1、Designation: F 256 05e1Standard Specification forChromium-Iron Sealing Alloys with 18 or 28 PercentChromium1This standard is issued under the fixed designation F 256; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTENote 1 and 16.1.2 were updated editorially in August 2005.1. Scope1.1 This specification covers two chromium-iron alloys, thefo
3、rmer, (UNS K91800), nominally 18 % chromium, balanceiron, the latter, (UNS K92801), nominally 28 % chromium, instrip, bar, wire, and rod forms intended primarily for sealing toglass in electronic applications.NOTE 1UNS K92801 should only be considered for use at servicetemperatures below 300C. The a
4、lloy is prone to sigma phase formation attemperatures close to 620C, and exhibits brittle mechanical behaviorafter prolonged exposures at temperatures close to 475C.1.2 The values stated in inch-pound units are to be regardedas the standard. The values given in parentheses are forinformation only.1.
5、3 The following hazard caveat pertains only to the testmethod portion, Sections 16 and 17, of this specification. Thisstandard does not purport to address all of the safety concerns,if any, associated with its use. It is the responsibility of the userof this standard to establish appropriate safety
6、and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2A 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsE3 Methods of Preparation of Metallographic SpecimensE18 Test Methods for Rockwell Hardness
7、 and RockwellSuperficial Hardness of Metallic MaterialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE38 Methods for Chemical Analysis of Nickel-Chromiumand Nickel-Chromium-Iron AlloysE 228 Test Method for Linear Thermal Expansion of SolidMaterials
8、 with a Vitreous Silica DilatometerF14 Practice for Making and Testing Reference Glass-Metal Bead-SealF 140 Practice for Making Reference Glass-Metal ButtSeals and Testing for Expansion Characteristics by Polari-metric MethodsF 144 Practice for Making Reference Glass-Metal Sand-wich Seal and Testing
9、 for Expansion Characteristics byPolarimetric Methods3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 bar:3.1.1.1 hot-finished rounds, squares, and hexagons,14 in.(6.4 mm) and over in diameter or size.3.1.1.2 hot-finished flats,14 in. to 10 in. (6.4 to 254 mm),inclusive, in wid
10、th and18 in. (3.2 mm) and over in thickness.3.1.1.3 cold-finished rounds, squares, octagons, hexagonsand shapes, over12 in. (12.7 mm) in diameter or size.3.1.1.4 cold-finished flats,38 in. (9.5 mm) and over in widthand18 in. (3.2 mm) and over in thickness (see Discussions).DiscussionWidths less than
11、38 in. (9.5 mm) and thick-nesses less than316 in. (4.8 mm) are generally described as flatwire.DiscussionThicknesses of18 in. (3.2 mm) to under316 in.(4.8 mm) can also be described as cold-rolled strip or, if in cutlengths, bar.3.1.2 rodhot-rolled, or hot-rolled, annealed, and pickled,rounds, square
12、s, octagons, hexagons and shapes, in coils, forsubsequent cold drawing or cold rolling,14 in. or34 in. (6.4 or19.0 mm) in diameter or size.3.1.3 stripcold-finished coils or cut lengths, under 24 in.(610 mm) down to and including316 in. (4.8 mm) in width, andunder316 in. down to and including 0.005 i
13、n. (0.13 mm) inthickness.3.1.4 No. 1 edgea rolled edge either round or square asspecified.1This specification is under the jurisdiction of Committee F01 on Electronicsand is the direct responsibility of Subcommittee F01.03 on Metallic Materials.Current edition approved Jan. 1, 2005. Published Januar
14、y 2005. Originallyapproved in 1951 as F 256 51 T. Last previous edition approved in 1999 asF 256 94 (1999)e1. Consolidated with F 257 in 1972.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vol
15、ume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.5 No. 3 edgean edge produced by slitting.3.1.6 No. 5 edgean approximately square edge producedby rol
16、ling or filing after slitting.DiscussionCold-finished product 0.005 in. (0.13 mm) inthickness and under 24 in. (609.6 mm) in width is sometimesidentified as foil.3.1.7 wire:3.1.7.1 cold finished only, round or square,12 in. (12.7 mm)and under in diameter or size.3.1.7.2 cold finished only, flat wire
17、 of116 in. (1.6 mm) tounder38 in. (9.5 mm) in width and 0.010 in. (0.25 mm) tounder316 in. (4.8 mm) in thickness.4. Classification4.1 The alloys covered by this specification are classified bynominal chemical composition, specifically by chromium con-tent, in two types:4.1.1 Type I18 % chromium (UNS
18、 K91800) and4.1.2 Type II28 % chromium (UNS K92801).5. Ordering Information5.1 Orders for material under this specification shall includethe following information:5.1.1 Quantity (weight (Note 2) or number of pieces),5.1.2 Name of material (chromium-iron alloy),5.1.3 Type (Section 4),5.1.4 Form (Sect
19、ion 3),5.1.5 Temper and finish (Section 7),5.1.6 Permissible variations in dimensions for rod (Section13),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: F 256, and5.1.11 Exceptions to the
20、 specification or special require-ments.NOTE 2The term “weight” is temporarily used in this standardbecause of established trade usage. The word is used to mean both “force”and“ mass,” and care must be taken to determine which is meant in eachcase (SI unit for force = newton and for mass = kilogram)
21、.5.2 If possible, the intended end use of the item should begiven on the purchase order especially when the item is orderedfor a specific end use or uses. Such information will enable themanufacturer to produce a material more satisfactory for thepurchasers process and product.NOTE 3A typical orderi
22、ng description is as follows: 2000 kg,chromium-iron alloy. Type II, wire, annealed, cold drawn, commercialpackaging,14 in. (6.4 mm) round by coil, ASTM F 256, end use-redraw.6. Process6.1 The purchaser shall specify that the alloy be made byone or more of the following processes: electric-arc, elect
23、ric-induction, or other process approved by the purchaser.7. Temper and Finish7.1 The desired temper of the material shall be specified onthe purchase order as follows:7.1.1 Annealed for forming (strip),7.1.2 Annealed for deep drawing (strip),7.1.3 Cold rolled or cold drawn to a specified mechanical
24、property level, or7.1.4 As hot rolled.7.2 The desired surface of the material shall be specified onthe purchase order as follows:7.2.1 Pickled,7.2.2 Cold drawn (wire and bar),7.2.3 Centerless ground (wire and bar), or7.2.4 Cold rolled (strip).8. Chemical Composition8.1 The material shall conform to
25、the chemical compositionspecified in Table 1.8.2 Ladle AnalysisA ladle analysis of each heat of steelshall be made by the manufacturer to determine the percent-ages of the elements specified in Table 1. The analysis shall bemade from test castings made during the pouring of the heat.The chemical com
26、position thus determined shall conform tothe requirements specified in Table 1.8.3 Check AnalysisIf check analysis is made by thepurchaser, the chemical composition thus determined shallconform to the requirements specified in Table 1 subject to thepermissible tolerances of Table 2.9. Chemical Analy
27、sis9.1 Chemical analysis shall be made in accordance withMethod E38or equivalent methods.TABLE 1 Chemical RequirementsNOTE 1Round observed or calculated values to the nearest unit in thelast right-hand place of figures used in expressing the limiting value, inaccordance with the rounding-off method
28、of Practice E29.ElementComposition, %Type I Type IICarbon, max 0.08 0.12Manganese, max 1.00 1.00Silicon, max 0.75 0.75Phosphorus, max 0.040 0.040Sulfur, max 0.030 0.030Chromium, nominal 18.0 28.0Nickel, max 0.50 0.50Nitrogen, max . 0.20TitaniumA.Iron remainder remainderAFive times the carbon content
29、, minimum, and 0.60, max.TABLE 2 Check Analysis TolerancesTolerances over maxi-Element mum or under minimumlimits, percentage pointsCarbon 0.01Manganese 0.03Phosphorus 0.005Sulfur 0.005Silicon 0.05Nickel 0.03Nitrogen 0.01Titanium 0.05F25605e1210. Thermal Expansion Requirements Thermal ExpansionRequi
30、rements10.1 The material shall conform to the thermal expansionrequirements prescribed in Table 3.11. Mechanical Property Requirements11.1 The material shall conform to the mechanical propertyrequirements prescribed in Table 4. Rockwell hardness shall bedetermined in accordance with Test Method E18.
31、12. Transformation Requirements12.1 The material shall show no evidence of transformationto martensite. For Type I alloy, the austenite formed duringheat treating will transform to martensite at or above roomtemperature. The presence of austenite, as may be noted inType II alloy, is acceptable if th
32、e thermal expansion require-ment is met.13. Permissible Variations in Dimensions13.1 Material furnished under this specification, except rod,shall conform to the dimensional requirements of Tables 5-15.13.2 Permissible variations in dimensions for rod for re-drawing or rerolling shall be as agreed u
33、pon between purchaserand manufacturer.14. Workmanship, Finish, and Appearance14.1 The material shall be commercially smooth and uni-form in cross section, composition, and temper; it shall be freeof scale corrosion, cracks, seams, scratches, slivers, processinglubricants, and other defects as best c
34、ommercial practice willpermit.15. Number of Tests and Retests15.1 Test specimens for thermal expansion and phase-transformation requirements shall be selected on the basis of aminimum of one specimen per heat.15.2 Test specimens for mechanical properties shall beselected on the basis of a minimum of
35、 one specimen per size,each heat, each lot annealed or otherwise heat treated under thesame conditions, and each lot with like processing.15.3 If any test specimen shows defective machining ordevelops flaws, it may be discarded and another specimensubstituted.15.4 If the results of any test lot are
36、not in conformance withthe requirements of this specification, such lots may beretreated at the option of the manufacturer. The material shallbe acceptable if the results of tests on the retreated material arewithin the requirements of this specification.16. Specimen Heat Treatment16.1 The specimens
37、 for thermal-expansion and phase-transformation tests shall be heat treated prior to testing asfollows:16.1.1 Type IHeat the specimen to 1200 6 10C and holdat temperature for 15 min. Air cool to room temperature.16.1.2 Type IIHeat the specimen to 1100 6 10C andhold at temperature for 15 min. Air coo
38、l to room temperature.The cooling rate is recommended to be faster than 300C perhour between 600 and 300C. Slower cooling rates could leadto brittle mechanical behavior.TABLE 3 Thermal Expansion RequirementsA,BTemperatureRange, CMean Coefficient of Linear ThermalExpansion, m/m CUNS K91800 UNS K92801
39、30 to 530 11.3 to 11.7 10.8 to 11.4ATypical thermal expansion data for the alloys covered by this specification aregiven for information only in the Appendix.BThese requirements apply to specimens heat treated prior to test in accordancewith Section 16.TABLE 4 Mechanical Property RequirementsAThickn
40、ess, in. (mm)RockwellHardness (orequivalent)(max)Tensile Strength,max.ksi MPaUnder 0.015 (0.38) . 85 5900.015 (0.38) to 1 (25.4), incl B 85 . .Over 1 (25.4) B 88 . .AApplicable to strip in the annealed condition only. All other mechanicalproperties as agreed upon between purchaser and manufacturer.T
41、ABLE 5 Permissible Variations in Size of Cold-Finished RoundBarsSpecified Size, in.(mm)Permissible Variations from SpecifiedSize, in. (mm)A,BOver UnderOver12 (12.7) to 1(25.4), excl0.002 (0.05) 0.002 (0.05)1 (25.4) to 112 (38.1),excl0.0025 (0.064) 0.0025 (0.064)112 (38.1) to 4 (101.6),inclC0.003 (0.
42、08) 0.003 (0.08)AUnless otherwise specified, size tolerances are over and under as shown inthe above table. When required, however, they may be specified all over andnothing under, or all under and nothing over, or any combination of over and under,if the total spread in size tolerance for a specifi
43、ed size is not less than the totalspread shown in the table.BWhen it is necessary to heat treat or heat treat and pickle after cold finishing,size tolerances are double those shown in the table.CCold-finished bars over 4 in. (101.6 mm) in diameter are produced; sizetolerances for such bars have not
44、been evolved.TABLE 6 Permissible Variations in Length of Hot-Finished orCold-Finished BarsASpecified Size ofRounds, Squares,Hexagons, Octagons,and Widths of Flats,in. (mm)BPermissible Variations in Length, in.(mm)For Lengths up to12 ft (3.7 m), inclFor Lengths over12 ft (3.7 m), to 25 ft(7.6 m), inc
45、lOver Under Over UnderTo 2 (50.8), incl12 (12.7) 034 (19.0) 0Over 2 (50.8) to 4 (101.6), incl34 (19.0) 0 1 (25) 0Over 4 (101.6) to 6 (152.4), incl 1 (25) 0 114 (32) 0Over 6 (152.4) to 9 (228.6), incl 114 (32) 0 112 (38) 0Over 9 (228.6) to 12 (304.8), incl 112 (38) 0 2 (51) 0AThe order should specify
46、 random lengths or specific lengths. When randomlengths are ordered, the length tolerance is not less than 2 ft (609.6 mm). Whenspecific lengths are ordered, Table 8 or Table 9 shall apply.BThe maximum width of bar flats is 10 in. (254.0 mm).F25605e1317. Test Methods17.1 Thermal Expansion (Note 4)Af
47、ter heat treatment ofthe specimen in accordance with Section 16, determine thethermal expansion characteristics in accordance with TestMethod E 228.NOTE 4Although not required, the thermal expansion match betweenthe alloy and a glass may be evaluated by preparing and testing anassembly in accordance
48、 with Practices F14, F 140,orF 144.17.2 TransformationCut the specimen from any part ofthe material, preferably including the entire cross section,degrease it, and then heat treat it as described in Section 16.When cool, polish the cross section of the specimen and etch inaccordance with Methods E3(
49、Note 5). Examine the specimenat a magnification of 1503 for the presence of the acicularcrystals of the martensite phase. Because these crystals mayoccur only in small localized areas, examine carefully theentire polished cross section.NOTE 5A suggested etchant is a solution of 3 parts by volume ofconcentrated hydrochloric acid and 1 part by volume of concentrated nitricacid saturated with cupric chloride (CuCl22H2O). This etchant is moreeffective when allowed to stand for 20 min after mixing. After severalhours it lo
