in ASME Section II, Part D (Table 1A).

Note that since H1150M is not listed in ASME Section II, Part D so I will use the values listed in ASME Section II, Part A.

SA-564 Type 630 (min TS - Table 4: Mechanical Test Requirements After Age Hardening Heat Treatment):

min TS of H1150M = 795 MPa
min TS of H1150 = 930 MPa

Ratio of H1150M : H1150 = 795 : 930 = 0.855.

Also note that the TS for H1150 listed in ASME Section II, Part D (Table 1A) is non-mandatory and is superseded by ASME Section II, Part A.

 

[EdStainless]

But as I recall the yield is reduced more than UTS, you may need to check that and base allowed stress off of the Yield and not UTS.

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Plymouth Tube

 

[auzie5]

Thanks for the comment EdStainless.

Yes you are correct that the ratio of YS values for H1150M to H1150 is less than the TS ratio:

TS Ratio:

H1150 : H1150M = 795 MPa : 930 MPa = 0.855

YS Ratio:

H1150 : H1150M = 520 MPa : 725 MPa = 0.717

However, ASME allowable stress values (as listed in ASME Section II, Part D or ASME B31.3) are based on 1/3 TS at design temperature. Therefore I believe it is more correct to use the H1150 values listed in Table 1A (ASME Section II, Part D) adjusted using the TS ratio (as listed above) to determine H1150M allowable stress values at elevated temperatures (i.e. 1/3 TS of H1150 values times the room temperature TS ratio of H1150M : H1150).

If I was designing a component based on 2/3 YS (ex: when calculating pipe wall thickness using ASME B31.3 Chapter IX formula) I would agree that the YS ratio should be used to convert the H1150 elevated temperature YS values listed in Table Y-1 (ASME Section II, Part D). But when working in Table 1A it seems logical to keep conversion factors in terms of TS.

Note: Elevated YS values for SA-564 Type 630 H1150 can be found on page 580 of ASME Section II, Part D, Table Y-1, line 5 (2011 edition).

Any thoughts?

 

[mrfailure]

I would use minimum tensile strength ratio to compute room temperature allowabe stress and multiply this by the 1150 allowable stress: Hence, 38.6 ksi * 0.855 = 33.0 ksi. However, instead of maintaing the ratio, I would maintain the difference: at specified design temperature 1150M would be 5.6 ksi (39 MPa) below 1150 design stress. I tried this comparison using the Table 1A allowable stress for other SA564 630 treatments listed and found this correlation worked well.

Aaron Tanzer

http://www.lehightesting.com

 

[EdStainless]

What max temp are you going to?
For all heat treatment conditions other than H1150M, with exposure at 950F or lower, the long term strength will increase.
This does not happen with H1150M material.

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Plymouth Tube

 

[auzie5]

Design temp is 344 deg C (650 deg F). It's the highest temp that ASME Section II, Part D lists allowable stress values for H1150.

EdStainless,

Just to clarify, are you saying the H1150M will not strengthen or incress in hardness over time when exposed to temperatures at or below 950 deg F? This is an attractive characteristic to aging the 17-4 PH stainless steel to the H1150M condition since in sour service applications (NACE MR-0175) maintaing low hardness is a critical defense against hydrogen stress corrosion cracking.

Do you have a good link that outlines the tensile strength, yield strength, or harness as a function of the logarithm of aging time at constant temperatures for this specific material (i.e. H1150, H1150M, and H1150D)? If so I would greatly appreciate being able to review this data.

It is my understanding that aging to condition H1150D will also prevent changes in strength/hardness over time. Would you agree that H1150D can be exposed to 950 deg F or lower without the long term strength/hardness increasing?

Thanks!

 

[EdStainless]

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

Is the best that I can find, but it is far less data than the original Armco alloy handbook.
There is not high temp exposure data for H1150M.

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Plymouth Tube

 

[auzie5]

Ha! Thanks EdStainless. I'm actually waiting for a research expert at AK Steel to return my call regarding this issue. I'll keep you posted on his position.

 

[auzie5]

Also noticed that SA-564 Type 630 Condition A is not listed in ASME Section II, Part D. How can it be that this material is not acceptable!!

To summarize:

Neither SA-564 Type 630 Condition A, Condition 1150M, nor Condition 1150D have published elevated temperature allowable stress values in ASME Section II, Part D.

Is the use of these materials at design temperature only permissible if elevated temperature destructive tests are conducted so we have "actual" values to use during design? Seems like I'm overlooking something.

 

[metengr]

No, you are not overlooking anything. Listing of materials for use in ASME Boiler and Pressure Vessel Code design and construction is dependent on users or vendors to formally request acceptance. This means the user or vendor submits the necessary technical information to the code committee so that material properties can be evaluated, confirmed and allowable stress lines can be assigned with any material limitations. If there are no requests for use of a material, it will not be listed. In other cases, material may never be acceptable for use as pressure retaining material in boiler and pressure vessel construction.

ASME Boiler and Pressure Vessel code is not a clearing house for use of all materials.

 

[mighoser]

Check out MMPDS. It has some data on the H1150M condition and some strength at temperature charts. Aerospace Structural Metals HDBK is really good but pricey. FYI, beware of long term aging in the 700-900F region which can lead to embrittlment (low impact strength + ductility).