ASTM A350/A350M-24

Standard Specification for Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Components

ABSTRACT
This specification covers several grades of carbon and low alloy steel forged or ring-rolled flanges, forged fittings and valves for low-temperature service. The steel specimens shall be melt processed using open-hearth, basic oxygen, electric furnace or vacuum-induction melting. A sufficient discard shall be made to secure freedom from injurious piping and undue segregation. The materials shall be forged and shall undergo heat treatment such as normalizing, tempering, quenching and precipitation heat treatment. Heat analysis and product analysis shall be performed wherein the steel materials shall conform to the required chemical compositions of carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, copper, columbium, vanadium, and nitrogen. The materials shall also undergo tension tests and shall conform to the required values of tensile strength, yield strength and elongation. Impact tests shall also be performed and the steel materials shall conform to the required values of minimum impact energy, temperature, and minimum equivalent absorbed energy. Hardness and hydrostatic tests shall also be performed.
SCOPE
1.1 This specification2 covers several grades of carbon and low-alloy steel forged or ring-rolled flanges, forged fittings and valves intended primarily for low-temperature service and requiring notch toughness testing. They are made to specified dimensions, or to dimensional standards, such as the ASME and API Specifications referenced in Section 2. Although this specification covers some piping components machined from rolled bar and seamless tubular materials (see 5.3.3), it does not cover raw material produced in these product forms.  
1.2 No limitation on size is intended beyond the ability of the manufacturer to obtain the specified requirements. However, Class 3 of Grade LF787 is only available in the quenched-and-precipitation heat treated condition.  
1.3 Supplementary requirements are provided for use when additional testing or inspection is desired. These shall apply only when specified by the purchaser in the order.  
1.4 This specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units.  
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. 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.  
1.6 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: 29-Feb-2024
• ICS: 23.040.40 - Metal fittings
• Technical Committee: A01 - Steel, Stainless Steel and Related Alloys
• Drafting Committee: A01.22 - Steel Forgings and Wrought Fittings for Piping Applications and Bolting Materials for Piping and Special Purpose Applications

Relations

• Replaces: ASTM A350/A350M-23 - Standard Specification for Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Components
• Effective Date: 01-Mar-2024
• Referred By: ASTM A727/A727M-14(2019) - Standard Specification for Carbon Steel Forgings for Piping Components with Inherent Notch Toughness
• Effective Date: 01-Mar-2024
• Referred By: ASTM A961/A961M-23 - Standard Specification for Common Requirements for Steel Flanges, Forged Fittings, Valves, and Parts for Piping Applications
• Effective Date: 01-Mar-2024
• Referred By: ASTM A420/A420M-22 - Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Low-Temperature Service
• Effective Date: 01-Mar-2024

Overview

ASTM A350/A350M-24 is the authoritative standard specification for carbon and low-alloy steel forgings, specifically those requiring notch toughness testing for piping components designed for low-temperature service. This standard, developed by ASTM International, covers a broad range of forged or ring-rolled flanges, forged fittings, and valves. It sets out key manufacturing, chemical analysis, mechanical property, and testing requirements to ensure the safety and reliability of piping components used in challenging environments where low-temperature performance and tough mechanical properties are critical.

Key Topics

• Scope and Application: Specifies several grades of carbon and low-alloy steel forgings for use in low-temperature environments, with particular emphasis on the need for notch toughness.
• Manufacturing Processes: Permits steel production through open-hearth, basic oxygen, electric furnace, and vacuum-induction melting, with further secondary processing allowed.
• Heat Treatment: Mandates normalization, tempering, quenching, or precipitation heat treatment as appropriate for different grades to achieve required mechanical properties.
• Chemical Requirements: Enforces strict limits for chemical elements including carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, copper, columbium (niobium), vanadium, and nitrogen, varying by grade.
• Mechanical Testing: Requires conformance through tension tests, impact (Charpy V-notch) tests, hardness tests, and hydrostatic tests to verify properties such as tensile strength, yield strength, elongation, reduction of area, and minimum impact energy at specified temperatures.
• Dimensional Standards: Aligns forging dimensions with relevant ASME and API specifications, ensuring interoperability with widely used piping systems.
• Supplementary and Purchaser Requirements: Provides for additional testing or inspection as specified by the purchaser, and gives guidance on marking, documentation, and certification.

Applications

ASTM A350/A350M-24 steel forgings are essential for:

• Industrial Piping Systems: Used in industries such as oil & gas, petrochemical, power generation, and chemical processing, especially in low-temperature service conditions.
• Pressure Vessels: Suitable for manufacturing pressure-retaining components, including flanges and valves requiring verified notch toughness performance.
• Cryogenic and Cold Weather Installations: Ensures reliability and safety in applications where materials are subjected to very low service temperatures.
• Pipeline Infrastructure: Commonly specified in transmission lines and process systems where resistance to brittle fracture is vital.

Components engineered under this standard are frequently required in installations where failure due to brittle fracture must be avoided, such as in arctic environments, refrigerated process streams, or where high cyclic loadings occur.

Related Standards

For manufacturers, suppliers, and end-users referencing ASTM A350/A350M-24, several related standards are often used in conjunction:

• ASTM A788/A788M: General requirements for steel forgings for piping applications
• ASTM A961/A961M: Common requirements for steel flanges, forged fittings, valves, and parts for piping applications
• ASME B16.5, B16.9, B16.10, B16.11, B16.30, B16.34, and B16.47: Dimensional and design standards for pipe flanges, fittings, and valves
• ASME Boiler and Pressure Vessel Code, Section IX: Welding procedure and qualification requirements
• AWS A5.1 & A5.5: Specifications for mild and low-alloy steel covered arc-welding electrodes
• API 600, 602, 605: Standards for steel gate valves and flanges

Practical Value

Adhering to ASTM A350/A350M-24 ensures:

• Material Consistency: Reliable performance in demanding low-temperature environments
• Safety Assurance: Minimizes risk of brittle fracture through rigorous notch toughness testing
• Global Acceptance: Facilitates international trade and compliance, with dual SI and inch-pound units and alignment with WTO TBT principles
• Quality Documentation: Provides clear requirements for marking, traceability, and test reporting, supporting quality assurance and regulatory compliance

By following ASTM A350/A350M-24, organizations ensure that critical piping components meet stringent mechanical and chemical standards, vital for long-term operational safety and efficiency in cold and low-temperature service applications.

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: A350/A350M − 24
Standard Specification for
Carbon and Low-Alloy Steel Forgings, Requiring Notch
Toughness Testing for Piping Components
This standard is issued under the fixed designation A350/A350M; 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* Development of International Standards, Guides and Recom-
2 mendations issued by the World Trade Organization Technical
1.1 This specification covers several grades of carbon and
Barriers to Trade (TBT) Committee.
low-alloy steel forged or ring-rolled flanges, forged fittings and
valves intended primarily for low-temperature service and
2. Referenced Documents
requiring notch toughness testing. They are made to specified
2.1 ASTM Standards:
dimensions, or to dimensional standards, such as the ASME
A788/A788M Specification for Steel Forgings, General Re-
and API Specifications referenced in Section 2. Although this
quirements
specification covers some piping components machined from
A961/A961M Specification for Common Requirements for
rolled bar and seamless tubular materials (see 5.3.3), it does not
Steel Flanges, Forged Fittings, Valves, and Parts for
cover raw material produced in these product forms.
Piping Applications
1.2 No limitation on size is intended beyond the ability of
2.2 ASME Standards:
the manufacturer to obtain the specified requirements.
B 16.5 Steel Pipe Flanges and Flanged Fittings
However, Class 3 of Grade LF787 is only available in the
B 16.9 Factory-Made Wrought Steel Butt-Welding Fittings
quenched-and-precipitation heat treated condition.
B 16.10 Face-to-Face and End-to-End Dimensions of Fer-
1.3 Supplementary requirements are provided for use when
rous Valves
additional testing or inspection is desired. These shall apply
B 16.11 Forged Steel Fittings, Socket-Welding and
only when specified by the purchaser in the order.
Threaded
B 16.30 Unfired Pressure Vessel Flange Dimensions
1.4 This specification is expressed in both inch-pound units
B 16.34 Valves-Flanged, Threaded, and Welding End
and in SI units. However, unless the order specifies the
B 16.47 Large Diameter Steel Flanges
applicable “M” specification designation (SI units), the mate-
2.3 ASME Boiler and Pressure Vessel Code:
rial shall be furnished to inch-pound units.
Section IX
1.5 The values stated in either SI units or inch-pound units
2.4 AWS Standards:
are to be regarded separately as standard. Within the text, the
A 5.1 Mild Steel Covered Arc-Welding Electrodes
SI units are shown in brackets. The values stated in each
A 5.5 Low-Alloy Steel Covered Arc-Welding Electrodes
system may not be exact equivalents; therefore, each system
2.5 API Standards:
shall be used independently of the other. Combining values
600 Steel Gate Valves with Flanged or Butt-Welding Ends
from the two systems may result in non-conformance with the
602 Compact Design Carbon Steel Gate Valves for Refinery
standard.
Use
1.6 This international standard was developed in accor-
605 Large Diameter Carbon Steel Flanges
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
This specification is under the jurisdiction of ASTM Committee A01 on Steel, Standards volume information, refer to the standard’s Document Summary page on
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee the ASTM website.
A01.22 on Steel Forgings and Wrought Fittings for Piping Applications and Bolting Available from American Society of Mechanical Engineers (ASME), ASME
Materials for Piping and Special Purpose Applications. International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
Current edition approved March 1, 2024. Published March 2024. Originally www.asme.org.
approved in 1952. Last previous edition approved in 2023 as A350/A350M – 23. Available from American Welding Society (AWS), 550 NW LeJeune Rd.,
DOI: 10.1520/A0350_A0350M-24. Miami, FL 33126, http://www.aws.org.
2 6
For ASME Boiler and Pressure Vessel Code applications see related Specifi- Available from American Petroleum Institute (API), 1220 L. St., NW,
cation SA-350 in Section II of that Code. Washington, DC 20005-4070, http://api-ec.api.org.
*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
A350/A350M − 24
3. Ordering Information 5.3.3 Hollow parts may be machined from rolled bar or
seamless tubular materials provided the longitudinal axis of the
3.1 It is the purchaser’s responsibility to specify in the
part is parallel to the longitudinal axis of the bar. Other parts,
purchase order information necessary to purchase the needed
up to and including NPS4, may be machined from hot-rolled or
material. In addition to the ordering information guidelines in
forged bar provided the longitudinal axis of the part is parallel
Specification A961/A961M, orders should include the follow-
to the longitudinal axis of the bar. Flanges, elbows, return
ing information:
bends, tees, and header tees shall not be machined directly
3.1.1 The number of test reports required (see Section 14).
from bar stock.
3.1.2 Additional requirements (see Table 1 footnotes).
3.1.3 Options in the specification. See 5.4.2.1. 5.4 Heat Treatment:
5.4.1 After hot working and before reheating for heat
4. General Requirements
treatment, the forging shall be allowed to cool substantially
below the transformation range.
4.1 Product furnished to this specification shall conform to
5.4.2 Forgings of grades other than Grade LF787 shall be
the requirements of Specification A961/A961M, including any
furnished in the normalized, or normalized and tempered, or
supplementary requirements that are indicated in the purchase
quenched and tempered condition. At the option of the
order. Failure to comply with the general requirements of
manufacturer, forgings furnished in the quenched and tempered
Specification A961/A961M constitutes nonconformance with
condition may be normalized prior to the austenitize/quench
this specification. In case of conflict between the requirements
operation.
of this specification and Specification A961/A961M, this
5.4.2.1 Quenching shall consist of either:
specification shall prevail.
(1) fully austenitizing the forgings followed by quenching
in a suitable liquid medium, or
5. Manufacture
(2) using a multiple stage procedure whereby the forging is
5.1 Melting Process—The steel shall be produced by any of
first fully austenitized and rapidly cooled, then reheated to
the following primary processes: open-hearth, basic oxygen,
partially re-asutenitize, followed by quenching in a suitable
electric-furnace, or vacuum-induction melting (VIM). The
liquid medium.
primary melting may incorporate separate degassing or
(3) Unless otherwise specified by the purchaser, the choice
refining, and may be followed by secondary melting using
of (1) or (2) shall be at the option of the manufacturer.
electroslag remelting (ESR), or vacuum-arc remelting (VAR).
5.4.2.2 All quenched forgings shall be tempered to 5.4.2.3
5.1.1 The steel shall be fully killed, fine-grain practice.
5.4.2.3 Forgings, when tempered, shall be tempered at
5.1.2 The molten steel may be vacuum treated prior to or
1100 °F [590 °C], minimum, holding at temperature a mini-
during pouring of the ingot.
mum of 30 min/in. [30 min/25 mm] of maximum thickness, but
5.2 Discard—A sufficient discard shall be made to secure
in no case less than 30 min.
freedom from injurious piping and undue segregation.
5.4.3 Grade LF787 forgings shall be furnished in either the
normalized-and-precipitation heat treated condition or in the
5.3 Forging Process:
5.3.1 Material for forgings shall consist of ingots, or forged, quenched-and-precipitation heat treated condition. The heat
treatment procedures shall be as follows:
rolled, or strandcast blooms, billets, slabs, or bars.
5.3.2 The finished product shall be a forging as defined in 5.4.3.1 Normalized-and-Precipitation Heat Treated—
the Terminology section of Specification A788/A788M. Austenitize in the range from 1600 to 1725 °F [870 to 940 °C]
TABLE 1 Chemical Requirements
Composition, wt. %
Element
Grade LF1 Grade LF2 Grade LF3 Grade LF5 Grade LF6 Grade LF9 Grade LF787
Carbon, max 0.30 0.30 0.20 0.30 0.22 0.20 0.07
Manganese 0.60–1.35 0.60–1.35 0.90 max 0.60–1.35 1.15–1.50 0.40–1.06 0.40–0.70
Phosphorus, 0.035 0.035 0.035 0.035 0.025 0.035 0.025
max
Sulfur, max 0.040 0.040 0.040 0.040 0.025 0.040 0.025
A
Silicon 0.15–0.30 0.15–0.30 0.20–0.35 0.20–0.35 0.15–0.30 . 0.40 max
B B B
Nickel 0.40 max 0.40 max 3.3–3.7 1.0–2.0 0.40 max 1.60–2.24 0.70–1.00
B,C B,C C C B,C C
Chromium 0.30 max 0.30 max 0.30 max 0.30 max 0.30 max 0.30 max 0.60–0.90
B,C B,C C C B,C C
Molybdenum 0.12 max 0.12 max 0.12 max 0.12 max 0.12 max 0.12 max 0.15–0.25
B B B
Copper 0.40 max 0.40 max 0.40 max 0.40 max 0.40 max 0.75–1.25 1.00–1.30
E D D
Niobium 0.02 max 0.02 max 0.02 max 0.02 max 0.02 max 0.02 max 0.02 min
Vanadium 0.08 max 0.08 max 0.03 max 0.03 max 0.04–0.11 0.03 max 0.03 max
Nitrogen . . . . . . . . . . . . 0.01–0.030 . . . . . .
A
When vacuum carbon-deoxidation is required by Supplementary Requirement S4, the silicon content shall be 0.12 % maximum.
B
The sum of copper, nickel, chromium, vanadium and molybdenum shall not exceed 1.00 % on heat analysis.
C
The sum of chromium and molybdenum shall not exceed 0.32 % on heat analysis.
D
By agreement, the limit for niobium (columbium) may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
E
Niobium and columbium are interchangeable names for the same element and both names are acceptable for use in A01.22 specifications.
A350/A350M − 24
for not less than ⁄2 h, and remove from the furnace and cool in tion and the same heat treatment as the finished products
air. Subsequently, artificially age in the range from 1000 to represented. The test material shall be treated in the same
1200 °F [540 to 650 °C] for not less than ⁄2 h, and cool at any furnace at the same time as the forging it represents, subject to
convenient rate. the requirements of 7.1.2.1.
5.4.3.2 Quenched-and-Precipitation Heat Treated—
7.1.1.2 The test specimen shall represent all forgings from
Austenitize in the range from 1600 to 1725 °F [870 to 940 °C]
the same heat and heat-treatment load whose maximum thick-
for not less than ⁄2 h and quench in a suitable liquid medium
nesses do not exceed the thickness of the test forging or blank
by immersion; artificially age in the range from 1000 to
by more than ⁄4 in. [6 mm].
1225 °F [540 to 665 °C] for not less than ⁄2 h, and cool at any
7.1.2 Number of Tests—One tension test at room tempera-
convenient rate.
ture shall be made in accordance with 7.1.1.2 from each heat in
each heat-treatment load.
6. Chemical Composition
7.1.2.1 If heat treatment is performed in either a continuous
6.1 Heat Analysis:
or a batch-type furnace controlled within 625 °F [614 °C] of
6.1.1 A chemical heat analysis in accordance with Specifi-
the required heat-treatment temperature and equipped with
cation A961/A961M shall be made and conform to the
recording pyrometers so that complete records of heat treat-
requirements as to chemical composition prescribed in Table 1.
ment are available and if the same heat-treating cycles are used
Leaded steels shall not be permitted.
on the forgings represented by the tension test, then one tension
test from each heat shall be required, instead of one tension test
6.2 Product Analysis:
from each heat in each heat treatment load in accordance with
6.2.1 The purchaser may make a product analysis on prod-
7.1.1.2.
ucts supplied to this specification in accordance with Specifi-
cation A961/A961M. 7.1.3 Test Locations and Orientations—The test specimen
shall be removed from the heaviest section of the forging or
7. Mechanical Properties
test blank, at locations described in 7.1.3.1, 7.1.3.2, 7.1.3.5 or
as close to these locations as practical, subject to forging size
7.1 Tension Tests:
and geometry.
7.1.1 Requirements—The material shall conform to require-
ments for tensile properties in Table 2. 7.1.3.1 For forgings or test blanks having a maximum
7.1.1.1 The test specimen shall be obtained from a rough or heat-treated thickness, T, of 2 in. [50 mm] or less, the
finished forging, or prolongation thereof. For forgings under longitudinal axis of the test specimen shall be taken at
10 000 lbs, at time of heat treatment, it may be obtained from mid-thickness and its mid-length shall be at least 2 in. [50 mm]
separately forged test blanks from the same heat of steel as the from all other heat treated surfaces, exclusive of the T
production forgings. The test blank shall be reduced by forging dimension surfaces. (This is normally referred to as ⁄2 T by 2
in a manner similar to that for the products represented, and in. [50 mm]). See Fig. 1 for test specimen location in separately
forged test blanks.
shall receive approximately the same hot working and reduc-
A
TABLE 2 Tensile Properties at Room Temperature
Grades
LF1 and LF5 LF2 LF3 LF6 LF9 LF787
Class 1 Classes Classes 1
Class 1 Classes 2 Class 2 Class 3
1 and 2 and 2
and 3
LF5
Class 2
Tensile strength, ksi [MPa] 60–85 70–95 70–95 66–91 75–100 63–88 65–85 75–95
[415–585] [485–655] [485–655] [455–630] [515–690] [435–605] [450–585] [515–655]
B
Yield strength, min, ksi [MPa] 30 [205] 36 [250] 37.5 [260] 52 [360] 60 [415] 46 [315] 55 [380] 65 [450]
Elongation:
Standard round specimen, or 25 22 22 22 20 25 20 20
small proportional specimen,
min % in 4D gauge length
Strip specimen for wall thickness 28 30 30 30 28 28 28 28
⁄16 in. [7.94 mm] and over
and for all small sizes tested
in full section; min % in 2 in.
[50 mm]
Formula for calculating minimum
elongation for strip specimens
thinner than ⁄16 in. [7.94 mm];
min % in 2 in. [50 mm]
t = actual thickness in inches 48t + 13 48t + 15 48t + 15 48t + 15 48t + 13 48t + 13 48t + 13 48t + 13
t = actual thickness in mm 1.9t +13 1.9t + 15 1.9t + 15 1.9t + 15 1.9t + 13 1.9t + 13 1.9t + 13 1.9t + 13
C
Reduction of area, min, % 38 30 35 40 40 38 45 45
A
See 7.3 for hardness tests.
B
Determined by either the 0.2 % offset method or the 0.5 % extension under load method.
C
For round specimens only.
A350/A350M − 24
NOTE 1—For clarity, only the Charpy V-notch specimen is shown in Figs. 1-4. The tension test specimen shall be located such that its orientation and
the mid-length location meet the same requirements as that for the Charpy V-notch test specimen shown in Figure 1.
FIG. 1 Separately Forged Test Bar for Forgings with T # 2 in. [50 mm]
7.1.3.2 For forgings or test blanks having a maximum freedom from cracks unless the welded areas are completely
heat-treated thickness, T, greater than 2 in. [50 mm]: removed by subsequent machining.
(1) Except as stated in 7.1.3.2 (2) and 7.1.3.2 (3), the
7.1.3.4 The test specimen shall have its longitudinal axis
central axis of the test specimen shall be taken at least ⁄4 T
located parallel to the direction of major working of the forging
from the nearest heat-treated surface and its mid-length shall be
or test blank.
at least 2 in. [50 mm] from all other heat treated surfaces,
7.1.3.5 With prior purchaser approval, tests may be taken at
exclusive of the T dimension surfaces. See Fig. 2 for test
a depth (t) corresponding to the distance from the area of
specimen location in separately forged test blanks.
significant loading to the nearest heat treated surface and at
(2) For quenched-and-tempered or for quenched-and-
least twice this distance (2t) from any second surface.
precipitation-heat-treated forgings, the central axis of the test
However, the test depth shall not be nearer to one treated
specimen shall be taken at least ⁄4 T from the nearest heat- 3
surface than ⁄4 in. [19 mm] and to the second treated surface
treated surface, and the mid-length of the test specimen shall be 1
than 1 ⁄2 in. [38 mm]. This method of test location would
at least T from all other heat treated surfaces, exclusive of the
normally apply to contour-forged parts, or parts with thick
T dimension surfaces. See Fig. 3 for test specimen location in 1
cross-sectional areas where ⁄4 T × T testing (7.1.3.2) is not
separately forged test blanks.
practical. Sketches showing the exact test locations shall be
(3) For quenched-and-tempered or for quenched-and-
approved by the purchaser when this method is used.
precipitation–heat-treated forgings that have a W/T ratio < 2,
7.1.4 Test Method—Testing shall be performed as specified
the central axis of the test specimen shall be taken at least ⁄4 T
in Specification A961/A961M. The test specimen shall be as
from the nearest heat-treated surface, and at mid-width of the
large as is practicable and shall be machined to the form and
forging, where W is the width of the forging. The test specimen
dimensions in Specification A961/A961M. When seamless
mid-length shall be at least T from the ends of the forging or
tubular materials are used, testing shall be performed on
test blank. See Fig. 4 for test specimen location in separately
longitudinal specimens as specified in Specification A961/
forged test blank.
A961M.
7.1.3.3 Metal Buffers—The required distances from heat
7.2 Impact Test:
treated surfaces for the test locations described in 7.1.3.1 and
7.1.3.2 may be obtained with metal buffers instead of integral 7.2.1 Requirements—The material shall conform to the
expansions. Buffer material may be carbon or low alloy steel, requirements for impact properties in Table 3 when tested at
and shall be joined to the forging with a partial penetration the applicable standard temperature in Table 4 within the limits
weld that seals the buffered surface. Specimens shall be located of 7.2.4.2 and 7.2.4.3. When subsize specimens are used, the
at ⁄2 in. [13 mm] minimum from the buffered surface of the impact energy values obtained shall conform to Table 5 at
forging. Buffers shall be removed after heat treatment an
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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: A350/A350M − 23 A350/A350M − 24
Standard Specification for
Carbon and Low-Alloy Steel Forgings, Requiring Notch
Toughness Testing for Piping Components
This standard is issued under the fixed designation A350/A350M; 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*
1.1 This specification covers several grades of carbon and low-alloy steel forged or ring-rolled flanges, forged fittings and valves
intended primarily for low-temperature service and requiring notch toughness testing. They are made to specified dimensions, or
to dimensional standards, such as the ASME and API Specifications referenced in Section 2. Although this specification covers
some piping components machined from rolled bar and seamless tubular materials (see 5.3.3), it does not cover raw material
produced in these product forms.
1.2 No limitation on size is intended beyond the ability of the manufacturer to obtain the specified requirements. However, Class
3 of Grade LF787 is only available in the quenched-and-precipitation heat treated condition.
1.3 Supplementary requirements are provided for use when additional testing or inspection is desired. These shall apply only when
specified by the purchaser in the order.
1.4 This specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M”
specification designation (SI units), the material shall be furnished to inch-pound units.
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units
are shown in brackets. 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.
1.6 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:
A788/A788M Specification for Steel Forgings, General Requirements
This specification is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.22
on Steel Forgings and Wrought Fittings for Piping Applications and Bolting Materials for Piping and Special Purpose Applications.
Current edition approved May 1, 2023March 1, 2024. Published May 2023March 2024. Originally approved in 1952. Last previous edition approved in 20182023 as
A350/A350M – 18.A350/A350M – 23. DOI: 10.1520/A0350_A0350M-23.10.1520/A0350_A0350M-24.
For ASME Boiler and Pressure Vessel Code applications see related Specification SA-350 in Section II of that Code.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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
A350/A350M − 24
A961/A961M Specification for Common Requirements for Steel Flanges, Forged Fittings, Valves, and Parts for Piping
Applications
2.2 ASME Standards:
B 16.5 Steel Pipe Flanges and Flanged Fittings
B 16.9 Factory-Made Wrought Steel Butt-Welding Fittings
B 16.10 Face-to-Face and End-to-End Dimensions of Ferrous Valves
B 16.11 Forged Steel Fittings, Socket-Welding and Threaded
B 16.30 Unfired Pressure Vessel Flange Dimensions
B 16.34 Valves-Flanged, Threaded, and Welding End
B 16.47 Large Diameter Steel Flanges
2.3 ASME Boiler and Pressure Vessel Code:
Section IX
2.4 AWS Standards:
A 5.1 Mild Steel Covered Arc-Welding Electrodes
A 5.5 Low-Alloy Steel Covered Arc-Welding Electrodes
2.5 API Standards:
600 Steel Gate Valves with Flanged or Butt-Welding Ends
602 Compact Design Carbon Steel Gate Valves for Refinery Use
605 Large Diameter Carbon Steel Flanges
3. Ordering Information
3.1 It is the purchaser’s responsibility to specify in the purchase order information necessary to purchase the needed material. In
addition to the ordering information guidelines in Specification A961/A961M, orders should include the following information:
3.1.1 The number of test reports required (see Section 14).
3.1.2 Additional requirements (see Table 1 footnotes).
3.1.3 Options in the specification. See 5.4.2.1.
4. General Requirements
4.1 Product furnished to this specification shall conform to the requirements of Specification A961/A961M, including any
supplementary requirements that are indicated in the purchase order. Failure to comply with the general requirements of
TABLE 1 Chemical Requirements
Composition, wt. %
Element
Grade LF1 Grade LF2 Grade LF3 Grade LF5 Grade LF6 Grade LF9 Grade LF787
Carbon, max 0.30 0.30 0.20 0.30 0.22 0.20 0.07
Manganese 0.60–1.35 0.60–1.35 0.90 max 0.60–1.35 1.15–1.50 0.40–1.06 0.40–0.70
Phosphorus, 0.035 0.035 0.035 0.035 0.025 0.035 0.025
max
Sulfur, max 0.040 0.040 0.040 0.040 0.025 0.040 0.025
A
Silicon 0.15–0.30 0.15–0.30 0.20–0.35 0.20–0.35 0.15–0.30 . 0.40 max
B B B
Nickel 0.40 max 0.40 max 3.3–3.7 1.0–2.0 0.40 max 1.60–2.24 0.70–1.00
B,C B,C C C B,C C
Chromium 0.30 max 0.30 max 0.30 max 0.30 max 0.30 max 0.30 max 0.60–0.90
B,C B,C C C B,C C
Molybdenum 0.12 max 0.12 max 0.12 max 0.12 max 0.12 max 0.12 max 0.15–0.25
B B B
Copper 0.40 max 0.40 max 0.40 max 0.40 max 0.40 max 0.75–1.25 1.00–1.30
E D D
Niobium 0.02 max 0.02 max 0.02 max 0.02 max 0.02 max 0.02 max 0.02 min
Vanadium 0.08 max 0.08 max 0.03 max 0.03 max 0.04–0.11 0.03 max 0.03 max
Nitrogen . . . . . . . . . . . . 0.01–0.030 . . . . . .
A
When vacuum carbon-deoxidation is required by Supplementary Requirement S4, the silicon content shall be 0.12 % maximum.
B
The sum of copper, nickel, chromium, vanadium and molybdenum shall not exceed 1.00 % on heat analysis.
C
The sum of chromium and molybdenum shall not exceed 0.32 % on heat analysis.
D
By agreement, the limit for niobium (columbium) may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
E
Niobium and columbium are interchangeable names for the same element and both names are acceptable for use in A01.22 specifications.
Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
www.asme.org.
Available from American Welding Society (AWS), 550 NW LeJeune Rd., Miami, FL 33126, http://www.aws.org.
Available from American Petroleum Institute (API), 1220 L. St., NW, Washington, DC 20005-4070, http://api-ec.api.org.
A350/A350M − 24
Specification A961/A961M constitutes nonconformance with this specification. In case of conflict between the requirements of this
specification and Specification A961/A961M, this specification shall prevail.
5. Manufacture
5.1 Melting Process—The steel shall be produced by any of the following primary processes: open-hearth, basic oxygen,
electric-furnace, or vacuum-induction melting (VIM). The primary melting may incorporate separate degassing or refining, and
may be followed by secondary melting using electroslag remelting (ESR), or vacuum-arc remelting (VAR).
5.1.1 The steel shall be fully killed, fine-grain practice.
5.1.2 The molten steel may be vacuum treated prior to or during pouring of the ingot.
5.2 Discard—A sufficient discard shall be made to secure freedom from injurious piping and undue segregation.
5.3 Forging Process:
5.3.1 Material for forgings shall consist of ingots, or forged, rolled, or strandcast blooms, billets, slabs, or bars.
5.3.2 The finished product shall be a forging as defined in the Terminology section of Specification A788/A788M.
5.3.3 Hollow parts may be machined from rolled bar or seamless tubular materials provided the longitudinal axis of the part is
parallel to the longitudinal axis of the bar. Other parts, up to and including NPS4, may be machined from hot-rolled or forged bar
provided the longitudinal axis of the part is parallel to the longitudinal axis of the bar. Flanges, elbows, return bends, tees, and
header tees shall not be machined directly from bar stock.
5.4 Heat Treatment:
5.4.1 After hot working and before reheating for heat treatment, the forging shall be allowed to cool substantially below the
transformation range.
5.4.2 Forgings of grades other than Grade LF787 shall be furnished in the normalized, or normalized and tempered, or quenched
and tempered condition. At the option of the manufacturer, forgings furnished in the quenched and tempered condition may be
normalized prior to the austenitize/quench operation.
5.4.2.1 Quenching shall consist of either:
(1) fully austenitizing the forgings followed by quenching in a suitable liquid medium, or
(2) using a multiple stage procedure whereby the forging is first fully austenitized and rapidly cooled, then reheated to partially
re-asutenitize, followed by quenching in a suitable liquid medium.
(3) Unless otherwise specified by the purchaser, the choice of (1) or (2) shall be at the option of the manufacturer.
5.4.2.2 All quenched forgings shall be tempered to 5.4.2.3
5.4.2.3 Forgings, when tempered, shall be tempered at 1100 °F [590 °C], minimum, holding at temperature a minimum of 30
min/in. [30 min/25 mm] of maximum thickness, but in no case less than 30 min.
5.4.3 Grade LF787 forgings shall be furnished in either the normalized-and-precipitation heat treated condition or in the
quenched-and-precipitation heat treated condition. The heat treatment procedures shall be as follows:
5.4.3.1 Normalized-and-Precipitation Heat Treated—Austenitize in the range from 1600 to 1725 °F [870 to 940 °C] for not less
than ⁄2 h, and remove from the furnace and cool in air. Subsequently, artificially age in the range from 1000 to 1200 °F [540 to
650 °C] for not less than ⁄2 h, and cool at any convenient rate.
5.4.3.2 Quenched-and-Precipitation Heat Treated—Austenitize in the range from 1600 to 1725 °F [870 to 940 °C] for not less than
⁄2 h and quench in a suitable liquid medium by immersion; artificially age in the range from 1000 to 1225 °F [540 to 665 °C] for
not less than ⁄2 h, and cool at any convenient rate.
A350/A350M − 24
6. Chemical Composition
6.1 Heat Analysis:
6.1.1 A chemical heat analysis in accordance with Specification A961/A961M shall be made and conform to the requirements as
to chemical composition prescribed in Table 1. Leaded steels shall not be permitted.
6.2 Product Analysis:
6.2.1 The purchaser may make a product analysis on products supplied to this specification in accordance with Specification
A961/A961M.
7. Mechanical Properties
7.1 Tension Tests:
7.1.1 Requirements—The material shall conform to requirements for tensile properties in Table 2.
7.1.1.1 The test specimen shall be obtained from a rough or finished forging, or prolongation thereof. For forgings under 10 000
lbs, at time of heat treatment, it may be obtained from separately forged test blanks from the same heat of steel as the production
forgings. The test blank shall be reduced by forging in a manner similar to that for the products represented, and shall receive
approximately the same hot working and reduction and the same heat treatment as the finished products represented. The test
material shall be treated in the same furnace at the same time as the forging it represents, subject to the requirements of 7.1.2.1.
7.1.1.2 The test specimen shall represent all forgings from the same heat and heat-treatment load whose maximum thicknesses do
not exceed the thickness of the test forging or blank by more than ⁄4 in. [6 mm].
7.1.2 Number of Tests—One tension test at room temperature shall be made in accordance with 7.1.1.2 from each heat in each
heat-treatment load.
A
TABLE 2 Tensile Properties at Room Temperature
Grades
LF1 and LF5 LF2 LF3 LF6 LF9 LF787
Class 1 Classes Classes 1
Class 1 Classes 2 Class 2 Class 3
1 and 2 and 2
and 3
LF5
Class 2
Tensile strength, ksi [MPa] 60–85 70–95 70–95 66–91 75–100 63–88 65–85 75–95
[415–585] [485–655] [485–655] [455–630] [515–690] [435–605] [450–585] [515–655]
B
Yield strength, min, ksi [MPa] 30 [205] 36 [250] 37.5 [260] 52 [360] 60 [415] 46 [315] 55 [380] 65 [450]
Elongation:
Standard round specimen, or 25 22 22 22 20 25 20 20
small proportional specimen,
min % in 4D gauge length
Strip specimen for wall thickness 28 30 30 30 28 28 28 28
⁄16 in. [7.94 mm] and over
and for all small sizes tested
in full section; min % in 2 in.
[50 mm]
Formula for calculating minimum
elongation for strip specimens
thinner than ⁄16 in. [7.94 mm];
min % in 2 in. [50 mm]
Equation for calculating min 48t + 13 48t + 15 48t + 15 48t + 15 48t + 13 48t + 13 48t + 13 48t + 13
elongation for strip specimens
thinner than ⁄16 in. [7.94 mm];
min % in 2 in. [50 mm]
t = actual thickness in inches
t = actual thickness in inches 48t + 13 48t + 15 48t + 15 48t + 15 48t + 13 48t + 13 48t + 13 48t + 13
t = actual thickness in mm 1.9t +13 1.9t + 15 1.9t + 15 1.9t + 15 1.9t + 13 1.9t + 13 1.9t + 13 1.9t + 13
C
Reduction of area, min, % 38 30 35 40 40 38 45 45
A
See 7.3 for hardness tests.
B
Determined by either the 0.2 % offset method or the 0.5 % extension under load method.
C
For round specimens only.
A350/A350M − 24
7.1.2.1 If heat treatment is performed in either a continuous or a batch-type furnace controlled within 625 °F [614 °C] of the
required heat-treatment temperature and equipped with recording pyrometers so that complete records of heat treatment are
available and if the same heat-treating cycles are used on the forgings represented by the tension test, then one tension test from
each heat shall be required, instead of one tension test from each heat in each heat treatment load in accordance with 7.1.1.2.
7.1.3 Test Locations and Orientations—The test specimen shall be removed from the heaviest section of the forging or test blank,
at locations described in 7.1.3.1, 7.1.3.2, 7.1.3.5 or as close to these locations as practical, subject to forging size and geometry.
7.1.3.1 For forgings or test blanks having a maximum heat-treated thickness, T, of 2 in. [50 mm] or less, the longitudinal axis of
the test specimen shall be taken at mid-thickness and its mid-length shall be at least 2 in. [50 mm] from all other heat treated
surfaces, exclusive of the T dimension surfaces. (This is normally referred to as ⁄2 T by 2 in. [50 mm]). See Fig. 1 for test specimen
location in separately forged test blanks.
7.1.3.2 For forgings or test blanks having a maximum heat-treated thickness, T, greater than 2 in. [50 mm]:
(1) Except as stated in 7.1.3.2 (2) and 7.1.3.2 (3), the central axis of the test specimen shall be taken at least ⁄4 T from the
nearest heat-treated surface and its mid-length shall be at least 2 in. [50 mm] from all other heat treated surfaces, exclusive of the
T dimension surfaces. See Fig. 2 for test specimen location in separately forged test blanks.
(2) For quenched-and-tempered or for quenched-and-precipitation-heat-treated forgings, the central axis of the test specimen
shall be taken at least ⁄4 T from the nearest heat-treated surface, and the mid-length of the test specimen shall be at least T from
all other heat treated surfaces, exclusive of the T dimension surfaces. See Fig. 3 for test specimen location in separately forged
test blanks.
(3) For quenched-and-tempered or for quenched-and-precipitation–heat-treated forgings that have a W/T ratio < 2, the central
axis of the test specimen shall be taken at least ⁄4 T from the nearest heat-treated surface, and at mid-width of the forging, where
W is the width of the forging. The test specimen mid-length shall be at least T from the ends of the forging or test blank. See Fig.
4 for test specimen location in separately forged test blank.
7.1.3.3 Metal Buffers—The required distances from heat treated surfaces for the test locations described in 7.1.3.1 and 7.1.3.2 may
be obtained with metal buffers instead of integral expansions. Buffer material may be carbon or low alloy steel, and shall be joined
to the forging with a partial penetration weld that seals the buffered surface. Specimens shall be located at ⁄2 in. [13 mm] minimum
from the buffered surface of the forging. Buffers shall be removed after heat treatment and the welded areas subjected to magnetic
particle test to assure freedom from cracks unless the welded areas are completely removed by subsequent machining.
NOTE 1—For clarity, only the Charpy V-notch specimen is shown in Figs. 1-4. The tension test specimen shall be located such that its orientation and
the mid-length location meet the same requirements as that for the Charpy V-notch test specimen shown in Figure 1.
FIG. 1 Separately Forged Test Bar for Forgings with T # 2 in. [50 mm]
A350/A350M − 24
7.1.3.4 The test specimen shall have its longitudinal axis located parallel to the direction of major working of the forging or test
blank.
7.1.3.5 With prior purchaser approval, tests may be taken at a depth (t) corresponding to the distance from the area of significant
loading to the nearest heat treated surface and at least twice this distance (2t) from any second surface. However, the test depth
3 1
shall not be nearer to one treated surface than ⁄4 in. [19 mm] and to the second treated surface than 1 ⁄2 in. [38 mm]. This method
of test location would normally apply to contour-forged parts, or parts with thick cross-sectional areas where ⁄4 T × T testing
(7.1.3.2) is not practical. Sketches showing the exact test locations shall be approved by the purchaser when this method is used.
FIG. 2 Separately Forged Test Bar for Forgings with T > 2 in. [50 mm] and Not Quenched and Tempered
7.1.4 Test Method—Testing shall be performed as specified in Specification A961/A961M. The test specimen shall be as large as
is practicable and shall be machined to the form and dimensions in Specification A961/A961M. When seamless tubular materials
are used, test
...