ASTM A768/A768M-05(2015)
(Specification)Standard Specification for Vacuum-Treated 12% Chromium Alloy Steel Forgings for Turbine Rotors and Shafts (Withdrawn 2018)
Standard Specification for Vacuum-Treated 12% Chromium Alloy Steel Forgings for Turbine Rotors and Shafts (Withdrawn 2018)
ABSTRACT
This specification covers vacuum-treated 12% chromium alloy steel forgings for turbine rotors and shafts. Materials shall be manufactured by specified melting processes, heat treatment (quenching, tempering, and austenitizing), rough machining, boring, and stress relieving. Product analysis shall be used to evaluate if the elemental chemical compositions of the forgings are within specified range. Specimens shall also undergo tension and impact tests to evaluate their conformance to tensile and notch toughness requirements, which include tensile strength, yield strength, elongation, and reduction of area. Nondestructive tests, such as ultrasonic and internal inspection, and stability tests shall be performed as well. Forgings may be retreated one or more times, but not exceeding three additional times, if the results of mechanical tests fail to meet required values.
SCOPE
1.1 This specification covers vacuum-treated 12 % chromium steel forgings for turbine rotors and shafts.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
WITHDRAWN RATIONALE
This specification covers vacuum-treated 12 % chromium steel forgings for turbine rotors and shafts.
Formerly under the jurisdiction of Committee A01 on Steel, Stainless Steel, and Related Alloys, this specification was withdrawn in May 2018. This standard is being withdrawn without replacement due to its limited use by industry.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: A768/A768M −05 (Reapproved 2015)
Standard Specification for
Vacuum-Treated 12 % Chromium Alloy Steel Forgings for
Turbine Rotors and Shafts
This standard is issued under the fixed designationA768/A768M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope the inquiry and order a detailed drawing, sketch, or written
description of the forging, including the mechanical test
1.1 This specification covers vacuum-treated 12 % chro-
specimen location.
mium steel forgings for turbine rotors and shafts.
1.2 The values stated in either SI units or inch-pound units
4. General Requirements
are to be regarded separately as standard. The values stated in
4.1 Material supplied to this specification shall conform to
each system may not be exact equivalents; therefore, each
the requirements of Specification A788/A788M which outlines
system shall be used independently of the other. Combining
additional ordering information, manufacturing requirements,
values from the two systems may result in non-conformance
testing and retesting methods and procedures, marking,
with the standard.
certification,productanalysisvariations,andadditionalsupple-
1.3 This standard does not purport to address all of the
mentary requirements.
safety concerns, if any, associated with its use. It is the
4.2 If the requirements of this specification are in conflict
responsibility of the user of this standard to establish appro-
with the requirements of Specification A788/A788M, the
priate safety and health practices and determine the applica-
requirements of this specification shall prevail.
bility of regulatory limitations prior to use.
5. Manufacture
2. Referenced Documents
5.1 The melting processes of Specification A788/A788M
2.1 ASTM Standards:
shall be applicable except that the open-hearth or basic oxygen
A275/A275M Practice for Magnetic Particle Examination of
methods of primary melting shall not be used, and the molten
Steel Forgings
steelshallbevacuumdegassedpriortoorduringpouringofthe
A370 Test Methods and Definitions for Mechanical Testing
ingot.
of Steel Products
5.1.1 If the ESR process is used, then the electrodes shall
A418/A418M Practice for Ultrasonic Examination of Tur-
have been produced from vacuum degassed primary heat(s).
bine and Generator Steel Rotor Forgings
A472/A472M Specification for Heat Stability of Steam Tur-
5.2 In addition to the requirements of Specification A788/
bine Shafts and Rotor Forgings
A788M, it is important to maintain the axial center of the
A788/A788M Specification for Steel Forgings, General Re-
forging in common with the axial center of the original ingot.
quirements
5.3 Heat Treatment:
5.3.1 The heat treatment for mechanical properties shall
3. Ordering Information
consist of quenching and tempering.
3.1 In addition to the ordering information required by
5.3.1.1 The preliminary heat treatment shall consist of
Specification A788/A788M, the purchaser shall include with
normalizing well above the transformation temperature range.
This operation may be performed before preliminary machin-
This specification is under the jurisdiction of ASTM Committee A01 on Steel,
ing (see 5.4.1).
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee
5.3.1.2 The quenching treatment shall be from above the
A01.06 on Steel Forgings and Billets.
transformation range but below the normalizing temperature
Current edition approved March 1, 2015. Published March 2015. Originally
described in 5.3.1.1. This treatment shall be performed after
approved in 1979. Last previous edition approved in 2010 as A768/A768M – 05
(2010). DOI: 10.1520/A0768_A0768M-05R15.
preliminary machining (see 5.4.1). Austenitizing temperatures
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
shall be in accordance with Table 1.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.3.1.3 The final tempering temperature shall be in accor-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. dance with Table 1.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A768/A768M − 05 (2015)
TABLE 1 Heat Treating Temperature, °F [°C], Requirements
5.4.4 Machining to Purchaser’s Requirements for
Grade Austenitizing 1st 2nd Shipment—The forging as shipped shall conform to the finish
Tempering, Tempering
and dimension requirements specified on the purchaser’s
min
drawing or order.
1 1725–1825 1125 1100
[940–995] [605] [595]
2 1900–1940 1040 1010–1040
6. Chemical Composition
[1035–1060] [560] [545–560]
3 1700–1800 1120 1100 6.1 Thesteelshallconformtotherequirementsforchemical
[925–980] [605] [595]
composition prescribed in Table 2.
4 1700–1800 975 950
[925–980] [525] [510]
6.2 ProductAnalysis—The manufacturer shall make a prod-
uct analysis from each forging. The chemical composition thus
determined shall not vary from the requirements specified in
Table 1 by more than the amounts prescribed in Specification
A788/A788M.
5.3.1.4 After heat treatment and subsequent rough machin-
ing and boring (see 5.4.2 and 5.4.3), the forging shall be
stress-relieved at a temperature not more than 100°F [55°C] 7. Mechanical Properties
belowthefinaltemperingtemperature,butnotlessthan1100°F
7.1 Tension Test:
[595°C].
7.1.1 The steel shall conform to the tensile requirements of
5.3.1.5 With the prior approval of the purchaser, the stress-
Table 3.
relief temperature may approach, equal, or slightly exceed the
7.1.2 The number and location of tension test specimens
final tempering temperature as a means of adjusting final
shall be as specified on the forging drawings furnished by the
strength or toughness. If the stress relief temperature is within
purchaser.
25°F [15°C] of the final tempering temperature, or higher,
7.1.3 Final acceptance tests shall be made after heat treat-
additional tension tests must be obtained (see 7.1.3).
ment of the forging for mechanical properties prior to stress
5.3.1.6 The method of cooling during quenching and from
relief,unlessthestressrelieftemperatureiswithin25°F[15°C]
the final tempering and stress relieving temperatures shall be
of the tempering temperature, or higher, in which case check
reported.
tests shall be made after the stress relief treatment and reported
5.4 Machining:
to the purchaser. The purchaser may require check tests after
5.4.1 Preliminary Rough Machining—All exterior surfaces
completion of all heating cycles, including stress relief and the
of the forging shall be machined prior to heat treatment for
heat stability tests.
mechanical properties.
7.1.4 The yield strength prescribed in Table 3 shall be
5.4.2 Second Rough Machining—After heat treatment for
determined by the offset method of Test Methods and Defini-
mechanicalproperties,allsurfacesoftheforgingshallberough
tions A370.
machined prior to stress relief and the stability test.
7.2 Impact Test:
5.4.3 Boring:
7.2.1 The steel shall conform to the requirements for notch
5.4.3.1 Forgings shall be bored to permissible bore size and
toughness (both transition temperature and room temperature
tolerance when required by the purchaser’s drawing.
impact values) prescribed in Table 3.
5.4.3.2 Forgings may be bored to limits agreed to by the
purchaser or indicated on the purchaser’s drawing, to remove 7.2.2 The notch toughness specimens shall be machined
objectionable center conditions revealed by ultrasonic inspec- from radial bars taken from the main body of the forging, as
tion. shown in the forging drawing. The specimens shall be Charpy
5.4.3.3 Unless otherwise specified by the purchaser, the V-notch, Type A, as shown in Test Methods and Definitions
manufacturer may bore the forging at any time prior to stress A370. Th
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