1、CEN EN124003 93 3404587 00470i12 561 H EUROPEAN STANDARD EN 24003 NORME EUROPENNE EUROPISCHE NORM April 1993 UDC 6621.762.5 : 669-492.2 : 620.1 : 539.217 Descriptors: Powder metallurgy, sintered products, porous metal, porosity, physical tests, bubble tests, pores, dimensional measurements English v
2、ersion Permeable sintered metal materials - Determination of bubble test pore size (IS0 4003 : 1977) Matriaux en mtal fritt permable - Dtermination de la dimension des pores - Mthode bulloscopique (IS0 4003 : 1977) Durchlssige Sintermetalle - Ermittlung der Porengre mittels Gasblasentest (IS0 4003 :
3、 1977) This European Standard was approved by CEN on 1993-04-02. CEN members are bound to comply with the CENCENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical re
4、ferences concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member
5、 into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden
6、, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels O 1993 Copyright reserved to CEN members Ref. No. EN 24003 : 1993 E CEN ENr24003 93 m 3404589 0047043 4T
7、8 m Page 2 EN 24003 : 1993 Foreword In 1992, IS0 4003 : 1977 Permeable sintered metal materEals - Determination of bubble test pore size was submitted to the CEN Primary Questionnaire procedure. Following the positive result of the CENCS Proposal IS0 4003 : 1977 was submitted to the Formal Vote. The
8、 result of the Formal Vote was positive. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 1993, and conflicting national standards shall be withdrawn at the latest by October 1993. Accordin
9、g to the CENXENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom. NOTE. The Euro
10、pean references to international publications are given in annex ZA (normative). CEN EN+ZOO 93 = 34045 0047044 334 m Page 3 EN 24003 : 1993 1 SCOPE AND FIELD OF APPLICATION This International Standard specifies a method, known as the bubble test method, for the determination of the pore size of perm
11、eable sintered powder metallurgical materials, .e. filters, porous bearings, porous electrodes and other parts with interconnected porosity. NOTE - The bubble test shall be considered as a quality control test and not as a test for defining filter grades or determining exact pore size and pore size
12、distribution. 2 REFERENCE IS0 2738, Permeable sintered metal materials - Determi- nation of density and open porosity. 3 PRINCIPLE Impregnation of a test piece with a test liquid. Immersion of the test piece in the test liquid and introduction of a gas (usually air) into the test piece at gradually
13、increasing press- ure. Determination of the pressure at which bubbles are emitted from the surface of the test piece. Evaluation of the equivalent bubble test pore size by means of a math- ematical formula. 4 DEFINITION bubble test pore size : The maximum equivalent capillary diameter in the test pi
14、ece which is calculated from the measured minimum pressure required to force the first bubble of gas through the test piece (under standardized conditions) impregnated with a liquid. The first bubble of gas will form at the pore having the greatest throat, the throat being the narrowest section of t
15、his pore. For calculation purposes, it is assumed that this bubble forms at the end of a capillary tube of circular cross-section which is initially filled with the same liquid of known surface tension. For a circular capillary, the diameter is related to the bubble pressure by the equation : . d=-
16、47 ap where d is the capillary diameter corresponding to the bubble test pore size, in metres; y is the surface tension of the test liquid, in newtons per metre; pl being the pressure in the liquid at the level of bubble formation, in pascals : . . . (3) pi =9,81 xp, xh where pi is the density of th
17、e test liquid, in kilograms per cubic metre; h is the height of the surface of the test liquid, in metres, above the highest throat in the test piece. CEN EN+24003 93 D 3404589 O047045 270 Page 4 EN 24003 : 1993 Liquid pressure p1 Test piece l Gas pressure p, L Test liquid FIGURE - Bubble test assem
18、bly NOTES 1 The bubble test pore size corresponds to the minimum differen- tial pressure at which constant bubbling first occurs. For this reason, this pressure is sometimes termed “minimum bubble pressure“ or “first bubble point“. The corresponding capillary diameter is some- times termed “maximum
19、pore size“ or “maximum pore diameter“, or “largest pore size“. However, the maximum pore size determined with this method may be the result of a single local defect, and therefore not representative of the pore population. 2 As the gas pressure increases beyond the minimum bubble press- ure (first b
20、ubble point), different aspects of bubbling occur on the test piece. The pressure for a given aspect can lead to the definition of a conventional pore size. For example, the pressure for which a generalized bubbling occurs is frequently specified (foaming over the whole surface). These particular de
21、finitions should be agreed between the sugplier and the user. Moreover, the uniformity of distribution of pores approaching the maximum pore size may be observed by gradually increasing the gas pressure. Cracks and clogged areas are easily discerned by this operation. 3 The bubble test does not cons
22、titute a measurement of the maximum size of paiticle that the permeable test piece will pass (retentivity of a filter). A filter may be expected to retain all par- ticles larger than the maximum pore size as defined by the bubble test; but, because of irregularity in shape of pores and other phenom-
23、 ena related to the filtration process, the same filter will retain particles which are much smaller than the maximum pore size. The determination of the size of the largest nondeforming particle which can pass through the porosity requires timeconsuming methods, for example a glass-bead test. For e
24、stimation purposes it is useful to take empirical factors, which are to be multiplied with the bubble test pore size calculated from equation (1). The factor is about 0,4 for porous metal made from uniform spherical particles; and about 0.2 for porous metal mede from irregular particles. 5 APPARATUS
25、 5.1 Dry and filtered gas (generally air) supply, at an adequate pressure. 5.2 Pressure regulator affording constant and precise control of the gas pressure, .e. a gradual increase of the pressure at a predetermined rate, or a stepwise increase of pressure and the facility to maintain a constant pre
26、ssure at each step. 5.3 Flow-meter, if required. 5.4 Device to measure the effective gas pressure, measuring to an accuracy of f 1 % (mechanical pressure gauge, or water or mercury manometer). This device shall be placed close to the bubble test cell, in order to facilitate the simul- taneous observ
27、ation of the bubble appearance and the pressure value. 5.5 Assembly for observing the bubble appearance at the surface of the test piece, according to the shape of the test piece, and for ensuring that the test piece is completely saturated with the liquid, and immersed under a constant depth of the
28、 liquid throughout the test. If the test piece is hollow or of a shape other than flat, it should be rotated with its maior axis horizontal so that the whole surface is examined. CEN ENx24003 93 m 3404569 0047046 107 m 5.6 Test liquid, selected in relation to the kind of metal composing the test pie
29、ce. Among pure liquids which wet metals perfectly, 95 % ethanol, methanol, isopropanol or carbon tetrachloride are most generally employed (see the table for properties). The test is carried out at room tem- perature (20 f 5 OC). The surface tension, 7, of the test liquid may be obtained from tables
30、 of physical constants. TABLE - Test liquids suitable for use with permeable metals Test liquid Methanol Ethanol, 95 % Isopropanol Carbon tetrachloride ) Density glcm3 0.79 0,805 0.79 1.59 iurface tensior at 20C N/m 0,022 5 0,023 0,021 5 0,027 1) As carbon tetrachloride vapour can be dangerous to he
31、alth, the usual laboratory precautions should be taken. 6 PROCEDURE The test piece shall be clean, dry and free from extraneous material and any trace of grease or similar substances likely to hinder the perfect and uniform wetting action of the test liquid. Impregnate the test piece completely with
32、 the test liquid. Insert it in the bubble test apparatus and maintain it fixed, immersed under the smallest depth of test liquid consistent with the convenient observation of the appearance of the bubbles. Measure this depth h (see the figure) and the temperature of the liquid. From an effective gas
33、 pressure of zero, increase the pressure regularly at a rate of between 20 and 100 Pa/s (according to the estimated pore size), while the surface of the test piece is under constant observation. In the case of a hollow cylindrical test piece, rotate it so that all of the surface is observed; in this
34、 case, increase the pressure in steps, each of from 50 to 500 Pa (according to the estimated pore size), so that each new pressure value is maintained whilst the surface is observed during the rotation. Note the first bubble pressure when a string of bubbles occurs from one distinct point (or perhap
35、s several distinct points at the same time). Page 5 EN 24003 : 1993 If there is a defect, the first bubble may appear in a zone remote from the upper surface. In this event, reduce the pressure and repeat the test after rotating the sample on its own axis; increase the pressure again incrementally.
36、NOTES 1 The test piece shall be impregnated to ensure the saturation of its open porosity. A vacuum impregnation in accordance with the requirements given in IS0 2738 is recommended. 2 When a determination is repeated on the same sample, it is necessary to re-impregnate the sample totally before ret
37、esting. 3 It is important that the test piece be properly sealed in the apparatus. If bubbles emerge from the proximity of the seals, the result shall be ignored and the test repeated with improved seals. 4 When the test piece is composed of a layer of fine pores supported on a base of coarser pores
38、, the bubble test pore size characterizing the material is that of the fine pore layer. The test piece shall be tested in such a way that the bubbles appear at the surface of the fine pore layer. 5 By agreement between user and supplier, pore sizes correspond- ing to other bubbling conditions may be
39、 determined as indicated in clause 4, note 2. 7 EXPRESSION OF RESULTS Calculate the bubble test pore size, using the formula in clause 4. Report the arithmetical mean of three determi- nations rounded to the nearest 5 %. 8 TESTREPORT The test report shall include the following information : a) refer
40、ence to this International Standard; b) all details necessary for identification of the test sample; c) the liquid used; d) the rate of pressure increase; e) the position of the first bubble; f) the result obtained; g) all operations not specified by this International Standard, or regarded as optio
41、nal; h) details of any occurrence which may have affected the result. CEN EN+24003 93 3404589 0047047 043 W Page 6 EN 24003 : 1993 Annex ZA (normative) Normative references to international publications with their relevant European publications This European Standard incorporates by dated or undated
42、 reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). Publication Year Title Permeable sintered metal materials - Determina- - tion of density, oil content and open porosity - IS0 2738 .
