Standard Specification for Vacuum Treated Steel Forgings, Alloy, Differentially Heat Treated, for Turbine Rotors

ABSTRACT
This specification covers vacuum treated and differentially heat treated alloy steel forgings for turbine rotors. Materials shall be manufactured by melting process, heat treatment (consisting of normalizing and tempering to achieve creep resistance in the high pressure portion, and quenching and tempering to achieve high toughness in the low pressure portion), rough machining, and boring. Heat and product analyses shall be performed to evaluate conformance of the steel to required chemical compositions. Tension and impact tests shall also be executed to make sure that forgings adhere to tensile and notch toughness requirements, including tensile strength, yield strength, elongation, and reduction of area. Final products shall be free of cracks, seams, laps, shrinkage, and other injurious imperfections. To evaluate such imperfections, nondestructive tests, such as ultrasonic and internal inspection procedures, may be conducted at the preference of the purchaser. Forgings that do not meet the requirements specified, may be retreated one or more times, but not more than three additional times.
SCOPE
1.1 This specification covers vacuum treated, alloy steel forgings, differentially heat treated for turbine rotors.
1.2 Differential heat treatment of a rotor forging involves subjecting two portions of the forging concurrently to two different austenitizing temperatures followed by two different cooling rates for normalizing and quenching, and then tempering, to achieve creep resistance in the high pressure (HP) portion and high toughness in the low pressure (LP) portion.
1.3 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.

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ASTM A940/A940M-06 - Standard Specification for Vacuum Treated Steel Forgings, Alloy, Differentially Heat Treated, for Turbine Rotors
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: A940/A940M – 06
Standard Specification for
Vacuum Treated Steel Forgings, Alloy, Differentially Heat
1
Treated, for Turbine Rotors
This standard is issued under the fixed designationA940/A940M; 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.
1. Scope A788/A788M Specification for Steel Forgings, General Re-
quirements
1.1 This specification covers vacuum treated, alloy steel
E139 Test Methods for Conducting Creep, Creep-Rupture,
forgings, differentially heat treated for turbine rotors.
and Stress-Rupture Tests of Metallic Materials
1.2 Differential heat treatment of a rotor forging involves
subjecting two portions of the forging concurrently to two
3. Ordering Information
different austenitizing temperatures followed by two different
3.1 In addition to the ordering information required by
cooling rates for normalizing and quenching, and then temper-
Specification A788/A788M, the purchaser shall include with
ing, to achieve creep resistance in the high pressure (HP)
2 the inquiry and order a detailed drawing, sketch, or written
portion and high toughness in the low pressure (LP) portion.
description of the forging, including the mechanical test
1.3 The values stated in either SI units or inch-pound units
locations, the portion of the forging to be included in the
are to be regarded separately as standard. The values stated in
heating chamber during the stability test, and the minimum
each system may not be exact equivalents; therefore, each
stability test temperature.
system shall be used independently of the other. Combining
3.2 Thepurchasershallspecifyifchecktestsformechanical
values from the two systems may result in non-conformance
properties are required after stress relief or heat stability tests.
with the standard.
3.3 Supplementary Requirements—Supplementary require-
2. Referenced Documents ments are provided. These requirements shall apply only when
3
specified in the purchase order.
2.1 ASTM Standards:
A275/A275M Practice for Magnetic Particle Examination
4. General Requirements
of Steel Forgings
4.1 Material supplied to this specification shall conform to
A370 Test Methods and Definitions for Mechanical Testing
the requirements of Specification A788/A788M, which out-
of Steel Products
lines additional ordering information, manufacturing require-
A418/A418M Practice for Ultrasonic Examination of Tur-
ments, testing and retesting methods and procedures, marking,
bine and Generator Steel Rotor Forgings
certification,productanalysisvariations,andadditionalsupple-
A470/A470M Specification for Vacuum-Treated Carbon
mentary requirements.
and Alloy Steel Forgings for Turbine Rotors and Shafts
4.2 If the requirements of this specification are in conflict
A472/A472M Specification for Heat Stability of Steam
with the requirements of Specification A788/A788M, the
Turbine Shafts and Rotor Forgings
requirements of this specification shall prevail.
5. Manufacture
1
This specification is under the jurisdiction of ASTM Committee A01 on Steel,
5.1 Melting processes of Specification A788/A788M shall
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee
A01.06 on Steel Forgings and Billets.
be applicable, except that the open hearth or basic oxygen
Current edition approved March 1, 2006. Published March 2006. Originally
methods of primary melting shall not be used and the molten
approved in 1995. Last previous edition approved in 2001 as A940 – 96 (2001).
steel shall be vacuum treated during processing. Except for
DOI: 10.1520/A0940_A0940M-06.
2
vacuum stream degassed ingots, the hydrogen content shall be
Symposium on Steel Forgings, ASTM STP 903, ASTM International, West
Conshohocken, PA, 1984, pp. 59–86.
determined. The acceptable hydrogen limit as well as the stage
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
in processing when sampling, the sample preparation proce-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
dure and the method of analysis shall be established between
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the manufacturer and the purchaser.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

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A940/A940M – 06
5.1.1 If the ESR process is used, the electrodes shall have 6. Chemical Composition
been produced from vacuum treated primary heat(s).
6.1 Heat Analysis—An analysis of each heat of steel shall
5.2 In addition to the requirements of Spec
...

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