ASM Online Member Community

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

In my experience the PH grades are far more sensitive to temperature than times (compare Figure 4 and 5 in your reference).  I would be comfortable adding 1/2 hour per inch of cross section, and worry more about the uniformity of my furnace.  A lot of specifications for PH grades require a +/- 10F uniformity according to AMS 2750.

I think specs are hesitant to suggest soak times since furnaces and shops always vary place-to-place.  No one I know has ever gotten a good answer out of customers/spec writers on that topic.

I admit 8" sounds pretty hefty - not sure I'd go much larger than that.  I wonder if there's a suggested size restriction somewhere.  AMS doesn't say anything?

------------------------------
George Shannon
Xerox
Fairport NY
------------------------------

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

Thank you for the feedback George.

I agree with you that temperature is the main focus.  We typically stick to aging in +/- 10 F equipment for that reason/spec compliance.  For some jobs we will soak for a bit just below the aging temperature to equalize the part temperature before bringing it up to the final aging temperature.

I didn't think of AMS for some reason!  AMS5643 provides the same 4 hour guidelines, except with a +/- 15 minutes timeline.  Curiously, the solution treatment time includes the note "time commensurate with thickness, heating equipment, and procedure used..." but does not have a similar note for the Aging times.  Sizewise it does say in 3.4.3.2 that product up to 8" cross section "...precipitation heat treated in accordance with the corresponding temperatures and times shown in Table 2 [which specifies 4 hrs], and cooled in air, shall have the properties shown in Table 2 for that particular condition..."

To me, that reads that all parts less than 8" cross section shall be held for four hours.

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
3178482570
------------------------------

Original Message:
Sent: 03-20-2020 09:01
From: George Shannon
Subject: 17-4 PH Aging

In my experience the PH grades are far more sensitive to temperature than times (compare Figure 4 and 5 in your reference).  I would be comfortable adding 1/2 hour per inch of cross section, and worry more about the uniformity of my furnace.  A lot of specifications for PH grades require a +/- 10F uniformity according to AMS 2750.

I think specs are hesitant to suggest soak times since furnaces and shops always vary place-to-place.  No one I know has ever gotten a good answer out of customers/spec writers on that topic.

I admit 8" sounds pretty hefty - not sure I'd go much larger than that.  I wonder if there's a suggested size restriction somewhere.  AMS doesn't say anything?

------------------------------
George Shannon
Xerox
Fairport NY

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

Hi Ryan, 
Have you checked AMS 2759/3?  In Table 4 of rev E ( I don't have a later revision), it gives guidance of 30 minutes per inch for 17-4 PH. Hope that this helps.

------------------------------
Lawrence Cheung
Sr. Principal Metallurgist
Northrup Grunman
West Covina CA
(323) 715-1525
------------------------------

Original Message:
Sent: 03-20-2020 14:43
From: Ryan Wilmes
Subject: 17-4 PH Aging

Thank you for the feedback George.

I agree with you that temperature is the main focus.  We typically stick to aging in +/- 10 F equipment for that reason/spec compliance.  For some jobs we will soak for a bit just below the aging temperature to equalize the part temperature before bringing it up to the final aging temperature.

I didn't think of AMS for some reason!  AMS5643 provides the same 4 hour guidelines, except with a +/- 15 minutes timeline.  Curiously, the solution treatment time includes the note "time commensurate with thickness, heating equipment, and procedure used..." but does not have a similar note for the Aging times.  Sizewise it does say in 3.4.3.2 that product up to 8" cross section "...precipitation heat treated in accordance with the corresponding temperatures and times shown in Table 2 [which specifies 4 hrs], and cooled in air, shall have the properties shown in Table 2 for that particular condition..."

To me, that reads that all parts less than 8" cross section shall be held for four hours.

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
3178482570

Original Message:
Sent: 03-20-2020 09:01
From: George Shannon
Subject: 17-4 PH Aging

In my experience the PH grades are far more sensitive to temperature than times (compare Figure 4 and 5 in your reference).  I would be comfortable adding 1/2 hour per inch of cross section, and worry more about the uniformity of my furnace.  A lot of specifications for PH grades require a +/- 10F uniformity according to AMS 2750.

I think specs are hesitant to suggest soak times since furnaces and shops always vary place-to-place.  No one I know has ever gotten a good answer out of customers/spec writers on that topic.

I admit 8" sounds pretty hefty - not sure I'd go much larger than that.  I wonder if there's a suggested size restriction somewhere.  AMS doesn't say anything?

------------------------------
George Shannon
Xerox
Fairport NY

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

Replying to Ryan Wilmes:

I had a professor at school who reminded us that in a pretty conductive material like most metals, while being heat treated the surface cannot be more than a certain amount hotter than the interior.  Another way of saying that the surface cannot be at the furnace temperature while the core is lagging in a uniform part.  There is only so much (depending on thickness and conductivity) that the center CAN lag while the surface has reached.  S17400 does have the typical lower conductivity of many stainless steels.

You mentioned H925 to H1150.  The toughness and SCC resistance of the H925 is far below that of the higher treatment grades.  Certainly you're most interested in crack initiation from the surface so it's there that the properties are most important to meet specification, though if there is surface finishing or machining post-heat-treatment that's a new surface.  The choice of the heat treatment specification is of course the designer's issue, not the heat treater's. 

The latter's success will be judged by the hardness test almost certainly.  However this grade has fairly wide resulting hardness ranges at each temperature, which make it difficult as an end-user to reliably differentiate one heat treatment from the next up or down.  So having a well documented heat treatment process is invaluable for parts acceptance.  I know because I was asked to "accept" parts based only on hardness tests, which means they can only be accepted based on other corroborating evidence of supplier compliance and competence, though they can be rejected if a hardness result is sufficiently far from the mark.  For that matter, Condition A hardnesses overlapped some of the properly aged ranges.

------------------------------
Paul Tibbals, P.E.
------------------------------

Original Message:
Sent: 03-21-2020 03:53
From: Lawrence Cheung
Subject: 17-4 PH Aging

Hi Ryan, 
Have you checked AMS 2759/3?  In Table 4 of rev E ( I don't have a later revision), it gives guidance of 30 minutes per inch for 17-4 PH. Hope that this helps.

------------------------------
Lawrence Cheung
Sr. Principal Metallurgist
Northrup Grunman
West Covina CA
(323) 715-1525

Original Message:
Sent: 03-20-2020 14:43
From: Ryan Wilmes
Subject: 17-4 PH Aging

Thank you for the feedback George.

I agree with you that temperature is the main focus.  We typically stick to aging in +/- 10 F equipment for that reason/spec compliance.  For some jobs we will soak for a bit just below the aging temperature to equalize the part temperature before bringing it up to the final aging temperature.

I didn't think of AMS for some reason!  AMS5643 provides the same 4 hour guidelines, except with a +/- 15 minutes timeline.  Curiously, the solution treatment time includes the note "time commensurate with thickness, heating equipment, and procedure used..." but does not have a similar note for the Aging times.  Sizewise it does say in 3.4.3.2 that product up to 8" cross section "...precipitation heat treated in accordance with the corresponding temperatures and times shown in Table 2 [which specifies 4 hrs], and cooled in air, shall have the properties shown in Table 2 for that particular condition..."

To me, that reads that all parts less than 8" cross section shall be held for four hours.

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
3178482570

Original Message:
Sent: 03-20-2020 09:01
From: George Shannon
Subject: 17-4 PH Aging

In my experience the PH grades are far more sensitive to temperature than times (compare Figure 4 and 5 in your reference).  I would be comfortable adding 1/2 hour per inch of cross section, and worry more about the uniformity of my furnace.  A lot of specifications for PH grades require a +/- 10F uniformity according to AMS 2750.

I think specs are hesitant to suggest soak times since furnaces and shops always vary place-to-place.  No one I know has ever gotten a good answer out of customers/spec writers on that topic.

I admit 8" sounds pretty hefty - not sure I'd go much larger than that.  I wonder if there's a suggested size restriction somewhere.  AMS doesn't say anything?

------------------------------
George Shannon
Xerox
Fairport NY

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

Some thoughts:
1. 15-5 has much better through-thickness properties than 17-4 and is preferred for thick section parts. (Note that the specifications partially overlap.)
2. Condition A material has inconsistent toughness. Even though it has hardness (strength) comparable with some of the aged conditions, using the aged materials is far safer. In recognition of this, some organizations have forbidden the use of condition A 17-4.
3. After thinking about it for quite some time (years now), I believe that the minutes-per-inch paradigm makes physical sense only if the rate limiting step is heat transfer from the furnace into the part. The thermal conductivity of any metal distributes heat faster than the heat is introduced into the part.


------------------------------
John Grubb FASM
New Kensington PA
(724) 448-5272
------------------------------

Original Message:
Sent: 03-22-2020 03:17
From: Paul Tibbals
Subject: 17-4 PH Aging

Replying to Ryan Wilmes:

I had a professor at school who reminded us that in a pretty conductive material like most metals, while being heat treated the surface cannot be more than a certain amount hotter than the interior.  Another way of saying that the surface cannot be at the furnace temperature while the core is lagging in a uniform part.  There is only so much (depending on thickness and conductivity) that the center CAN lag while the surface has reached.  S17400 does have the typical lower conductivity of many stainless steels.

You mentioned H925 to H1150.  The toughness and SCC resistance of the H925 is far below that of the higher treatment grades.  Certainly you're most interested in crack initiation from the surface so it's there that the properties are most important to meet specification, though if there is surface finishing or machining post-heat-treatment that's a new surface.  The choice of the heat treatment specification is of course the designer's issue, not the heat treater's. 

The latter's success will be judged by the hardness test almost certainly.  However this grade has fairly wide resulting hardness ranges at each temperature, which make it difficult as an end-user to reliably differentiate one heat treatment from the next up or down.  So having a well documented heat treatment process is invaluable for parts acceptance.  I know because I was asked to "accept" parts based only on hardness tests, which means they can only be accepted based on other corroborating evidence of supplier compliance and competence, though they can be rejected if a hardness result is sufficiently far from the mark.  For that matter, Condition A hardnesses overlapped some of the properly aged ranges.

------------------------------
Paul Tibbals, P.E.

Original Message:
Sent: 03-21-2020 03:53
From: Lawrence Cheung
Subject: 17-4 PH Aging

Hi Ryan, 
Have you checked AMS 2759/3?  In Table 4 of rev E ( I don't have a later revision), it gives guidance of 30 minutes per inch for 17-4 PH. Hope that this helps.

------------------------------
Lawrence Cheung
Sr. Principal Metallurgist
Northrup Grunman
West Covina CA
(323) 715-1525

Original Message:
Sent: 03-20-2020 14:43
From: Ryan Wilmes
Subject: 17-4 PH Aging

Thank you for the feedback George.

I agree with you that temperature is the main focus.  We typically stick to aging in +/- 10 F equipment for that reason/spec compliance.  For some jobs we will soak for a bit just below the aging temperature to equalize the part temperature before bringing it up to the final aging temperature.

I didn't think of AMS for some reason!  AMS5643 provides the same 4 hour guidelines, except with a +/- 15 minutes timeline.  Curiously, the solution treatment time includes the note "time commensurate with thickness, heating equipment, and procedure used..." but does not have a similar note for the Aging times.  Sizewise it does say in 3.4.3.2 that product up to 8" cross section "...precipitation heat treated in accordance with the corresponding temperatures and times shown in Table 2 [which specifies 4 hrs], and cooled in air, shall have the properties shown in Table 2 for that particular condition..."

To me, that reads that all parts less than 8" cross section shall be held for four hours.

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
3178482570

Original Message:
Sent: 03-20-2020 09:01
From: George Shannon
Subject: 17-4 PH Aging

In my experience the PH grades are far more sensitive to temperature than times (compare Figure 4 and 5 in your reference).  I would be comfortable adding 1/2 hour per inch of cross section, and worry more about the uniformity of my furnace.  A lot of specifications for PH grades require a +/- 10F uniformity according to AMS 2750.

I think specs are hesitant to suggest soak times since furnaces and shops always vary place-to-place.  No one I know has ever gotten a good answer out of customers/spec writers on that topic.

I admit 8" sounds pretty hefty - not sure I'd go much larger than that.  I wonder if there's a suggested size restriction somewhere.  AMS doesn't say anything?

------------------------------
George Shannon
Xerox
Fairport NY

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

the hold time is per inch of cross section.
a good reference book: "Heat Treatment Master Control Manual" --William E. Bryson
17-4 PH Stainless Steel pages 276 & 277

------------------------------
Joseph DeAngelo
Director of Technical Development
Oberg Industries
Freeport PA
(724) 235-6207
------------------------------

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

Thick 17-4 PH sections seem problematic at best.  Thick 17-4PH forgings are used of critical applications in the new oil industry and the heat treat cycles developed from specific pro-typing and not shared or published.  The critical issue is that thick sections cannot be uniformly solution treated and aged without cracking due to time/temperature (Arrhenius) sensitivity not only due to furnace temperature uniformity but the low heat conductivity of the alloy itself.

I afraid there are no easy answers and each case make you earn your pay.

------------------------------
Edward Vojcak
Senior Metallurgical Engineer
SGS North America
Blue Island IL
(708) 595-8734
------------------------------

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

If you're doing this repeatedly, it can make sense to take an 8" round slug and drill a hole down the center that a thermocouple can fit into.  Then you've got a heat sink of the appropriate size to tell you how long it takes for the center to heat up.​

Good Luck!

------------------------------
Lee Gearhart
Senior Metallurgical Engineer
Moog Inc
East Aurora NY
(716) 687-4475
------------------------------

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

------------------------------
Ryan Wilmes
Thermal Modification Technologies
Tigard OR
------------------------------

Ryan, Lee's comment is spot on. Using type K work thermocouples is a must in any heat treat operation. They need to be inserted as Lee recommend in a hole for accurate readings. If you have holes in the parts that's great if not the dummy block works. Use a minimum of three thermocouples to measure surface, mid part, and coolest or thickest area. Best of luck. 

Roger A. Jones FASM
CEO Emeritus 
Solar Atmospheres 

------------------------------
Roger Jones FASM
CEO Emeritus
Solar Atmospheres Incorporated
Souderton PA
(215) 721-1502 Ext. 1201
------------------------------

Original Message:
Sent: 03-22-2020 21:01
From: Lee Gearhart
Subject: 17-4 PH Aging

If you're doing this repeatedly, it can make sense to take an 8" round slug and drill a hole down the center that a thermocouple can fit into.  Then you've got a heat sink of the appropriate size to tell you how long it takes for the center to heat up.​

Good Luck!

------------------------------
Lee Gearhart
Senior Metallurgical Engineer
Moog Inc
East Aurora NY
(716) 687-4475

Original Message:
Sent: 03-19-2020 17:30
From: Ryan Wilmes
Subject: 17-4 PH Aging

Does anyone have experience with aging times for large 17-4 PH parts?

The heat treating guide shows a 4 hour aging times for H925-H1150 with a +45 minutes/-0 minutes note.  ASMT A564/A705 also calls out a 4 hour aging time with a note of "Time refers to minimum time material is at temperature and may be varied to obtain required ductility properties."  There are none of the typical "increase soak time for large section sizes" or 1 hour/inch

For large section sizes how should soak times be adjusted?  For say an 8" section, starting the soak countdown when the surface temperature hits set point will result in the core being undersoaked, while the opposite will have the surface oversoaked. 

I've found some sources below showing a decrease in hardness with the increased soak time, and with the print requirement often only listing hardness requirement, that can potentially be an issue if basing soak off the core temperature.  I haven't found any strong information relating to corrosion or other properties, except for the ductility comment in the ASTM spec.

With many applications that we see 17-4 used for being primarily concerned with surface wear and corrosion resistance, the outer part of the section is generally the most critical.  Does anyone have experience with this situation/know of any other effects from undersoaking/oversoaking 17-4?

https://ars.els-cdn.com/content/image/1-s2.0-S0254058409001424-gr5.gif from https://www.sciencedirect.com/science/article/abs/pii/S0254058409001424

Thanks,

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Ryan Wilmes
Thermal Modification Technologies
Tigard OR
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