1、Designation: F2730/F2730M 13F2730/F2730M 14Standard 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, nsintering additive based phases, for example yttria and alumina, which appear darkeror darkeror lighter than the silicon nitride matrix b
9、ut are not highly reflective in nature.nature when viewed under reflected light microscopyand bright field illumination.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 e
10、dition approved Oct. 1, 2013March 15, 2014. Published October 2013March 2014. Originally approved in 2008. Last previous edition approved in 20112013as F2708/F2708M11.13. DOI: 10.1520/F2730_F2730M-13.10.1520/F2730_F2730M-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or cont
11、actASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the 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 10016-59
12、90, http:/www.asme.org.4 Available from Japanese Standards Organization (JSA), 4-1-24 Akasaka Minato-Ku, Tokyo, 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 Amer
13、ican National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This 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 te
14、chnically 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 published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, P
15、O Box C700, West Conshohocken, PA 19428-2959. United States13.1.2 chips, nbreak-outs of material greater in extent than 0.25 mm 0.1 in. typically at the corner chamfers or the junctionof the chamfers with the cylindrical surface or end face.3.1.3 color variation, nan area that appears lighter or dar
16、ker than the surrounding area under reflected light microscopy butwith no discernible physical discontinuity associated with it.3.1.3.1 DiscussionColor variation is often not visible under scanning electron microscopy (SEM) examination.3.1.4 cracks, nirregular, narrow breaks in the surface of the ro
17、ller typically having a visible width of less than 0.002 mm.0.00008 in.3.1.4.1 DiscussionMost cracks are formed after densification but 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
18、processing with a suitable fluorescent penetrant.3.1.5 cuts, nshort linear or circumferential grooves having a width of more than 0.005 mm 0.002 in. and a length of morethan 0.20 mm 0.008 in. Cuts are normally assessed under roller surface appearance but large or numerous cuts, or both can beconside
19、red defects.3.1.6 flats, nflat bands running along the length of the cylindrical part of the roller, usually caused by a stop in rotation of theroller during machining.3.1.6.1 DiscussionFlats can also be formed at one end only by incorrect approach into a machining operation.3.1.7 grooves, nshallow
20、machining marks having a width of more than 0.005 mm 0.002 in. extending more than one quarterof the circumference on the cylindrical surface or having a length of more than one quarter of the roller diameter on the end faces.3.1.8 inclusion, nany discrete imhomogeneity in the microstructure that is
21、 not intended to be included in the material.3.1.8.1 DiscussionInclusions typically consist of foreign material as a result of unintended external powder contamination and resulting reactionproduct after sintering.3.1.9 material lot, nsingle process lot of silicon nitride a blended powder (blended w
22、ith additives), produced from a singlelot of silicon nitride or silicon metal raw powder received from a material supplier.3.1.9.1 DiscussionWhat constitutes a “single process lot” of blended powder can vary depending on the standard practices of the vendor and therequirements of the customer and ap
23、plication. For example, for many customers/applications, combining multiple mill chargesfrom one raw material lot into a single material lot is acceptable while for others, each mill charge would be considered a separatematerial lot. It is difficult, if not impossible, for a single definition of mat
24、erial lot to apply to all applications.The material lot shouldbe defined such that application-appropriate traceability is maintained and adequate testing appropriate for the intended applicationis performed to ensure that the chemistry and material properties of densified parts meet specifications.
25、 The material lotrequirements should be discussed and agreed between the vendor and customer.3.1.10 mean roller diameter, none half the sum of the largest and smallest of individual diameters measured in a single radialplane.3.1.11 mean roller length, none half the sum of the largest and smallest le
26、ngths measured on a roller.3.1.12 metallic phase, nmaterial phase that is highly reflective when viewed by light microscopy.reflected light microscopyand bright field illumination.3.1.13 metallic smears, nmetallic material from machining or measuring equipment transferred onto the roller surface.3.1
27、.14 pits, nvoids or cavities in the roller surface.3.1.14.1 DiscussionF2730/F2730M 142Pits can be formed by severe material pullout during roller finishing. Pits can also be a result of the breakout of inclusions duringmachining.3.1.15 porosity, nsmall, closely spaced voids permeating a region of th
28、e roller surface or the whole roller.3.1.16 pressing defects, nthe result of cracks in roller preforms prior to densification.3.1.16.1 DiscussionSome pressing defects heal more or less completely on densification resulting in a region of material with slightly differentcomposition and optical charac
29、teristics than the 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.3.1.17 raw material lot, nsingle process lot of raw silicon nitride or raw silicon metal powder received from a materi
30、alsupplier.3.1.18 scratches, nnarrow, linear, shallow abrasions on the surface.3.1.19 snowflakes, nregions of localized incomplete densification or regions in which the glassy phase is incompletely bondedto the silicon nitride grains. microporosity in the grain boundary phase that often display a de
31、ndritic appearance.3.1.19.1 DiscussionSnowflakes show up as white dendritic features when viewed with oblique illumination or with ultraviolet light after processingwith a fluorescent penetrant. The individual micropores are often submicron in size and the snowflakes can range in size from lessthan
32、10 m .00039 in. to over 1,000 m .039 in in extreme cases.3.1.20 steps, nregions at the edge of a roller end face that have been machined to a lower depth than the rest of the end face.3.1.21 surface roughness, Ra, nsurface irregularities with relative small spacings, which usually include irregulari
33、tiesresulting from the method of manufacture being used, other influences, or both.3.1.22 tears, ncircumferential machining marks associated with lateral surface cracks.3.1.23 unfinished areas, nregions on the roller surfaces that should be machined but have not been machined at all, or havenot been
34、 completely machined and finished, because of either faults in blank geometry or errors in the machining process.4. Classification4.1 Silicon nitride materials for bearing applications are specified according to the following material classes:4.1.1 Class IHighest grade of material in terms of proper
35、ties and microstructure and suitable for use in the most demandingapplications. This group adds high reliability and durability for extreme performance requirements.4.1.2 Class IIGeneral class of material for most bearing applications. This group addresses the concerns of roller defects asis relativ
36、e 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, chemical inertness, lubricant life extension because of dissimi
37、laritywith race materials, 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 Cylindrical rollers are generally identified using a nominal diameter (D) and
38、nominal length (L) where the first value is thatof nominal diameter (for example, 9 9 mm, 18 21 mm).5.2 Rollers are normally manufactured to millimetre dimensions with D equal to L. However, many variations exist where Lis larger or smaller than D. There may be a practical limitation to this as L be
39、comes significantly larger than D because of pressinglimitations. In these cases, the roller blank supplier should be consulted.5.3 There should be sufficient stock allowance on the roller blank so that all surface skin effects are removed during machining.5.4 Silicon nitride rollers should be machi
40、ned 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 Unless otherwise specified, physical and mechanical property requirements will apply to all materi
41、al classes.F2730/F2730M 1436.2 Silicon nitride rollers shouldTo be classified as Class I, silicon nitride rollers shall be produced from either silicon nitridepowder having the compositional limits listed in Table 1 or from silicon metal powder, which, after nitridation, complies with thecomposition
42、al limits listed in Table 1.6.3 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 between suppliers and their customers.6.4 Compounds may be added to promote
43、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 minimize contamination by foreign materials during all stages of processing u
44、p 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 supplier.6.9 Notification will be made upon process changes.6.10 Specific require
45、ments 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 shall bein addition to the general requirements established in this specificati
46、on.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 mechanical properties within the range givenin Table 2. In the case of properties i
47、ndicated 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 strength (bend strength/modulus of rupture) for a minimum of 20 individualde
48、terminations 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), EN 843-5, or JIS R 1601. Weibull modulusfor each test series shall also exceed the minimum p
49、ermitted values given in Table 3. If a sample set of specimens for a materiallot does not meet the Weibull modulus requirement in Table 3, then a second sample set may be tested to establish conformance.7.1.2 The hardness (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 44 lbs. Fracture resistance shall be measured by either an indentation technique (see Annex A1) or by astandard fracture toughness test method. Average values for hardness an
