1、Designation: B344 11Standard 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, in the c
2、ase 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.1. Scope1.1 This specification covers annealed, drawn, or rolledshapes for electrical heating purpose
3、s, of alloys having thenominal compositions of 80 % nickel and 20 % chromium;60 % nickel, 16 % chromium, and remainder iron; and 35 %nickel, 20 % chromium, and remainder iron.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconv
4、ersions to SI units that are provided for information onlyand are not considered standard.2. Referenced Documents2.1 ASTM Standards:2A751 Test Methods, Practices, and Terminology for Chemi-cal Analysis of Steel ProductsB63 Test Method for Resistivity of Metallically ConductingResistance and Contact
5、MaterialsB70 Test Method for Change of Resistance With Tempera-ture of Metallic Materials for Electrical HeatingB76 Test Method for Accelerated Life of Nickel-Chromiumand Nickel-Chromium-Iron Alloys for Electrical Heating3. Significance and Use3.1 This specification on nickel-chromium and nickel-chr
6、omium-iron alloys contains the requirements for chemistry,electrical resistance, mechanical properties, and packaging.4. Requirements4.1 The alloys shall conform to the requirements as tochemical composition prescribed in Table 1.4.2 Samples for Chemical AnalysisSpecimens for chemi-cal analysis may
7、be taken from either the melt or from a sampleof finished wire that is representative of the lot.4.2.1 The lot size for determining compliance with therequirements of this specification shall be one heat.4.3 Chemical AnalysisThe chemical analysis shall bemade in accordance with Test Methods A751, or
8、 by otheranalytical methods approved by the purchaser.4.4 Actual chemical analysis is not required for routineacceptance.5. Physical Requirements5.1 The material shall be thoroughly and uniformly an-nealed.5.2 Wire shall conform to the following elongation require-ments:Size Elongation in 10 in.,min
9、, %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 resistivityof the wire as quenched from a temperatu
10、re above 1450F(788C). The numerical value of the nominal resistivity shallbe as shown in Table 2.6.2 Determination is not required for routine acceptance.NOTE 1The characteristics of these alloys are such that the actualresistivity of annealed wire may be as much as 6 % higher than thenominal, depen
11、ding on its method of manufacture.7. Test for Resistivity7.1 The resistivity shall be determined in accordance withTest 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 wireshall b
12、e calculated from the nominal resistivity and the nominalcross-sectional area.NOTE 2When ribbon or flat wire is produced by rolling from roundwire, the cross section departs from that of a true rectangle by an amountdepending on the width-to-thickness ratio and the specific manufacturingpractice. Th
13、e conventional formula for computing ohms per foot and feet1This specification is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.10 on Thermostat Metals and Electrical Resistance Heating Materials.Current edition approv
14、ed Oct. 1, 2011. Published November 2011. Originallyapproved in 1959. Last previous edition approved in 2001 as B344 - 01 which waswithdrawn May 2011 and reinstated in October 2011. DOI: 10.1520/B034411.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Ser
15、vice at serviceastm.org. For Annual Book of ASTMStandards volume 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.per pound is to consider the cross section
16、as 17 % less than a true rectanglewhen width is more than 15 times the thickness and 6 % less than a truerectangle in other cases. This is not valid in view of modern rollingequipment and practices, but still is widely used as a basis of description.Ribbon actually is made to a specified resistance
17、per foot, and no toleranceis specified for thickness.An alternative and a closer approximation wouldbe that for ribbon rolled from round wire, the electrical resistance wouldbe calculated on a cross 6 % less than a true rectangle.9. Tolerance on Electrical Resistance per Unit Length9.1 The actual re
18、sistance per unit length shall not vary fromthe nominal resistance by more than the amounts shown inTable 3.NOTE 3Dimensional TolerancesTolerances on dimensions are notspecified since the material is used for resistance purposes in which theresistivity and the electrical resistance per unit length r
19、ather than thedimensions are of prime importance. The electrical resistance per unitlength can be determined more accurately than the dimensions of verysmall sizes of wire or strip.10. Resistance Change with Temperature10.1 Nominal values for resistance change with temperatureare contained in Append
20、ix X1.10.2 The change in resistance with change in temperatureshall be measured in accordance with Test Method B70.11. Durability11.1 When it is desired to determine the durability of thematerial at high temperatures, life tests shall be made inaccordance with Test Method B76. Test results may be re
21、portedeither in hours or in percentage of an accepted standard. Thetemperature of the life tests for the three alloys shall be asfollows:80 Nickel-20 Chromium Alloy 2175F (1190C)60 Nickel-16 Chromium Alloy 2100F (1150C)38 Nickel-21 Chromium Alloy 2050F (1120C)35 Nickel-20 Chromium Alloy 2025F (1105C
22、)11.2 The life or durability value shall be the average of atleast three simultaneous determinations each, on wire speci-mens of the material and on the reference standard. If any testresult varies more than 10 % from the average of the threedeterminations, that group shall be discarded and the test
23、repeated.11.3 Determination is not required for routine acceptance.12. Finish12.1 The material shall be as uniform and free from surfacedefects such as splits, kinks, laminations, scale, and otherirregularities as the best commercial practice will permit. Thefinish shall be either bright annealed or
24、 oxidized, as specified.13. Packaging and Marking13.1 Packaging shall be subject to agreement between themanufacturer and the purchaser.13.2 The material as furnished under this specification shallbe identified by the name or symbol and color code of themanufacturer and by melt number.14. Precision
25、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 thetest method for durability is contained in Test Method B76.15. Keywords15.1 flat wire; heating element; nickel chro
26、me alloys; resis-tance alloyTABLE 1 Chemical RequirementsElementComposition, %80 Nickel-20 Chromium Alloy 60 Nickel-16 Chromium Alloy 38 Nickel-21 Chromium Alloy 35 Nickel-20 Chromium AlloyNickelAremainder 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
27、1.0 max 1.0 maxCarbon 0.15 max 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 0.20AQuantities of less than 1 % cobalt included shal
28、l be reported as nickel.TABLE 2 Specific ResistanceAlloy Specific Resistance80 Nickel-20 Chromium 650V cm/ft510 Vmil2/ft1.081VM1.081 VM60 Nickel-16 Chromium 675 Vcm/ft530 Vmil2/ft1.122VM1.122 VM38 Nickel-21 Chromium 638 Vcm2/ft500 Vmil2/ft1.06 VM1.06 VM35 Nickel-20 Chromium 610 Vcm/ft479 Vmil2/ft1.0
29、14VM1.014 VMTABLE 3 Electrical Resistance ToleranceTolerance,%Round Wire:0.005-in. (0.127-mm) diameter and larger 65Finer than 0.005 in. to 0.002-in. 68(0.014-mm) diameter, inclFiner than 0.002-in. diameter 610Strip:Cold rolled 65Hot rolled 68B344 112APPENDIX(Nonmandatory Information)X1. BASIS FOR E
30、STABLISHMENT OF PERCENT CHANGE IN RESISTANCE WITH TEMPERATUREX1.1 The conditions of test, wire or strip size, chemistry ofheats, and the environment are so varied it is not possible toaccurately specify the resistance change versus temperature fornickel-chromium and nickel-chromium-iron alloys.X1.2
31、Since this information is of general value to thosedesigning appliances, furnaces, or other apparatus, the data inTable X1.1 is included for general guidance only. See also Fig.X1.1. The change in resistance values in this table wereobtained using free coils of wire tested in accordance with TestMet
32、hod B70.X1.3 The electrical properties of 80 nickel-20 chromiumalloys can be changed by heat treatment in the temperaturerange from 500 to 1450F (260 to 788C). The wire as suppliedby the manufacturer will normally have been strand annealed attemperatures higher than 1450F. This results in rapid cool
33、ingof the alloy. It will therefore have a resistivity near theminimum for the alloy. After heating or slow cooling in therange from 500 to 1450F the resistivity may increase as muchas 6 %. The resistivity above 1450F is reproducible regardlessof previous treatment below this temperature. (The 60nick
34、el-16 chromium alloy may change up to 2 % under similartreatment while the change for 35 nickel-20 chromium will beinsignificant.)X1.4 The minimum resistance change with temperaturewill be obtained for heavy sizes while the maximum changewill occur for small sizes. Therefore, for extreme accuracy it
35、 isadvisable to run tests on a protoype to determine the resistancechange with temperature.TABLE X1.1 Nominal Percent Change in Resistance with TemperatureTemperature80 Nickel-20Chromium Alloy60 Nickel-16Chromium Alloy38 Nckel-21Chromium Alloy35 Nickel-20Chromium Alloy2000F 1.66 8.66 21.7 23.51800F
36、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 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 113ASTM International takes no position re
37、specting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This
38、 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 withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM Inter
39、national Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown b
40、elow.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single 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 ASTM website (www.astm.org/COPYRIGHT/).FIG. X1.1 Nominal Percent Change in Resistance with TemperatureB344 114
