1、Designation: B797 15Standard Test Method forSurface Finger-Oxide Penetration Depth and Presence ofInterparticle Oxide Networks in Powder Forged (PF) SteelParts1This standard is issued under the fixed designation B797; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in 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.1. Scope*1.1 This test method covers a metallographic method fordetermining the max
3、imum depth of surface finger-oxide pen-etration and the concentration of subsurface interparticle oxidenetworks in critical areas of powder forged steel parts.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard
4、 does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Document2.1 ASTM S
5、tandards:2E3 Guide for Preparation of Metallographic SpecimensE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.
6、1 surface finger-oxidessurface finger-oxides are sur-face oxides that follow prior particle boundaries into a powderforged part from the surface and cannot be removed byphysical means such as rotary tumbling. Examples of surfacefinger-oxides are shown in Fig. 1.3.1.2 interparticle oxide networksinte
7、rparticle oxide net-works are continuous or discontinuous oxides that follow priorparticle boundaries in powder forged parts. Examples ofinterparticle oxide networks are shown in Fig. 2.4. Summary of Test Method4.1 A section representing both surface and subsurfaceregions of a critical area is cut f
8、rom the powder forged part andmounted for metallographic grinding and polishing.4.2 For surface finger-oxide penetration, the polished andunetched sample is examined microscopically at a magnifica-tion of 400 to 500. The maximum depth of penetration ofsurface finger-oxides is measured.4.3 For interp
9、article oxide network concentration, the pol-ished and unetched sample is examined microscopically at amagnification of 200 to 500 to determine the presence ofinterparticle oxide networks.5. Significance and Use5.1 The presence of surface finger-oxide penetration andinterparticle oxide networks are
10、two of the properties used toevaluate powder forged steel parts for proper processing.Maximum acceptable depths of penetration of surface finger-oxide penetration and acceptable concentrations of subsurfaceinterparticle oxide networks depend on the component and itsservice environment.5.2 Results of
11、 tests may be used to qualify parts forshipment.6. Apparatus6.1 Equipment for the metallographic preparation of testspecimens.6.2 A metallographic microscope permitting observationand measurement up to a magnification of 500.7. Sampling7.1 A metallographic specimen shall be removed from thepowder fo
12、rged part to cover each designated critical area.Critical areas shall be defined by the applicable part drawing orthe purchaser order. Specimens shall be taken from the powderforged part in the condition in which it is to be supplied. The1This test method is under the jurisdiction of ASTM Committee
13、B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.11 on Near Full Density Powder Metallurgy Materials.Current edition approved Oct. 1, 2015. Published November 2015. Originallyapproved in 1988. Last previous edition approved in 2007 as B797 93(2007).
14、 DOI:10.1520/B0797-15.2For 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.*A Summary of Changes section appears a
15、t the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1FIG. 1 Example of Surface Finger-Oxide Penetration Extending Inward from the Powder Forged Part Surface (Shown more clearly athigh magnification.)B797 152FIG. 2
16、 Example of Interparticle Oxide Networks Within a Powder Forged Part (Shown more clearly at high magnification.)B797 153polished surface of the specimens shall be parallel to theforging direction, that is, parallel to the direction of travel ofthe forging punch.8. Procedure8.1 Preparation of Specime
17、nsIn mounting the specimenfor grinding and polishing, protection from rounding the edgeof the part is essential. In polishing the specimen it is importantthat a clean polish be obtained and that edge detail of the partnot be destroyed. Specimens shall be examined in the as-polished condition, free o
18、f the effects of any prior etching (ifused). It is recommended that the procedures described inMethods E3 be followed. Automated grinding and polishingprocedures are recommended.8.2 Measurement of Surface Finger-Oxide PenetrationDepthScan the perimeter of the metallographic specimen,initially at a m
19、agnification of 100, and carefully examine eachdesignated critical area at a higher magnification, for example,400 to 500. Measure the maximum depth of penetration ofsurface finger-oxides from the finished part surface in mi-crometres for each designated critical area.8.3 Measurement of Interparticl
20、e Oxide NetworkConcentrationScan the perimeter of the metallographicspecimen at a magnification of 100. Carefully examine eachdesignated critical area at a higher magnification, for example,200 to 500. Record the presence of any interparticle oxidenetworks in the designated critical areas.9. Report9
21、.1 The test report shall include the following information:9.1.1 Identification of the part and location of the testspecimen,9.1.2 The maximum depth of penetration of surface finger-oxides from the finished part surface in micrometres for eachdesignated critical area, and9.1.3 The presence or lack o
22、f interparticle oxide networks ineach designated critical area. If interparticle oxide networks arepresent, if possible, prepare a photomicrograph for recordpurposes and report the magnification used.10. Precision and Bias10.1 The precision of this test method is based on anintralaboratory study of
23、ASTM B797, Standard Test Methodfor Surface Finger Oxide Penetration Depth and Presence ofInterparticle Oxide Networks in Powder Forged (PF) SteelParts, conducted in 2014. A single laboratory participated inthis study, testing a powder forged connecting rod. Every “testresult” represents an individua
24、l determination. The laboratoryreported 20 replicate test results. Except for the use of only onelaboratory, Practice E691 was followed for the design andanalysis of the data; the details are given in ASTM ResearchReport No. B09-1023.310.1.1 Repeatability (r)The difference between repetitiveresults
25、obtained by the same operator in a given laboratoryapplying the same test method with the same apparatus underconstant operating conditions on identical test material withinshort intervals of time would in the long run, in the normal andcorrect operation of the test method, exceed the followingvalue
26、s only in one case in 20.10.1.1.1 Repeatability can be interpreted as maximum dif-ference between two results, obtained under repeatabilityconditions, which is accepted as plausible due to randomcauses under normal and correct operation of the test method.10.1.1.2 Repeatability limits are listed in
27、Table 1 below.10.1.2 Reproducibility (R)The difference between twosingle and independent results obtained by different operatorsapplying the same test method in different laboratories usingdifferent apparatus on identical test material would, in the longrun, in the normal and correct operation of th
28、e test method,exceed the following values only in one case in 20.10.1.2.1 Reproducibility can be interpreted as maximumdifference between two results, obtained under reproducibilityconditions, which is accepted as plausible due to randomcauses under normal and correct operation of the test method.10
29、.1.2.2 Reproducibility limits cannot be calculated from asingle laboratorys results. The reproducibility of this testmethod is being determined and will be available on or beforeDecember 2020.10.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E1
30、77.10.1.4 Any judgment in accordance with statement 10.1.1would normally have an approximate 95% probability of beingcorrect. The precision statistics obtained in this ILS must not,however, be treated as exact mathematical quantities which areapplicable to all circumstances and uses. The limited num
31、berof laboratories reporting replicate results essentially guaranteesthat there will be times when differences greater than predictedby the ILS results will arise, sometimes with considerablygreater or smaller frequency than the 95% probability limitwould imply. Consider the repeatability limit as a
32、 generalguide, and the associated probability of 95% as only a roughindicator of what can be expected.10.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.10.3 The precision stat
33、ement was determined through sta-tistical examination of 20 results, from a single laboratory, ona powder forged connecting rod.10.4 The test method for interparticle oxide network con-centration is a “go-no go” test designed to give a qualitativeestimate. This method will be subject to sample prepa
34、rationcare and to interpretation.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:B09-1023. ContactASTM CustomerService at serviceastm.org.TABLE 1 Finger-Oxide Penetration Depth (m)AverageRepeatabilityStandard DeviationRepeatabil
35、ity Limitx SrrPF Connecting Rod 53.3 0.98 2.7B797 15411. Measurement Uncertainty11.1 The precision of Test Method B797 shall be consideredby those performing the test when reporting surface finger-oxide penetration depth results.12. Keywords12.1 interparticle oxide networks; powder-forged (PF) steel
36、parts; surface finger-oxidesSUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this standard since the last issue(B79793(2007) that may impact the use of this standard.(1) Added a statement on units as subsection 1.2.(2) Changed the magnification in subsections 4.2 an
37、d 8.2 from400 to “from 400 to 500.”(3) Changed the magnification in subsection 4.3 and 8.3 from“200 to 400” to “from 200 to 500.”(4) Changed the magnification in subsection 6.2 to 500.(5) Added, “and report the magnification used” to subsection9.1.3.(6) Added a precision statement in Section 10.ASTM
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