1、Designation: D 785 03Standard Test Method forRockwell Hardness of Plastics and Electrical InsulatingMaterials1This standard is issued under the fixed designation D 785; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers two procedures for testing theindention hardness of plastics and related plastic electricalins
3、ulating materials by means of the Rockwell hardness tester.1.2 The values stated in SI units are to be regarded as thestandard. The values given in brackets are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theres
4、ponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE 1This test method and ISO 2039-2 are equivalent. Procedure Aof this test method is equivalent to the test method in the main bod
5、y of ISO2039-2. Procedure B of this test method is equivalent to the test methodin the integral annex part of ISO 2039-2.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 2240 Test Method for Rubber PropertyDuromete
6、rHardnessD 4000 Classification System for Specifying Plastic Mate-rialsE 18 Test Methods for Rockwell Hardness and RockwellSuperficial Hardness of Metallic MaterialsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards3ISO 2039-2 PlasticsD
7、etermination of HardnessPart 2:Rockwell Hardness3. Terminology3.1 Definitions used in this test method are in accordancewith Terminology D 883.4. Significance and Use4.1 A Rockwell hardness number is a number derived fromthe net increase in depth impression as the load on an indenteris increased fro
8、m a fixed minor load to a major load and thenreturned to a minor load (Procedure A). A Rockwell alpha (a)hardness number represents the maximum possible remainingtravel of a short-stroke machine from the net depth of impres-sion, as the load on the indenter is increased from a fixed minorload to a m
9、ajor load (Procedure B). Indenters are round steelballs of specific diameters. Rockwell hardness numbers arealways quoted with a scale symbol representing the indentersize, load, and dial scale used. This test method is based on TestMethods E 18. Procedure A (Section 11) yields the indentationof the
10、 specimen remaining 15 s after a given major load isreleased to a standard 10-kg minor load. Procedure B (Section12) yields the indentation of the indenter into the specimenafter a 15-s application of the major load while the load is stillapplied. Each Rockwell scale division represents 0.002-mm0.00
11、008-in. vertical movement of the indenter. In practice,the Rockwell hardness number is derived from the followingrelationship:HR 5 130 2 e (1)where:HR = the Rockwell hardness number, ande = the depth of impression after removal of the majorload, in units of 0.002 mm. This relation only holdsfor the
12、E, M, L, R, and K scales.4.2 A Rockwell hardness number is directly related to theindentation hardness of a plastic material, with the higher thereading the harder the material. An a hardness number is equalto 150 minus the instrument reading. Due to a short overlap of1This method is under the juris
13、diction of ASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved November 1, 2003. Published January 2004. Originallyapproved in 1944. Last previous edition approved in 1998 as D 785 - 98e1.2For referenced ASTM standar
14、ds, 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 Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, N
15、ew York, NY 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Rockwell hardness scales by Procedure A, two different dialreadings on different scales may be obtain
16、ed on the samematerial, both of which may be technically correct.4.3 For certain types of materials having creep and recovery,the time factors involved in applications of major and minorloads have a considerable effect on the results of the measure-ments.4.4 The results obtained by this test method
17、are not gener-ally considered a measure of the abrasion or wear resistance ofthe plastic materials in question.4.5 Indentation hardness is used as an indication of cure ofsome thermosetting materials at room temperature. Generally,an uncured specimen has a hardness reading below normal.4.6 Each Rock
18、well hardness scale in Table 1 is an extensionof the proceeding less severe scale, and while there is someoverlap between adjacent scales, a correlation table is notdesirable. Readings on one material may be satisfactory forsuch a table, but there is no guarantee that other plasticmaterials will giv
19、e corresponding readings because of differ-ences in elasticity, creep, and shear characteristics.4.7 Before proceeding with this test method, referenceshould be made to the specification of the material being tested.Any test specimen preparation, conditioning, dimensions,and/or testing parameters co
20、vered in the materials specificationshall take precedence over those mentioned in this test method.If there are no material specifications, then the default condi-tions apply.5. Factors Affecting Reproducibility and Accuracy5.1 Rockwell hardness readings have been found reproduc-ible to 62 divisions
21、 for certain homogeneous materials with aYoungs modulus in compression over 3400 MPa 5 3 105psi. Softer plastics and coarse-filled materials will have awider range of variation. A large ball indenter will distributethe load more evenly and decrease the range of test results(Note 2). The sensitivity
22、of the instrument decreases with anincrease in the dial reading and becomes very poor for readingsof 100 and over due to the shallow indentation of the steel ball.It is desirable to use the smallest ball and highest load that ispractical because of this loss of sensitivity. Rockwell hardnessreadings
23、 over 115 are not satisfactory and shall not be reported.Readings between zero and 100 are recommended, but read-ings to 115 are permissible. For comparison purposes, it maybe desirable to take readings higher than 115 or lower than zeroon any single scale. In such cases, Rockwell hardness readingsm
24、ay be reported, but the corresponding correct readings shallfollow in parentheses, if possible. Such alternate readings arenot always feasible when the specimen is subjected to con-stantly changing conditions or irreversible reactions.NOTE 2Molded specimens containing coarse fiber fillers, such aswo
25、ven glass fabric, will influence the penetration obtained. These varia-tions in hardness may be reduced by testing with the largest ball indenterconsistent with the overall hardness of the material.5.2 If the bench or table on which a Rockwell hardnesstester is mounted is subject to vibration, such
26、as is experiencedin the vicinity of other machines, the tester should be mountedon a metal plate with sponge rubber at least 25 mm 1 in.thick, or on any other type of mounting that will effectuallyeliminate vibration from the machine. Otherwise the indenterwill indent further into the material than
27、when such vibrationsare absent.5.3 Dust, dirt, grease, and scale or rust should not beallowed to accumulate on the indenter, as this will affect theresults. Steel ball indenters that have nicks, burrs, or are out ofround shall not be used.5.4 The condition of the test equipment is an importantfactor
28、 in the accuracy of the test results. Dust, dirt or heavy oilact as a cushion to the load supporting members of the testequipment and cause erroneous readings of the instrument dial.The shoulders of the instrument housing, indenter chuck, ballseat in the instrument housing, capstan, capstan screw, a
29、ndanvil shoulder seat should be kept clean and true. The capstanand screw should be lightly oiled. Pitted anvil surfaces may berefinished with 600 grit paper.5.5 Surface conditions of the specimen have a marked effecton the readings obtained in a test. Generally, a molded finishwill give a higher Ro
30、ckwell reading than a machined face dueto the high resin content or filled materials or better orientationand lower plasticizer content of unfilled plastic materials.Tubular or unsupported curved specimens are not recom-mended for plastic hardness testing. Such curved surfaces havea tendency to yiel
31、d with the load and produce an unsymmetri-cal indentation pattern.5.6 Many plastic materials have anisotropic characteristicswhich cause indentation hardness to vary with the direction oftesting. In such cases, the hardest face is generally that oneperpendicular to the molding pressure. Specimens wi
32、th flash-ing on the side supported by the anvil also may give erroneousresults.5.7 Ambient temperature variations can significantly affecthardness for many materials.5.8 Rockwell hardness tests of the highest accuracy aremade on pieces of sufficient thickness so that the Rockwellreading is not affec
33、ted by the supporting anvil. A bulge, changein color, or other marking on the under surface of the testspecimen closest to the anvil is an indication that the specimenis not sufficiently thick for precision testing. Stacking of thinspecimen is permitted provided they are flat, parallel, and freefrom
34、 dust or burrs. The precision of the test is reduced forTABLE 1 Rockwell Hardness ScalesRockwellHardnessScale(Red DialNumbers)MinorLoad,kgMajorLoad,kgAIndenter Diameterin. mmR 10 60 0.5000 6 12.700 60.0001 0.0025L 10 60 0.2500 6 6.350 60.0001 0.0025M 10 100 0.2500 6 6.350 60.0001 0.0025E 10 100 0.12
35、50 6 3.175 60.0001 0.0025K 10 150 0.1250 6 3.175 60.0001 0.0025AThis major load is not the sum of the actual weights at the back of the frame butis a ratio of this load, depending on the leverage arm of machine. One make andmodel has a 25 to 1 leverage arm.D785032stacked specimens, and results shoul
36、d not be compared to a testspecimen of standard thickness.6. Apparatus6.1 Rockwell Hardness Tester, in accordance with the re-quirements of Section 7. A flat anvil at least 50 mm 2 in. indiameter shall be used as a base plate for flat specimens.6.2 For Rockwell hardness testing, it is necessary that
37、 themajor load, when fully applied, be completely supported by thespecimen and not held by other limiting elements of themachine. To determine whether this condition is satisfied, themajor load should be applied to the test specimen. If anadditional load is then applied, by means of hand pressure on
38、the weights, the needle should indicate an additional indenta-tion. If this is not indicated, the major load is not being appliedto the specimen, and a long-stroke (PL) machine or less severescale should be used. For the harder materials with a modulusaround 5500 MPa 8 3 105psi or over, a stroke equ
39、ivalent to150 scale divisions, under major load application, may beadequate; but for softer materials the long-stroke (250 scaledivisions under major load) machine is required.7. Test Specimen7.1 The standard test specimen shall have a minimumthickness of 6 mm 14 in. The specimen may be a piece cutf
40、rom a molding or sheet. Care should be taken that the testspecimen has parallel flat surfaces to ensure good seating onthe anvil and thus avoid the deflection that may be caused bypoor contact. The specimen shall be at least 25 mm 1 in.square if cut from sheet stock, or at least 6 cm21 in.2 in areai
41、f cut from other shapes. The minimum width shall be 13 mm12 in. plus the width of the indentation resulting from theconduct of a test using the chosen indenter.NOTE 3Specimen with a thickness other than 6 mm may be used if ithas been verified that, for that thickness, the hardness values are notaffe
42、cted by the supporting surface and that no imprint shows under thesurface of the specimen after testing. The specimen may be composed ofa pile-up of several pieces of the same thickness, provided that precautionis taken that the surfaces of the pieces are in total contact and not heldapart by sink m
43、arks, burrs from saw cuts, or other protrusions andprovided the hardness values are not affected by the stacking of thinspecimens.8. Calibration8.1 Check the Rockwell hardness tester periodically with asmall machinists level along both horizontal axes from a flatanvil for correct positioning. Minor
44、errors in leveling are notcritical, but correct positioning is desirable.8.2 The adjustment of speed-of-load application is of greatimportance. Adjust the dashpot on the Rockwell tester so thatthe operating handle completes its travel in 4 to 5 s with nospecimen on the machine or load applied by the
45、 indenter to theanvil. The major load shall be 100 kg for this calibration. Whenso adjusted, the period taken for the mechanism to come to astop with the specimen in place will vary from 5 to 15 s,depending upon the particular specimen, the indenter, and theload used. The operator should check the i
46、nstrument manualfor this adjustment.8.3 Select a standardized test block as near as possible to thehardness of the material being tested. If more than onehardness scale is used in testing, choose a standardized testblock for each scale used (Note 4). Make five impressions onthe test surface of the b
47、lock. Compare the average of these fivetests against the hardness calibration of the blocks. If the erroris more than 62 hardness numbers, bring the machine intoadjustment as described in 8.4 or in 5.3 and 5.4. If adjustmentcan not be achieved, more extensive servicing of the instru-ment may be need
48、ed.NOTE 4Standard test blocks for the R, L, E, K, and M scales areavailable from Wilson Instruments, 100 Royal Street, Canton, Ma 02021(A Division of Instron Corporation).8.4 Check the index lever adjustment periodically and makeadjustments if necessary. To adjust the index lever, place aspecimen (p
49、lastic with low creep or soft metal) on the anvil andturn the knurled elevating ring to bring the specimen in contactwith the indenter. Keep turning the ring to elevate the specimenuntil positive resistance to further turning is felt, which will beafter the 10-kg load is encountered. When excessive powerwould have to be used to raise, the specimen higher, set the dialso that the set position is at the top and take note of the positionof the pointer on the dial. If the pointer is between B 50 and B70 on the red scale, no adjustment is necessary; if the point
