1、Designation: F 2730/F 2730M 08Standard Specification forSilicon Nitride Cylindrical Bearing Rollers1This standard is issued under the fixed designation F 2730/F 2730M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of lastreapproval. 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 s
3、ilicon 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 o
4、f the other. Combining valuesfrom the two systems may result in nonconformance with thespecification.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 precedence. Nothing in this
5、document, however, super-sedes applicable laws and regulations unless a specific exemp-tion has been obtained.2.2 ASTM Standards:2C 1161 Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureC 1421 Test Methods for Determination of Fracture Tough-ness of Advanced Ceramics at Am
6、bient 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 CEN Standards:5EN
7、 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 Analysis3. Terminology3.1 Definitions of Terms
8、Specific to This Standard:3.1.1 chipsbreak-outs of material greater in extent than0.25 mm typically at the corner chamfers or the junction of thechamfers with the cylindrical surface or end face.3.1.2 cracksirregular, narrow breaks in the surface of theroller typically having a visible width of less
9、 than 0.002 mm.Most cracks are formed after densification but occasionallymay be present as material faults. Some cracks may not bevisible with normal white light microscopy and may only showup under ultraviolet light after processing with a suitablefluorescent penetrant.3.1.3 cutsshort linear or ci
10、rcumferential grooves having awidth of more than 0.005 mm and a length of more than 0.20mm. Cuts are normally assessed under roller surface appear-ance but large and/or numerous cuts can be considered defects.3.1.4 flatsflat bands running along the length of thecylindrical part of the roller, usuall
11、y caused by a stop inrotation of the roller during machining. Flats can also beformed at one end only by incorrect approach into a machiningoperation.3.1.5 groovesshallow machining marks having a width ofmore than 0.005 mm extending more than14 of the circum-ference on the cylindrical surface or hav
12、ing a length of morethan14 of the roller diameter on the end faces.3.1.6 inclusionsisolated areas of ceramic second phasesor metallic appearing phases. Inclusions are often the result ofcontamination by foreign material during the roller blankmanufacturing process.3.1.7 material lotsingle process lo
13、t of silicon nitride rawpowder received from a material supplier.3.1.8 mean roller diameterone half the sum of the largestand smallest of individual diameters measured in a single radialplane.1This specification is under the jurisdiction ofASTM Committee F34 on RollingElement Bearings and is the dir
14、ect responsibility of Subcommittee F34.01 onRolling Element.Current edition approved Nov. 15, 2008. Published January 2009.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, re
15、fer to the standards Document Summary page onthe ASTM website.3Available from American Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org.4Available from Japanese Standards Organization (JSA), 4-1-24 AkasakaMinato-Ku,
16、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.9 mean ro
17、ller lengthone half the sum of the largestand smallest lengths measured on a roller.3.1.10 metallic smearsmetallic material from machiningor measuring equipment transferred onto the roller surface.3.1.11 pitsvoids or cavities in the roller surface. Pits canbe formed by severe material pullout during
18、 roller finishing.Pits can also be a result of the breakout of inclusions duringmachining.3.1.12 porositysmall, closely spaced voids permeating aregion of the roller surface or the whole roller.3.1.13 pressing defectsthe result of cracks in roller pre-forms prior to densification. Some pressing defe
19、cts heal moreor less completely on densification resulting 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 c
20、racks or fissures.3.1.14 snowflakesregions of localized incomplete densi-fication or regions in which the glassy phase is incompletelybonded to the silicon nitride grains. Snowflakes show up aswhite dendritic features when viewed with oblique illuminationor with ultraviolet light after processing wi
21、th a fluorescentpenetrant.3.1.15 stepsregions at the edge of a roller end face thathave been machined to a lower depth than the rest of the endface.3.1.16 surface roughness (Ra)surface irregularities withrelative small spacings, which usually include irregularitiesresulting from the method of manufa
22、cture being used, otherinfluences, or both.3.1.17 tearscircumferential machining marks associatedwith lateral surface cracks.3.1.18 unfinished areasregions on the roller surfaces thatshould be machined but have not been machined at all, or havenot been completely machined and finished, due to either
23、 faultsin blank geometry or errors in the machining process.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. Suitable for use in the most
24、 demand-ing applications. This group adds high reliability and durabilityfor 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 Cla
25、ss IIILower grade of material for low dutyapplications only. This group of applications primarily takesadvantage of silicon nitride material properties (for example,light weight, chemical inertness, lubricant life extension due todissimilarity with race materials, etc.).4.1.4 A material grade approv
26、ed 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 valueis that of nominal diameter (for
27、 example, 939 mm, 18321mm).5.2 Rollers are normally manufactured to millimeter 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 of pressing limitations. In thes
28、e 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 surfaces. Corner chamfers need no
29、tbe 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 Silicon nitride rollers should be produced from eithersilicon ni
30、tride powder having the compositional limits listed inTable 1 or from silicon metal powder, which after nitridationcomplies with the compositional limits listed in Table 1.6.3 Composition is measured in weight percent. Testingshall be carried out by a facility qualified and approved by thesupplier.
31、Specific equipment, tests, and/or methods are subjectto agreement between suppliers and their customers.6.4 The following compounds may be added to promotedensification and/or enhance product performance and quality.The following may be added as oxides, nitrides, oxynitrides, ormixtures:6.4.1 Alumin
32、um,6.4.2 Magnesium,6.4.3 Barium,6.4.4 Lanthanum,6.4.5 Yttrium,6.4.6 Calcium, and6.4.7 Other rare earths.6.5 The following may be added as nitrides, oxynitrides, orcarbonitrides:6.5.1 Titanium,6.5.2 Tantalum, and6.5.3 Zirconium.6.6 Aluminum silicon oxynitrides (aluminum nitride poly-types) may be add
33、ed to promote densification.TABLE 1 Compositional Limits for Starting Silicon NitridePowders or Silicon Powder Converted to Silicon NitrideAConstituents Limits (wt %)Silicon nitride 97.0 minFree silicon 0.3 maxCarbon 0.3 maxIron 0.5 maxAOther impurities or elements such as sodium, potassium, chlorin
34、e, etc.individually shall not exceed 0.02 wt % max.F 2730/F 2730M 0826.7 Iron oxides may be added to promote densification withthe total iron content for the final product not to exceed 1.0weight %.6.8 Precautions should be taken to minimize contaminationby foreign materials during all stages of pro
35、cessing up to andincluding densification.6.9 A residual content of up to 2 % tungsten carbide frompowder processing is allowable.6.10 Final composition shall meet and be reported accord-ing to the specification of the individual supplier.6.11 Notification will be made upon process changes.6.12 Speci
36、fic requirements such as specific material gradedesignation, physical/mechanical property requirements (forexample, density) or quality or testing requirements shall beestablished by specific application. The special requirementsshall be in addition to the general requirements established inthis spe
37、cification.6.13 Typical mechanical properties will fall within the rangelisted in Table 2. Individual requirements 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 proper
38、ties indicated by(+), the provision of the data is not mandatory.7. Physical Properties7.1 The following physical 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
39、 determinations shall exceed the minimum valuesgiven in Table 3. Either 3-point or 4-point test methods may beused for flexural strength, which should be measured inaccordance with Test Method C 1161 (size B), CEN 843-5, orJIS R 1601. Weibull modulus for each test series shall alsoexceed the minimum
40、 permitted values given in Table 3.Ifasample set of specimens for a material lot does not meet theWeibull modulus requirement in Table 3, then a second sampleset may be tested to establish conformance.7.1.2 The hardness (HV) shall be determined by the Vickersmethod (see Annex A1) using a load of at
41、least 5 kg but notexceeding 20 kg. Fracture resistance shall be measured byeither an indentation technique (seeAnnexA1) or by a standardfracture toughness test method. Average values for hardnessand fracture resistance shall exceed the minimum of values forthe specified material class given in Table
42、 4.7.1.3 Microstructure constituents visible at magnification inthe range 3100 to 3200 shall not exceed the maximum valuesgiven in Table 5 for the specified material class.7.1.4 The number of ceramic metallic or mixed inclusionsobserved in transverse sections shall not exceed the limitsgiven in Tabl
43、e 6.7.1.5 Macrostructure variation visible at 13 on a polishedsection is not permissible.7.1.6 Density variation from the mean value of a sample ofat least 10 pieces taken from a batch of components manufac-tured under the same conditions shall not exceed the values for3 times the standard deviation
44、 (3 3 sigma) given in Table 7,according to the volume of the component after any finishingoperations and the specified material class.8. Inspection and Verification8.1 The intent of this section is to list potential defects andmethods of inspection of finished rollers. The type of defects,methods of
45、 inspection, and limits should be agreed upon by thecustomer and vendor to meet the specific requirements for agiven application.8.2 Unless otherwise specified, all dimensional and forminspections shall be performed under the following conditions:8.2.1 TemperatureRoom ambient 20 to 25C 68 to 77F.8.2
46、.2 Humidity50 % relative, maximum.8.3 Certain manufacturer to manufacturer or lot to lotvariation in color is acceptable. Color variation within a singleroller should be investigated per 8.4.TABLE 2 Typical Mechanical PropertiesAProperties Minimum MaximumDensity, g/cc lb/ft3 3.0 187 3.4 212Elastic m
47、odulus, GPa ksi 270 39 150 330 47 850Poissons ratio 0.23 0.29Thermal conductivity,W/m-K Btu/h-ft-F 20C (room temp.)20 11.5 38 21.9Specific heat, J/kg-KBtu/1bm-F650 0.167 800 0.191Coefficient of thermalexpansion, 3106/C(room temp, to 500C)2.3 3.4+ Resistivity, Ohm-m 10101016+ Compressive strength,MPa
48、 ksi3000 435ASpecial material data should be obtained from individual suppliers.TABLE 3 Minimum Values for Mean Flexural Strength andWeibull ModulusMaterial ClassUnit I II IIITransverse-rupture strengthA3 point s3,40(s3,30)MPa 900 920 800 825 600 625Weibull modulus 12 9 7Transverse-rupture strengthA
49、4-point s4,40(s4,30)MPa 765 805 660 705 485 530Weibull modulus 12 9 7AThe flexural strength equivalents are based on Weibull volume or surfacescaling using the value of m for each cell and are rounded to the nearest 5 MPa.sn,L= denotes the flexure strength, n=3or4point,onspans of size L.s4,40= 660 MPa means the four point flexure strength, on 40 mm spans is 660MPa as per Test Method C 1161 (size B) and CEN EN 843-1.s4,30= 705 MPa means the four point flexure strength, on 30 mm spans is 705MPa as per
