ASTM A940-96
(Specification)Standard Specification for Vacuum Treated Steel Forgings, Alloy, Differentially Heat Treated, for Turbine Rotors
Standard Specification for Vacuum Treated Steel Forgings, Alloy, Differentially Heat Treated, for Turbine Rotors
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 inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
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NOTICE: This standard has either been superseded and replaced by a new version or
withdrawn.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: A 940 – 96 An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Specification for
Vacuum Treated Steel Forgings, Alloy, Differentially Heat
1
Treated, for Turbine Rotors
This standard is issued under the fixed designation A 940; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope inquiry and order a detailed drawing, sketch, or written
description of the forging, including the mechanical test
1.1 This specification covers vacuum treated, alloy steel
locations, the portion of the forging to be included in the
forgings, differentially heat treated for turbine rotors.
heating chamber during the stability test, and the minimum
1.2 Differential heat treatment of a rotor forging involves
stability test temperature.
subjecting two portions of the forging concurrently to two
3.2 The purchaser shall specify if check tests for mechanical
different austenitizing temperatures followed by two different
properties are required after stress relief or heat stability tests.
cooling rates for normalizing and quenching, and then temper-
3.3 Supplementary Requirements—Supplementary require-
ing, to achieve creep resistance in the high pressure (HP)
2
ments are provided. These requirements shall apply only when
portion and high toughness in the low pressure (LP) portion.
specified in the purchase order.
1.3 The values stated in inch-pound units are to be regarded
as the standard. The values given in parentheses are for
4. General Requirements
information only.
4.1 Material supplied to this specification shall conform to
2. Referenced Documents the requirements of Specification A 788, which outlines addi-
tional ordering information, manufacturing requirements, test-
2.1 ASTM Standards:
ing and retesting methods and procedures, marking, certifica-
A 275/A 275M Test Methods for Magnetic Particle Exami-
3
tion, product analysis variations, and additional supplementary
nation of Steel Forgings
requirements.
A 370 Test Methods and Definitions for Mechanical Testing
3 4.2 If the requirements of this specification are in conflict
of Steel Products
with the requirements of Specification A 788, the requirements
A 418 Test Method of Ultrasonic Examination Inspection of
3 of this specification shall prevail.
Turbine and Generator Steel Rotor Forgings
A 470 Specification for Vacuum-Treated Carbon and Alloy
5. Manufacture
3
Steel Forgings for Turbine Rotors and Shafts
5.1 Melting processes of Specification A 788 shall be appli-
A 472 Test Method for Heat Stability of Steam Turbine
cable, except that the open hearth or basic oxygen methods of
3
Shafts and Rotor Forgings
primary melting shall not be used and the molten steel shall be
A 751 Test Methods, Practices, and Terminology for
vacuum treated during processing. When the ladle degassing
4
Chemical Analysis of Steel Products
process is used, the evacuation system shall be capable of
A 788 Specification for Steel Forgings, General Require-
reducing the system vacuum pressure to a low level (usually
3
ments
less than 1000 μm). The molten metal shall be stirred ad-
E 139 Practice for Conducting Creep, Creep-Rupture, and
equately for a sufficient length of time to maximize exposure to
5
Stress-Rupture Tests of Metallic Materials
the evacuated atmosphere. When this process is used, hydrogen
3. Ordering Information testing per Supplementary Requirement S4 is mandatory.
5.1.1 If the ESR process is used, the electrodes shall have
3.1 In addition to the ordering information required by
been produced from vacuum treated primary heat(s), and
Specification A 788, the purchaser shall include with the
Supplementary Requirement S4 is mandatory.
5.2 In addition to the requirements of Specification A 788, it
1
This specification is under the jurisdiction of ASTM Committee A-1 on Steel, is important to maintain the axial center of the forging in
Stainless Steel, and Related Alloys and is the direct responsibility of Subcommittee
common with the axial center of the original ingot.
A01.06 on Steel Forgings and Billets.
5.3 Differential Heat Treatment—The heat treatment for
Current edition approved Sept. 10, 1996. Published July 1997. Originally
mechanical properties shall consist of normalizing and temper-
published as A 940–95. Last previous edition A 940–95.
2
Symposium on Steel Forgings, ASTM STP 903, ASTM, Philadelphia, PA, 1984,
ing of the creep resistant portion, HP portion, and quenching
pp. 59-86.
and tempering of the high toughness portion, LP por
...
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