1、Designation: B795 07B795 13Standard Test Method forDetermining the Percentage of Alloyed or Unalloyed IronContamination Present in Powder Forged (PF) SteelMaterials1This standard is issued under the fixed designation B795; the number immediately following the designation indicates the year oforigina
2、l adoption 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 procedure for determinin
3、g the percentage of alloyed or unalloyed ironcontamination present in powder forged low-alloy steel materials and the percentage of alloyed iron contamination in powderforged iron and carbon steel materials.1.2 PropertyThe values stated in SI units are the standard. to be regarded as standard. No ot
4、her units of measurement areincluded in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability o
5、f regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B243 Terminology of Powder MetallurgyE3 Guide for Preparation of Metallographic SpecimensE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to
6、Determine the Precision of a Test Method3. Terminology3.1 DefinitionsDefinitions of powder metallurgy terms can be found in Terminology B243.Additional descriptive informationis available in the Related Material Section of Vol 02.05 of the Annual Book of ASTM Standards.3.2 Definitions of Terms Speci
7、fic to This Standard:3.2.1 cross product cross-product contaminationthe unintentional mixing of powders with distinct differences in chemicalcomposition.4. Summary of Test Method4.1 A section representing the core region is taken from the powder forged material and prepared for metallographicexamina
8、tion.4.2 The polished and etched sample is examined microscopically at a magnification of 100 and a systematic point count madeof features with etching characteristics different from that of the matrix.4.3 The amount of contaminant is reported as a percentage to the nearest 0.1 %.5. Significance and
9、 Use5.1 Cross product Cross-product contamination occurs whenever alloy steel powders are processed in the same equipment asiron powders.1 This test method is under the jurisdiction ofASTM Committee B09 on Metal Powders and Metal Powder Productsand is the direct responsibility of Subcommittee B09.11
10、on Near Full Density Powder Metallurgy Materials.Current edition approved Oct. 1, 2007Oct. 1, 2013. Published November 2007 November 2013. Originally approved in 1988. Last previous edition approved in 20022007as B795 93B795 07.(2002)e1. DOI: 10.1520/B0795-07.10.1520/B0795-13.2 For referencedASTM st
11、andards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an
12、 ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as publis
13、hed by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 Unalloyed iron particles, because they may not harden upon heat
14、 treatment, are a potential source of soft spots in low-alloysteel parts.5.3 Alloyed iron particles, having higher hardenability than an iron or carbon steel matrix, are a potential source of hard spots.5.4 Hard or soft spots may cause problems in service or machining.5.5 The results of the tests ma
15、y be used to qualify parts for shipment in accordance with guidelines agreed between purchaserand manufacturer or to check the suitability of mixes for use in powder forging.6. Apparatus6.1 Equipment for the metallographic preparation of test specimens.6.2 A metallographic microscope permitting obse
16、rvation and measurement at a magnification of 100.7. Sampling7.1 Take a metallographic specimen from the powder forged material. The polished surface of the specimen should be not lessthan that required to superimpose 2500 grid points at a magnification of 100. Multiple sections are permitted in ord
17、er to obtainthe necessary area for measurement on small parts or test pieces.7.2 The polished surface shall be parallel to the direction of forging, that is, parallel to the direction of travel of the forgingpunch, or as specified in the contract or purchase order, and shall represent an area away f
18、rom the surface of the material.8. Procedure8.1 Preparation of Specimens:8.1.1 PolishingIn polishing the specimens, it is highly important that the polished surface be free from artifacts and debris.It is recommended that the procedures described in Practice E3 be followed. Automated grinding and po
19、lishing procedures arerecommended.8.1.2 EtchingLightly etch the freshly polished specimen with 2 % nital (2 mL nitric acid, 98 mL ethyl alcohol). Next, etchthe polished and lightly etched specimen by immersion in a freshly prepared aqueous solution containing 3 g potassiummetabisulfite and 10 g sodi
20、um thiosulfate per 100 mL. Rinse the specimen in running water, then rinse with low residue alcoholand dry with a blast of dry air.8.1.2.1 The etching time will depend on alloy type, carbon content, and microstructure. The greater the alloy content, the slowerthe etching rate; the greater the carbon
21、 content, the faster the etching rate.8.1.2.2 Agood contrast is developed between the matrix and the contaminant because of a combination of etching and staining.The areas containing the highest alloy content are the least affected. Unalloyed iron will become darkened in a low-alloy matrixand low-al
22、loy particles will remain light in an iron or carbon steel matrix. In a low-alloy matrix, contaminant particles of anotherlow-alloy powder can be distinguished from unalloyed iron contamination because the particles etch differently (see Fig. 1 and Fig.2).FIG. 1 Illustration of Iron and Low-Alloy Co
23、ntaminants in PF-4650B795 1328.2 ExaminationSuperimpose a grid of between 100 and 250 systematically placed points upon a 100 magnified image (thatis, a field of view) of the polished and etched specimen. Count and record the number of grid points falling upon contaminantparticles; if necessary, a s
24、eparate count may be kept to distinguish between alloy contamination and unalloyed iron contaminationin low-alloy steel materials, or, types of alloy contaminant in iron or carbon steel materials. (See Note 1.) Counting of randomlyselected discrete fields should be continued until at least 2500 grid
25、 points have been superimposed on the specimen. The totalnumber of points falling on contaminant particles for all fields counted shall be divided by the total number of grid pointssuperimposed and multiplied by 100 to determine the area percentage of contamination.NOTE 1Any grid point that falls on
26、 a contaminant particle boundary should be counted as one half. To avoid bias, questionable points should becounted as one half.9. Report9.1 Report the area percentage of contaminant to the nearest 0.1 %.10. Precision and Bias10.1 The precision and bias that can be expected through the use of this t
27、est method is currently under review by SubcommitteeB09.11 on Near Full Density Powder Metallurgy Materials.Precision:10.1.1 The precision of this test method is based on an intralaboratory study of Test Method B795, conducted in 2012.Asinglelaboratory participated in this study, testing one materia
28、l for alloy contamination and iron contamination. Every “test result”represents an individual determination. The laboratory reported fifteen replicate test results for each analysis. Except for the useof only one laboratory, Practice E691 was followed for the design and analysis of the data; the det
29、ails are given inASTM ResearchReport No. B09-1019.33 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:B09-1019. Contact ASTM CustomerService at serviceastm.org.FIG. 2 Illustration of Low-Alloy Contaminant in PF-1060TABLE 1 Alloy
30、Contamination (%)AveragexRepeatability StandardDeviationSrRepeatability LimitrA 1.3 0.26 0.73TABLE 2 Iron Contamination (units)AveragexRepeatability StandardDeviationSrRepeatability LimitrB 1.2 0.20 0.56B795 13310.1.2 Repeatability (r)The difference between repetitive results obtained by the same op
31、erator in a given laboratory applyingthe same test method with the same apparatus under constant operating conditions on identical test material within short intervalsof time would in the long run, in the normal and correct operation of the test method, exceed the following values only in one casein
32、 20.10.1.2.1 Repeatability can be interpreted as maximum difference between two results, obtained under repeatability conditions,that is accepted as plausible due to random causes under normal and correct operation of the test method.10.1.2.2 Repeatability limits are listed in Table 1 and Table 2.10
33、.1.3 Reproducibility (R)The difference between two single and independent results obtained by different operators applyingthe same test method in different laboratories using different apparatus on identical test material would, in the long run and in thenormal and correct operation of the test meth
34、od, exceed the following values only in one case in 20.10.1.3.1 Reproducibility can be interpreted as maximum difference between two results, obtained under reproducibilityconditions, that is accepted as plausible due to random causes under normal and correct operation of the test method.10.1.3.2 Re
35、producibility limits cannot be calculated from a single laboratorys results.10.1.4 The above terms (repeatability limit and reproducibility limit) are used as specified in Practice E177.10.1.5 Any judgment in accordance with statement 10.1.2 would normally have an approximate 95 % probability of bei
36、ngcorrect, however the precision statistics obtained in this ILS must not be treated as exact mathematical quantities which areapplicable to all circumstances and uses. The limited number of laboratories reporting replicate results essentially guarantees thatthere will be times when differences grea
37、ter than predicted by the ILS results will arise, sometimes with considerably greater orsmaller frequency than the 95 % probability limit would imply. Consider the repeatability limit as a general guide, and theassociated probability of 95 % as only a rough indicator of what can be expected.10.1.6 T
38、he precision statement was determined through statistical examination of 30 results, from a single laboratory, on the twomaterials described below. 15 repetitions were performed for each material. The reproducibility of this test method is beingdetermined and will be available on or before December
39、2018.310.1.6.1 Material A : Ancorsteel 1000B + 0.22 % graphite + 1 % Ancorsteel 737 SH10.1.6.2 Material B : Ancorsteel 737 SH + 0.22 % graphite + 1 % Ancorsteel 1000B10.2 Bias:10.2.1 No information can be presented on the bias of the procedure in Test Method B795 for measuring the percentage ofalloy
40、ed or unalloyed contamination present in powder-forged steel materials because no material having an accepted referencevalue is available.11. Measurement Uncertainty11.1 The precision of Test Method B795 shall be considered by those performing the test when reporting the percentage ofalloyed or unal
41、loyed contamination present in powder forged steel materials.12. Keywords12.1 cross product cross-product contamination; powder forging (PF); powder forged (PF) parts and test specimens; powderforged (PF) steelsSUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this s
42、tandard since the last issue (B795-93(Reapproved 2002)- 07) e1) that may impact the use of this standard.(1) Changed “Parts” to “Materials” in title of standard.(1) Revised statement on units in Section 1.2.(2) Added repeatability data in Section 10.1.(3) Added a statement on measurement uncertainty
43、 in Section 11.(4) Added a statement on bias in Section 10.2.(2) Changed “parts” to “materials” in Section 1.1 (two places).(3) Changed “part” to material in Section 4.1.(4) Added, “or to check the suitability of mixes for use in powder forging.” to Section 5.5.(5) Changed “part” to “material” in Se
44、ction 7.1 and added “or test pieces” at the end of the sentence.B795 134(6) Changed “part” to “material” in Section 7.2.(7) Changed “parts” to “materials” in Section 8.2 (two places).(8) Added “and test specimens” after powder forged parts in Section 11.ASTM International takes no position respectin
45、g 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 standa
46、rd 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 International
47、 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 below.Thi
48、s 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/).B795 135
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