1、Designation: F2730/F2730M 11Standard 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.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 docu
5、ment, 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 Advanced Ceramics at Ambient
6、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 843-1
7、 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 Specif
8、ic 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 than
9、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 circumfe
10、rential 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, usually caus
11、ed 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 having a
12、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 lot of s
13、ilicon nitride rawpowder received from a material supplier.1This specification is under the jurisdiction ofASTM Committee F34 on RollingElement Bearings and is the direct responsibility of Subcommittee F34.01 onRolling Element.Current edition approved June 1, 2011. Published June 2011. Originallyapp
14、roved in 2008. Last previous edition approved in 2008 as F2708/F2708M08.DOI: 10.1520/F2730_F2730M-11.2For 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 D
15、ocument 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, Tokyo, 107-8440, Japan
16、, 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.3.1.8 mean roller diameterone half
17、the sum of the largestand smallest of individual diameters measured in a single radialplane.3.1.9 mean roller 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 surfac
18、e.3.1.11 pitsvoids or cavities in the roller surface. Pits canbe formed by severe material pullout during 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
19、.1.13 pressing defectsthe result of cracks in roller pre-forms prior to densification. Some pressing defects 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
20、healedor partially healed pressing defects. Unhealed or open pressingdefects can have the appearance of cracks 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 aswh
21、ite dendritic features when viewed with oblique illuminationor with ultraviolet light after processing with 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 irregulari
22、ties withrelative small spacings, which usually include irregularitiesresulting from the method of manufacture 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 ma
23、chined but have not been machined at all, or havenot been completely machined and finished, due to either 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
24、Class IHighest grade of material in terms of prop-erties and microstructure. Suitable for use in the most 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 addr
25、esses the concerns of rollerdefects as is relative to fatigue life, levels of torque, and noise.4.1.3 Class IIILower grade of material for low dutyapplications only. This group of applications primarily takesadvantage of silicon nitride material properties (for example,light weight, chemical inertne
26、ss, lubricant life extension due todissimilarity with race materials, etc.).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 u
27、sing a nomi-nal diameter (D) and nominal length (L) where the first valueis that of nominal diameter (for 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 pra
28、cticallimitation to this as L becomes significantly larger than Dbecause of 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 ni
29、tride rollers should be machined entirely overthe diameter and end face surfaces. 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 requirement
30、s will apply to all material classes.6.2 Silicon nitride rollers should be produced from eithersilicon nitride 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 meas
31、ured in weight percent. Testingshall be carried 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 qual
32、ity.6.5 Iron oxides may be added to promote 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 o
33、f up to 2 % tungsten carbide frompowder processing 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
34、/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 specification.TABLE 1 Compositional Limits for Starting Silicon NitrideP
35、owders 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, chlorine, etc.individually shall not exceed 0.02 wt % max.F2730/F2730M 1126.11 Typical mechan
36、ical 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 properties indicated by(+), the prov
37、ision 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 determinations shall exceed t
38、he 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 C1161 (size B), CEN 843-5, orJIS R 1601. Weibull modulus for each test series shall alsoexceed the minimum permitted values given in Tabl
39、e 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 least 5 kg but notexceeding 20
40、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 4.7.1.3 Microstructure constit
41、uents 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 Table 6.7.1.5 Macrostructure variat
42、ion 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 (3 3 sigma) given in Table 7,a
43、ccording 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 inspection, and limits should
44、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.8.2.2 Humidity50 % relative, maxim
45、um.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 modulus, GPa ksi 270 39 150 330
46、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 ksi3000 435ASpecial material d
47、ata 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 strengthA4-point s4,40(s4,30)MPa 765 805
48、 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
49、 strength, on 40 mm spans is 660MPa as per Test Method C1161 (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 JIS R 1601.TABLE 4 Minimum Values for Hardness and ToughnessMaterial ClassProperty Unit Load I II IIIHardnessHV5 kg/mm25 kg 1500 1400 1350HV10 10 kg 1480 1380 1325HV20 20 kg 1460 1360 1300Indentation Fracture Resistance, IFR(or“TP”)(Annex A1)MPa=m 6.0 5.0 5.0Fracture Toughness, K(Test Methods C1421 or JIS R 1607)MPa=m 6.0 5.0 5.
