1、Designation: F2730/F2730M 18Standard Specification forSilicon Nitride Cylindrical Bearing Rollers1This standard is issued under the fixed designation F2730/F2730M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers the establishment of the basicquality, physical/mechanical property, and test requirementsfor silic
3、on nitride rollers Classes I, II, and III to be used forcylindrical roller bearings.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system are not exact equivalents; therefore, each systemmust be used independently of th
4、e other. Combining valuesfrom the two systems may result in nonconformance with thespecification.1.3 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International S
5、tandards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 Order of Precedence:2.1.1 In the event of a conflict between the text of thisdocument and the references herein, the text of this documenttakes precedenc
6、e. Nothing in this document, however, super-sedes applicable laws and regulations unless a specific exemp-tion has been obtained.2.2 ASTM Standards:2C1161 Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureC1421 Test Methods for Determination of Fracture Tough-ness of Advanc
7、ed Ceramics at Ambient Temperature2.3 ASME Standard:3B 46.1 Surface Texture (Surface Roughness, Waviness, andLay)2.4 JIS Standards:4R 1601 Testing Method for Flexural Strength (Modulus ofRupture) of High Performance CeramicsR 1607 Testing Method for Fracture Toughness of HighPerformance Ceramics2.5
8、CEN Standards:5EN 843-1 Advanced Technical CeramicsMonolithicCeramicsMechanical Properties at Room Temperature,Part 1, Determination of Flexural StrengthENV 843-5 Advanced Technical CeramicsMonolithicCeramicsMechanical Properties at Room Temperature,Part 5, Statistical Analysis2.6 ISO Standard:6Hard
9、metals-Metallographic determination of porosity anduncombined carbon3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 ceramic second phase, nsintering additive basedphases, for example yttria and alumina, which appear darker orlighter than the silicon nitride matrix but are not
10、highlyreflective in nature when viewed under reflected light micros-copy and bright field illumination.3.1.2 chips, nbreak-outs of material greater in extent than0.25 mm 0.1 in. typically at the corner chamfers or thejunction of the chamfers with the cylindrical surface or endface.3.1.3 color variat
11、ion, nan area that appears lighter ordarker than the surrounding area under reflected light micros-copy but with no discernible physical discontinuity associatedwith it.1This specification is under the jurisdiction ofASTM Committee F34 on RollingElement Bearings and is the direct responsibility of S
12、ubcommittee F34.01 onRolling Element.Current edition approved April 1, 2018. Published July 2018. Originallyapproved in 2008. Last previous edition approved in 2014 as F2708/F2708M14.DOI: 10.1520/F2730_F2730M-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cus
13、tomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Two Park Ave., New York, NY 10016-5990, http:/www.as
14、me.org.4Available from Japanese Standards Organization (JSA), 4-1-24 AkasakaMinato-Ku, Tokyo, 107-8440, Japan, http:/www.jsa.or.jp.5Available from European Committee for Standardization (CEN), 36 rue deStassart, B-1050, Brussels, Belgium, http:/www.cenorm.be.6Available from International Organizatio
15、n for Standardization (ISO), ISOCentral Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed
16、 in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.3.1 DiscussionColor
17、 variation is often not visibleunder scanning electron microscopy (SEM) examination.3.1.4 cracks, nirregular, narrow breaks in the surface ofthe roller typically having a visible width of less than 0.002mm. 0.00008 in.3.1.4.1 DiscussionMost cracks are formed after densifica-tion but occasionally may
18、 be present as material faults. Somecracks may not be visible with normal white light microscopyand may only show up under ultraviolet light after processingwith a suitable fluorescent penetrant.3.1.5 cuts, nshort linear or circumferential grooves havinga width of more than 0.005 mm 0.002 in. and a
19、length ofmore than 0.20 mm 0.008 in. Cuts are normally assessedunder roller surface appearance but large or numerous cuts, orboth can be considered defects.3.1.6 flats, nflat bands running along the length of thecylindrical part of the roller, usually caused by a stop inrotation of the roller during
20、 machining.3.1.6.1 DiscussionFlats can also be formed at one endonly by incorrect approach into a machining operation.3.1.7 grooves, nshallow machining marks having a widthof more than 0.005 mm 0.002 in. extending more than onequarter of the circumference on the cylindrical surface orhaving a length
21、 of more than one quarter of the roller diameteron the end faces.3.1.8 inclusion, nany discrete imhomogeneity in the mi-crostructure that is not intended to be included in the material.3.1.8.1 DiscussionInclusions typically consist of foreignmaterial as a result of unintended external powder contami
22、na-tion and resulting reaction product after sintering.3.1.9 material lot, nsingle process lot of a blended powder(blended with additives), produced from a single lot of siliconnitride or silicon metal raw powder received from a materialsupplier.3.1.9.1 DiscussionWhat constitutes a “single process l
23、ot”of blended powder can vary depending on the standardpractices of the vendor and the requirements of the customerand application. For example, for many customers/applications, combining multiple mill charges from one rawmaterial lot into a single material lot is acceptable while forothers, each mi
24、ll charge would be considered a separatematerial lot. It is difficult, if not impossible, for a singledefinition of material lot to apply to all applications. Thematerial lot should be defined such that application-appropriatetraceability is maintained and adequate testing appropriate forthe intende
25、d application is performed to ensure that thechemistry and material properties of densified parts meetspecifications. The material lot requirements should be dis-cussed and agreed between the vendor and customer.3.1.10 mean roller diameter, none half the sum of thelargest and smallest of individual
26、diameters measured in asingle radial plane.3.1.11 mean roller length, none half the sum of the largestand smallest lengths measured on a roller.3.1.12 metallic phase, nmaterial phase that is highlyreflective when viewed by reflected light microscopy andbright field illumination.3.1.13 metallic smear
27、s, nmetallic material from machin-ing or measuring equipment transferred onto the roller surface.3.1.14 pits, nvoids or cavities in the roller surface.3.1.14.1 DiscussionPits can be formed by severe materialpullout during roller finishing. Pits can also be a result of thebreakout of inclusions durin
28、g machining.3.1.15 porosity, nsmall, closely spaced voids permeating aregion of the roller surface or the whole roller.3.1.16 pressing defects, nthe result of cracks in rollerpreforms prior to densification.3.1.16.1 DiscussionSome pressing defects heal more orless completely on densification resulti
29、ng in a region ofmaterial with slightly different composition and optical char-acteristics than the rest of the roller. These are known as healedor partially healed pressing defects. Unhealed or open pressingdefects can have the appearance of cracks or fissures.3.1.17 raw material lot, nsingle proce
30、ss lot of raw siliconnitride or raw silicon metal powder received from a materialsupplier.3.1.18 scratches, nnarrow, linear, shallow abrasions onthe surface.3.1.19 snowflakes, nregions of microporosity in the grainboundary phase that often display a dendritic appearance.3.1.19.1 DiscussionSnowflakes
31、 show up as white den-dritic features when viewed with oblique illumination or withultraviolet light after processing with a fluorescent penetrant.The individual micropores are often submicron in size and thesnowflakes can range in size from less than 10 m .00039 in.to over 1,000 m .039 in in extrem
32、e cases.3.1.20 steps, nregions at the edge of a roller end face thathave been machined to a lower depth than the rest of the endface.3.1.21 surface roughness, Ra, nsurface irregularities withrelative small spacings, which usually include irregularitiesresulting from the method of manufacture being u
33、sed, otherinfluences, or both.3.1.22 tears, ncircumferential machining marks associ-ated with lateral surface cracks.3.1.23 unfinished areas, nregions on the roller surfacesthat should be machined but have not been machined at all, orhave not been completely machined and finished, because ofeither f
34、aults in blank geometry or errors in the machiningprocess.4. Classification4.1 Silicon nitride materials for bearing applications arespecified according to the following material classes:4.1.1 Class IHighest grade of material in terms of prop-erties and microstructure and suitable for use in the mos
35、tdemanding applications. This group adds high reliability anddurability for extreme performance requirements.4.1.2 Class IIGeneral class of material for most bearingapplications. This group addresses the concerns of rollerdefects as is relative to fatigue life, levels of torque, and noise.4.1.3 Clas
36、s IIILower grade of material for low dutyapplications only. This group of applications primarily takesF2730/F2730M 182advantage of silicon nitride material properties (for example,light weight, chemical inertness, lubricant life extension be-cause of dissimilarity with race materials, and so forth.)
37、.4.1.4 A material grade approved as a Class I material maybe supplied where Class II or III is specified and, similarly, aClass II material for a Class III.5. Roller Dimensions5.1 Cylindrical rollers are generally identified using a nomi-nal diameter (D) and nominal length (L) where the first valuei
38、s that of nominal diameter (for example, 9 9 mm, 18 21mm).5.2 Rollers are normally manufactured to millimetre dimen-sions with D equal to L. However, many variations exist whereL is larger or smaller than D. There may be a practicallimitation to this as L becomes significantly larger than Dbecause o
39、f pressing limitations. In these cases, the roller blanksupplier should be consulted.5.3 There should be sufficient stock allowance on the rollerblank so that all surface skin effects are removed duringmachining.5.4 Silicon nitride rollers should be machined entirely overthe diameter and end face su
40、rfaces. Corner chamfers need notbe machined providing the corners are uniform and have asmooth transition from the diameter to the end face.6. Material6.1 Unless otherwise specified, physical and mechanicalproperty requirements will apply to all material classes.6.2 To be classified as Class I, sili
41、con nitride rollers shall beproduced from either silicon nitride powder having the com-positional limits listed in Table 1 or from silicon metal powder,which, after nitridation, complies with the compositional limitslisted in Table 1.6.3 Composition is measured in weight percent. Testingshall be car
42、ried out by a facility qualified and approved by thesupplier. Specific equipment, tests, and/or methods are subjectto agreement between suppliers and their customers.6.4 Compounds may be added to promote densification andenhance product performance and quality.6.5 Iron oxides may be added to promote
43、 densification withthe total iron content for the final product not to exceed 1.0weight %.6.6 Precautions should be taken to minimize contaminationby foreign materials during all stages of processing up to andincluding densification.6.7 A residual content of up to 2 % tungsten carbide frompowder pro
44、cessing is allowable.6.8 Final composition shall meet and be reported accordingto the specification of the individual supplier.6.9 Notification will be made upon process changes.6.10 Specific requirements such as specific material gradedesignation, physical/mechanical property requirements (forexamp
45、le, density) or quality or testing requirements shall beestablished by specific application. The special requirementsshall be in addition to the general requirements established inthis specification.6.11 Typical mechanical properties will fall within the rangelisted in Table 2. Individual requiremen
46、ts may have tighterranges. The vendor shall certify that the silicon nitride materialsupplied has physical and mechanical properties within therange given in Table 2. In the case of properties indicated by(+), the provision of the data is not mandatory.7. Physical Properties7.1 The following physica
47、l properties shall be measured, ata minimum, on each material lot.7.1.1 Average values for room temperature rupture strength(bend strength/modulus of rupture) for a minimum of 20individual determinations shall exceed the minimum valuesgiven in Table 3. Either 3-point or 4-point test methods may beus
48、ed for flexural strength, which should be measured inaccordance with Test Method C1161 (size B), EN 843-5, or JISR 1601. Weibull modulus for each test series shall also exceedthe minimum permitted values given in Table 3. If a sample setof specimens for a material lot does not meet the Weibullmodulu
49、s requirement in Table 3, then a second sample set maybe tested to establish conformance.7.1.2 The hardness (HV) shall be determined by the Vickersmethod (see AnnexA1) using a load of at least 5 kg 11 lbs butnot exceeding 20 kg 44 lbs. Fracture resistance shall bemeasured by either an indentation technique (see AnnexA1)orby a standard fracture toughness test method. Average valuesfor hardness and fracture resistance shall exceed the minimumof values for the specified material class given in Table 4.7.1.3 Microstructur
