1、Designation: A 848 01 (Reapproved 2006)Standard Specification forLow-Carbon Magnetic Iron1This standard is issued under the fixed designation A 848; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numbe
2、r in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers the requirements for wroughtlow-carbon iron having a carbon content of 0.015 % or lesswith the remainder of the a
3、nalysis being substantially iron.1.1.1 Two alloy types are covered: Type 1 is a low-phosphorous grade andType 2 contains a phosphorous additionto improve machinability.1.2 This specification also covers alloys supplied by aproducer or converter in the form and condition suitable forfabrication into
4、parts which will be subsequently heat treated tocreate the desired magnetic characteristics. It covers alloyssupplied in the form of forging billets, hot-rolled products, andcold-finished bar, wire, and strip.1.3 This specification does not cover iron powders capableof being processed into magnetic
5、components.1.4 This specification does not cover flat-rolled, low-carbonelectrical steels.1.5 The values stated in customary (cgs-emu and inch-pound) units are to be regarded as standard. The values givenin parentheses are mathematical conversions to SI units whichare provided for information only a
6、nd are not consideredstandard.2. Referenced Documents2.1 ASTM Standards:2A 34/A 34M Practice for Sampling and Procurement Test-ing of Magnetic MaterialsA 341/A 341M Test Method for Direct Current MagneticProperties of Materials Using D-C Permeameters and theBallistic Test MethodsA 596/A 596M Test Me
7、thod for Direct-Current MagneticProperties of Materials Using the Ballistic Method andRing SpecimensA 773/A 773M Test Method for dc Magnetic Properties ofMaterials Using Ring and Permeameter Procedures withdc Electronic Hysteresigraphs2.2 Other:IEC Publication 60404-7 Ed. 1 Method of Measurement oft
8、he Coercivity of Magnetic Materials in an Open MagneticCircuit33. Ordering Information3.1 Orders to this specification shall include as much of thefollowing information as is required to describe the desiredmaterial:3.1.1 ASTM specification number and alloy type.3.1.2 Dimensions and TolerancesThe to
9、lerances are to bemutually agreed upon between the user and the producer.3.1.3 Quantity (weight or number of pieces).3.1.4 Form and condition.3.1.5 Magnetic property requirements if they are other thanstated herein.3.1.6 Certification of chemical analysis or magnetic prop-erty evaluation, or both.3.
10、1.7 Marking and packaging.3.1.8 End UseWhenever possible, the user should specifywhether the product will be machined, blanked into flat pieces,blanked and formed, or deep drawn to shape. This informationwill help the producer provide the most suitable product for theusers fabrication practice.3.1.9
11、 Exceptions to this specification or special require-ments.4. Chemical Composition4.1 Alloys supplied to this specification shall conform to therequirements in Table 1. Three of the elements listed in Table1, namely vanadium, titanium, and aluminum, are not requiredbut may be added to suppress magne
12、tic aging. If present, theymust be analyzed and reported.5. Form and Condition5.1 These two alloys are capable of being produced in awide variety of forms and conditions for fabrication intomagnetic components. The desired form and condition shall bediscussed with the producer to assure receiving th
13、e correctproduct. Available forms and conditions are:1This specification is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and is the direct responsibility of Subcommittee A06.02 onMaterial Specifications.Current edition approved May 1, 2006. Published May 2006. Originallyapprove
14、d in 1985. Last previous edition approved in 2001 as A 848 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website
15、.3Available from American National Standards Institute, 25 W. 43rd St., 4thFloor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.1.1 Forging BilletHot worked and surface conditionedby grinding.5.1.2 Hot-Rolled P
16、roductHot rolled; hot rolled and acidcleaned; hot rolled and annealed; hot rolled, annealed, and acidcleaned; hot rolled and mechanically cleaned; mechanicalproperties as specified.5.1.3 Cold-Finished BarsCold drawn, centerless ground,mechanical properties as specified; or relay condition.5.1.3.1 Re
17、lay condition applies to 1 in. (25.4 mm) roundand less in diameter and certain shapes supplied in thecold-worked condition having up to 25 % reduction in area andcapable of meeting Class 2 magnetic property requirements asdefined in 6.5.5.1.4 StripCold rolled, cold rolled and annealed, deepdraw qual
18、ity, mechanical properties as specified; or relaycondition.5.1.4.1 Relay condition applies to cold-rolled strip 0.020 to0.200 in. (0.51 to 5.1 mm) thick having up to 25 % reductionin thickness and capable of meeting Class 2 magnetic propertyrequirements as defined in 6.5.5.1.4.2 Ordering information
19、 for strip must include edgecondition and mechanical property requirements.5.1.5 WireCold drawn, annealed, mechanical propertiesas specified or relay condition.5.1.5.1 Relay condition applies to cold-drawn wire whencapable of being supplied having up to 25 % reduction in areaand capable of meeting C
20、lass 2 magnetic property require-ments as defined in 6.5.6. Magnetic Property Requirements6.1 DensityThe density for test purposes is 7.86 g/cm3(7860 kg/m3).6.2 Test SpecimenWhenever possible, test specimen sizeand shape shall conform to Practice A 34/A 34M. Shapes suchas ring laminations, solid rin
21、gs, Epstein specimens, or straightlengths having a uniform cross section are preferred. If,however, it is impossible to prepare a preferred test specimenshape from the product, specimen shape and size shall bemutually agreed upon by the user and the producer.6.3 Heat TreatmentIt is recommended that
22、the userspecify the desired heat treatment method to be applied to thetest specimens.6.3.1 When relay condition is specified, the test specimenshall be heat treated in a dry forming gas atmosphere (5 to15 % hydrogen in nitrogen with a dew point less than 40C)at a temperature of 845C for1hattemperatu
23、re and cooled ata rate from 55 to 100C/h to 500C and cooled at any ratethereafter.6.3.2 If relay condition is not specified and no heat-treatingprocedure is specified by the user, the producer is free tochoose a heat treatment procedure. Refer to Appendix X3 forheat treatment recommendations.6.4 Tes
24、t MethodMagnetic testing shall be conducted inaccordance with Test MethodsA 341/A 341M,A 596/A 596M,or A 773/A 773M or by use of a coercimeter. Under thisspecification only the coercive field strength (Hc) must bemeasured.6.5 RequirementsThe coercive field strength (Hc) mea-sured from a maximum magn
25、etic flux density of 15 kG (1.5 T)or higher must meet the maximum values listed in Table 2when the test specimen is heat treated in accordance with 6.3.1.6.5.1 When a coercimeter is used, the supplier must be ableto demonstrate that the flux density in the test specimen reachesat least 15 kG (1.5 T)
26、 during the magnetization cycle. Inaddition, the test equipment and method should conform tothose specified in IEC Publication 60404-7.7. Packaging and Marking7.1 Packaging shall be subject to agreement between theproducer and the user.7.2 Material furnished under this specification shall beidentifi
27、ed by the name or symbol of the producer, by alloy type,melt number, and material size. Each lot applied on a givenorder must be identified and packaged separately.8. Investigation of Claim8.1 Where any order fails to meet the requirements of thisspecification, disposition of the material so designa
28、ted shall besubject to agreement between the user and the producer.9. Keywords9.1 coercive field strength; magnetic iron; relay steelTABLE 1 Chemical Requirements (Weight Percent)Alloy Type 1 Alloy Type 2Carbon, max 0.020 0.020Manganese, max 0.35 0.35Silicon, max 0.15 0.15Phosphorous 0.030 max 0.10/
29、0.18Sulfur, max 0.025 0.025Chromium, max 0.20 0.20Nickel, max 0.15 0.15Vanadium, max 0.10 0.10Titanium, max 0.10 0.10Aluminum, max 0.10 0.10Iron balance balanceTABLE 2 Direct Current Coercive Field Strength RequirementsClass 1 0.75 Oe (60 A/m)Class 2 (Relay Condition) 1.0 Oe (80 A/m)Class 3 1.5 Oe (
30、120 A/m)A 848 01 (2006)2APPENDIXES(Nonmandatory Information)X1. TYPICAL MAGNETIC PROPERTIESX1.1 Typical magnetic properties of these alloys are shownin Fig. X1.1, Fig. X1.2, and Fig. X1.3 and are listed in TableX1.1. There is no statistically significant difference in magneticproperties between Type
31、 1 and Type 2 alloys for a givenproduct size, condition, and heat treatment. The data providedare for information only and are not requirements in thisspecification.FIG. X1.1 Direct Current Hysteresis Loops for Specimen of Low-Carbon Magnetic Iron Exhibiting Class 1 Behavior. Coercive FieldStrength
32、is 0.534 Oe (42.5 A/m)A 848 01 (2006)3FIG. X1.2 Direct Current Hysteresis Loops for Specimen of Low-Carbon Magnetic Iron Exhibiting Class 3 Behavior. Coercive FieldStrength is 1.18 Oe (93.9 A/m)FIG. X1.3 Direct Current Normal Induction Curves to 50 Oe (4 kA/m) for Low-Carbon Magnetic Iron Exhibiting
33、 Class 1 and Class 3PropertiesA 848 01 (2006)4X2. TYPICAL PHYSICALAND MECHANICAL PROPERTIESX2.1 Typical physical properties other than magnetic areshown in Table X2.1. Typical mechanical properties are shownin Table X2.2. The data provided in these tables are forinformation only and are not requirem
34、ents in this specification.X3. HEAT TREATMENT OF LOW-CARBON MAGNETIC IRONX3.1 Magnetic test specimens shall be heat treated inaccordance with the procedure listed in 6.3.1 for qualifyingmaterial to meet this specification.X3.2 Parts fabricated from magnetic iron can be heattreated in several differe
35、nt manners depending on the applica-tion and the heat-treating equipment available. General com-ments regarding the heat treatment procedure are as follows:X3.2.1 AtmosphereDecarburizing atmospheres typicallyresult in the lowest coercivity material. The following atmo-spheres are listed in order of
36、decreasing effectiveness ofdecarburization:X3.2.1.1 Wet Hydrogen(dew point from 20 to 5C) donot use at temperatures greater than 950C.X3.2.1.2 Wet Forming Gas (5 to 15 % hydrogen balancenitrogen)do not use at temperatures greater than 950C.X3.2.1.3 Dry Hydrogen(dew point less than 40C) canbe used at
37、 all temperatures.X3.2.1.4 Dry Forming Gascan be used at all tempera-tures.X3.2.1.5 Vacuumcan be used at all temperatures.X3.2.1.6 Endothermic Atmospherescarburizing potentialis inversely proportional to dew point.X3.3 Temperature:X3.3.1 The lowest suggested heat treatment temperature is700C. These
38、alloys are ferritic up to a temperature of about890C. Above this temperature austenite forms. Decarburiza-tion is most readily obtained in the ferritic state.X3.3.2 Heat treatment in the austenite phase (at tempera-tures above 890C) will result in grain size refinement uponcooling through the austen
39、ite to ferrite transformation. Con-versely, heat treatment at very high temperature followed byslow cooling through the transformation will maximize theferrite grain size thus improving the magnetic properties.X3.3.2.1 A suggested high temperature heat treatment pro-cedure is: heat to and hold at 85
40、0 6 25C for4hinwethydrogen, purge out wet hydrogen with dry hydrogen and heatto 1120C and hold at temperature for 4 h then cool at a rate of55 to 100C per hour to a temperature of 550C followed bycooling at any convenient rate.TABLE X1.1 Typical dc Magnetic PropertiesNOTEData for solid ring specimen
41、s machined from hot-rolled bar,annealed at 843C for4hinwethydrogen and tested in accordance withTest Method A 596/A 596M. Residual induction (Br) and coercive fieldstrength (Hc) are measured from a maximum flux density of 15 kG (1.5T).Maximum relative permeability 9400Residual induction 14 400 G (1.
42、44 T)Coercive field strength 0.85 Oe (68 A/m)TABLE X2.1 Typical Room Temperature Physical PropertiesSpecific gravity 7.86Electrical resistivity 13 Vcm (130 Vmm)Specific heat 0.108 cal/gC (452 J/kgK)Thermal conductivity 0.175 cal/cmsC (73.2 W/mK)Thermal expansivity (20200C) 12.6 106/CSaturation flux
43、density 21.5 kG (2.15 T)Curie temperature 770CTABLE X2.2 Typical Room Temperature Mechanical Properties0.2 % Offset UltimateCondition HardnessYieldStressTensileStress%ElongationHot-rolled bar 50 HRB 36 ksi (250 MPa) 46 ksi (320 MPa) 47Relay condition bar 68 HRB 55 ksi (380 MPa) 65 ksi (450 MPa) 15An
44、nealed bar 55 HRB 40 ksi (280 MPa) 45 ksi (310 MPa) 35A 848 01 (2006)5X4. MAGNETIC AGING OF LOW-CARBON MAGNETIC IRONX4.1 Trace amounts of carbon and especially nitrogenpresent either in the as-melted material or introduced duringprocessing such as heat treatment in atmospheres containingnascent or a
45、tomic nitrogen can cause time-dependent changesin magnetic behavior termed magnetic aging. These changesmay occur over a period of weeks or even months at roomtemperature and are due to the precipitation of nitrides andcarbides.X4.2 Magnetic aging typically impairs magnetic perfor-mance, especially
46、in relays. The magnetic properties mostsubject to aging include low-induction permeability and coer-cive field strength. High-induction properties and magneticsaturation are not measurably affected by magnetic aging.X4.3 Magnetic aging can be effectively eliminated by useof iron containing trace add
47、itions of strong nitride formers suchas vanadium, titanium, and aluminum. Vanadium and titaniumare also strong carbide formers and will suppress aging causedby carbon.X4.4 Magnetic aging can also be reduced or eliminated byannealing in wet hydrogen to reduce the carbon and nitrogencontent and by slo
48、w cooling after the anneal.X4.5 A procedure for determination of the potential formagnetic aging is to measure the coercive field strength of afreshly heat-treated specimen, heat at 100C for a period ofeight days to accelerate the aging process and remeasure thecoercive field strength.X4.6 The magne
49、tic behavior of parts can be stabilized byheating to 175 to 260C for several hours to cause overaging.Note that the magnetic properties will be inferior to freshlyheat-treated parts, but the time dependency will be largelyeliminated.ASTM 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 determination of the validity of any such patent rights, and the riskof infringement of such righ
