ASTM F256-05(2010)

Standard Specification for Chromium-Iron Sealing Alloys with 18 or 28 Percent Chromium

ABSTRACT
This specification covers two chromium-iron alloys, one is UNS K91800 with nominally 18% chromium, balance iron, and the other is UNS K92801 with nominally 28% chromium, both in strip, bar, wire, and rod forms intended primarily for sealing to glass in electronic applications. The alloys are classified by nominal chemical composition, specifically by chromium content, in two types: Type I (UNS K91800) and Type II (UNS K92801). The materials shall show no evidence of transformation to martensite. For Type I alloy, the austenite formed during heat treating will transform to martensite at or above room temperature. The presence of austenite, as may be noted in Type II alloy, is acceptable if the thermal expansion requirement is met. Different tests shall be performed in order to determine the following properties of the alloys: thermal expansion, Rockwell hardness, and tensile strength.
SCOPE
1.1 This specification covers two chromium-iron alloys, the former, (UNS K91800), nominally 18 % chromium, balance iron, the latter, (UNS K92801), nominally 28 % chromium, in strip, bar, wire, and rod forms intended primarily for sealing to glass in electronic applications.
Note 1—UNS K92801 should only be considered for use at service temperatures below 300°C. The alloy is prone to sigma phase formation at temperatures close to 620°C, and exhibits brittle mechanical behavior after prolonged exposures at temperatures close to 475°C.
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 16 and 17, 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 30-Sep-2010
• ICS: 21.140 - Seals, glands
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.03 - Metallic Materials, Wire Bonding, and Flip Chip

Relations

• Replaces: ASTM F256-05e1 - Standard Specification for Chromium-Iron Sealing Alloys with 18 or 28 Percent Chromium
• Effective Date: 01-Oct-2010
• Replaced By: ASTM F256-05(2015) - Standard Specification for Chromium-Iron Sealing Alloys with 18 or 28 Percent Chromium
• Effective Date: 01-Jul-2015
• Referred By: ASTM F140-98(2020) - Standard Practice for Making Reference Glass-Metal Butt Seals and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-Oct-2010
• Referred By: ASTM F144-80(2019) - Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-Oct-2010
• Referred By: ASTM F14-80(2019) - Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
• Effective Date: 01-Oct-2010

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:F256 −05(Reapproved2010)
Standard Specification for
Chromium-Iron Sealing Alloys with 18 or 28 Percent
Chromium
ThisstandardisissuedunderthefixeddesignationF256;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope and Nickel-Chromium-Iron Alloys
E228Test Method for Linear Thermal Expansion of Solid
1.1 This specification covers two chromium-iron alloys, the
Materials With a Push-Rod Dilatometer
former, (UNS K91800), nominally 18% chromium, balance
F14Practice for Making andTesting Reference Glass-Metal
iron, the latter, (UNS K92801), nominally 28% chromium, in
Bead-Seal
strip, bar, wire, and rod forms intended primarily for sealing to
F140Practice for Making Reference Glass-Metal Butt Seals
glass in electronic applications.
and Testing for Expansion Characteristics by Polarimetric
NOTE 1—UNS K92801 should only be considered for use at service
Methods
temperaturesbelow300°C.Thealloyispronetosigmaphaseformationat
F144Practice for Making Reference Glass-Metal Sandwich
temperatures close to 620°C, and exhibits brittle mechanical behavior
Seal and Testing for Expansion Characteristics by Polari-
after prolonged exposures at temperatures close to 475°C.
metric Methods
1.2 The values stated in inch-pound units are to be regarded
as standard. The values given in parentheses are mathematical
3. Terminology
conversions to SI units that are provided for information only
3.1 Definitions of Terms Specific to This Standard:
and are not considered standard.
3.1.1 bar:
1.3 The following hazard caveat pertains only to the test
3.1.1.1 hot-finished rounds, squares, and hexagons, ⁄4 in.
method portion, Sections 16 and 17, of this specification. This
(6.4 mm) and over in diameter or size.
standard does not purport to address all of the safety concerns,
3.1.1.2 hot-finished flats, ⁄4 in. to 10 in. (6.4 to 254 mm),
if any, associated with its use. It is the responsibility of the user
inclusive, in width and ⁄8 in. (3.2 mm) and over in thickness.
of this standard to establish appropriate safety and health
3.1.1.3 cold-finished rounds, squares, octagons, hexagons
practices and determine the applicability of regulatory limita-
and shapes, over ⁄2 in. (12.7 mm) in diameter or size.
tions prior to use.
3.1.1.4 cold-finishedflats, ⁄8in.(9.5mm)andoverinwidth
and ⁄8 in. (3.2 mm) and over in thickness (see Discussions).
2. Referenced Documents 3
Discussion—Widths less than ⁄8 in. (9.5 mm) and thick-
nesseslessthan ⁄16in.(4.8mm)aregenerallydescribedasflat
2.1 ASTM Standards:
wire.
A370Test Methods and Definitions for Mechanical Testing
1 3
Discussion—Thicknesses of ⁄8 in. (3.2 mm) to under ⁄16 in.
of Steel Products
(4.8 mm) can also be described as cold-rolled strip or, if in cut
E3Guide for Preparation of Metallographic Specimens
lengths, bar.
E18Test Methods for Rockwell Hardness of Metallic Ma-
3.1.2 rod—hot-rolled, or hot-rolled, annealed, and pickled,
terials
rounds, squares, octagons, hexagons and shapes, in coils, for
E29Practice for Using Significant Digits in Test Data to
1 3
subsequent cold drawing or cold rolling, ⁄4 in. or ⁄4 in. (6.4 or
Determine Conformance with Specifications
19.0 mm) in diameter or size.
E38Methods for Chemical Analysis of Nickel-Chromium
3.1.3 strip—cold-finished coils or cut lengths, under 24 in.
(610mm)downtoandincluding ⁄16in.(4.8mm)inwidth,and
This specification is under the jurisdiction of ASTM Committee F01 on
under ⁄16 in. down to and including 0.005 in. (0.13 mm) in
Electronics and is the direct responsibility of Subcommittee F01.03 on Metallic
thickness.
Materials.
Current edition approved Oct. 1, 2010. Published November 2010. Originally
3.1.4 No. 1 edge—a rolled edge either round or square as
approved in 1951 as F256–51T. Last previous edition approved in 2005 as
specified.
ε1
F256–94(2005) . Consolidated with F257 in 1972. DOI: 10.1520/F0256-05R10.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.1.5 No. 3 edge—an edge produced by slitting.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.1.6 No. 5 edge—an approximately square edge produced
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. by rolling or filing after slitting.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F256−05(2010)
Discussion—Cold-finished product 0.005 in. (0.13 mm) in 7.1.4 As hot rolled.
thickness and under 24 in. (609.6 mm) in width is sometimes
7.2 The desired surface of the material shall be specified on
identified as foil.
the purchase order as follows:
3.1.7 wire: 7.2.1 Pickled,
3.1.7.1 coldfinishedonly,roundorsquare, ⁄2in.(12.7mm) 7.2.2 Cold drawn (wire and bar),
and under in diameter or size. 7.2.3 Centerless ground (wire and bar), or
3.1.7.2 cold finished only, flat wire of ⁄16 in. (1.6 mm) to 7.2.4 Cold rolled (strip).
under ⁄8 in. (9.5 mm) in width and 0.010 in. (0.25 mm) to
8. Chemical Composition
under ⁄16 in. (4.8 mm) in thickness.
8.1 The material shall conform to the chemical composition
4. Classification
specified in Table 1.
4.1 Thealloyscoveredbythisspecificationareclassifiedby
nominal chemical composition, specifically by chromium
TABLE 1 Chemical Requirements
content, in two types:
4.1.1 Type I—18% chromium (UNS K91800) and
NOTE 1—Round observed or calculated values to the nearest unit in the
4.1.2 Type II—28% chromium (UNS K92801).
last right-hand place of figures used in expressing the limiting value, in
accordance with the rounding-off method of Practice E29.
5. Ordering Information
Composition, %
Element
Type I Type II
5.1 Ordersformaterialunderthisspecificationshallinclude
the following information: Carbon, max 0.08 0.12
Manganese, max 1.00 1.00
5.1.1 Quantity (weight (Note 2) or number of pieces),
Silicon, max 0.75 0.75
5.1.2 Name of material (chromium-iron alloy),
Phosphorus, max 0.040 0.040
Sulfur, max 0.030 0.030
5.1.3 Type (Section 4),
Chromium, nominal 18.0 28.0
5.1.4 Form (Section 3),
Nickel, max 0.50 0.50
5.1.5 Temper and finish (Section 7),
Nitrogen, max . 0.20
A
Titanium .
5.1.6 Permissible variations in dimensions for rod (Section
Iron remainder remainder
13),
A
Five times the carbon content, minimum, and 0.60, max.
5.1.7 Certification if required (Section 21),
5.1.8 Packaging required (Section 22),
5.1.9 Dimensions (width, thickness, diameter, etc.),
5.1.10 ASTM designation: F256, and
8.2 Ladle Analysis—A ladle analysis of each heat of steel
5.1.11 Exceptions to the specification or special require-
shall be made by the manufacturer to determine the percent-
ments.
ages of the elements specified in Table 1.The analysis shall be
NOTE 2—The term “weight” is temporarily used in this standard made from test castings made during the pouring of the heat.
becauseofestablishedtradeusage.Thewordisusedtomeanboth“force”
The chemical composition thus determined shall conform to
and“ mass,” and care must be taken to determine which is meant in each
the requirements specified in Table 1.
case (SI unit for force = newton and for mass = kilogram).
8.3 Check Analysis—If check analysis is made by the
5.2 If possible, the intended end use of the item should be
purchaser, the chemical composition thus determined shall
givenonthepurchaseorderespeciallywhentheitemisordered
conform to the requirements specified in Table 1 subject to the
fora specific end useoruses.Suchinformationwill enablethe
permissible tolerances of Table 2.
manufacturer to produce a material more satisfactory for the
purchaser’s process and product.
NOTE 3—A typical ordering description is as follows: 2000 kg, TABLE 2 Check Analysis Tolerances
chromium-iron alloy. Type II, wire, annealed, cold drawn, commercial
Tolerances over maxi-
packaging, ⁄4 in. (6.4 mm) round by coil, ASTM F256, end use-redraw.
Element mum or under minimum
limits, percentage points
6. Process
Carbon 0.01
Manganese 0.03
6.1 The purchaser shall specify that the alloy be made by
Phosphorus 0.005
Sulfur 0.005
one or more of the following processes: electric-arc, electric-
Silicon 0.05
induction, or other process approved by the purchaser.
Nickel 0.03
Nitrogen 0.01
7. Temper and Finish
Titanium 0.05
7.1 The desired temper of the material shall be specified on
the purchase order as follows:
7.1.1 Annealed for forming (strip),
9. Chemical Analysis
7.1.2 Annealed for deep drawing (strip),
7.1.3 Cold rolled or cold drawn to a specified mechanical 9.1 Chemical analysis shall be made in accordance with
property level, or Method E38 or equivalent methods.
F256−05(2010)
TABLE 5 Permissible Variations in Size of Cold-Finished Round
10. Thermal Expansion Requirements
Bars
10.1 The material shall conform to the thermal expansion
Permissible Variations from Specified
Specified Size, in.
requirements prescribed in Table 3. A,B
Size, in. (mm)
(mm)
Over Under
Over ⁄2 (12.7) to 1 0.002 (0.05) 0.002 (0.05)
A,B
TABLE 3 Thermal Expansion Requirements (25.4), excl
1 (25.4) to 1 ⁄2 (38.1), 0.0025 (0.064) 0.0025 (0.064)
Mean Coefficient of Linear Thermal
Temperature
excl
Expansion, µm/m ·°C
Range,° C 1
1 ⁄2 (38.1) to 4 (101.6), 0.003 (0.08) 0.003 (0.08)
UNS K91800 UNS K92801
C
incl
30 to 530 11.3 to 11.7 10.8 to 11.4
A
A Unless otherwise specified, size tolerances are over and under as shown in the
Typical thermal expansion data for the alloys covered by this specification are
above table. When required, however, they may be specified all over and nothing
given for information only in the Appendix.
B under, or all under and nothing over, or any combination of over and under, if the
These requirements apply to specimens heat treated prior to test in accordance
total spread in size tolerance for a specified size is not less than the total spread
with Section 16.
shown in the table.
B
When it is necessary to heat treat or heat treat and pickle after cold finishing, size
tolerances are double those shown in the table.
C
Cold-finished bars over 4 in. (101.6 mm) in diameter are produced; size
11. Mechanical Property Requirements
tolerances for such bars have not been evolved.
11.1 The material shall conform to the mechanical property
requirementsprescribedinTable4.Rockwellhardnessshallbe
TABLE 6 Permissible Variations in Length of Hot-Finished or
A
Cold-Finished Bars
A
Permissible Variations in Length, in.
TABLE 4 Mechanical Property Requirements
Specified Size of
(mm)
Rockwell Tensile Strength,
Rounds, Squares,
For Lengths over
Hardness (or max.
Hexagons, Octagons, For Lengths up to
Thickness, in. (mm)
12 ft (3.7 m), to 25 ft
equivalent)
and Widths of Flats, 12 ft (3.7 m), incl
(7.6 m), incl
(max) ksi MPa B
in. (mm)
Under 0.015 (0.38) . 85 590
Over Under Over Under
0.015 (0.38) to 1 (25.4), incl B85 . .
1 3
To 2 (50.8), incl ⁄2 (12.7) 0 ⁄4 (19.0) 0
Over 1 (25.4) B88 . .
Over 2 (50.8) to 4 (101.6), incl ⁄4 (19.0) 0 1 (25) 0
A
Applicable to strip in the annealed condition only. All other mechanical properties
Over 4 (101.6) to 6 (152.4), incl 1 (25) 0 1 ⁄4 (32) 0
1 1
as agreed upon between purchaser and manufacturer. Over 6 (152.4) to 9 (228.6), incl 1 ⁄4 (32) 0 1 ⁄2 (38) 0
Over 9 (228.6) to 12 (304.8), incl 1 ⁄2 (38) 0 2 (51) 0
A
The order should specify random lengths or specific lengths. When random
lengths are ordered, the length tolerance is not less than 2 ft (609.6 mm). When
determined in accordance with Test Method E18.
specific lengths are ordered, Table 8 or Table 9 shall apply.
B
The maximum width of bar flats is 10 in. (254.0 mm).
12. Transformation Requirements
12.1 The material shall show no evidence of transformation
15.2 Test specimens for mechanical properties shall be
to martensite. For Type I alloy, the austenite formed during
selected on the basis of a minimum of one specimen per size,
heat treating will transform to martensite at or above room
eachheat,eachlotannealedorotherwiseheattreatedunderthe
temperature. The presence of austenite, as may be noted in
same conditions, and each lot with like processing.
Type II alloy, is acceptable if the thermal expansion require-
ment is met.
15.3 If any test specimen shows defective machining or
develops flaws, it may be discarded and another specimen
13. Permissible Variations in Dimensions
substituted.
13.1 Material furnished under this specification, except rod,
15.4 Iftheresultsofanytestlotarenotinconformancewith
shall conform to the dimensional requirements of Tables 5-15.
the requirements of this specification, such lots may be
13.2 Permissible variations in dimensions for rod for re-
retreated at the option of the manufacturer. The material shall
drawingorrerollingshallbeasagreeduponbetweenpurchaser
beacceptableiftheresultsoftestsontheretreatedmaterialare
and manufacturer.
within the requirements of this specification.
14. Workmanship, Finish, and Appearance
16. Specimen Heat Treatment
14.1 The material shall be commercially smooth and uni-
16.1 The specimens for thermal-expansion and phase-
form in cross section, composition, and temper; it shall be free
transformation tests shall be heat treated prior to testing as
ofscalecorrosion,cracks,seams,scratches,slivers,processing
follows:
lubricants, and other defects as best commercial practice will
16.1.1 Type I—Heat the specimen to 1200 6 10°C and hold
permit.
at temperature for 15 min. Air cool to room temperature.
16.1.2 Type II—Heatthespecimento1100 610°Candhold
15. Number of Tests and Retests
at temperature for 15 min. Air cool to room temperature. The
15.1 Test specimens for thermal expansion and phase- cooling rate is recommended to be faster than 300°C per hour
transformation requirements shall be selected on the basis of a between 600 and 300°C. Slower cooling rates could lead to
minimum of one specimen per heat. brittle mechanical behavior.
F256−05(2010)
TABLE 7 Permissible Variations in Straightness of Machine-Straightened Hot-Finished or Cold-Finished Bars
Measure the length of the maximum gap between the bar and a straightedge of appropriate length when the straightedge is laid along the length of the bar on its
concave side. Unless otherwise specified, hot-finished or cold-finished bars for machining purposes are furnished machine straightened to the following tolerances
(maximum gap length), in in. (mm):
Hot-Finished
1 1 length in ft (m)
⁄8 in. (3.2 mm) in any 5 ft (1.5 m), but may not exceed ⁄8 in. (3.2 mm)× ⁄5 ft (1.5 m)
Cold-Finished
1 1 length in ft (m)
⁄16 in. (1.6 mm) in any 5 ft (1.5 mm), but may not exceed ⁄16 in. (1.6 mm)× ⁄5 ft
...