ASTM F15-04(2022)

Standard Specification for Iron-Nickel-Cobalt Sealing Alloy

ABSTRACT
This specification covers an iron-nickel-cobalt alloy for use in sealing to glass in electronic applications. The alloy shall conform to the chemical composition specified and shall be manufactured in the form of wire, rod, bar, strip, sheet, and tube, with each form available in the specified temper condition. For example, tubes shall be bright annealed and supplied in the annealed temper condition. Strip and sheet shall be of temper A, B, C, D, or E or in deep-drawing temper condition, while wire and rod shall be bright annealed and supplied in temper A condition unless specified otherwise. The material shall be smooth, uniform in cross section, composition, and temper, and free of scale, corrosion, cracks, seams, scratches, slivers, and other defects. Tests for hardness, tensile strength, thermal expansion, and transformation shall be performed and shall conform to the requirements specified.
SCOPE
1.1 This specification covers an iron-nickel-cobalt alloy, UNS K94610 containing nominally 29 % nickel, 17 % cobalt, and 53 % iron, in the forms of wire, rod, bar, strip, sheet, and tubing, intended primarily for sealing to glass in electronic applications.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 The following hazard caveat pertains only to the test method portion, Sections 13 and 14 of this specification. 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-2022
• ICS: 77.120.40 - Nickel, chromium and their alloys
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.03 - Metallic Materials, Wire Bonding, and Flip Chip

Relations

• Refers: ASTM F14-80(2019) - Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
• Effective Date: 01-Nov-2019
• Refers: ASTM F144-80(2019) - Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-Nov-2019
• Refers: ASTM E18-18 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2018
• Refers: ASTM E18-17 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2017
• Refers: ASTM E228-11(2016) - Standard Test Method for Linear Thermal Expansion of Solid Materials With a Push-Rod Dilatometer
• Effective Date: 01-Sep-2016
• Refers: ASTM F144-80(2015) - Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-May-2015
• Refers: ASTM F14-80(2015) - Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
• Effective Date: 01-May-2015
• Refers: ASTM E18-12 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Dec-2012
• Refers: ASTM E112-12 - Standard Test Methods for Determining Average Grain Size
• Effective Date: 15-Nov-2012
• Refers: ASTM E18-11 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Nov-2011
• Refers: ASTM E112-10 - Standard Test Methods for Determining Average Grain Size
• Effective Date: 01-Nov-2010
• Refers: ASTM F144-80(2010) - Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-Apr-2010
• Refers: ASTM F14-80(2010) - Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
• Effective Date: 01-Apr-2010
• Refers: ASTM E18-08a - Standard Test Methods for Rockwell Hardness of Metallic Materials <a href="#fn00002"></a>
• Effective Date: 15-May-2008
• Refers: ASTM F140-98(2008) - Standard Practice for Making Reference Glass-Metal Butt Seals and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-Apr-2008

Overview

ASTM F15-04(2022) - Standard Specification for Iron-Nickel-Cobalt Sealing Alloy defines the requirements for an iron-nickel-cobalt alloy (UNS K94610) primarily used for glass-to-metal sealing in electronic applications. This specification outlines the material’s chemical composition, physical properties, and available product forms-including wire, rod, bar, strip, sheet, and tubing-ensuring reliable performance in demanding environments such as electronic and vacuum equipment manufacturing.

With its precise control over thermal expansion characteristics, this alloy, often referred to as Kovar-type or controlled expansion alloy, is essential for achieving a hermetic seal with glass in electronic devices. The standard establishes guidelines for ordering, inspection, surface finish, mechanical testing, and quality assurance, supporting manufacturers in producing advanced components for global markets.

Key Topics

• Chemical Composition: Specifies nominal values-53% iron, 29% nickel, 17% cobalt-along with controlled limits for elements such as manganese, silicon, carbon, and minor alloying agents. Manufacturers must ensure the final composition meets the requirements for coefficient of thermal expansion (CTE).
• Product Forms and Tempers: The alloy is available in various forms (wire, rod, bar, strip, sheet, tube), each supplied in specified tempers (annealed, half hard, hard, etc.) according to the application needs.
• Mechanical Properties: Material must meet defined criteria for hardness and tensile strength, measured according to relevant ASTM methods (e.g., ASTM E8 for tension testing, ASTM E18/E92 for hardness).
• Thermal Expansion: The alloy’s thermal expansion characteristics are tightly regulated to match the expansion rates of compatible glasses, a critical factor for reliable glass-to-metal sealing.
• Finishing and Quality: Requires materials to be smooth, uniform, and free of defects such as scale, cracks, or corrosion; surface finishes include hot rolling, forging, centerless grinding, cold rolling, and wire drawing.
• Testing Procedures: Standardizes test methods for mechanical properties, thermal expansion (ASTM E228), and phase transformation temperature, ensuring consistency and interoperability.
• Packaging and Identification: Mandates clear labeling and packaging practices to support traceability and quality control.

Applications

• Glass-to-Metal Seals: The primary application of the F15 alloy is in the manufacture of hermetic seals between glass and metal, essential for vacuum tubes, electronic components, and lighting products.
• Vacuum Electronics: Utilized in microwave tubes, photomultiplier tubes, and X-ray tubes where stable glass-metal joints are crucial for device longevity and reliability.
• Semiconductor and Sensor Technology: Ideal for housing electronic chips, diodes, or sensor elements requiring robust, stable, gas-tight enclosures.
• Scientific and Medical Equipment: Supports applications involving critical feedthroughs and sensor assemblies exposed to variable thermal conditions.

Related Standards

• ASTM E3 - Preparation of metallographic specimens for material analysis.
• ASTM E8 - Tension testing of metallic materials.
• ASTM E18/E92/E140 - Hardness testing and conversion for metals.
• ASTM E112 - Grain size determination in metals.
• ASTM E228 - Measurement of linear thermal expansion.
• ASTM F14/F140/F144 - Practices for making and testing reference glass-metal seals for expansion characteristics.
• Other Controlled Expansion Alloys: This standard is related to other materials designed for glass-to-metal sealing, such as ASTM F1466 (Iron-Nickel Sealing Alloy).

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By adhering to the ASTM F15-04(2022) specification, manufacturers and engineers can ensure consistent performance, manufacturability, and safety compliance in high-reliability electronic assemblies where the integrity of the glass-to-metal seal is paramount. This positions ASTM F15 as a critical reference in the controlled expansion alloy standards portfolio.

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:F15 −04 (Reapproved 2022)
Standard Specification for
Iron-Nickel-Cobalt Sealing Alloy
ThisstandardisissuedunderthefixeddesignationF15;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E112Test Methods for Determining Average Grain Size
E140Hardness Conversion Tables for Metals Relationship
1.1 This specification covers an iron-nickel-cobalt alloy,
Among Brinell Hardness, Vickers Hardness, Rockwell
UNS K94610 containing nominally 29% nickel, 17% cobalt,
Hardness, Superficial Hardness, Knoop Hardness, Sclero-
and 53% iron, in the forms of wire, rod, bar, strip, sheet, and
scope Hardness, and Leeb Hardness
tubing, intended primarily for sealing to glass in electronic
E228Test Method for Linear Thermal Expansion of Solid
applications.
Materials With a Push-Rod Dilatometer
1.2 The values stated in inch-pound units are to be regarded
F14Practice for Making andTesting Reference Glass-Metal
as standard. The values given in parentheses are mathematical
Bead-Seal
conversions to SI units that are provided for information only
F140Practice for Making Reference Glass-Metal Butt Seals
and are not considered standard.
and Testing for Expansion Characteristics by Polarimetric
1.3 The following hazard caveat pertains only to the test Methods
method portion, Sections 13 and 14 of this specification. This
F144Practice for Making Reference Glass-Metal Sandwich
standard does not purport to address all of the safety concerns, Seal and Testing for Expansion Characteristics by Polari-
if any, associated with its use. It is the responsibility of the user
metric Methods
of this standard to establish appropriate safety, health, and
environmental practices and determine the applicability of
3. Ordering Information
regulatory limitations prior to use.
3.1 Ordersformaterialunderthisspecificationshallinclude
1.4 This international standard was developed in accor-
the following information:
dance with internationally recognized principles on standard-
3.1.1 Size,
ization established in the Decision on Principles for the
3.1.2 Temper (Section 6),
Development of International Standards, Guides and Recom-
3.1.3 Surface finish (Section 10),
mendations issued by the World Trade Organization Technical
3.1.4 Marking and packaging (Section 17), and
Barriers to Trade (TBT) Committee.
3.1.5 Certification if required.
2. Referenced Documents
4. Chemical Requirements
2.1 ASTM Standards:
4.1 The material shall conform to the requirements as to
E3Guide for Preparation of Metallographic Specimens
chemical composition prescribed in Table 1.
E8Test Methods for Tension Testing of Metallic Materials
[Metric] E0008_E0008M
5. Surface Lubricants
E18Test Methods for Rockwell Hardness of Metallic Ma-
terials
5.1 All lubricants used during cold-working operations,
E92Test Methods for Vickers Hardness and Knoop Hard-
such as drawing, rolling, or spinning, shall be capable of being
ness of Metallic Materials
removed readily by any of the common organic degreasing
solvents.
This specification is under the jurisdiction of ASTM Committee F01 on
6. Temper
Electronics and is the direct responsibility of Subcommittee F01.03 on Metallic
Materials, Wire Bonding, and Flip Chip.
6.1 The desired temper of the material shall be specified in
Current edition approved May 1, 2022. Published May 2022. Originally
the purchase order.
approvedin1961asF15–61T.Lastpreviouseditionapprovedin2017 as F15–04
(2017). DOI: 10.1520/F0015-04R22.
6.2 Tube—Unless otherwise agreed upon by the supplier or
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
manufacturer and the purchaser, these forms shall be given a
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
final bright anneal by the manufacturer and supplied in the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. annealed temper.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F15−04 (2022)
150×
FIG. 1 Normal Annealed Specimen Showing No Transformation
150×
FIG. 2 Partially Transformed Specimen
F15−04 (2022)
TABLE 1 Chemical Requirements TABLE 3 Tensile Strength Requirements for Wire and Rod
Element Composition, % Temper Designation Tensile Strength, ksi (MPa)
A
Iron, nominal 53 A 85 (585) max
A
Nickel, nominal 29 B 85 to 105 (585 to 725)
A
Cobalt, nominal 17 C 95 to 115 (655 to 795)
Manganese, max 0.50 D 105 to 125 (725 to 860)
Silicon, max 0.20 E 125 (860) min
Carbon, max 0.04
B
Aluminum, max 0.10
B
Magnesium, max 0.10
B
Zirconium, max 0.10
9.1.1 Tensile strength shall be the basis for acceptance or
B
Titanium, max 0.10
rejection for the tempers given in Table 2 and shall conform
Copper, max 0.20
with the requirements prescribed.
Chromium, max 0.20
Molybdenum, max 0.20
9.1.2 Tension test specimens shall be taken so the longitu-
A
The iron, nickel, and cobalt requirements listed are nominal. They shall be dinalaxisisparalleltothedirectionofrollingandthetestshall
adjusted by the manufacturer so that the alloy meets the requirements for
be performed in accordance with Test Methods E8.
coefficient of thermal expansion given in Table 4.
B
The total of aluminum, magnesium, zirconium, and titanium shall not exceed
9.2 Wire and Rod:
0.20 %.
9.2.1 Tensile strength shall be the basis for acceptance or
rejectionforthetempersgiveninTable3.andshallconformto
the requirements prescribed.
6.3 Strip and Sheet—Theseformsshallbesuppliedinoneof
9.2.2 The test shall be performed in accordance with Test
the tempers given in Table 2 or in deep-drawing temper, as
Method E8.
specified.
10. Surface Finish
6.4 Wire and Rod—These forms shall be supplied in one of
the tempers given in Table 3 as specified. Unless otherwise
10.1 The standard surface finishes available shall be those
specified, the material shall be bright annealed and supplied in
resulting from the following operations:
temper A (annealed).
10.1.1 Hot rolling,
10.1.2 Forging,
7. Grain Size
10.1.3 Centerless grinding (rod),
7.1 Strip and sheet for deep drawing shall have an average
10.1.4 Belt polishing,
grain size not larger thanASTM No. 5 (Note 1), and no more
10.1.5 Cold rolling, and
than 10% of the grains shall be larger than No. 5 when
10.1.6 Wire drawing.
measured in accordance with Test Methods E112.
11. Thermal Expansion Characteristics
NOTE1—Thiscorrespondstoagrainsizeof0.065mm,or16grains/in.
11.1 The average linear coefficients of thermal expansion
of image at 100×.
shall be within the limits specified in Table 4.
8. Hardness
12. Test for Thermal Expansion
8.1 Deep-Drawing Temper—Fordeepdrawing,thehardness
shall not exceed 82 HRB for material 0.100 in. (2.54 mm) and 12.1 Heat the specimen in a hydrogen atmosphere for1hat
less in thickness and 85 HRB for material over 0.100 in. in 900 °C, followed by 15 min at 1100 °C. Between the 900 °C
thickness when determined in accordance with Test Methods and 1100 °C heat-treatment periods, the specimen may be
E18.SeealsoTestMethodE92forVickersHardnessandTable cooledtoroomtemperatureifdesired.Coolthespecimenfrom
3, E140 for the appropriate conversion between various hard- 1100 °C to 200 °C in the hydrogen atmosphere at a rate not to
ness scales. exceed 5 °C/min.
8.2 Rolled and Annealed Tempers—Hardness tests when 12.2 Determine the thermal expansion characteristics in
properlyappliedcanbeindicativeoftensilestrength.Hardness
accordance with Test Method E228.
scales and ranges for these tempers, if desirable, shall be
NOTE 2—For critical glass sealing applications, it is recommended that
negotiated between supplier and purchaser.
theuserconductfunctionaltestinginaccordancewithPracticesF14,F140
or F144. Such tests circumvent possible problems with thermal expansion
9. Tensile Strength
measurements and glass setting point estimates.
NOTE3—Thethermaltreatmentdescribedinthissectionisforpurposes
9.1 Sheet and Strip:
TABLE 4 Coefficients of Thermal Expansion
TABLE 2 Tensile Strength Requirements for Sheet and Strip
Average Linear Coefficient
Temper
Temper Name Tensile Strength, ksi(MPa) A
Temperature Range, °C of Thermal Expansion,
Designation
µm/m·°C
A annealed 82 max (570 max)
30 to 400 4.60 to 5.20
B ⁄4 hard 75 to 90 (520 to 630)
30 to 450 5.10 to 5.50
C half hard 85 to 100 (590 to 700)
A
D ⁄4 hard 95 to 110 (660 to 770) Typical thermal expansion data for the alloy covered by these specifications are
E hard 100 min (700 min)
provided in Appendix X1.
F15−04 (2022)
of the thermal expansion test only. Consult the non-mandatory appendix
15. Dimensions and Permissible Variations
ofthisdocumentforguidanceonannealingconditionsforvariousproduct
15.1 Cold-Rolled Strip—Cold-rolled strip shall conform to
forms.
the permissible variations in dimensions prescribed in Table 5,
13. Transformation
Table 6, and Table 7.
13.1 Thetemperatureofthegamma-to-alphatransformation
15.2 Round Wire and Rod—Wire and rod shall conform to
shall be below−78.5 °C when the material is tested in
the permissible variations in dimensions prescribed in Table 8.
accordance with Section 14. However, for material whose
15.3 Cold-Drawn Tubing—Cold-drawntubing,availableei-
smallest dimension is over ⁄8in. (22.2 mm), some localized
ther as seamless or welded, shall conform to the permissible
transformation, acceptable to the purchaser, may be tolerated.
variations prescribed in Table 9.
NOTE4—Lowertransformationtemperatures,rangingtoaslowas−196
°C, may be negotiated between supplier and purchaser. The −196 °C
16. General Requirements
transformation temperature corresponds to immersing a sample (prepared
according to 14.1) in liquid nitrogen for a minimum of 1 h.
16.1 Thematerialshallbecommerciallysmooth,uniformin
cross section, in composition, and in temper; it shall be free of
14. Test for Transformation
scale, corrosion, cracks, seams, scratches, slivers, and other
14.1 Cut the specimen from any part of the material, but
defects as best commercial practice will permit.
preferably including the entire cross section, degrease it, then
heat treat it as described in 12.1. When cool, polish the cross
17. Packaging and Marking
sectionofthespecimenandetch(Note5)itinaccordancewith
17.1 Packaging shall be subject to agreement between the
Method E3. Then subject the specimen to the temperature
purchaser and the seller.
produced by an excess of dry ice in acetone (−78.5 °C) for at
least 4 h. After the low-temperature treatment, examine the 17.2 The material as furnished under this specification shall
specimen at a magnification of 150× for the presence of the
beidentifiedbythenameorsymbolofthemanufacturerandby
acicular crystals characteristic of the alpha phase. Because melt number.The lot size for determining compliance with the
thesecrystalsmayoccuronlyinsmalllocalizedareas,examine
requirements of this specification shall be one heat.
carefully the entire polished cross section.
18. Investigation of Claims
14.2 Specimens that show no transformation and that show
18.1 Where any material fails to meet the requirements of
partial transformation are illustrated in Fig. 1 and Fig. 2,
respectively. thisspecification,thematerialsodesignatedshallbehandledin
accordance with a mutual agreement between the purchaser
NOTE 5—Asuggested etchant is a solution of three parts by volume of
and the seller.
concentrated hydrochloric acid and one part of concentrated nitric acid
saturated with cupric chloride (CuCl ·2H O). This etchant is more
2 2
effective when allowed to stand for 20 min after mixing. After several 19. Keywords
hours it loses its strength and should be discarded at the end of the day.
19.1 controlled expansion alloy; glass to metal sealing;
Etching is best accomplished by swabbing the specimen with cotton
iron-nickel-cobalt alloy; UNS #K94610; vacuum electronic
soaked with the etchant. Etching is usually complete when the surface of
the metal appears to have turned dull. applications
TABLE 5 Permissible Variations in Thickness of Cold-Rolled Strip
NOTE 1— Measurement shall be made at least ⁄8 in. (9.5 mm) from the edge of strip over 1 in. (25.4 mm) wide.
Permissible Variations in Thickness for Width Given, ± in. (mm)
Specified Thickness, in. (mm)
Under 3 (76) Over 3 to 6 (76 to 152) Over 6 to 12 (152 to 305) Over 12 to 16 (305 to 406)
0.160 to 0.100 (4.06 to 2.54), incl 0.002 (0.051) 0.003 (0.076) 0.004 (0.102) 0.004 (0.102)
0.099 to 0.069 (2.51 to 1.75), incl 0.002 (0.051) 0.003 (0.076) 0.003 (0.076) 0.004 (0.102)
0.068 to 0.050 (1.73 to 1.27
...