1、Designation: B344 11B344 14Standard Specification forDrawn or Rolled Nickel-Chromium and Nickel-Chromium-Iron Alloys for Electrical Heating Elements1This standard is issued under the fixed designation B344; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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
3、1.1 This specification covers annealed, drawn, or rolled shapes for electrical heating purposes, of alloys having the nominalcompositions of 80 % nickel and 20 % chromium; 60 % nickel, 16 % chromium, and remainder iron; and 35 % nickel, 20 %chromium, and remainder iron; 38 % nickel, 21 % chromium, a
4、nd remainder iron; and 35 % nickel, 20 % chromium remainderiron.1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information only and are not considered standard.2. Referenced Docum
5、ents2.1 ASTM Standards:2A751 Test Methods, Practices, and Terminology for Chemical Analysis of Steel ProductsB63 Test Method for Resistivity of Metallically Conducting Resistance and Contact MaterialsB70 Test Method for Change of Resistance With Temperature of Metallic Materials for Electrical Heati
6、ngB76 Test Method for Accelerated Life of Nickel-Chromium and Nickel-Chromium-Iron Alloys for Electrical Heating3. Significance and Use3.1 This specification on nickel-chromium and nickel-chromium-iron alloys contains the requirements for chemistry, electricalresistance, mechanical properties, and p
7、ackaging.4. Requirements4.1 The alloys shall conform to the requirements as to chemical composition prescribed in Table 1.4.2 Samples for Chemical AnalysisSpecimens for chemical analysis may be taken from either the melt or from a sample offinished wire that is representative of the lot.4.2.1 The lo
8、t size for determining compliance with the requirements of this specification shall be one heat.4.3 Chemical AnalysisThe chemical analysis shall be made in accordance with Test Methods A751, or by other analyticalmethods approved by the purchaser.4.4 Actual chemical analysis is not required for rout
9、ine acceptance.5. Physical Requirements5.1 The material shall be thoroughly and uniformly annealed.5.2 Wire shall conform to the following elongation requirements:1 This specification is under the jurisdiction of ASTM Committee B02 on Nonferrous Metals and Alloys and is the direct responsibility of
10、Subcommittee B02.10 onThermostat Metals and Electrical Resistance Heating Materials.Current edition approved Oct. 1, 2011Oct. 1, 2014. Published November 2011October 2014. Originally approved in 1959. Last previous edition approved in 20012011as B344 01B344 which was withdrawn May 2011 and reinstate
11、d in October 2011. DOI: 10.1520/B0344-11. 11. DOI: 10.1520/B0344-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standardsstandards Document Summary page on t
12、he ASTM website.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. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users c
13、onsult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Size Elongation in 10 in.,min, %
14、0.0035 in. (0.0889 mm) (No. 39 Awg) and larger 200.0031 in. (0.0787 mm) to 0.002 in.(0.0508 mm) (Nos. 40 to 44 Awg)105.3 Determination is not required for routine acceptance.6. Nominal Resistivity6.1 The nominal resistivity (Note 1) shall be the resistivity of the wire as quenched from a temperature
15、 above 1450F (788C).The numerical value of the nominal resistivity shall be as shown in Table 2.6.2 Determination is not required for routine acceptance.NOTE 1The characteristics of these alloys are such that the actual resistivity of annealed wire may be as much as 6 % higher than the nominal,depen
16、ding on its method of manufacture.7. Test for Resistivity7.1 The resistivity shall be determined in accordance with Test Method B63.7.2 Determination is not required for routine acceptance.8. Nominal Electrical Resistance for Unit Length8.1 The nominal resistance per unit length for round wire shall
17、 be calculated from the nominal resistivity and the nominalcross-sectional area.NOTE 2When ribbon or flat wire is produced by rolling from round wire, the cross section departs from that of a true rectangle by an amountdepending on the width-to-thickness ratio and the specific manufacturing practice
18、. The conventional formula for computing ohms per foot and feet perpound is to consider the cross section as 17 % less than a true rectangle when width is more than 15 times the thickness and 6 % less than a true rectanglein other cases. This is not valid in view of modern rolling equipment and prac
19、tices, but still is widely used as a basis of description. Ribbon actually ismade to a specified resistance per foot, and no tolerance is specified for thickness. An alternative and a closer approximation would be that for ribbonrolled from round wire, the electrical resistance would be calculated o
20、n a cross 6 % less than a true rectangle.9. Tolerance on Electrical Resistance per Unit Length9.1 The actual resistance per unit length shall not vary from the nominal resistance by more than the amounts shown in Table3.NOTE 3Dimensional TolerancesTolerances on dimensions are not specified since the
21、 material is used for resistance purposes in which the resistivityand the electrical resistance per unit length rather than the dimensions are of prime importance. The electrical resistance per unit length can be determinedmore accurately than the dimensions of very small sizes of wire or strip.TABL
22、E 1 Chemical RequirementsElement Composition, %80 Nickel-20 Chromium Alloy 60 Nickel-16 Chromium Alloy 38 Nickel-21 Chromium Alloy 35 Nickel-20 Chromium AlloyNickelA remainder 57 min 36 to 39 34 to 37Chromium 19 to 21 14 to 18 20 to 23 18 to 21Manganese 1.0 max 1.0 max 1.0 max 1.0 maxCarbon 0.15 max
23、 0.15 max 0.12 max 0.15 maxSilicon 0.75 to 1.75 0.75 to 1.75 1.3 to 2.2 1.0 to 3.0Sulfur 0.01 max 0.01 max 0.03 max 0.01 maxIron 1.0 max remainder remainder remainderPhosphorus 0.03 maxCopper 0.5 maxLanthanum 0.03 to 0.20A Quantities of less than 1 % cobalt included shall be reported as nickel.TABLE
24、 2 Specific ResistanceAlloy Specific Resistance80 Nickel-20 Chromium 650cm/ft510 mil2/ft1.081M1.081 M60 Nickel-16 Chromium 675 cm/ft530 mil2/ft1.122M1.122 M38 Nickel-21 Chromium 638 cm2/ft500 mil2/ft1.06 M1.06 M35 Nickel-20 Chromium 610 cm/ft479 mil2/ft1.014M1.014 MB344 14210. Resistance Change with
25、 Temperature10.1 Nominal values for resistance change with temperature are contained in Appendix X1.10.2 The change in resistance with change in temperature shall be measured in accordance with Test Method B70.11. Durability11.1 When it is desired to determine the durability of the material at high
26、temperatures, life tests shall be made in accordancewith Test Method B76. Test results may be reported either in hours or in percentage of an accepted standard. The temperature ofthe life tests for the threefour alloys shall be as follows:80 Nickel-20 Chromium Alloy 2175F (1190C)60 Nickel-16 Chromiu
27、m Alloy 2100F (1150C)38 Nickel-21 Chromium Alloy 2050F (1120C)35 Nickel-20 Chromium Alloy 2025F (1105C)11.2 The life or durability value shall be the average of at least three simultaneous determinations each, on wire specimens ofthe material and on the reference standard. If any test result varies
28、more than 10 % from the average of the three determinations,that group shall be discarded and the test repeated.11.3 Determination is not required for routine acceptance.12. Finish12.1 The material shall be as uniform and free from surface defects such as splits, kinks, laminations, scale, and other
29、irregularities as the best commercial practice will permit. The finish shall be either bright annealed or oxidized, as specified.13. Packaging and Marking13.1 Packaging shall be subject to agreement between the manufacturer and the purchaser.13.2 The material as furnished under this specification sh
30、all be identified by the name or symbol and color code of themanufacturer and by melt number.14. Precision and Bias14.1 Precision and bias on chemistry, electrical resistance, and resistance change with temperature are contained in TestMethods A751, B63, and B70. The precision and bias on the test m
31、ethod for durability is contained in Test Method B76.15. Keywords15.1 flat wire; heating element; nickel chrome alloys; resistance alloyTABLE 3 Electrical Resistance ToleranceTolerance,%Round Wire:0.005-in. (0.127-mm) diameter and larger 5Finer than 0.005 in. to 0.002-in. 8(0.014-mm) diameter, inclF
32、iner than 0.002-in. diameter 10Strip:Cold rolled 5Hot rolled 8B344 143APPENDIX(Nonmandatory Information)X1. BASIS FOR ESTABLISHMENT OF PERCENT CHANGE IN RESISTANCE WITH TEMPERATUREX1.1 The conditions of test, wire or strip size, chemistry of heats, and the environment are so varied it is not possibl
33、e to accuratelyspecify the resistance change versus temperature for nickel-chromium and nickel-chromium-iron alloys.X1.2 Since this information is of general value to those designing appliances, furnaces, or other apparatus, the data in Table X1.1is included for general guidance only. See also Fig.
34、X1.1. The change in resistance values in this table were obtained using freecoils of wire tested in accordance with Test Method B70.X1.3 The electrical properties of 80 nickel-20 chromium alloys can be changed by heat treatment in the temperature range from500 to 1450F (260 to 788C). The wire as sup
35、plied by the manufacturer will normally have been strand annealed at temperatureshigher than 1450F. This results in rapid cooling of the alloy. It will therefore have a resistivity near the minimum for the alloy.After heating or slow cooling in the range from 500 to 1450F the resistivity may increas
36、e as much as 6 %. The resistivity above1450F is reproducible regardless of previous treatment below this temperature. (The 60 nickel-16 chromium alloy may changeup to 2 % under similar treatment while the change for 35 nickel-20 chromium will be insignificant.)X1.4 The minimum resistance change with
37、 temperature will be obtained for heavy sizes while the maximum change will occurfor small sizes. Therefore, for extreme accuracy it is advisable to run tests on a protoype to determine the resistance change withtemperature.TABLE X1.1 Nominal Percent Change in Resistance with TemperatureTemperature
38、80 Nickel-20Chromium Alloy 60 Nickel-16Chromium Alloy 38 Nckel-21Chromium Alloy 35 Nickel-20Chromium Alloy2000F 1.66 8.66 21.7 23.51800F 1.18 8.00 20.6 22.51600F 0.79 7.35 19.3 21.41400F 0.71 6.70 17.6 19.61200F 1.04 6.15 16.0 17.81000F 1.90 5.77 14.5 15.6900F 1.88 5.52 13.6 14.4800F 1.94 5.03 12.8
39、13.0600F 1.46 3.67 9.9 10.0400F 0.93 2.32 5.8 6.5200F 0.43 0.78 5.7 2.677F 0.0 0.0 0.0 0.0B344 144ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determ
40、ination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or w
41、ithdrawn.Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that y
42、our comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (si
43、ngle or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ X1.1 Nominal Percent Change in Resistance with TemperatureB344 145
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