1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (412) 772-8512 FAX: (412) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (412) 776-4970 FAX: (412) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1983 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICEAn American National StandardJ419REV.DEC83Issued 1959
4、-05Revised 1983-12Superseding J419 JUN79METHODS OF MEASURING DECARBURIZATIONForewordThis Document has not changed other than to put it into the new SAE Technical Standards BoardFormat.1. ScopeThis report covers the recommended practice for the evaluation and measurement of decarburizationin ferrous
5、material. Included are definitions of types with charts and micrographs and methods mostcommonly used for the measurement of decarburization.2. References2.1 Applicable PublicationThe following publication forms a part of this specification to the extent specifiedherein. Unless otherwise specified,
6、the latest issue of SAE publications shall apply.2.1.1 SAE PUBLICATIONAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001SAE J423Methods of Measuring Case Depth3. Definitions3.1 DecarburizationDecarburization is the loss of carbon at the surface of commercial ferrous materials whic
7、hhave been heated for fabrication or when heated to modify mechanical properties.3.2 Complete DecarburizationComplete loss of carbon as determined by examination.3.3 Partial DecarburizationAny measurable loss of carbon content, less than complete, with respect to carbonlevel of base material.3.4 Eff
8、ective DecarburizationAny measurable loss of carbon content which results in mechanical propertiesbelow the minimum acceptable specifications for hardened material.4. Types Of DecarburizationThree general types of decarburization may be prevalent in ferrous materialsdependent on manner and degree of
9、 carbon loss from the material. Classifying decarburization into threetypes may aid in selecting the process necessary to utilize the material to meet a product specification.Accompanying photomicrographs are illustrations of typical conditions which may be encountered.SAE J419 Revised DEC83-2-4.1 T
10、ype 1 DecarburizationIndicated by the curve and photomicrographs in Figure 1, covers that condition inwhich carbon free ferrite exists for a measurable distance below the surface. Underneath the ferrite will existvarying degrees of partial decarburization.4.2 Type 2 DecarburizationIndicated by the c
11、urve and photomicrographs in Figure 2, covers that condition inwhich there is a loss of more than 50% of the base carbon at the surface but where no measurable depth ofcomplete decarburization is evident.4.3 Type 3 DecarburizationIndicated by the curve and photomicrographs in Figure 3, covers that c
12、onditionwhere some loss of carbon at the surface is evident but to a degree less than 50% of the base carbon of thematerial.4.3.1 Further subdividing of Type 3 Decarburization may be necessary for highly stressed members such as springor high strength materials. In this category, the effective decar
13、burization may be determined bymicrohardness testing for materials lower than 0.6% base carbon.Chemical analysis procedures may be required when examining high carbon materials.5. Methods Of Measuring DecarburizationThe common methods used for the measurement ofdecarburization are:a. microscopic;b.
14、hardness, including cross section microhardness traverse, longitudinal traverse, and file hardness; andc. chemical analysis.The accuracy of the method to be used is dependent on the degree of decarburization, microstructure, andbase carbon content of the steel. The metallographic method is sufficien
15、tly accurate for most annealed and hotrolled materials, but inaccurate for small amounts of decarburization in high carbon (above 0.60%), highhardness steels. The hardness method is also insensitive in this latter case and recourse must be taken tochemical analysis.The file method is often suitable
16、for detecting decarburization of hardened materials during shop processingbut not for accurate measurement.It is fundamental that true measure of decarburization lies in chemical analysis for carbon content. Thismethod is normally used only in research investigations or to check accuracy of other me
17、thods. With thepossible exception of specialized electron microprobe analytical techniques, which are recommended whenavailable, analysis is difficult and slow in application because of limitations of size and section of material. Themethod of procuring sample itself depends upon shape and hardness
18、of test piece. Parts and/or testspecimens too hard to machine should be tempered at 600 to 650 C (1100 to 1200 F) to permit machining ofsurface layers into chips for subsequent carbon analysis. Obviously, a sample which is annealed to permitmilling of chips may be modified in its condition of decarb
19、urization. Standard methods for carbondetermination are described in textbooks of analytical chemistry.5.1 Microscopic Method5.1.1 SPECIMENThe area to be examined should be cut at right angles to the surface. Samples are preferablytaken when the material is in full annealed or in hot rolled conditio
20、n. Other conditions, such as spheroidizedannealed, hardened, or cold worked material, may be examined but care must be used in interpretation. Forsections up to 13 mm (1/2 in), the entire cross section is normally mounted for examination. For largersections, a specimen should be cut to include about
21、 19 mm (3/4 in) of the surface to be examined. Cornersof straight sided sections should not be included, since they are not considered representative.SAE J419 Revised DEC83-3-FIGURE 1TYPE 1 DECARBURIZATIONSAE J419 Revised DEC83-4-FIGURE 2TYPE 2 DECARBURIZATIONSAE J419 Revised DEC83-5-FIGURE 3TYPE 3
22、DECARBURIZATIONSAE J419 Revised DEC83-6-5.1.2 PREPARATIONIn mounting the specimen for grinding and polishing, protection from rounding the surface tobe examined is essential. The specimen should be mounted in a clamp or in a plastic mount, the latter beingthe preferred method. An additional method o
23、f protection is to deposit (by electroless or electroplating) ametallic coating of 0.030.08 mm (0.0010.003 in) on the specimen before mounting.After mounting, the surface should be ground and polished in accordance with good metallographic practice.Etching in a 3% nital (concentrated nitric acid in
24、alcohol) is usually suitable for showing changes inmicrostructure caused by decarburization.5.1.3 MEASUREMENTMagnification for examination can be agreed on between purchaser and producer.However, it is recommended that 100X magnification be used. If the microscope is of a type with a groundglass scr
25、een, the extent of decarburization can be measured directly with a scale. If an eyepiece is used formeasurement, it should be an appropriate type containing a cross hair or a scale.5.2 Hardness Methods5.2.1 CROSS SECTION MICROHARDNESS TRAVERSE5.2.1.1 SpecimenSample to be checked should be cut at rig
26、ht angles to the surface. If cross section is too large,a portion of suitable size including surface to be checked should be cut before examination.5.2.1.2 PreparationThe specimen shall be hardened by quenching from equipment under conditions whichminimize further change in carbon distribution. The
27、time at temperature should be minimized to avoidexcessive carbon diffusion. In the case of finished parts, which have been previously quenched andtempered, no further treatment is necessary. For sections up to 13 mm (1/2 in), the entire cross section isnormally mounted in plastic. After mounting, th
28、e surface should be ground and polished in accordancewith good metallographic practice.5.2.1.3 MeasurementA series of microhardness impressions made by pyramidal or Knoop indentors should beextended from the surface until the hardness of the base metal is obtained.5.2.2 LONGITUDINAL TRAVERSE (TAPER
29、OR STEP GRIND)5.2.2.1 SpecimenA specimen containing the surface on which decarburization is to be measured is prepared sothat it can be manipulated on a superficial hardness tester.5.2.2.2 PreparationIf the specimen is not in the hardened condition, it is recommended that it be hardened byquenching
30、from heating equipment under conditions which avoid further change in carbon distribution.For the taper grind specimen, a shallow taper is ground through the decarburized layer, see SAERecommended Practice, Methods of Measuring Case DepthSAE J423. The angle is chosen so thathardness readings spaced
31、equal distances apart will represent the hardness at the desired incrementsbelow the surface. Unless special anvils are used on the hardness tester, a parallel section should beprepared so that indentations will be at right angles to the tapered surface.For the step grind procedure, flats are ground
32、 at predetermined intervals below the original surface. Theseflats should have sufficient area to allow several hardness readings to be taken on each flat.5.2.2.3 MeasurementA superficial hardness tester such as a Rockwell Superficial or Vickers Tester using a lightload should be employed in making
33、the hardness measurements. The depth of decarburization is definedas the distance measured from the nearest original surface to the point at which no increase in hardness isfound.SAE J419 Revised DEC83-7-5.2.3 FILE METHOD5.2.3.1 SpecimenA specimen of suitable size is obtained from the desired locati
34、on.5.2.3.2 PreparationThe specimen shall be hardened by quenching from heating equipment under conditionswhich avoid further decarburization.5.2.3.3 MeasurementAfter hardening, the sample is filed. Base metals expected to harden to above 60 HRCand found to be file soft are probably decarburized. Dec
35、arburization of base metals that will not harden to60 HRC cannot be detected by this method unless specially prepared files are used. The extent andseverity of any decarburization detected by this method should be verified by either of the other twomethods.5.3 Chemical AnalysisProcedure is the same
36、as SAE J423.6. Notes6.1 Marginal IndiciaThe change bar (l) located in the left margin is for the convenience of the user in locatingareas where technical revisions have been made to the previous issue of the report. An (R) symbol to the leftof the document title indicates a complete revision of the
37、report.PREPARED BY THE SAE IRON AND STEEL TECHNICAL COMMITTEESAE J419 Revised DEC83RationaleNot applicable.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThis report covers the recommended practice for the evaluation and measurement ofdecarburization in ferrous material. Included are definitions of types with charts and micrographs andmethods most commonly used for the measurement of decarburization.Reference SectionSAE J423Methods of Measuring Case DepthDeveloped by the SAE Iron And Steel Technical Committee
