AMS 2759-9
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Hydrogen Embrittlement Relief (Baking) of Steel Parts
1.SCOPE:1.1
Form:
This specification covers the requirements for embrittlement relief (baking) of heat treated steel parts to remove hydrogen infused during plating and other chemical processing (e.g., stripping, chemical milling, pickling, and etching).1.2
Application:
This specification is applicable to parts made from carbon, low-alloy, and martensitic stainless steel heat treated to a minimum strength of 180 ksi (1241 MPa) or higher or heat treated to a minimum hardness of 40 HRC or equivalent, or harder. It is also applicable to threaded fasteners made from carbon, low-alloy, or martensitic stainless steels heat treated to a minimum strength of 150 ksi (1034 MPa) or 34 HRC or equivalent, parts made from high strength precipitation hardening stainless steels other than A-286, and steel parts which have been case hardened (carburized, nitrided, nitrocarburized, or carbonitrided). See 8.2.2.APPLICABLE DOCUMENTS:
The issue of the following documents in effect on the date of the purchase order forms a part of this specification to the extent specified herein. The supplier may work to a subsequent revision of a document unless a specific document issue is specified. When the referenced document has been canceled and no superseding document has been specified, the last published issue of that document shall apply.2.1
SAE Publications:
Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001 or https://www.sodocs.net/doc/b65621936.html,.
AMS 2750 Pyrometry
AMS 2759Heat Treatment of Steel Parts
AEROSPACE MATERIAL
SPECIFICATION
AMS 2759/9B
Issued NOV 1996Revised
APR 2003
Superseding AMS 2759/9A
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3.TECHNICAL REQUIREMENTS:
3.1Pyrometry:
Shall conform to AMS 2750. Temperature uniformity shall be ±25 °F (±14 °C).
3.2Heat Treatment Equipment:
Shall conform to AMS 2759 and requirements specified herein. Furnaces shall be circulating-air type.
3.3Baking (See 8.2):
Parts shall be baked after completion of each plating or other chemical process except when not required after etch inspection (surfactant addition to etchant) and under the following multiple step processing conditions:
3.3.1Baking is not required after preplate strikes and after the nickel plate for diffused nickel-cadmium.
3.3.2Baking is not required between steps in a multiple step (plating/chemical process) sequence if
interruptions do not exceed two hours, baking is started within four hours after the final step, and total time between start of first step and start of baking does not exceed 24 hours.
3.3.2.1When the conditions of 3.3.1 or 3.3.2 are not met, baking is required but the soaking time may be
reduced for parts other than those covered by 3.3.2.2. The minimum soaking time shall be three hours for parts heat treated to a minimum strength of 240 ksi (1655 MPa) or lower, or a minimum hardness of 49 HRC or less; for higher strength or harder parts, the minimum soaking time shall be six hours.
3.3.2.2For nickel plated parts heat treated to a minimum strength of 200 ksi (1379 MPa) or higher or a
minimum hardness of 43 HRC, or equivalent, or harder, no reduction is permitted; baking soak
time between steps shall be as specified in Table 1.
3.4Procedure:
3.4.1Cleaning: Parts shall be clean prior to baking.
3.4.2Racking and Spacing: Parts shall be placed in racks or trays, made of mesh or expanded metal, or
supported or suspended so as to allow free circulation of the heating medium, except small parts may be randomly arranged in trays providing that layers of parts are not thicker than two inches
(51 mm) and the distance between the layers is not less than two inches (51 mm).
3.4.2.1Thickness of layers of small parts randomly arranged in trays may be greater than two inches
(51 mm) providing that tests have been made with load thermocouples to confirm that the center
of the coldest load will reach the set temperature minus 25 °F (14 °C) degrees within
one hour of loading.--` ` , , ` ` , ` , ` , , , , , ` , ` , , ` ` , , , ` ` , , -` -` , , ` , , ` , ` , , ` ---
TABLE 1 - Minimum Baking Time (Hours) at Standard Temperature of
375 °F (191 °C) Except Where Indicated by *
Specified
Temper,
Minimum Strength Platings
(9)
Platings
(9)
Chemical
Treatments
Chemical
Treatments
Steel/Part or Minimum Cd &Ni Platings (9)Platings (9)Platings (9)Platings (9)Platings (9)Chem Etch Description Hardness (1)Cd-Ti(2)Cr Ag Au Sn Zn-Ni(3)(4) AISI 1095180 ksi
(1241 MPa)
or 40 HRC (5)
23238335834
Nitrided
Nitrocarburized
All883333834
Music Wire
Carburized
Carbo-nitrided
All23*23*8* (8)8*5*5*23*8*8* 52100All23*23*8* (8)8*5*5*23*8*4* AF1410
HP 9Ni-4Co
-0.3C
AerMet100All232388552384
Other High Strength Carbon, Low-Alloy, Tool
220 ksi
(1517 MPa)
46 HRC (6)2323233352384
Lower Strength Carbon, Low-Alloy, Tool
180 ksi
(1241 MPa)
or 40 HRC
(5)(7)
883333834
440C
Stainless
46 HRC (6)23*23*8* (8)5*5*8*23*8*NA
Martensitic Stainless other than 440C
220 ksi
(1517 MPa)
or 46 HRC
(6)
23238335238NA
Martensitic Stainless
180 ksi
(1241 MPa)
or 40 HRC (7)33333383NA
17-7PH, 15-7PH 17-4PH, 15-5PH Stainless CH900, H900,
H925,
H950,RH9502323833383NA
CUSTOM 455
PH13-8 MO
Stainless H950, H100033333383NA NOTES:
*Nonstandard Temperatures: for parts tempered below 375 °F (191 °C), 275 °F (135 °C) for carburized: 300 °F (149 °C) for 52100 and 440C; 325 °F (163 °C) for music wire NA - Not applicable
(1) Or
equivalent
(2)Includes electroless nickel unless age hardened within four hours
(3) Chemical Processing: Etching, Stripping, Pickling, Chemical Milling
(4) Etch Inspection, without surfactant addition to etchant, to detect abusive grinding/machining
(5) Or higher, but having minimum less than 220 ksi (1517 MPa) or 46 HRC
(6) Or higher minimum
(7) Threaded fasteners - minimum 150 ksi (1034 MPa) and higher or 34 HRC or equivalent but minimum less than 180 ksi (1241 MPa) or 40 HRC or equivalent -
three hours for all processes
(8)If thin dense chrome (e.g. AMS 2438), 96 hours at 275 °F (135 °C) for parts tempered lower than 375 °F (191 °C) and 23 hours at 375 °F (191 °C) for parts tempered
at 375 °F (191 °C) or higher.
(9)For platings not listed, use baking time shown for cadmium.
3.4.3Delay Time: The elapsed time between completion of plating or other chemical processing
operations and start of heating parts in the baking furnace shall not exceed four hours except,
when baking is required after etch inspection to detect abusive grinding or machining, the elapsed time may be 24 hours.
3.4.4Baking Set Temperature: Standard baking set temperature shall be 375 °F (191 °C); nonstandard
baking set temperatures shall be used for parts made from the following materials/conditions, as specified.
3.4.4.1Carburized carbon and low-alloy steels, 275 °F (135 °C).
3.4.4.2AISI 52100 and 440C heat treated to a minimum strength of 220 ksi (1517 MPa) or higher, or a
minimum hardness of 46 HRC, or equivalent, or higher, 300 °F (149 °C).
3.4.4.3Music wire, 325 °F (163 °C).
3.4.5Baking Soak Times: Shall conform to Table 1.
3.4.5.1Start of Soak Time: Soaking time shall commence when parts are placed in the furnace, the
furnace door(s) are closed, and the temperature indicated by the furnace control instrument is
within 25 °F (14 °C) degrees of the set temperature.
3.4.5.2Soaking Interruptions: If the delay time (3.4.3) is less than two hours, soaking may be interrupted
for the purpose of adding or removing parts. If the delay time (3.4.3) is two hours or more, parts shall be soaked for at least one hour before any such interruption.
3.4.5.2.1If the temperature indicated by the control instrument drops more than 25 °F (14 °C) degrees
below the set temperature, the time during which the indicated temperature was below that
temperature shall not be considered part of the soaking time of any parts in the furnace.
3.5Records:
Records shall be maintained which show the identification and the following for each lot:.
3.5.1Date and time of completion of the plating or other chemical process.
3.5.2Date and time of start of baking.
3.5.3Date and time of start of soak.
3.5.4Date and time of completion of baking.
3.5.5Furnace control instrument set temperature.
3.5.6Furnace identification.
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4.QUALITY ASSURANCE PROVISIONS:
4.1Reports:
Processor’s reports shall include the baking time and temperature and shall state that baking was performed in accordance with this specification.
4.2Records:
Shall be retained for at least five years, including all information required in 3.5, and shall be
available for review by authorized representatives of purchaser.
5.PREPARATION FOR DELIVERY:
See AMS 2759.
6.ACKNOWLEDGMENT:
See AMS 2759.
7.REJECTIONS:
See AMS 2759.
8.NOTES:
8.1 A change bar ( l ) located in the left margin is for the convenience of the user in locating areas where
technical revisions, not editorial changes, have been made to the previous issue of this specification.
An (R) symbol to the left of the document title indicates a complete revision of the specification, including technical revisions. Change bars and (R) are not used in original publications, nor in
specifications that contain editorial changes only.
8.2Ordering Data:
In order to ensure that the appropriate baking treatment is applied to each lot of parts, it is essential that the processor be furnished with information identifying the material and its minimum strength or hardness or, in the case of precipitation hardening stainless steel, its temper. Additionally, the
tempering temperatures shall be furnished to the processor for carburized or carbonitrided parts and parts fabricated from music wire, 52100 and 440C.
PREPARED UNDER THE JURISDICTION OF “AMEC” AND AMS COMMITTEE “B”--` ` , , ` ` , ` , ` , , , , , ` , ` , , ` ` , , , ` ` , , -` -` , , ` , , ` , ` , , ` ---