1、Designation: D351 14D351 18Standard Classification forNatural Muscovite Block Mica and Thins Based on VisualQuality1This standard is issued under the fixed designation D351; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This classification covers th
3、e determination of commercially available natural muscovite block mica and is intended to beindependent of the basic color of the mica or its source.1.2 Muscovite mica is characterized by having an optical axial angle between 50 and 75 (see Appendix X1); and has a weightloss when heated for 5 min at
4、 600C not exceeding 0.2 % (based on the weight after drying at 120C).1.3 The visual system of classifying the quality of natural muscovite mica covered by this specification is based upon relativeamounts of visible foreign inclusions such as air bubbles, stains, and spots in combination with relativ
5、e amounts and types ofwaviness, as well as other physical properties. In this system, a perfectly clear, transparent, flat specimen of mica is the visualstandard of perfection. Increasing amounts of visual defects lower the visual quality, and a total of 13 levels of visual quality arecovered by thi
6、s standard. This method of classification, generally known as the Bengal India System, is purely qualitative and isentirely dependent on personal opinion and judgment.1.4 The standards for visual quality classification that are covered in this classification are the best commercially availableconcep
7、t of the various qualities and their relative positions. Variations in the methods of using and applying these standards fromthose herein defined may be are specified by the purchaser, or defined by agreement between the supplier and the purchaser.1.5 Standard size classifications are defined, based
8、 upon available usable rectangular areas and the minimum dimensions of therectangles that the pieces will yield. Precautions to be taken in making thickness measurements are also described.1.6 This standard covers the following two definite forms of commercial preparation:1.6.1 Form 1Full-trimmed na
9、tural block mica, 0.007 in. 0.007 in. (0.178 mm) minimum thickness.1.6.2 Form 2Partially-trimmed natural block mica, 0.007 in. minimum thickness.1.7 The basic color of mica, such as white, ruby, light green, dark green, brownish green, and rum, as well as other colors, andthe method of controlling t
10、he color and other problems associated with the basic color, are not a part of this classification.1.8 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information only and are not cons
11、idered standard.1.9 Section 5 is technically identical to procedures specified in ISO 67-1981.1.10 Section 6 differs somewhat in procedure from ISO 5972-1978, but data obtained by either should is expected to beidentical.1.11 Section 7 is technically identical to procedures specified in ISO 2185-197
12、2.1.12 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to
13、 Trade (TBT) Committee.1 This classification is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of SubcommitteeD09.01 on Electrical Insulating Products.Current edition approved Jan. 15, 2014Nov. 1, 2018. Published March
14、2014November 2018. Originally approved in 1932. Last previous edition approved in 20082014as D351 97 (2008)D351 14.1. DOI: 10.1520/D0351-14. 10.1520/D0351-18.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 mad
15、e to the previous version. Becauseit may not be technically 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.Copy
16、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12. Referenced Documents2.1 ASTM Standards:2D374 Test Methods for Thickness of Solid Electrical Insulation (Metric) D0374_D0374MD1711 Terminology Relating to Electrical Insulation2.2 ISO Publ
17、ications:ISO 67-1981 Muscovite Mica Blocks, Thins, and FilmsGrading by Size3ISO 2185-1972 Muscovite Mica Blocks, Thins, and FilmsVisual Classification3ISO 5972-1978 Mica Blocks, Thins, Films, and Splittings Measurement of Thickness33. Terminology3.1 For definitions of terms relating to mica refer to
18、 Terminology D1711, Part III.3.2 Definitions of Terms Specific to This Standard:3.2.1 “A”a series of rulings or striations intersecting at an angle of about 60.3.2.2 blocksmica thickness of 0.007 in. (0.178 mm) minimum thickness, full-trimmed, unless otherwise designated.3.2.3 buckleone or more larg
19、e depression(s) and elevation(s).3.2.4 cracksirregular fractures within the crystal that may be are natural or may arise from blasting, rough handling, etc.andso forth.3.2.5 full-trimmed micamica trimmed on all sides with all cracks, reeves, and cross-grains removed.3.2.6 haircracks or hairline crac
20、ksminute, irregular cracks that are barely noticeable until mica is split into films, resultingin production of torn films.3.2.7 reeves or cross grainstangled laminations giving imperfect cleavage, that results in tears or breaks during splitting.3.2.8 ribboned or rules micamica that breaks into nar
21、row strips because of parallel fractures.3.2.9 ribs or ridgescrenulations in the form of steps.3.2.10 ripplemultiple short waves.3.2.11 stainsstains arise from foreign materials, resulting in a partial or total loss of transparency. They may be are in the formof specks or patches of appreciable area
22、 for example, slight stain, “vegetable” stain, clay stain, black stain, red stain, blackspeckled, light dot or spot, black, red or green dot or spot, etc. (see “inclusions” in Terminology D1711).3.2.12 stones and stone holessmall embedded crystals or holes resulting from them.3.2.13 thinsknife-dress
23、ed mica, 0.002 in. (0.05 mm) to less than 0.007 in. (0.18 mm) in thickness. They may be are classifiedas follows:3.2.13.1 Thins, 0.002 to 0.004 in. (0.05 to 0.10 mm), and3.2.13.2 Thick-thins, 0.004 to 0.007 in. (0.10 to 0.18 mm).3.2.14 unmanufactured micacommercial form of mica known as blocks, thin
24、s, films, and splittings, as described.3.2.15 wavesalternate elevations and depressions that may be are classified as slight, medium, or heavy.4. Significance and Use4.1 The properties included in this standard are those required to control the visual quality, usable area, thickness, hardness, andst
25、iffness.5. Grading for Size5.1 Full-TrimmedAll full-trimmed mica blocks and thins shall be fully trimmed to remove all cracks, holes, reeves, andcross-grains according to the quality desired. As far as possible, all marginal cracks should are to be removed by recutting. Theaverage area of the pieces
26、 for Grade 4 and larger shall be not more than 1.54 times the average area of the largest usable rectangles.This would constitute a minimum yield of 65 %. For Grades 5 and smaller, the average area of the pieces shall be not more thantwo times the average area of the largest usable rectangles. This
27、would constitute a yield of 50 %.5.2 Half-TrimmedFor half-trimmed mica, follow the grading described in 5.1 for trimmed sides with no cracks extending fromthe trimmed sides, except for sizes 6 and 512 on which only side must be trimmed free of cracks. On the untrimmed sides, nodefects of the designa
28、ted quality are acceptable within the minimum rectangle of the designated grade.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 standards Document Summary page o
29、n the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.D351 1825.3 Natural Block and ThinsNatural block and thins, muscovite mica shall be graded for size according to the area of therectangle (maximum recta
30、ngle for full-trimmed, maximum rectangle of designated quality for half-trimmed) having at least theminimum dimension of one side for the specified grade. The area within such a rectangle shall meet the requirements of the qualityspecified by the purchaser as listed in Table 1.5.4 Method of Grading
31、for SizeThe Standard ASTM Chart shown in Fig. 1 shall be used for grading natural block and thins,muscovite mica according to size. In grading natural block mica and thins for size, all dimensions apply to the smaller surfacemeasured from the foot of the bevel-trimmed edge. The specimen to be graded
32、 shall be laid upon the chart so that it covers pointO and has its maximum and minimum dimensions extending along and covering lines OA and OB, respectively. The specimenshall be shifted until the usable area completely covers the largest rectangle, determined by a diagonal extending from point O to
33、or beyond a point on any of the curves. The number of the curve at the greatest distance from O cut by the diagonal of the rectangledesignates the grade of the specimen.6. Thickness of Block Mica6.1 Measure the thickness with a micrometer as specified in Test Methods D374. In determining thickness o
34、f mica that mustbe kept within small permissible variations, or where two or more specimens are to be measured at once, use Method A of TestMethods D374. Where the maximum accuracy is not required, Method B may be used.is suitable.6.2 Because of the abrasive nature of mica, test the micrometer frequ
35、ently for conformity to the requirements specified in TestMethods D374. Clean the anvil and spindle as frequently as necessary to prevent the accumulation of mica dust on the surfacesand to preserve the accuracy of the measurements. To clean, close the micrometer lightly on a clean sheet of bond pap
36、er and movethe paper between the surfaces.6.3 Be careful, when moving from one measurement location to another, to maintain the surfaces of the anvil and spindleparallel to the surfaces of the specimen at all times, so as to avoid scratching the mica and accumulating mica dust under themicrometer su
37、rfaces, thereby causing false readings.7. Classification of Visual Quality of Block Mica7.1 The classification of the visual quality of muscovite blocks and thins shall fall into the following thirteen categories:7.1.1 V-1 Clear,7.1.2 V-2 Clear and Slightly Stained,7.1.3 V-3 Fair Stained,7.1.4 V-4 G
38、ood Stained,7.1.5 V-5 Stained A Quality,7.1.6 V-5.1 Stained A1 Quality,7.1.7 V-6 Stained B Quality,7.1.8 V-7 Heavy Stained,7.1.9 V-8 Densely Stained,7.1.10 V-9 Black Dotted,7.1.11 V-10 Black Spotted,7.1.12 V-11 Black StainedStained, and7.1.13 V-12 Black/Red StainedStained.TABLE 1 ASTM Grade Sizes of
39、 Muscovite Uncut Mica Block andThinsASTMGradeSizesArea ofMinimumRectangleMinimumDimen-sion ofOne Sidein.2 Equiva-lent, cm2 in. Equiva-lent, mmOOEE Special 100 650 4 100OEE Special 80 520 4 100EE Special 60 390 4 100E Special 48 310 4 100A-1 (Special) 36 235 312 89No. 1 24 155 3 76No. 2 15 97 2 51No.
40、 3 10 65 2 51No. 4 6 40 112 38No. 5 3 20 1 25No. 512 214 15 78 22No. 6 1 6.5 34 19D351 1837.2 The classification of the visual quality of block mica shall be judged in accordance with the requirements specified in Table2 using the visual descriptions given.8. Keywords8.1 Bengal India System; block;
41、classification; foreign inclusions; form; grading; muscovite mica; size; thins; visual qualityNOTE 1This chart may be is readily extended for Grades OOEE Special, OEE Special, EE Special, and E Special, using the information given inTable 1 of ASTM Specification D351.FIG. 1 ASTM Chart for Grading Na
42、tural Muscovite Block and Film MicaD351 184TABLE 2 Quality Classification of Muscovite Block and Thins Based on Visual PropertiesA,B,C,D,E,F,G,H,I,JASymbols:=PermissibleNot permissibleSPermissible only if specifiedFew and tiny in one-fourth of usable area.B In one-half usable areaC SlightD In two-th
43、irds usable areaE Uniformly distributedD351185F Not heavily concentrated over more than an area equivalent to 14 in. square (6.4 mm square) for grade 5 and up and over more than an area equivalent to 18 in. 2 (3.2 mm2) for Grade 512 and lowerG Not exceeding two specks within the usable areaH MediumI
44、 HeavyJ Dispersed black dotsNote 1The visual properties of block mica usually are judged under the following light conditions:For stains and inclusions Transmitted daylight or its equivalent.For air inclusionsReflected daylight or its equivalent.For waves, buckles, ridges, etc.Reflected daylight or
45、its equivalent where distortion of parallel and vertical lines of reflected image, such as a window frame, can be judged.is distinguishable.Note 2The hardness or mechanical properties of muscovite mica are usually judged by a sharp, clear ring when mica is dropped on a hard surface.Note 3Muscovite m
46、ica occurs in various colors which are more pronounced the thicker the block. Some typical colors are ruby, white, light green, rum, etc.Note 4Cracks, tears, stones, or pin holes are judged by transmitted daylight or equivalent.Note 5Rigidity is judged by the relative stiffness when flexing with the
47、 fingers.Note 6See Section 3 for definition of terms used in Table 2.Note 7The following are verbal descriptions of the classification of muscovite blocks and thins, judged in terms of requirements of Table 2:V-1 ClearHard, of uniform color, flat, free from all stains and foreign inclusions, waves,
48、cracks, buckles, and other similar defects.V-2 Clear and Slightly StainedHard, of uniform color, nearly flat, free from all vegetable and mineral stains, cracks, buckles and other similar defects, and foreign inclusions except for a few tiny air inclusions innot more than one-fourth of the usable ar
49、ea. Slight crystallographic discoloration is permitted to a limited extent.V-3 Fair StainedHard, of uniform color, free of all vegetable and mineral stains, cracks, buckles and other similar defects, and foreign inclusions, except may be slightly wavy, and may contain slightly wavy ispermitted, and slight air inclusions are permitted in not more than one-half of the usable area, these inclusions shouldare not to be concentrated. Slight crystallographic discoloration is permitted to a limited extent.V-4 Good StainedH
