1、SAE-J423ADOPTION NOTICESAE-J423, “CASE DEPTH, METHODS OF MEASURING“, was adopted on27-JAN-95 for use by the Department of Defense (DoD). Proposedchanges by DoD activities must be submitted to the DoD AdoptingActivity: Commander, Atlantic Division, Naval FacilitiesEngineering Command, Criteria Office
2、, 1510 Gilbert St, Norfolk,VA 23511-2699. Copies of this document may be purchased fromthe Society of Automotive Engineers 400 Commonwealth DriveWarrendale, Pennsylvania, United States, 15096-0001. http:/www.sae.org/_Custodians: Adopting Activity:Navy - YDArmy - MRNavy - YDAir Force - 11Reviewer Act
3、ivities:Navy - ASAREA NDTIDISTRIBUTION STATEMENT A: Approved for public release; distributionis unlimited.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 it
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6、h Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICEAn American National StandardJ423REAF.FEB1998Issued 1950-01Reaffirmed 1998-02Superseding J423 DEC83Methods of Measuring Case DepthForewordThis Document has not changed other than to put it into the new SAE Technical Standards BoardFormat. Referenc
7、es were added as Section 2. Definitions were changed to Section 3. All other section numbershave changed accordingly. 1. ScopeCase hardening may be defined as a process for hardening a ferrous material in such a manner thatthe surface layer, known as the case, is substantially harder than the remain
8、ing material, known as the core.The process embraces carburizing, nitriding, carbonitriding, cyaniding, induction, and flame hardening. Inevery instance, chemical composition, mechanical properties, or both are affected by such practice.This testing procedure describes various methods for measuring
9、the depth to which change has been made ineither chemical composition or mechanical properties. Each procedure has its own area of applicationestablished through proved practice, and no single method is advocated for all purposes.Methods employed for determining the depth of case are either chemical
10、, mechanical, or visual, and thespecimens or parts may be subjected to the described test either in the soft or hardened condition. Themeasured case depth may then be reported as either effective or total case depth on hardened specimens,and as total case depth on unhardened specimens.It should be r
11、ecognized that the relationship between case depths as determined by the different methods canvary extensively. Factors affecting this relationship include case characteristics, parent steel composition,quenching conditions, and others. It is not possible to predict, in some instances for example, e
12、ffective casedepth by chemical or visual means. It is important, therefore, that the method of case depth determination becarefully selected on the basis of specific requirements, consistent with economy.2. References2.1 Applicable PublicationThe following publication forms a part of the specificati
13、on to the extent specifiedherein. Unless otherwise indicated the latest revision of SAE publications shall apply.2.1.1 ASM INTERNATIONAL PUBLICATIONAvailable from: ATTN: MSC/Book Order, ASM International, PO Box473, Novelty, OH 44072-9901.“The Application of MsPoints to Case Depth Measurement,“ by E
14、. S. Rowland and S. R. Lyle, ASMTransactions, Vol. 37 (1946) pp. 2647.SAE J423 Reaffirmed FEB1998-2-3. Definitions3.1 Effective Case DepthThe perpendicular distance from the surface of a hardened case to the furthest pointwhere a specified level of hardness is maintained. The hardness criterion is 5
15、0 HRC normally, but see Table 1under 5.1.Effective case depth should always be determined on the part itself, or on samples or specimens having aheat-treated condition representative of the part under consideration.3.2 Total Case DepthThe distance (measured perpendicularly) from the surface of the h
16、ardened or unhardenedcase to a point where differences in chemical or physical properties of the case and core no longer can bedistinguished.4. Chemical Methods4.1 GeneralThis method is generally applicable only to carburized cases, but may be used for cyanided orcarbonitrided cases. The procedure c
17、onsists in determining the carbon content (and nitrogen when applicable)at various depths below the surface of a test specimen. This method is considered the most accurate formeasuring total case depth on carburized cases.4.2 Procedure for Carburized CasesTest specimens shall normally be of the same
18、 grade of steel as partsbeing carburized. Test specimens may be actual parts, rings, or bars and should be straight or otherwisesuitable for accurate machining of surface layers into chips for subsequent carbon analysis.Test specimens shall be carburized with parts or in a manner representative of t
19、he procedure to be used forparts in question. Care should be exercised to avoid distortion and decarburization in cooling test specimensafter carburizing. In cases where parts and test specimens are quenched after carburizing, such specimensshould be tempered at approximately 600 to 650 C (1100 to 1
20、200 F) and straightened to 0.04 mm (0.0015 in)max total indicator reading (TIR) before machining is attempted. The time at temperature should be minimizedto avoid excessive carbon diffusion.Test specimens must have clean surfaces and shall be machined dry in increments of predetermined depth.The ana
21、lysis of machined chips will then accurately reveal the depth of carbon penetration. Chosenincrements usually vary between 0.05 and 0.25 mm (0.002 and 0.010 in) depending upon the accuracy desiredand expected depth of case.Chips from each increment shall be kept separate and analyzed individually fo
22、r carbon content by an acceptedmethod. Total case depth is considered to be the distance from the surface equivalent to the depth of the lastincrement of machining whose chips analyze to a carbon content 0.04% higher than that of the establishedcarbon content of the core.Specialized electron micropr
23、obe analyses on carefully prepared cross-sections represent an alternateprocedure with potentially greater accuracy and speed, and is recommended when equipment is available.5. Mechanical Methods5.1 GeneralThis method is considered to be one of the most useful and accurate of the case depth measurin
24、gmethods. It can be effectively used on all types of hardened cases, and is the preferred method fordetermination of effective case depth. The use of this method requires the obtaining and recording ofhardness values at known intervals through the case. For determination of effective case depth, the
25、 50 HRCcriterion is generally used. The sample or part is considered to be through hardened when the hardness leveldoes not drop below the effective case depth hardness value. In some instances involving flame and inductionhardened cases, it is desirable to use a lower hardness criterion. Suggested
26、hardness levels are tabulated inTable 1 for various nominal carbon levels.SAE J423 Reaffirmed FEB1998-3-A plot of hardness versus depth from the surface will facilitate this reading. Figures 1, 2, 3, and 4 illustrate therecommended procedures. Hardness testers which produce small, shallow impression
27、s should be used for all of the following procedures,in order that the hardness values obtained will be representative of the surface or area being tested. Thosetesters which are used to produce Diamond Pyramid or Knoop Hardness Numbers are recommended,although testers using heavier loads, such as t
28、he Rockwell superficial, A or C scales, can be used in someinstances on flame and induction hardened cases.Considerable care should be exercised during preparation of samples for case depth determination by any ofthe mechanical methods, to insure against grinding or cutting burn. The use of an etcha
29、nt for burn detection isrecommended as a general precaution, because of the serious error which can be introduced by its presence.FIGURE 1SPECIMEN FOR TAPER GRIND PROCEDUREFIGURE 2SPECIMEN FOR CROSS SECTION PROCEDUREFIGURE 3SPECIMEN FOR ALTERNATE CROSS SECTION PROCEDUREFIGURE 4SPECIMEN FOR STEP GRIN
30、D PROCEDURETABLE 1CARBON CONTENTCarbon ContentEffective CaseDepth Hardness0.280.32% C 35 HRC0.330.42% C 40 HRC0.430.52% C 45 HRC0.53% and over 50 HRCSAE J423 Reaffirmed FEB1998-4-5.2 Hardness Traverse ProcedureCut specimens perpendicular to hardened surface at critical location beingcareful to avoid
31、 any cutting or grinding practice which would affect the original hardness.Grind and polish specimen. Surface finish of the area to be traversed shall be polished finely enough so thehardness impressions are unaffectedthat is, the lighter the indentor load, the finer the polish necessary.The procedu
32、re illustrated by Figure 2 is recommended for the measurement of light and medium cases. Thealternate procedure illustrated in Figure 3 is recommended for medium and heavier cases.The hardness traverse should be started far enough below the surface to ensure proper support from the metalbetween the
33、center of the impression and the surface. Subsequent impressions are spaced far enough apartso as not to distort hardness values. The distance from the surface of the case to the center of the impressionis measured on a calibrated optical instrument, micrometer stage, or other suitable means.5.3 Tap
34、er Grind ProcedureThis procedure, illustrated by Figure 1, is recommended for measurement of lightand medium cases.A shallow taper is ground through the case, and hardness measurements are made along the surface thusprepared. The angle is chosen so that readings, spaced equal distances apart, will r
35、epresent the hardness atthe desired increments below the surface of the case.Unless special anvils are used, a parallel section should be prepared so that readings are taken at right anglesto the surface. Care should be exercised in grinding to prevent tempering or rehardening.5.4 Step Grind Procedu
36、reThis procedure illustrated by Figure 4 is recommended for measurement of mediumand heavy cases.It is essentially the same as the taper grind section method with the exception that hardness readings aremade on steps which are known distances below the surface.A variation in this procedure is the st
37、ep grind method where two predetermined depths are ground to insurethat the effective case depth is within specified limits.6. Visual Methods6.1 GeneralThis method employs any visual procedure with or without the aid of magnification for reading thedepth of case produced by any of the various proces
38、ses. Samples may be prepared by combinations offracturing, cutting, grinding, and polishing methods. Etching with a suitable reagent is normally required toproduce a contrast between the case and core. Nital (concentrated nitric acid in alcohol) of various strengths isfrequently used for this purpos
39、e.6.2 MacroscopicMagnification methods for determination of case depth measurement are recommended forroutine process control, primarily because of the short time required for determinations, and the minimum ofspecialized equipment and trained personnel needed. They have the added advantage of being
40、 applicable tothe measurement of all types of cases. However, the accuracy can be improved by correlation with othermethods more in keeping with engineering specifications for the parts being processed. These methods areapplied normally to hardened specimens, and while a variety of etchants may be e
41、mployed with equal success,the following procedures are typical and widely used.6.2.1 FRACTUREPrepare product or sample by fracturing. Examine at a magnification not to exceed20diameters with no further preparation.SAE J423 Reaffirmed FEB1998-5-6.2.2 FRACTURE AND ETCHWater quench product or samples
42、directly from the carburizing temperature. Fractureand etch in 20% nitric acid in water for a time established to develop maximum contrast. Rinse in water andread while wet.6.2.3 FRACTURE OR CUT, AND ROUGH GRINDPrepare specimen by either fracturing, or cutting and rough grinding.Etch in 10% nital fo
43、r a period of time established to provide a sharp line of demarcation between case andcore. Examine at magnification not to exceed 20 diameters (Brinell glass) and read all the darkened area forapproximate total case depth.6.2.4 FRACTURE OR CUT, AND POLISH OR GRINDPrepare specimen by fracturing or c
44、utting. Polish or grindthrough No. 000 or finer metallographic emery paper or both. Etch in 5% nital for approximately 1 min.Rinse in two clean alcohol or water rinses. Examine at magnification not to exceed 20 diameters (Brinellglass) and read all of the darkened zone. After correlation, effective
45、case depth can be determined byreading from external surface of specimen to a selected line of the darkened zone.6.3 MicroscopicMicroscopic methods are generally for laboratory determination and require a completemetallographic polish and an etch suitable for the material and the process. The examin
46、ation is made mostcommonly at 100 diameters.6.3.1 CARBURIZED CASESThe microscopic method may be used for laboratory determinations of total case andeffective case depths in the hardened condition. When the specimen is annealed properly, the total casedepth and the depth of the various zoneshypereute
47、ctoid, eutectoid, and hypoeutectoidalso can bedetermined quite precisely.1a. Hardened Condition1. Fracture or cut specimen at right angles to the surface.2. Prepare specimen for microscope and etch in 2 to 5% nital (concentrated nitric acid in alcohol).3. For effective case depth, read from surface
48、to metallographic structures which have been shown tobe equivalent to 50 HRC.4. For total case depth, read to the line of demarcation between the case and core. In alloy steelsquenched from a high temperature, the line of demarcation is not sharp. Read all the darkened zonethat indicates a differenc
49、e in carbon from the uniform core structure.b. Annealed Condition1. For specimens previously hardened or not cooled under controlled conditions.2. The specimen to be annealed may be protected by copper plate or any suitable means forpreventing loss of carbon.3. Pack in a small, thin-wall container with a suitable material such as charcoal.4. Place container in furnace at 40 to 80 C (75 to 150 F) above the upper critical temperature (Ac3)for the core. (Generally an annealing temperature of 870 to 925 C (1600 to 1700 F) is satisfactory.)5
