ASTM A470/A470M-05(2020)
(Specification)Standard Specification for Vacuum-Treated Carbon and Alloy Steel Forgings for Turbine Rotors and Shafts
Standard Specification for Vacuum-Treated Carbon and Alloy Steel Forgings for Turbine Rotors and Shafts
ABSTRACT
This specification covers vacuum-treated carbon and alloy steel forgings for turbine rotors and shafts. Materials shall be manufactured and treated by: melting process via basic electric-furnace; secondary melting process via electrode-electroslag or vacuum-arc remelting; vacuum degassing; forging process via hot mechanical working; heat treatment via double-normalizing and tempering, or normalizing, quenching and tempering; and rough machining and axial boring. Tension and impact tests shall be done to evaluate the conformance of steel forgings with the following mechanical properties: tensile strength and toughness, notch toughness, yield strength, elongation, and reduction of area. Chemical composition conformances shall also be assessed by heat and product analyses. Nondestructive tests, such as ultrasonic and internal examination, and stability tests shall also be performed. Retreatments may be executed one or more times, but not more than three additional times, if results of the mechanical tests do not conform to specified requirements.
SCOPE
1.1 This specification covers vacuum-treated carbon and alloy 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 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.
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 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
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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:A470/A470M −05 (Reapproved 2020)
Standard Specification for
Vacuum-Treated Carbon and Alloy Steel Forgings for
Turbine Rotors and Shafts
This standard is issued under the fixed designationA470/A470M; 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 A418/A418M Practice for Ultrasonic Examination of Tur-
bine and Generator Steel Rotor Forgings
1.1 This specification covers vacuum-treated carbon and
A472/A472M Specification for Heat Stability of Steam Tur-
alloy steel forgings for turbine rotors and shafts.
bine Shafts and Rotor Forgings
1.2 The values stated in either SI units or inch-pound units
A788/A788M Specification for Steel Forgings, General Re-
are to be regarded separately as standard. The values stated in
quirements
each system are not necessarily exact equivalents; therefore, to
E139 Test Methods for Conducting Creep, Creep-Rupture,
ensure conformance with the standard, each system shall be
and Stress-Rupture Tests of Metallic Materials
used independently of the other, and values from the two
systems shall not be combined.
3. Ordering Information and General Requirements
1.3 This standard does not purport to address all of the
3.1 Material supplied to this specification shall conform to
safety concerns, if any, associated with its use. It is the
the requirements of Specification A788/A788M, which out-
responsibility of the user of this standard to establish appro-
lines additional ordering information, manufacturing methods
priate safety, health, and environmental practices and deter-
and procedures, marking, certification, production analysis
mine the applicability of regulatory limitations prior to use.
variations, and additional supplementary requirements.
1.4 This international standard was developed in accor-
3.2 In addition to the ordering information required by
dance with internationally recognized principles on standard-
Specification A788/A788M, the purchaser shall include with
ization established in the Decision on Principles for the
the inquiry and order, the grade and class of steel, alternative
Development of International Standards, Guides and Recom-
maximum for silicon content (see Table 1), the choice of yield
mendations issued by the World Trade Organization Technical
strength offset (0.2 % or 0.02 %), and any tests, supplementary
Barriers to Trade (TBT) Committee.
requirements, and purchase options desired.
2. Referenced Documents
3.3 Forging Drawing—Each forging shall be manufactured
in accordance with a drawing furnished by the purchaser
2.1 ASTM Standards:
showing the dimensions of the forging and bore hole, if any,
A275/A275M Practice for Magnetic Particle Examination of
and the location of mechanical test specimens.
Steel Forgings
A293 SpecificationforSteelForgings,CarbonandAlloy,for
3.4 Supplementary Requirements—Supplementary require-
Turbine Generator Rotors and Shafts; Replaced by A 470
ments are provided. These requirements shall apply only when
(Withdrawn 1984)
specified in the purchase order.
A370 Test Methods and Definitions for Mechanical Testing
3.5 If the requirements of this specification are in conflict
of Steel Products
with the requirements of Specification A788/A788M, the
requirements of this specification shall prevail.
This specification is under the jurisdiction ofASTM Committee A01 on Steel,
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee
4. Manufacture
A01.06 on Steel Forgings and Billets.
Current edition approved March 1, 2020. Published March 2020. Originally
4.1 Melting Process:
approved in 1962. Last previous edition approved in 2015 as A470/A470M – 05
4.1.1 The steel shall be made by the basic electric-furnace
(2015). DOI: 10.1520/A0470_A0470M–05R20.
process.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.1.2 Provisions for subsequent secondary melting of the
Standards volume information, refer to the standard’s Document Summary page on
steel by the consumable electrode-electroslag or vacuum-arc
the ASTM website.
3 remelting processes are included in Supplementary Require-
The last approved version of this historical standard is referenced on
www.astm.org. ment S7.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A470/A470M−05 (2020)
A
TABLE 1 Chemical Requirements
Grade A Grade B Grade C Grade D Grade E
Ni-Mo-V Ni-Mo-V Ni-Cr-Mo-V Cr-Mo-V Ni-Mo-V
Carbon 0.22–0.30 0.22–0.30 0.28 0.25–0.35 0.30
Manganese 0.20–0.60 0.20–0.60 0.20–0.60 1.00 0.70
Phosphorus 0.012 0.012 0.012 0.012 0.025
Sulfur 0.012 0.012 0.015 0.015 0.025
BBB,CB B
Silicon
Nickel 3.20–3.70 3.20–3.70 3.25–4.00 0.75 2.00 min.
Chromium 0.75 0.75 1.25–2.00 1.05–1.50 0.75
D
Molybdenum 0.40–0.60 0.40–0.60 0.25–0.60 1.00–1.50 0.25 min
Vanadium 0.04–0.12 0.04–0.12 0.05–0.15 0.20–0.30 0.03–0.12
EEEE E
Antimony
F
Aluminum 0.015 0.015 0.015 0.015 0.015
G
Equivalent . . . Classes 2 and 3 .
Specification A293
Grade Designation (replaced by
Specification A470)
A
Maximum or range, unless otherwise indicated.
B
0.10 % max, unless an alternative value, not in excess of 0.30 %, is specified in the purchase order.
C
0.15 to 0.30 % silicon is permitted for material that is subsequently VAR Processed.
D
Supplementary Requirement, see S1.
E
To be reported for information only on all Grades.
F
Total of soluble and insoluble.
G
Phosphorus of 0.035 max and sulfur of 0.035 max were specified for Specification A293.
4.2 Vacuum Treatment—The vacuum degassing require- limits in 4.5.1.4. However, with the prior approval of the
ments of Specification A788/A788M are mandatory. purchaser, the second tempering temperature may be equal, or
slightly exceed, the first tempering temperature as a means of
4.3 Discard—Sufficient discard shall be taken from each
adjusting final strength or toughness. The required tests for
ingot to secure freedom from pipe and harmful segregation in
mechanicalpropertiesshallbemadeafterthesecondtempering
the finished forging.
operation. Mechanical property tests after the first temper are
4.4 Forging Process—The forging shall receive its hot
optional with the manufacturer.
mechanical work under a press of ample power to adequately
4.5.1.4 After heat treatment and subsequent rough machin-
work the metal throughout the maximum section of the
ing and axial boring (see 4.6.2 and 4.6.3), the forging shall be
forging. It is important to maintain the axial center of the
stress-relieved at a temperature not more than 100 °F [55 °C]
forging in common with the axial center of the ingot.
below the final tempering temperature, but not less than
4.5 Heat Treatment:
1025 °F [550 °C].
4.5.1 The heat treatment for mechanical properties shall
4.5.1.5 With the prior approval of the purchaser, the stress-
consist of double-normalizing and tempering for Grades A, B,
relief temperature may approach, equal, or slightly exceed the
D,andEandnormalizing,quenching,andtemperingforGrade
final tempering temperature as a means of adjusting final
C. In normalizing treatments, the forging may be cooled in still
strength or toughness. If the stress-relief temperature is within
airorinanairblastatthemanufacturer’soption.Fastercooling
25 °F [14 °C] of the final tempering temperature, or higher,
rates for Grades A, B, D, and E may be used if authorized by
additional tension tests must be obtained (6.1.3).
the purchaser. These rates are obtained by liquid quenching, or
by the addition of water sprays of fog to the air blast. 4.6 Machining:
4.5.1.1 The first normalizing treatment shall be from well
4.6.1 Preliminary Rough Machining—All exterior surfaces
above the transformation temperature range. At the manufac-
of the forging shall be machined prior to heat treatment for
turer’s option, this operation may be performed as a part of the
mechanical properties.
preliminary treatment of the forging before preliminary ma-
4.6.2 Second Rough Machining—After heat treatment for
chining (see 4.6.1).
mechanicalproperties,allsurfacesoftheforgingshallberough
4.5.1.2 The second normalizing or quenching treatment
machined prior to stress relief and the stability test.
shallbefromabovethetransformationrangebutbelowthefirst
4.6.3 Axial Bore:
normalizing temperature described in 4.5.1.1. This treatment
4.6.3.1 Forgings shall be bored to permissible bore size and
shall be performed after preliminary machining (see 4.6.1).
tolerance when required by the purchaser’s drawing.
4.5.1.3 The final tempering temperature for GradesA, B, C,
4.6.3.2 Forgings may be bored to limits agreed to by the
and E shall be not less than 1075 °F [580 °C] and for Grade D
purchaser, or indicated on the purchaser’s drawing, to remove
not less than 1200 °F [650 °C]. With prior purchaser approval,
objectionable center conditions revealed by ultrasonic exami-
a second tempering operation shall be performed prior to the
nation.
operations described in 4.6.2 and 4.6.3 to complete the heat
treatment cycle. This second temper will be in place of the 4.6.3.3 Unless otherwise specified by the purchaser, the
stress relief specified in 4.5.1.4 and 4.5.1.5, and the tempera- manufacturer may bore the forging at any time prior to stress
tures applied to the second temper will meet the temperature relief (see Supplementary Requirement S2).
A470/A470M−05 (2020)
4.6.4 Machining to Purchaser’s Requirements for 6.2.1 The steel shall conform to the requirements for notch
Shipment—The forging as shipped shall conform to the finish toughness (both transition temperature and room temperature
and dimension requirements specified on the purchaser’s draw- impact values) prescribed in Table 2.
ing or order. 6.2.2 The impact specimens shall be machined from radial
bars taken from the main body of the forging, as shown in the
5. Chemical Composition
purchaser’s drawing. The specimens shall be Charpy V-notch,
as shown in Test Methods and Definitions A370. The notch
5.1 Thesteelshallconformtotherequirementsforchemical
direction of the Charpy specimens shall be tangential.
composition prescribed in Table 1.
6.3 The properties at the axial bore region may not neces-
5.2 Chemical Analysis:
sarily be the same as those determined at the surface radial or
5.2.1 Product Analysis—The manufacturer shall make a
axial prolongation regions. Slight variations in chemical
product analysis from each forging. The sample location and
homogeneity, different cooling rates, presence of non-
product analysis tolerances shall conform to Specification
metallics, and orientation of the test samples are some of the
A788/A788M.
factors that can contribute to the difference. If axial bore
6. Mechanical Properties properties are required, they can be obtained through Supple-
mentary Requirement S2.
6.1 Tension Test:
6.1.1 The steel shall conform to the tensile requirements of
7. Dimensions, Tolerances, and Finish
Table 2.
6.1.2 The number and location of tension test specimens
7.1 The steel shall conform to the tensile requirements of
shall be as specified on the drawing furnished by the purchaser.
Table 2.
6.1.3 Final acceptance tests shall be made after heat treat-
7.2 The finish on each forging shall conform to the finish
ment of the forging for mechanical properties prior to stress
specified on the purchaser’s drawing or order.
relief, unless the stress relief temperature is within 25 °F
[14 °C] of the tempering temperature, or higher, in which case
8. Nondestructive Tests
check tests shall be made after the stress relief treatment and
8.1 General Requirements:
reported to the purchaser. The purchaser may require check
tests after completion of all heating cycles, including stress 8.1.1 The forgings shall be free of cracks, seams, laps,
shrinkage, and similar imperfections.
relief and the heat stability tests.
6.1.4 Testing shall be performed in accordance with the 8.1.2 The purchaser may request ultrasonic, magnetic
particle, dye penetrant, etch, or other accepted nondestructive
latest revision of Test Methods and Definitions A370. Tension
specimens shall be the standard 0.5 in. diameter by 2 in. gage examination necessary to evaluate imperfections and ensure
compliance with this requirement.
length [or 12.5 mm by 50.0 mm type] as shown in Test
Methods and Definitions A370.
8.2 Ultrasonic Examination:
6.1.5 The yield strength prescribed in Table 2 shall be
8.2.1 An ultrasonic examination shall be made on the
determined by the offset method of Test Methods and Defini-
machined forging at the manufacturer’s plant. This examina-
tions A370.
tionshallbemadeinaccordancewithPracticeA418/A418Mto
6.2 Impact Test: demonstrate freedom from rejectable internal indications.
TABLE 2 Tensile and Notch Toughness Requirements
Grade A Grade B Grade C Grade D Grade E
Class 2 Class 3 Class 4 Class 5 Class 6 Class 7 Class 8 Class 9
Tensile strength, 80 [550] 90 [620] 105 [725] 90 to 110 105 to 125 120 to 135 105 to 125 95 [655]
min, ksi [MPa] [620–760] [725–860] [825–930] [725–860]
Yield strength, 55 [380] 70 [485] 85 [585] 70 [485] 85 [585] 95 [655] 85 [585] 70 [485]
min, ksi [MPa]
0.2 % offset 60 [415] 75 [520] 90 [620] 75 [520] 90 [620] 100 [690] 90 [620] 75 [520]
0.02 % offset 55 [380] 70 [485] 85 [585] 70 [485] 85 [585] 95 [655] 85 [585] 70 [485]
Elongation in 2 in. or
50 mm, min, %:
Longitudinal 22 20 17 20 18 18 17 20
prolongation
Radial body 20 17 16 18 17 17 14 15
Reduction of area,
min, %:
Longitudinal 50 48 45 52 52 52 43 40
prolongation
Radial body 50 45 40 50 50 50 38 35
Transition temperature 100 [38] 110 [43] 140 [60] 10 [−12] 20 [−7] 30 [−1] 250 [121] 175 [80]
FATT max, °F [°C]
Room temperature 28 [38] 25 [34] 20 [27] 50 [68] 45 [61] 40 [54] 6 [8] 12 [16]
impact, min, ft·lbf [J]
A470/A470M−05 (2020)
8.2.2 The ultrasonic examination shall be made from all 10.2 If bore core properties are specified under Supplemen-
available surfaces prior to removal of test specimens that tary Requirement S2 and retemper is necessary after boring,
would interfere with complete testing of the forging. the remaining portions of the bore core shall be replaced in the
8.2.3 Forgings with recordable ultrasonic indications shall bore during
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