ASTM A469/A469M-07(2022)

Standard Specification for Vacuum-Treated Steel Forgings for Generator Rotors

ABSTRACT
This specification covers vacuum-treated basic electric steel forgings for use in generator rotors. Steel materials shall be manufactured by vacuum degassing, heat treatment, rough machining, and boring. Heat and product analyses shall be carried out to examine conformation of the specimens with chemical compositions of carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, vanadium, and antimony. Forgings shall also go through tension, impact, and Charpy V-notch tests, and shall conform with the following tensile and notch toughness requirements: tensile strength, yield strength, elongation, reduction of area, FATT50, and Charpy absorbed energy. Nondestructive test methods such as ultrasonic and internal inspection shall be performed.
SCOPE
1.1 This specification covers vacuum-treated basic electric steel forgings for generator rotors.  
1.2 Supplementary requirements are provided, both in this standard and in Specification A788/A788M, for use when additional testing, inspection or processing is required by the purchaser.  
1.3 The values stated in either inch-pound units or SI (metric) units are to be regarded separately as standard. Within the text and tables, the SI units are shown in brackets. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.4 Unless the order specifies the applicable “M” specification designation, the material shall be furnished to the inch-pound units.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 28-Feb-2022
• ICS: 77.140.85 - Iron and steel forgings
• Technical Committee: A01 - Steel, Stainless Steel and Related Alloys
• Drafting Committee: A01.06 - Steel Forgings and Billets

Relations

• Refers: ASTM A418/A418M-24 - Standard Practice for Ultrasonic Examination of Turbine and Generator Steel Rotor Forgings
• Effective Date: 01-May-2024
• Refers: ASTM A370-24 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Mar-2024
• Refers: ASTM A275/A275M-23 - Standard Practice for Magnetic Particle Examination of Steel Forgings
• Effective Date: 01-Nov-2023
• Refers: ASTM A418/A418M-15(2020) - Standard Practice for Ultrasonic Examination of Turbine and Generator Steel Rotor Forgings
• Effective Date: 01-Mar-2020
• Refers: ASTM A370-19 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Jul-2019
• Refers: ASTM A788/A788M-19 - Standard Specification for Steel Forgings, General Requirements
• Effective Date: 01-May-2019
• Refers: ASTM A788/A788M-18b - Standard Specification for Steel Forgings, General Requirements
• Effective Date: 01-Nov-2018
• Refers: ASTM A788/A788M-18a - Standard Specification for Steel Forgings, General Requirements
• Effective Date: 01-Sep-2018
• Refers: ASTM A788/A788M-18 - Standard Specification for Steel Forgings, General Requirements
• Effective Date: 01-Mar-2018
• Refers: ASTM A370-17a - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 15-Nov-2017
• Refers: ASTM A788/A788M-17a - Standard Specification for Steel Forgings, General Requirements
• Effective Date: 01-Nov-2017
• Refers: ASTM A788/A788M-17 - Standard Specification for Steel Forgings, General Requirements
• Effective Date: 01-May-2017
• Refers: ASTM A370-17 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Jan-2017
• Refers: ASTM A788/A788M-16a - Standard Specification for Steel Forgings, General Requirements
• Effective Date: 01-Dec-2016
• Refers: ASTM A370-15 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Nov-2015

Overview

ASTM A469/A469M-07(2022), Standard Specification for Vacuum-Treated Steel Forgings for Generator Rotors, establishes comprehensive requirements for vacuum-treated, basic electric steel forgings utilized in generator rotors. Developed by ASTM International, this standard addresses the chemistry, mechanical properties, manufacturing, heat treatment, testing, and inspection protocols necessary to ensure high-quality steel forgings designed for critical power generation applications.

This specification outlines the necessary procedures, from vacuum degassing and heat treatment to machining and boring, ensuring optimal performance and durability of generator rotor forgings. Adherence to ASTM A469/A469M assures manufacturers and end users that the steel forgings will meet the stringent demands of modern power generation equipment.

Key Topics

• Material Requirements: Only vacuum-treated basic electric steel is permitted, ensuring controlled chemistry and high microstructural integrity.
• Chemical Composition: Strict limits are placed on elements such as carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, and vanadium to guarantee material consistency.
• Heat Treatment: Forgings must undergo heat treatments such as quenching, tempering, or, with approval, normalizing and tempering. Vertical heat treatment is recommended for certain applications.
• Mechanical Properties: The forgings must comply with defined minimum requirements for tensile strength, yield strength, elongation, reduction of area, fracture appearance transition temperature (FATT), and Charpy V-notch absorbed energy.
• Inspection and Testing:
  • Nondestructive Testing: Ultrasonic inspections and, if necessary, magnetic particle inspections are required to ensure freedom from injurious imperfections.
  • Destructive Testing: Tension and Charpy V-notch impact tests are conducted to verify mechanical performance.
• Dimensional Requirements: Forgings must meet detailed dimensional specifications furnished by purchasers.

Applications

ASTM A469/A469M is widely referenced in the power generation industry, especially in the production of large generator rotors for steam and gas turbines. These rotors demand steel forgings with excellent mechanical strength, superior toughness, and consistent macrostructure to endure extreme operating conditions, including high rotational speeds and fluctuating thermal loads.

In practice, this standard ensures:

• Operational Reliability: By mandating vacuum treatment and strict property controls, the specification minimizes the risk of failure due to inclusions, cracks, or brittle zones.
• Long Service Life: Consistent heat treatment and rigorous testing provide confidence in fatigue and fracture resistance, extending the life of generator rotors.
• Regulatory Compliance: Manufacturers can demonstrate adherence to internationally recognized best practices, facilitating project approval and cross-border equipment supply.

Related Standards

Adherence to ASTM A469/A469M often requires compliance with, or reference to, other ASTM standards for supplementary testing and processing, including:

• ASTM A788/A788M: General requirements for steel forgings
• ASTM A370: Test methods and definitions for mechanical testing of steel products
• ASTM A418/A418M: Ultrasonic examination of turbine and generator steel rotor forgings
• ASTM A275/A275M: Magnetic particle examination of steel forgings
• ASTM A341/A341M / A773/A773M: Test methods for DC magnetic properties of soft and low coercivity magnetic materials

Use of ASTM A469/A469M in conjunction with these related standards safeguards quality and consistency for critical components in modern power generation systems.

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Keywords: ASTM A469, vacuum-treated steel forgings, generator rotors, steel forgings standard, mechanical properties, heat treatment, nondestructive testing, power generation industry, ASTM standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:A469/A469M −07 (Reapproved 2022)
Standard Specification for
Vacuum-Treated Steel Forgings for Generator Rotors
This standard is issued under the fixed designationA469/A469M; 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 A341/A341M Test Method for Direct Current Magnetic
Properties of Soft Magnetic Materials Using D-C Per-
1.1 This specification covers vacuum-treated basic electric
meameters and the Point by Point (Ballistic)Test Methods
steel forgings for generator rotors.
A370 Test Methods and Definitions for Mechanical Testing
1.2 Supplementary requirements are provided, both in this
of Steel Products
standard and in Specification A788/A788M, for use when
A418/A418M Practice for Ultrasonic Examination of Tur-
additional testing, inspection or processing is required by the
bine and Generator Steel Rotor Forgings
purchaser.
A773/A773M Test Method for Direct Current Magnetic
1.3 The values stated in either inch-pound units or SI Properties of Low Coercivity Magnetic Materials Using
Hysteresigraphs
(metric) units are to be regarded separately as standard. Within
the text and tables, the SI units are shown in brackets. The A788/A788M Specification for Steel Forgings, General Re-
quirements
values stated in each system are not necessarily exact equiva-
lents; therefore, to ensure conformance with the standard, each
3. Ordering Information and General Requirements
system shall be used independently of the other, and values
3.1 In addition to the ordering information required by
from the two systems shall not be combined.
Specification A788/A788M, the purchaser shall include with
1.4 Unless the order specifies the applicable “M” specifica-
the inquiry and order, a dimensioned drawing showing the
tion designation, the material shall be furnished to the inch-
mechanical test specimen locations, together with:
pound units.
3.1.1 Details of any required magnetic permeability tests
1.5 This standard does not purport to address all of the
(6.1).
safety concerns, if any, associated with its use. It is the
3.1.2 If the yield strength is to be determined at an offset of
responsibility of the user of this standard to establish appro-
0.2%(Table 1), and number of tests (7.1.2 and 7.1.3).
priate safety, health, and environmental practices and deter-
3.1.3 If vertical heat treatment is required (Supplementary
mine the applicability of regulatory limitations prior to use.
Requirement S3).
1.6 This international standard was developed in accor-
3.1.4 If heat treatment by normalizing and tempering is
dance with internationally recognized principles on standard-
required (4.2.2 and 4.2.3).
ization established in the Decision on Principles for the
3.1.5 If post rough machining stress relief may be omitted
Development of International Standards, Guides and Recom-
for forgings that have been double tempered (4.2.2).
mendations issued by the World Trade Organization Technical
3.1.6 Details for boring including dimensions, finish, timing
Barriers to Trade (TBT) Committee.
and additional testing if required (8.3 and Supplementary
Requirement S1).
2. Referenced Documents
3.1.7 Any applicable instructions regarding the required
2.1 ASTM Standards:
nondestructive examinations (8).
A275/A275M Practice for Magnetic Particle Examination of 3.1.8 If vacuum arc remelted ingots are to be used, the
Steel Forgings
purchaser may require that footnoteA to Table 2 be applicable.
3.2 Material supplied to this specification shall conform to
1 the requirements of Specification A788/A788M, which out-
This specification is under the jurisdiction of ASTM Committee A01 on Steel,
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee lines additional ordering information, manufacturing
A01.06 on Steel Forgings and Billets.
requirements, testing and retesting methods and procedures,
Current edition approved March 1, 2022. Published March 2022. Originally
marking, certification, production analysis variations, and ad-
approved in 1962. Last previous edition approved in 2017 as A469/
ditional supplementary requirements.
A469M – 07(2017). DOI: 10.1520/A0469_A0469M-07R22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.3 Failure to comply with the applicable general require-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ments of Specification A788/A788M constitutes nonconfor-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. mance with this specification.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A469/A469M−07 (2022)
TABLE 1 Tensile and Notch Toughness Requirements
Grade
Tensile strength, min, ksi 80 90 100 110 100 110 120
[MPa] [550] [620] [690] [760] [690] [760] [825]
A
Yield strength, min, ksi 55 70 80 90 80 90 100
[MPa] [380] [485] [550] [620] [550] [620] [690]
Elongation in 2 in. or 50 mm, min, % 20 20 17 15 18 17 16
Reduction of area, min, % 50 50 45 40 55 50 45
FATT , max, F 100 100 120 175 0 20 40
[FATT , max, C] [38] [38] [49] [80] [−18] [−7] [4]
Charpy absorbed energy at 70 °F ± 30 30 25 15 60 50 40
5 °F [20 °C ± 3 °C],
min, ft·lbf [J] [40] [40] [34] [20] [80] [68] [55]
A
Yield strength at 0.02 % offset. Yield strength may also be specified at 0.2 % offset in which case 5000 psi [35 MPa] shall be added to these values.
TABLE 2 Chemical Requirements
Element Composition, %
Grade 2 Grade 3 Grade 4 Grade 5 Grades 6, 7, 8
Carbon, max 0.25 0.27 0.27 0.31 0.28
Manganese, max 0.60 0.60 0.70 0.70 0.60
Phosphorus, max 0.015 0.015 0.015 0.015 0.015
Sulfur, max 0.015 0.015 0.015 0.015 0.015
A
Silicon, max 0.30 0.30 0.30 0.30 0.30
Nickel 2.50 min 2.50 min 3.00 min 3.00 min 3.25 to 4.00
Chromium 0.50 max 0.50 max 0.50 max 0.50 max 1.25 to 2.00
Molybdenum 0.20 to 0.50 0.20 to 0.50 0.20 to 0.60 0.20 to 0.70 0.30 to 0.60
Vanadium 0.03 min 0.03 min 0.03 min 0.05 to 0.15 0.05 to 0.15
B
Antimony . . . . .
A
Optional: For steel that is to be vacuum arc remelted a minimum silicon of 0.15 % may be specified.
B
Report for information on Grades 6, 7, and 8.
3.4 If the requirements of this specification are in conflict 4.3 Machining:
with the requirements of Specification A788/A788M, the 4.3.1 Boring—The manufacturer may bore the forging at
requirements of this specification shall prevail. any time prior to stress-relief anneal. (See Supplementary
Requirement S1).
4. Materials and Manufacture
5. Chemical Composition
4.1 The vacuum degassing requirements of Specification
A788/A788M are mandatory. 5.1 Heat Analysis—The heat analysis obtained from sam-
4.1.1 Other vacuum methods of degassing may be used if pling in accordance with Specification A788/A788M shall
the supplier can demonstrate their adequacy to the satisfaction comply with Table 2.
of the purchaser, but in this case, hydrogen testing in accor-
5.2 ProductAnalysis—The manufacturer shall use the prod-
dance with Supplementary Requirement S4 is mandatory.
uct analysis provision of Specification A788/A788M to obtain
4.2 Heat Treatment: a product analysis from a forging representing each heat or
4.2.1 Vertical heat treatment of the rotor forging is multiple heat.
preferred, and Supplementary Requir
...