1、Designation: F2730/F2730M 11F2730/F2730M 13Standard 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
2、year of last revision. 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 basic quality, physical/mechanical property, and test requi
3、rements forsilicon nitride rollers Classes I, II, and III to be used for cylindrical roller bearings.1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem are not exact equivalents; therefore, each system must be used
4、independently of the other. Combining values from the twosystems may result in nonconformance with the specification.2. Referenced Documents2.1 Order of Precedence:2.1.1 In the event of a conflict between the text of this document and the references herein, the text of this document takesprecedence.
5、 Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has beenobtained.2.2 ASTM Standards:2C1161 Test Method for Flexural Strength of Advanced Ceramics at Ambient TemperatureC1421 Test Methods for Determination of Fracture Toughness of Advanced Ce
6、ramics at Ambient Temperature2.3 ASME Standard:3B 46.1 Surface Texture (Surface Roughness, Waviness, and Lay)2.4 JIS Standards:4R 1601 Testing Method for Flexural Strength (Modulus of Rupture) of High Performance CeramicsR 1607 Testing Method for Fracture Toughness of High Performance Ceramics2.5 CE
7、N Standards:5EN 843-1 Advanced Technical CeramicsMonolithic CeramicsMechanical Properties at Room Temperature, Part 1,Determination of Flexural StrengthENV 843-5 Advanced Technical CeramicsMonolithic CeramicsMechanical Properties at Room Temperature, Part 5,Statistical Analysis2.6 ISO Standard:6Hard
8、metals-Metallographic determination of porosity and uncombined carbon3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 ceramic second phase, nadditive phases, for example yttria and alumina, which appear darkeror lighter than the siliconnitride matrix but are not highly reflecti
9、ve in nature.1 This specification is under the jurisdiction of ASTM Committee F34 on Rolling Element Bearings and is the direct responsibility of Subcommittee F34.01 on RollingElement.Current edition approved June 1, 2011Oct. 1, 2013. Published June 2011October 2013. Originally approved in 2008. Las
10、t previous edition approved in 20082011 asF2708/F2708M08.11. DOI: 10.1520/F2730_F2730M-11.10.1520/F2730_F2730M-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the
11、 standards Document Summary page on the ASTM website.3 Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org.4 Available from Japanese Standards Organization (JSA), 4-1-24 Akasaka Minato-Ku, Tokyo
12、, 107-8440, Japan, http:/www.jsa.or.jp.5 Available from European Committee for Standardization (CEN), 36 rue de Stassart, B-1050, Brussels, Belgium, http:/www.cenorm.be.6 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.Th
13、is document is not an ASTM standard and is intended only to provide the user of an 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 editi
14、ons as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2 chipschips, nbreak-outs of material greater
15、in extent than 0.25 mm 0.1 in. typically at the corner chamfers or thejunction of the chamfers with the cylindrical surface or end face.3.1.3 crackscracks, nirregular, narrow breaks in the surface of the roller typically having a visible width of less than 0.002mm. Most cracks are formed after densi
16、fication but occasionally may be present as material faults. Some cracks may not be visiblewith normal white light microscopy and may only show up under ultraviolet light after processing with a suitable fluorescentpenetrant.0.00008 in.3.1.3.1 DiscussionMost cracks are formed after densification but
17、 occasionally may be present as material faults. Some cracks may not be visible withnormal white light microscopy and may only show up under ultraviolet light after processing with a suitable fluorescent penetrant.3.1.4 cutscuts, nshort linear or circumferential grooves having a width of more than 0
18、.005 mm 0.002 in. and a length ofmore than 0.20 mm. mm 0.008 in. Cuts are normally assessed under roller surface appearance but large and/or numerous cutsor numerous cuts, or both can be considered defects.3.1.5 flatsflats, nflat bands running along the length of the cylindrical part of the roller,
19、usually caused by a stop in rotationof the roller during machining. Flats can also be formed at one end only by incorrect approach into a machining operation.3.1.5.1 DiscussionFlats can also be formed at one end only by incorrect approach into a machining operation.3.1.6 groovesgrooves, nshallow mac
20、hining marks having a width of more than 0.005 mm 0.002 in. extending more than14one quarter of the circumference on the cylindrical surface or having a length of more than 14one quarter of the roller diameteron the end faces.3.1.7 inclusionsinclusion, nisolated areas of ceramic second phases or met
21、allic appearing phases. Inclusions are often theresult of contamination by foreign material during the roller blank manufacturing process.any discrete imhomogeneity in themicrostructure that is not intended to be included in the material.3.1.7.1 DiscussionInclusions typically consist of foreign mate
22、rial as a result of unintended external powder contamination and resulting reactionproduct after sintering.3.1.8 material lotlot, nsingle process lot of silicon nitride raw powder received from a material supplier.3.1.9 mean roller diameterdiameter, none half the sum of the largest and smallest of i
23、ndividual diameters measured in asingle radial plane.3.1.10 mean roller lengthlength, none half the sum of the largest and smallest lengths measured on a roller.3.1.11 metallic phase, nmaterial phase that is highly reflective when viewed by light microscopy.3.1.12 metallic smearssmears, nmetallic ma
24、terial from machining or measuring equipment transferred onto the rollersurface.3.1.13 pitspits, nvoids or cavities in the roller surface. Pits can be formed by severe material pullout during roller finishing.Pits can also be a result of the breakout of inclusions during machining.3.1.13.1 Discussio
25、nPits can be formed by severe material pullout during roller finishing. Pits can also be a result of the breakout of inclusions duringmachining.3.1.14 porosityporosity, nsmall, closely spaced voids permeating a region of the roller surface or the whole roller.3.1.15 pressing defectsdefects, nthe res
26、ult of cracks in roller preforms prior to densification. Some pressing defects healmore or less completely on densification resulting in a region of material with slightly different composition and opticalcharacteristics than the rest of the roller. These are known as healed or partially healed pres
27、sing defects. Unhealed or open pressingdefects can have the appearance of cracks or fissures.3.1.15.1 DiscussionF2730/F2730M 132Some pressing defects heal more or less completely on densification resulting in a region of material with slightly differentcomposition and optical characteristics than th
28、e rest of the roller. These are known as healed or partially healed pressing defects.Unhealed or open pressing defects can have the appearance of cracks or fissures.3.1.16 snowflakessnowflakes, nregions of localized incomplete densification or regions in which the glassy phase isincompletely bonded
29、to the silicon nitride grains. Snowflakes show up as white dendritic features when viewed with obliqueillumination or with ultraviolet light after processing with a fluorescent penetrant.3.1.16.1 DiscussionSnowflakes show up as white dendritic features when viewed with oblique illumination or with u
30、ltraviolet light after processingwith a fluorescent penetrant.3.1.17 stepssteps, nregions at the edge of a roller end face that have been machined to a lower depth than the rest of theend face.3.1.18 surface roughness (Ra)roughness, Ra, nsurface irregularities with relative small spacings, which usu
31、ally includeirregularities resulting from the method of manufacture being used, other influences, or both.3.1.19 tearstears, ncircumferential machining marks associated with lateral surface cracks.3.1.20 unfinished areasareas, nregions on the roller surfaces that should be machined but have not been
32、 machined at all,or have not been completely machined and finished, due tobecause of either faults in blank geometry or errors in the machiningprocess.4. Classification4.1 Silicon nitride materials for bearing applications are specified according to the following material classes:4.1.1 Class IHighes
33、t grade of material in terms of properties and microstructure. Suitable microstructure and suitable for usein the most demanding applications. This group adds high reliability and durability for extreme performance requirements.4.1.2 Class IIGeneral class of material for most bearing applications. T
34、his group addresses the concerns of roller defects asis relative to fatigue life, levels of torque, and noise.4.1.3 Class IIILower grade of material for low duty applications only. This group of applications primarily takes advantageof silicon nitride material properties (for example, light weight,
35、chemical inertness, lubricant life extension due tobecause ofdissimilarity with race materials, etc.).and so forth.).4.1.4 A material grade approved as a Class I material may be supplied where Class II or III is specified and, similarly, a ClassII material for a Class III.5. Roller Dimensions5.1 Cyl
36、indrical rollers are generally identified using a nominal diameter (D)(D) and nominal length (L)(L) where the first valueis that of nominal diameter (for example, 999 9 mm, 182118 21 mm).5.2 Rollers are normally manufactured to millimetermillimetre dimensions with D equal to L. However, many variati
37、ons existwhere L is larger or smaller than D. There may be a practical limitation to this as L becomes significantly larger than D becauseof pressing limitations. In these cases, the roller blank supplier should be consulted.5.3 There should be sufficient stock allowance on the roller blank so that
38、all surface skin effects are removed during machining.5.4 Silicon nitride rollers should be machined entirely over the diameter and end face surfaces. Corner chamfers need not bemachined providing the corners are uniform and have a smooth transition from the diameter to the end face.6. Material6.1 U
39、nless otherwise specified, physical and mechanical property requirements will apply to all material classes.6.2 Silicon nitride rollers should be produced from either silicon nitride powder having the compositional limits listed in Table1 or from silicon metal powder, which, after nitridation, compl
40、ies with the compositional limits listed in Table 1.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 maxA Other impurities or elements such as s
41、odium, potassium, chlorine, etc. and soforth individually shall not exceed 0.02 wt % max.F2730/F2730M 1336.3 Composition is measured in weight percent. Testing shall be carried out by a facility qualified and approved by the supplier.Specific equipment, tests, and/or methods are subject to agreement
42、 between suppliers and their customers.6.4 Compounds may be added to promote densification and enhance product performance and quality.6.5 Iron oxides may be added to promote densification with the total iron content for the final product not to exceed 1.0weight %.6.6 Precautions should be taken to
43、minimize contamination by foreign materials during all stages of processing up to andincluding densification.6.7 A residual content of up to 2 % tungsten carbide from powder processing is allowable.6.8 Final composition shall meet and be reported according to the specification of the individual supp
44、lier.6.9 Notification will be made upon process changes.6.10 Specific requirements such as specific material grade designation, physical/mechanical property requirements (forexample, density) or quality or testing requirements shall be established by specific application. The special requirements sh
45、all bein addition to the general requirements established in this specification.6.11 Typical mechanical properties will fall within the range listed in Table 2. Individual requirements may have tighter ranges.The vendor shall certify that the silicon nitride material supplied has physical and mechan
46、ical properties within the range givenin Table 2. In the case of properties indicated by (+), the provision of the data is not mandatory.7. Physical Properties7.1 The following physical properties shall be measured, at a minimum, on each material lot.7.1.1 Average values for room temperature rupture
47、 strength (bend strength/modulus of rupture) for a minimum of 20 individualdeterminations shall exceed the minimum values given in Table 3. Either 3-point or 4-point test methods may be used for flexuralstrength, which should be measured in accordance with Test Method C1161 (size B), CENEN 843-5, or
48、 JIS R 1601. Weibullmodulus for each test series shall also exceed the minimum permitted values given in Table 3. If a sample set of specimens fora material lot does not meet the Weibull modulus requirement in Table 3, then a second sample set may be tested to establishconformance.7.1.2 The hardness
49、 (HV) shall be determined by the Vickers method (see Annex A1) using a load of at least 5 kg 11 lbs butnot exceeding 20 kg. kg 44 lbs. Fracture resistance shall be measured by either an indentation technique (see Annex A1) or bya standard fracture toughness test method.Average values for hardness and fracture resistance shall exceed the minimum of valuesfor the specified material class given in Table 4.7.1.3 Microstructure constituents visible at magnification in the range 100 to 200 shall not exceed
