ASTM A800/A800M-20

Standard Practice for Estimating Ferrite Content of Stainless Steel Castings Containing Both Ferrite and Austenite

SIGNIFICANCE AND USE
4.1 The tensile and impact properties, the weldability, and the corrosion resistance of iron-chromium-nickel alloy castings may be influenced beneficially or detrimentally by the ratio of the amount of ferrite to the amount of austenite in the microstructure. The ferrite content may be limited by purchase order requirements or by the design construction codes governing the equipment in which the castings will be used. The quantity of ferrite in the structure is fundamentally a function of the chemical composition of the alloy and its thermal history. Because of segregation, the chemical composition, and therefore the ferrite content, may differ from point to point on a casting. Determination of the ferrite content by any of the procedures described in the following practice is subject to varying degrees of imprecision which must be recognized in setting realistic limits on the range of ferrite content specified. Sources of error include the following:  
4.1.1 In Determinations from Chemical Composition—Deviations from the actual quantity of each element present in an alloy because of chemical analysis variance, although possibly minor in each case, can result in substantial difference in the ratio of total ferrite-promoting to total austenite-promoting elements. Therefore, the precision of the ferrite content estimated from chemical composition depends on the accuracy of the chemical analysis procedure.  
4.1.2 In Determinations from Magnetic Response—Phases other than ferrite and austenite may be formed at certain temperatures and persist at room temperature. These may so alter the magnetic response of the alloy that the indicated ferrite content is quite different from that of the same chemical composition that has undergone different thermal treatment. Also, because the magnets or probes of the various measuring instruments are small, different degrees of surface roughness or surface curvature will vary the magnetic linkage with the material being measured.  
...
SCOPE
1.1 This practice covers procedures and definitions for estimating ferrite content in stainless steel alloys containing both austenite and ferrite phases in amounts controlled to be within specified limits. Methods are described for estimating ferrite content by chemical, magnetic, and metallographic means.  
Note 1: This practice can be used for cast austenitic and duplex stainless steel alloys (for example, CF-3, CF-3A, CF-8, CF-8A, CF-3M, CF-3MA, CF-8M, CF-8C, CG-8M, CH-10, CD4MCuN (1B), CD3MCuN (1C), CE8MN (2A), CD6MN (3A), CD3MN (4A), CE3MN (5A), CD3MWCuN (6A), and CD3MWN (7A)).  
1.2 The values stated in either inch-pound units or SI units are to be regarded separately as standard. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the practice.  
1.2.1 Within the text, the SI units are shown in brackets.  
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

• Status: Published
• Publication Date: 30-Apr-2020
• ICS: 77.140.80 - Iron and steel castings
• Technical Committee: A01 - Steel, Stainless Steel and Related Alloys
• Drafting Committee: A01.18 - Castings

Relations

• Replaces: ASTM A800/A800M-14 - Standard Practice for Steel Casting, Austenitic Alloy, Estimating Ferrite Content Thereof
• Effective Date: 01-May-2020
• Refers: ASTM A941-24 - Standard Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
• Effective Date: 01-Mar-2024
• Refers: ASTM A799/A799M-10(2020) - Standard Practice for Steel Castings, Stainless, Instrument Calibration, for Estimating Ferrite Content
• Effective Date: 01-Mar-2020
• Refers: ASTM E562-19e1 - Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count
• Effective Date: 15-Aug-2019
• Refers: ASTM A351/A351M-18e1 - Standard Specification for Castings, Austenitic, for Pressure-Containing Parts
• Effective Date: 01-May-2018
• Refers: ASTM A1067/A1067M-12a(2018) - Standard Specification for Test Coupons for Steel Castings
• Effective Date: 01-Mar-2018
• Refers: ASTM A941-17 - Standard Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
• Effective Date: 01-Sep-2017
• Refers: ASTM A351/A351M-16 - Standard Specification for Castings, Austenitic, for Pressure-Containing Parts
• Effective Date: 01-May-2016
• Refers: ASTM A941-15 - Standard Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
• Effective Date: 01-Nov-2015
• Refers: ASTM A799/A799M-10(2015) - Standard Practice for Steel Castings, Stainless, Instrument Calibration, for Estimating Ferrite Content
• Effective Date: 01-Nov-2015
• Refers: ASTM A351/A351M-15 - Standard Specification for Castings, Austenitic, for Pressure-Containing Parts
• Effective Date: 01-Sep-2015
• Refers: ASTM E353-14 - Standard Test Methods for Chemical Analysis of Stainless, Heat-Resisting, Maraging, and Other Similar Chromium-Nickel-Iron Alloys
• Effective Date: 15-Sep-2014
• Refers: ASTM A351/A351M-14 - Standard Specification for Castings, Austenitic, for Pressure-Containing Parts
• Effective Date: 01-May-2014
• Refers: ASTM A751-14 - Standard Test Methods, Practices, and Terminology for Chemical Analysis of Steel Products
• Effective Date: 01-Mar-2014
• Refers: ASTM A941-13b - Standard Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
• Effective Date: 01-Jun-2013

Overview

ASTM A800/A800M-20 is the recognized international standard that establishes procedures for estimating the ferrite content in stainless steel castings that contain both ferrite and austenite phases. The ferrite-to-austenite ratio is a critical feature of austenitic and duplex stainless steel castings, influencing mechanical properties, weldability, and corrosion resistance. The standard outlines approved methods for ferrite estimation, including chemical analysis, magnetic response, and metallographic examination.

Monitoring and controlling ferrite content is essential in several applications, especially those requiring specific mechanical performance or compliance with design codes and purchase order requirements for stainless steel components.

Key Topics

• Ferrite and Austenite Phases in Stainless Steel

  • Stainless steel castings often contain both ferrite and austenite. The ratio significantly affects tensile strength, impact resistance, corrosion resistance, and weldability.
  • Excessive deviations in ferrite content can compromise structural integrity and the lifespan of cast components.

• Estimation Methods

  • Chemical Analysis: Based on the actual or estimated chemical composition, using constitution diagrams such as the Schoefer, Schaeffler, or DeLong diagrams.
  • Magnetic Methods: Measuring magnetic response using calibrated instruments per ASTM standards. Magnetic methods are sensitive to structural and thermal history.
  • Metallographic Techniques: Direct estimation by microscopic examination and point count methodology per ASTM E562. Appropriate for most accurate assessment.

• Procedural Guidelines

  • The chemical analysis should include elements such as carbon, manganese, silicon, chromium, nickel, molybdenum, columbium, and nitrogen.
  • Different methods yield results with varying degrees of precision. Consistency and accuracy rely on methodical sampling, proper calibration, and adherence to specified procedures.
  • Orders for castings should specify alloy grade, ferrite content range, and supplement requirements for methods of estimation.

• Limitations and Units

  • Values can be stated in inch-pound or SI units, but systems must not be mixed in application.
  • For compliance, supplementary methods may be specified by agreement between purchaser and manufacturer.

Applications

• Pressure-Containing Parts: Used in industries such as petrochemical, power generation, and food processing, where reliable ferrite content is vital for pressure vessel and piping components.
• Welded Structures: Key in determining suitability for welding and post-weld heat treatment, affecting the creation and retention of ferrite in weld metal.
• Corrosion-Resistant Cast Components: Steels with controlled ferrite content ensure protection against stress corrosion cracking and enhanced mechanical stability in corrosive environments.
• Design Compliance: Supports adherence to construction codes and purchase order mandates, preventing premature failures and maintaining process integrity within regulated industries.
• Duplex Stainless Alloys: Applicable to a wide range of cast austenitic and duplex grades (e.g., CF-3, CF-8, CD4MCuN), expanding versatility for critical engineering applications.

Related Standards

• ASTM A351/A351M: Specification for austenitic steel castings for pressure-containing parts.
• ASTM A751: Test methods for chemical analysis of steel products.
• ASTM A799/A799M: Practice for instrument calibration in estimating ferrite content.
• ASTM E353: Test methods for chemical analysis of chromium-nickel-iron alloys.
• ASTM E562: Method for determining volume fraction by systematic manual point count.
• AWS A4.2: Procedures for calibrating magnetic instruments to measure delta ferrite content.

Summary

ASTM A800/A800M-20 provides standardized methods for estimating the ferrite content in stainless steel castings, which directly impacts the performance and durability of cast components used in demanding engineering environments. Adhering to this standard supports quality assurance, regulatory compliance, and optimized material selection in industries reliant on high-performance stainless steel alloys.

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: A800/A800M − 20
Standard Practice for
Estimating Ferrite Content of Stainless Steel Castings
Containing Both Ferrite and Austenite
This standard is issued under the fixed designationA800/A800M; 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* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers procedures and definitions for
A351/A351M Specification for Castings, Austenitic, for
estimating ferrite content in stainless steel alloys containing
Pressure-Containing Parts
both austenite and ferrite phases in amounts controlled to be
A751 Test Methods, Practices, and Terminology for Chemi-
within specified limits. Methods are described for estimating
cal Analysis of Steel Products
ferrite content by chemical, magnetic, and metallographic
A799/A799M Practice for Steel Castings, Stainless, Instru-
means.
ment Calibration, for Estimating Ferrite Content
NOTE 1—This practice can be used for cast austenitic and duplex A941 TerminologyRelatingtoSteel,StainlessSteel,Related
stainless steel alloys (for example, CF-3, CF-3A, CF-8, CF-8A, CF-3M,
Alloys, and Ferroalloys
CF-3MA, CF-8M, CF-8C, CG-8M, CH-10, CD4MCuN (1B), CD3MCuN
A1067/A1067M Specification for Test Coupons for Steel
(1C), CE8MN (2A), CD6MN (3A), CD3MN (4A), CE3MN (5A),
Castings
CD3MWCuN (6A), and CD3MWN (7A)).
E353 Test Methods for Chemical Analysis of Stainless,
1.2 The values stated in either inch-pound units or SI units
Heat-Resisting, Maraging, and Other Similar Chromium-
are to be regarded separately as standard. The values stated in
Nickel-Iron Alloys
each system are not exact equivalents; therefore, each system E562 Test Method for Determining Volume Fraction by
must be used independently of the other. Combining values Systematic Manual Point Count
from the two systems may result in nonconformance with the
2.2 Constitution Diagrams:
practice.
Schoefer Diagram for Estimating Ferrite Content of Stain-
1.2.1 Within the text, the SI units are shown in brackets. less Steel Castings (1980 revision)
Schaeffler Diagram for Estimating Ferrite Content of Stain-
1.3 This standard does not purport to address all of the
less Steel Weld Metal
safety concerns, if any, associated with its use. It is the
DeLong Diagram for Estimating Ferrite Content of Stain-
responsibility of the user of this standard to establish appro-
less Steel Weld Metal
priate safety, health, and environmental practices and deter-
2.3 American Welding Society Specification:
mine the applicability of regulatory limitations prior to use.
AWSA4.2 Procedures for Calibrating Magnetic Instruments
1.4 This international standard was developed in accor-
to Measure the Delta Ferrite Content of Austenitic Stain-
dance with internationally recognized principles on standard-
less Steel Weld Metal
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3. Terminology
mendations issued by the World Trade Organization Technical
3.1 Definitions:
Barriers to Trade (TBT) Committee.
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.
See Appendix X1.
1 4
This practice is under the jurisdiction of ASTM Committee A01 on Steel, Metal Progress Data Book, American Society for Metals, Mid June 1977, p.
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee 161.
A01.18 on Castings. Welding Journal, American Welding Society, Vol 38, No. 7, July 1973, p.
Current edition approved May 1, 2020. Published May 2020. Originally 293–s.
approved in 1982. Last previous edition approved in 2014 as A800/A800M – 14. Available from American Welding Society (AWS), 8669 NW 36 Street, #130,
DOI: 10.1520/A0800_A0800M-20. Miami, FL 33166-6672, http://www.aws.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
A800/A800M − 20
3.1.1 ferrite—the ferromagnetic, body-centered, cubic- 4.2 The estimation of ferrite percent by chemical composi-
microstructuralconstituentofvariablechemicalcompositionin tion offers the most useful and most common method of ferrite
iron-chromium-nickel alloys. This may be formed upon solidi- control during melting of the metal.
fication from the molten metal (delta ferrite) or by transforma-
4.3 For most accurate estimate of ferrite percent, a quanti-
tion from austenite or sigma phase on cooling in the solid state
tative metallographic method should be used.
(alpha ferrite).
5. Ordering Information
3.1.2 ferrite content—the proportion of total volume of an
iron-chromium-nickel alloy present as the ferrite phase.
5.1 Orders for material to this practice should include the
following as required:
3.1.3 ferrite number—the ferrite content expressed as an
5.1.1 ApplicableASTMproductspecificationorotherdocu-
arbitrary number based on the magnetic response of the alloy
ment covering product requirements,
in a weld deposit.
5.1.2 Alloy grade,
3.1.4 ferrite percentage—the ferrite content expressed as a
5.1.3 Required ferrite content range, in volume percent, of
volume percent.
the castings after final heat treatment. Also, if desired by the
3.1.5 heat treatment—the definitions in Terminology A941
purchaser, required ferrite content range, in ferrite number, for
are applicable to this practice.
weld deposits (Note 2) as deposited, and
5.1.4 Supplementary requirements, if any, desired.
4. Significance and Use
NOTE 2—There may be a substantial decrease in the ferrite content of
4.1 The tensile and impact properties, the weldability, and weld deposits after solution heat treatment in comparison with the
as-deposited value.
thecorrosionresistanceofiron-chromium-nickelalloycastings
may be influenced beneficially or detrimentally by the ratio of
6. General Caution
the amount of ferrite to the amount of austenite in the
6.1 In specifying ferrite content as required in 5.1.3, the
microstructure. The ferrite content may be limited by purchase
purchaser should not set limits that conflict with applicable
order requirements or by the design construction codes gov-
material specification requirements: for example, a maximum
erning the equipment in which the castings will be used. The
limit of 10 % ferrite for Grade CF-3A in Specification A351/
quantity of ferrite in the structure is fundamentally a function
A351M for which the minimum tensile strength requirement is
of the chemical composition of the alloy and its thermal
77 ksi [530 MPa].
history. Because of segregation, the chemical composition, and
therefore the ferrite content, may differ from point to point on
6.2 When Supplementary Requirement S1 is specified, the
a casting. Determination of the ferrite content by any of the
purchaser should set ferrite content limits that are compatible
procedures described in the following practice is subject to
with the measuring instrument to be used.
varying degrees of imprecision which must be recognized in
setting realistic limits on the range of ferrite content specified.
7. Estimation of Ferrite Content
Sources of error include the following:
7.1 Estimation in the base metal of the casting by chemical
4.1.1 In Determinations from Chemical Composition—
composition in accordance with the Schoefer diagram (see
Deviations from the actual quantity of each element present in
Appendix X1):
an alloy because of chemical analysis variance, although
7.1.1 A chemical analysis of the heat from which the
possibly minor in each case, can result in substantial difference
castings are poured shall include the following elements,
in the ratio of total ferrite-promoting to total austenite-
whether or not required by the chemical requirements of the
promoting elements. Therefore, the precision of the ferrite
product specification: carbon, manganese, silicon, chromium,
content estimated from chemical composition depends on the
nickel, molybdenum, columbium, and nitrogen.
accuracy of the chemical analysis procedure.
7.1.1.1 Upon written agreement between the purchaser and
4.1.2 In Determinations from Magnetic Response—Phases
the producer, an estimated nitrogen content may be reported
other than ferrite and austenite may be formed at certain
instead of an amount determined by analysis of the specific
temperatures and persist at room temperature. These may so
heatifactualchemicalanalyseshavebeenmadefornitrogenin
alter the magnetic response of the alloy that the indicated
a sufficient number of heats of the same alloy type, produced
ferrite content is quite different from that of the same chemical
by the same melting practice, to establish the average nitrogen
composition that has undergone different thermal treatment.
content to be expected.
Also, because the magnets or probes of the various measuring
7.1.2 The ferrite content of the casting shall be estimated
instrumentsaresmall,differentdegreesofsurfaceroughnessor
from the central line of the diagram at the composition ratio of
surface curvature will vary the magnetic linkage with the
“chromium equivalent” (Cr ) to “nickel equivalent” (Ni )
e e
material being measured.
determined from the following formula:
4.1.3 In Determinations from Metallographic
Cr % 11.5Si % 11.4Mo % 1Cb % 2 4.99 / Ni %
~ ~ ! ~ ! ~ ! ~ ! ! ~ ~ !
Examination—Metallographic point count estimates of ferrite
130C % 10.5Mn % 126 N 2 0.02% 12.77) 5 Cr / Ni
~ ! ~ ! ~ ! ~ ! ~ !
e e
percentage may vary with the etching technique used for
identification of the ferrite phase and with the number of grid 7.1.3 When a product analysis is made by the purchaser, it
points chosen for the examination, as explained inTest Method shall include the elements listed in 7.1.1. If a comparison is
E562. made of ferrite content estimated from a product analysis
A800/A800M − 20
performed by the purchaser, with that estimated from the heat 8.2 If lack of conformance with the ferrite content range
analysis (see 7.1.1), the reproducibility data in the precision specifiedin5.1.3isindicatedbyaproductanalysismadebythe
statements of Test Methods E353 shall be used as a guide. purchaser (7.1.3) and by a referee analysis as provided in
7.1.3.1 Test Methods A751 or Test Methods E353,as 7.1.3.1, rejection of material shall be subject to the tests of 7.3
applicable, shall be used as referee chemical analysis methods. as established by written agreement between the manufacturer
and the purchaser.
7.2 Estimation in weld deposits by chemical composition in
accordance with the Schaeffler or DeLong diagrams:
9. Certification
7.2.1 The ferrite content shall be estimated (1) from the
deposit chemical analysis included on the electrode manufac- 9.1 The manufacturer’s certification shall be furnished to
turer’s certified material test report, or (2) from chemical the purchaser stating that the material was sampled and tested
analysis of a weld deposit pad made by the casting manufac- in accordance with the specification (including year date) and
turer. was found to meet the requirements.
7.3 Estimation of ferrite content in heat, product, or weld 9.2 The test report shall contain the results of the actual
metal may be made by the magnetic response or metallo- chemicalanalysesrequiredby7.1.1and7.2.1andtheindicated
graphic methods by imposition of Supplementary Requirement ferri
...

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: A800/A800M − 14 A800/A800M − 20
Standard Practice for
Steel Casting, Austenitic Alloy, Estimating Ferrite Content
Thereofof Stainless Steel Castings Containing Both Ferrite
and Austenite
This standard is issued under the fixed designation A800/A800M; 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 practice covers procedures and definitions for estimating ferrite content in certain grades of austenitic iron-chromium-
nickel alloy castings that have compositions balanced to create the formation of ferrite as a second phase stainless steel alloys
containing both austenite and ferrite phases in amounts controlled to be within specified limits. Methods are described for
estimating ferrite content by chemical, magnetic, and metallographic means.
NOTE 1—This practice can be used for cast austenitic and duplex stainless steel alloys (for example, CF-3, CF-3A, CF-8, CF-8A, CF-3M, CF-3MA,
CF-8M, CF-8C, CG-8M, CH-10, CD4MCuN (1B), CD3MCuN (1C), CE8MN (2A), CD6MN (3A), CD3MN (4A), CE3MN (5A), CD3MWCuN (6A),
and CD3MWN (7A)).
1.2 The grades covered by this practice are: CF-3, CF-3A, CF-8, CF-8A, CF-3M, CF-3MA, CF-8M, CF-8C, CG-8M, and
CH-10.
1.2 The values stated in either inch-pound units or SI units are to be regarded separately as standard. The values stated in each
system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two
systems may result in nonconformance with the practice.
1.2.1 Within the text, the SI units are shown in brackets.
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 safety, health, and healthenvironmental 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.
2. Referenced Documents
2.1 ASTM Standards:
A351/A351M Specification for Castings, Austenitic, for Pressure-Containing Parts
A751 Test Methods, Practices, and Terminology for Chemical Analysis of Steel Products
A799/A799M Practice for Steel Castings, Stainless, Instrument Calibration, for Estimating Ferrite Content
A941 Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
A1067/A1067M Specification for Test Coupons for Steel Castings
E353 Test Methods for Chemical Analysis of Stainless, Heat-Resisting, Maraging, and Other Similar Chromium-Nickel-Iron
Alloys
E562 Test Method for Determining Volume Fraction by Systematic Manual Point Count
2.2 Constitution Diagrams:
Schoefer Diagram for Estimating Ferrite Content of Stainless Steel Castings (1980 Schoefer Diagram for Estimating Ferrite
Content of Stainless Steel Castings (1980 revision)
This practice is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.18
on Castings.
Current edition approved May 1, 2014May 1, 2020. Published June 2014May 2020. Originally approved in 1982. Last previous edition approved in 20102014 as
A800/A800M – 10.A800/A800M – 14. DOI: 10.1520/A0800_A0800M-14. 10.1520/A0800_A0800M-20.
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.
AppendixSee Appendix X1of this practice.
*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
A800/A800M − 20
Schaeffler Diagram for Estimating Ferrite Content of Stainless Steel Weld Metal Schaeffler Diagram for Estimating Ferrite
Content of Stainless Steel Weld Metal
DeLong Diagram for Estimating Ferrite Content of Stainless Steel Weld Metal DeLong Diagram for Estimating Ferrite Content
of Stainless Steel Weld Metal
2.3 American Welding Society Specification:
AWS A 4.2,A4.2 Procedures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic Stainless
Steel Weld Metal
3. Terminology
3.1 Definitions:
3.1.1 ferrite—the ferromagnetic, body-centered, cubic-microstructural constituent of variable chemical composition in
iron-chromium-nickel alloys. This may be formed upon solidification from the molten metal (delta ferrite) or by transformation
from austenite or sigma phase on cooling in the solid state (alpha ferrite).
3.1.2 ferrite content—the proportion of total volume of an iron-chromium-nickel alloy present as the ferrite phase.
3.1.3 ferrite number—the ferrite content expressed as an arbitrary number based on the magnetic response of the alloy in a weld
deposit.
3.1.4 ferrite percentage—the ferrite content expressed as a volume percent.
3.1.5 heat treatment—the definitions in Terminology A941 are applicable to this practice.
4. Significance and Use
4.1 The tensile and impact properties, the weldability, and the corrosion resistance of iron-chromium-nickel alloy castings may
be influenced beneficially or detrimentally by the ratio of the amount of ferrite to the amount of austenite in the microstructure.
The ferrite content may be limited by purchase order requirements or by the design construction codes governing the equipment
in which the castings will be used. The quantity of ferrite in the structure is fundamentally a function of the chemical composition
of the alloy and its thermal history. Because of segregation, the chemical composition, and, therefore,and therefore the ferrite
content, may differ from point to point on a casting. Determination of the ferrite content by any of the procedures described in the
following practice is subject to varying degrees of imprecision which must be recognized in setting realistic limits on the range
of ferrite content specified. Sources of error include the following:
4.1.1 In Determinations from Chemical Composition—Deviations from the actual quantity of each element present in an alloy
because of chemical analysis variance, although possibly minor in each case, can result in substantial difference in the ratio of total
ferrite-promoting to total austenite-promoting elements. Therefore, the precision of the ferrite content estimated from chemical
composition depends on the accuracy of the chemical analysis procedure.
4.1.2 In Determinations from Magnetic Response—Phases other than ferrite and austenite may be formed at certain temperatures
and persist at room temperature. These may so alter the magnetic response of the alloy that the indicated ferrite content is quite
different from that of the same chemical composition that has undergone different thermal treatment. Also, because the magnets
or probes of the various measuring instruments are small, different degrees of surface roughness or surface curvature will vary the
magnetic linkage with the material being measured.
4.1.3 In Determinations from Metallographic Examination—Metallographic point count estimates of ferrite percentage may
vary with the etching technique used for identification of the ferrite phase and with the number of grid points chosen for the
examination, as explained in Test Method E562.
4.2 The estimation of ferrite percent by chemical composition offers the most useful and most common method of ferrite control
during melting of the metal.
4.3 For most accurate estimate of ferrite percent, a quantitative metallographic method should be used.
5. Ordering Information
5.1 Orders for material to this practice should include the following as required:
5.1.1 Applicable ASTM product specification or other document covering product requirements,
5.1.2 Alloy grade,
5.1.3 Required ferrite content range, in volume percent, of the castings after final heat treatment. Also, if desired by the
purchaser, required ferrite content range, in ferrite number, for weld deposits (Note 12) as deposited, and
5.1.4 Supplementary requirements, if any, desired.
Metal Progress Data Book, American Society for Metals, Mid June 1977, p. 161.
Welding Journal, American Welding Society, Vol 38, No. 7, July 1973, p. 293–s.
Available from American Welding Society (AWS), 8669 NW 36 Street, #130, Miami, FL 33166-6672, http://www.aws.org.
A800/A800M − 20
NOTE 2—There may be a substantial decrease in the ferrite content of weld deposits after solution heat treatment in comparison with the as-deposited
value.
6. General Caution
6.1 In specifying ferrite content as required in 5.1.3, the purchaser should not set limits that conflict with applicable material
specification requirements: for example, a maximum limit of 10 % ferrite for Grade CF-3A in Specification A351/A351M for
which the minimum tensile strength requirement is 77 ksi [530 MPa].
6.2 When Supplementary Requirement S1 is specified, the purchaser should set ferrite content limits that are compatible with
the measuring instrument to be used.
7. Estimation of Ferrite Content
7.1 Estimation in the base metal of the casting by chemical composition in accordance with the Schoefer diagram (see Appendix
X1):
7.1.1 A chemical analysis of the heat from which the castings are poured shall include the following elements, whether or not
required by the chemical requirements of the product specification: carbon, manganese, silicon, chromium, nickel, molybdenum,
columbium, and nitrogen.
7.1.1.1 Upon written agreement between the purchaser and the producer, an estimated nitrogen content may be reported instead
of an amount determined by analysis of the specific heat if actual chemical analyses have been made for nitrogen in a sufficient
number of heats of the same alloy type, produced by the same melting practice, to establish the average nitrogen content to be
expected.
7.1.2 The ferrite content of the casting shall be estimated from the central line of the diagram at the composition ratio of
“chromium equivalent” (Cr ) to “nickel equivalent” (Ni ) determined from the following formula:
e e
~Cr~%!11.5Si~%!11.4Mo~%!1Cb~%!2 4.99!/~Ni ~%!
130C % 10.5Mn % 126 N 2 0.02% 12.77)5 Cr / Ni
~ ! ~ ! ~ ! ~ ! ~ !
e e
7.1.3 When a product analysis is made by the purchaser, it shall include the elements listed in 7.1.1. If a comparison is made
of ferrite content estimated from a product analysis performed by the purchaser, with that estimated from the heat analysis (see
7.1.1), the reproducibility data in the precision statements of Test Methods E353 shall be used as a guide.
7.1.3.1 Test Methods A751 or Test Methods E353, as applicable, shall be used as referee chemical analysis methods.
7.2 Estimation in weld deposits by chemical composition in accordance with the Schaeffler or DeLong diagrams:
7.2.1 The ferrite content shall be estimated (a1) from the deposit chemical analysis included on the electrode manufacturer’s
certified material test report, or (b2) from chemical analysis of a weld deposit pad made by the casting manufacturer.
7.3 Estimation of ferrite content in heat, product, or weld metal may be made by the magnetic response or metallographic
methods by imposition of Supplementary RequirementsRequirement S1 or S2, respectively.
8. Acceptance Standards
8.1 Conformance with the required ferrite content range specified in 5.1.3 as indicated by the estimation procedure of 7.1 and
7.2 shall be the basis for acceptance of material supplied under this practice unless other methods of estimation are ordered as
supplementary requirements, in which case the supplementary requirement shall be the basis of acceptance.
8.2 If lack of conformance with the ferrite content range specified in 5.1.3 is indicated by
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