ASTM A291/A291M-19

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: A291/A291M − 18a A291/A291M − 19
Standard Specification for
Steel Forgings, Carbon and Alloy, for Pinions, Gears and
Shafts for Reduction Gears
This standard is issued under the fixed designation A291/A291M; 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*
1.1 This specification covers normalized and tempered carbon steel and quenched and tempered alloy steel forgings for pinions,
gears, and shafts.
1.2 Several grades of steel are covered as follows:
1.2.1 Grade 1, Class A, is normalized and tempered carbon steel.
1.2.2 Grade 2, Class B, Grade 3, Class C, Grade 3A, Class D, Grades 4 to 7, Classes E, F, G, and H, Grade 8, Class I, and
Grade 9, Class J, are liquid quenched and tempered alloy steel.
1.3 All grades and classes are considered weldable under proper conditions. Welding technique is of fundamental importance
and it is presupposed that welding procedure and inspection shall be in accordance with approved methods for the class of material
used.
1.4 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.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
A275/A275M Practice for Magnetic Particle Examination of Steel Forgings
A388/A388M Practice for Ultrasonic Examination of Steel Forgings
A788/A788M Specification for Steel Forgings, General Requirements
3. Terminology
3.1 Definitions:
3.1.1 controlling cross section thickness (T )—the diameter of the largest theoretical sphere which can be inscribed within the
C
volume of the forging.
3.1.2 gears—rings, disks, cylinders or rectangular bars having gear teeth.
3.1.3 pinions—circular cross section forgings of multiple diameter with gear teeth on one or more diameters.
3.1.4 shafts—circular cross section forgings of one or more diameters which do not have integral gear teeth.
This specification is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.06
on Steel Forgings and Billets.
Current edition approved Nov. 1, 2018Nov. 1, 2019. Published November 2018November 2019. Originally approved in 1946. Last previous edition approved in 2018 as
A291/A291MA291/A291M – 18a.–18. DOI: 10.1520/A0291_A0291M–18A.10.1520/A0291_A0291M-19.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A291/A291M − 19
4. Ordering Information
4.1 Instructions for purchasing forgings to this specification should be in accordance with Specification A788/A788M. In
addition, a detailed drawing, sketch, or written description of the forging should be included with the inquiry or order.
4.2 Supplementary requirements are provided and shall apply only when specified in the purchase order.
5. Heat Treatment
5.1 Preliminary Heat Treatment:
5.1.1 The forgings shall be given such preliminary heat treatment as is proper for the design and composition. The forgings shall
be heated to a suitable temperature for a sufficient length of time for austenitization and shall be suitably cooled to bring about
complete transformation.
5.1.2 Forgings may be immediately treated for mechanical properties after preliminary heat treatment or they may be
preliminarily machined prior to treatment for mechanical properties.
5.2 Heat Treatment for Mechanical Properties—The forging shall be reheated to a temperature above the upper critical
temperature and held a sufficient length of time for complete austenitization. Grade 1 shall be air cooled while Grades 2 through
9 shall be liquid quenched.
5.3 Tempering—The forgings shall be tempered to develop the specified properties. Minimum tempering temperatures shall be
as follows:
Minimum Tempering Temperature
Grade Class °F [°C]
1 and 2 A and B 1150 [620]
3, 3A, and 4 C, D, and E 1075 [580]
5, 6, 7 F, G, and H 1050 [565]
8 I 1100 [595]
9 J 1000 [540]
The charge For all grades except Grade 1 Class A, the forgings shall be cooled under uniform conditions in the furnace at a
maximum rate of 100 °F [55 °C] per h to 600 °F [315 °C].
5.4 Stress Relief—If the manufacturer elects to heat treat for mechanical properties prior to machining, the forgings shall be
stress relieved after machining (see 5.5) at a temperature that is 50 to 100 °F [30 to 55 °C] below the last previous tempering
temperature but in no case below 1000 °F [540 °C]. The For all grades except Grade 1, Class A, the forgings shall be cooled under
uniform conditions in the furnace at a maximum rate of 100 °F [55 °C] ⁄h to 600 °F [315 °C].
5.5 Machining:
5.5.1 Machining before heat treatment for mechanical properties may be performed at the option of the manufacturer.
5.5.2 If the producer elects to heat treat for mechanical properties prior to machining, the forgings shall be stress relieved after
machining.
5.5.3 Boring—Forgings, after being heat treated for mechanical properties and subsequently bored, shall be stress relieved.
6. General Requirements
6.1 Unless otherwise specified herein, the requirements of Specification A788/A788M shall apply to forgings supplied to this
specification.
7. Chemical Requirements
7.1 The steel shall conform to the requirements for chemical composition prescribed in Table 1.
7.2 The limits for elements other than carbon, manganese, phosphorus, sulfur, and silicon in Grade 2 alloy shall be agreed upon
between the manufacturer and purchaser.
8. Mechanical Requirements
8.1 Tensile and Impact Requirements:
8.1.1 The material shall conform to the requirements for tensile and impact properties prescribed in Table 2 and impact
properties (see Supplementary Requirement S2) when agreed upon between the purchaser and the supplier.
8.1.2 Classification—The dimensions of the controlling cross section thickness (T ) of the forging at the time of heat treatment
C
determine the mechanical properties to be met within each class (see Table 2).
8.1.3 Number, Location, and Orientation of Test Specimens:
8.1.3.1 At least one tension test specimen either longitudinal or tangential at the option of the manufacturer shall be taken from
each forging unless a number of forgings are forged and treated in multiple, in which case one tension test specimen shall be taken
from each end of the multiple forging. When impact tests are specified in accordance with Supplementary Requirement S2, one
set of impact tests shall also be taken from each end of the multiple forging. When agreed upon between the manufacturer and the
purchaser, forgings weighing less than 500 lb [225 kg] each at time of heat treatment may be tested in lots; the number of forgings
to make up a lot shall be by mutual agreement.
A291/A291M − 19
TABLE 1 Chemical Requirements
Element Composition, %
Grade 1 Grade 2 Grade 3 Grade 3A Grades 4 to 7 Grade 8 Grade 9
Classes E, F, G,
Class A Class B Class C Class D and H Class I Class J
Carbon 0.55 max 0.50 max 0.45 max 0.45 max 0.35–0.50 0.38–0.45 0.25–0.39
Manganese 0.60–0.90 0.40–0.90 0.40–0.90 0.40–0.90 0.40–0.90 0.40–0.70 0.20–0.60
Phosphorus, max 0.040 0.040 0.040 0.040 0.040 0.040 0.015
Sulfur, max 0.040 0.040 0.040 0.040 0.040 0.040 0.015
A
Silicon, max 0.35 0.35 0.35 0.35 0.35 0.40 0.35
B
Nickel 0.30 max 0.50 max 1.00–3.00 1.65 min 0.30 max 3.25–4.00
B
Chromium 0.25 max 1.25 max 1.50 max 0.60 min 1.40–1.80 1.25–1.75
B
Molybdenum 0.10 max 0.15 min 0.15 min 0.20–0.60 0.30–0.45 0.30–0.70
Vanadium, max 0.06 0.10 0.05 0.10 0.10 0.03 0.05–0.15
Copper, max 0.35 0.35 0.35 0.35 0.35 0.35 0.35
Aluminum . . . . . . . . . . . . . . . 0.85–1.30 . . .
A
When vacuum carbon deoxidation is used, silicon maximum shall be 0.10 %.
B
Optional with manufacturer and purchaser.
TABLE 2 Mechanical Properties
Size, Solid
Diameter or Yield Strength, 0.2% Elongation in 2 in. Reduction
...