1、BRITISH STANDARD BS EN 24491-1:1993 ISO 4491-1: 1989 Metallic powders Determination of oxygen content by reduction methods Part 1: General guidelines The European Standard EN 24491-1:1993 has the status of a British Standard UDC 621.762:669-492.2:543.73:546.21BSEN 24491-1:1993 This British Standard,
2、 having been prepared under the directionof the Iron and Steel Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15 June 1993 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference ISM/65 Special anno
3、uncement in BSINews January 1993 ISBN 0 580 21916 X Cooperating organizations The European Committee for Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries: Austria Oesterreichisches Normungsin
4、stitut Belgium Institut belge de normalisation Denmark Dansk Standardiseringsraad Finland Suomen Standardisoimisliito, r.y. France Association franaise de normalisation Germany Deutsches Institut fr Normung e.V. Greece Hellenic Organization for Standardization Iceland Technological Institute of Icel
5、and Ireland National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Inspection du Travail et des Mines Netherlands Nederlands Normalisatie-instituut Norway Norges Standardiseringsforbund Portugal Instituto Portugus da Qualidade Spain Asociacin Espaola de Norm
6、alizacin y Certificacin Sweden Standardiseringskommissionen i Sverige Switzerland Association suisse de normalisation United Kingdom British Standards Institution Amendments issued since publication Amd. No. Date CommentsBSEN 24491-1:1993 BSI 11-1999 i Contents Page Cooperating organizations Inside
7、front cover National foreword ii Foreword 2 Introduction 3 1 Scope 3 2 Normative references 3 3 Sampling 3 4 Meaning of the results according to the method used 4 5 Practical application of the standard methods 5 6 Summary of the implementation of methods for oxygen determination by reduction 5 Anne
8、x ZA (normative) Normative references to international publications with their relevant European publications 6 National annex NA (informative) Committees responsible Inside back cover National annex NB (informative) Cross-references Inside back cover Table 1 Content determined depending on method u
9、sed 5BSEN 24491-1:1993 ii BSI 11-1999 National foreword This British Standard has been prepared under the direction of the Iron and Steel Standards Policy Committee and is the English language version of EN24491-1:1993 Metallic powders Determination of oxygen content by reduction methods Part 1: Gen
10、eral guidelines, published by the European Committee for Standardization (CEN). It is identical with ISO4491-1:1989, prepared by Technical Committee119, Powder metallurgy, of the International Organization for Standardization (ISO) with the active participation of the UK. A British Standard does not
11、 purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside fr
12、ont cover, pagesi andii, theEN title page, pages2to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPIS
13、CHE NORM EN 24491-1 April 1993 UDC 621.762:669-492.2:543.73:546.21 Descriptors: Powder metallurgy, metallic powder, chemical analysis, determination of content, oxygen, reduction method English version Metallic powders Determination of oxygen content by reduction methods Part 1: General guidelines (
14、ISO 4491-1:1989) Poudres mtalliques Dosage de loxygne par les mthodes de rduction Partie 1: Directive gnrales (ISO 4491-1:1989) Metallpulver Bestimmung des Sauerstoffgehaltes durch Reduktionsverfahren Teil 1: Allgemeine Hinweise (ISO 4491-1:1989) This European Standard was approved by CEN on 1993-04
15、-02. CEN members are bound to comply with the CEN/CENELEC 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 references concerning such national standards may be obtaine
16、d 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 into its own language and notified to the Central Secreta
17、riat 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, Switzerland and United Kingdom. CEN European Committee f
18、or Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1993 Copyright reserved to CEN members Ref. No. EN 24491-1:1993 EEN 24491-1:1993 BSI 11-1999 2 Foreword In 1992, ISO24491-1:1993 Metallic powders Determination of
19、 oxygen content by reduction methods Part 1: General guidelines was submitted to the CEN Primary Questionnaire procedure. Following the positive result of the CEN/CS Proposal ISO4491-1:1989 was submitted to the CEN Formal Vote. The result of the Formal Vote was positive. This European Standard shall
20、 be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October1993, and conflicting national standards shall be withdrawn at the latest by October1993. According to the Internal Regulations of CEN/CENELEC, the following countries a
21、re bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. NOTEThe European references to international publications are given inAnnex ZA
22、 (normative).EN 24491-1:1993 BSI 11-1999 3 Introduction In powder metallurgy, the purity of the powders is an important parameter for the manufacture of sintered metals. Among the various impurities which may be present in a powder, oxygen plays a particular role as it is always present in any metal
23、 or alloy powder, and in amounts greater than those encountered in compact metals. Oxygen is mostly combined in the form of oxides which appear in the following ways: Oxide film coatings on particle surfaces, spontaneously formed by oxidation of the metal by air or moisture during powder preparation
24、 and during handling and storage. Oxide inclusions, being either oxides of the main metal remaining locally unreduced during the production process (in the case of reduced powders), or other oxide impurities originating from the raw material and/or from the equipment (e.g.refractory ceramics from me
25、lting furnace in atomization processes). In practice, oxygen contents in metallic powders lie mostly in the range 0,1% (m/m) to1% (m/m). The determination of oxygen content can be made by means of many physical or chemical methods, for example a) specific methods, such as activation analysis or mass
26、 spectrometry, in which the element O is directly determined; b) reduction methods, in which oxides present are, totally or partially, reduced by hydrogen or by carbon. Oxygen content is related, either to the loss of mass of the sample through reduction, or to the amount of water or CO/CO 2produced
27、 by the reaction; c) separation methods, in which either the oxide phase is selectively dissolved and determined chemically (for example in copper powder, where copper oxide is dissolved by hydrochloric acid); or the metal phase is selectively dissolved, and the insoluble residue (assumed to be oxid
28、e) is evaluated (for example in aluminium powder, aluminium is dissolved in bromine-methanol reagent, leaving aluminium oxide). The present International Standard considers only reduction methods, as these are commonly used in laboratories for analysing a great variety of metal powders. 1 Scope This
29、 part of ISO4491is the first part of a series dealing with the determination of oxygen content in metallic powders by reduction methods. It gives general guidance to these methods, and gives some recommendations for the correct interpretation of the results obtained. The test methods are applicable
30、generally to all powders of metals, alloys, carbides and mixtures thereof. The constituents of the powder shall be non-volatile under the conditions of test. The powder shall be free of lubricant or organic binder. However, there exist certain limitations which depend upon the nature of the analysed
31、 metal. These limitations are discussed in clause4. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO4491. At the time of publication, the editions indicated were valid. All standards are subject to revi
32、sion, and parties to agreements based on this part of ISO4491 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 4491-2:1989, Metallic powders D
33、etermination of oxygen content by reduction methods Part 2: Loss of mass on hydrogen reduction (hydrogen loss). ISO 4491-3:1989, Metallic powders Determination of oxygen content by reduction methods Part 3: Hydrogen-reducible oxygen. ISO 4491-4:1989, Metallic powders Determination of oxygen content
34、by reduction methods Part 4: Total oxygen by reduction-extraction. 3 Sampling For sampling of the powder the procedures given in ISO3954:1977, Powders for powder metallurgical purposes Sampling, are recommended. The powder shall be tested in the as-received condition. Metallic powders are frequently
35、 reactive substances with respect to air and moisture. Therefore, particular attention shall be given to adequate conditions for handling and storage of the test sample. The test portion shall be taken immediately prior to the analysis.EN 24491-1:1993 4 BSI 11-1999 4 Meaning of the results according
36、 to the method used 4.1 Hydrogen as a reducing agent 4.1.1 At the test temperatures prescribed in the determination, only the following metals have oxides totally reducible by hydrogen: Fe, Ni, Co, Cu, Ag, Sn, Pb, W, Mo, Re All other common oxides are not reducible, in particular Al 2 O 3 , SiO 2 ,
37、ZrO 2and other oxides of alkali, alkali-earth and most rare-earth metals. Oxides of chromium, manganese, titanium, and vanadium may be partially reducible. 4.1.2 However, other reactions with constituents of the powder take place during the reduction process: a) Water vapour and/or hydrocarbons pres
38、ent in the sample, and also gases, which possibly by adsorption or occlusion are contained in the powder, are released during heating. b) Elements, such as carbon, nitrogen, sulfur, phosphorus, free or combined in the powder, may be completely or partially removed, either because they are volatile o
39、r because they react with hydrogen or with oxides in the powder, forming volatile compounds. c) Some metals present in the powder, such as lead, tin, cadmium, zinc, may be partially or completely volatilized, depending on the test conditions. d) Carbon present in the powder can also reduce oxides un
40、der the specified test conditions, and possibly also oxides that normally are not reduced or are only partially reduced by hydrogen, such as chromium, manganese and vanadium oxides. e) Alloy powders containing metallic elements with high affinity for oxygen, such as chromium, manganese, silicon, alu
41、minium and titanium, may be oxidized during the test by reaction with the atmosphere or with less refractory oxides, entailing an apparent decrease of measured oxygen content. 4.1.3 In the loss in hydrogen method (ISO 4491-2), the loss of mass of the test portion, when submitted to a specified heat
42、treatment in hydrogen, is measured. Originally this test was considered to give an estimate of the oxygen content of a metal powder, the oxide of which is reducible by hydrogen. However, with the advent of more complex or alloyed powders, all the reactions considered above(4.1.2) may contribute, pos
43、itively or negatively, to the measured loss of mass. Therefore this test method is purely conventional and its reproducibility requires a scrupulous respect of the operating procedure. This method is commonly used in routine control of powders of certain defined metals as stated in ISO4491-2. 4.1.4
44、In the method determination of oxygen emanating from hydrogen-reducible oxides (ISO4491-3), the quantity of water formed by hydrogen reduction of these oxides is measured by titration. In comparison with the loss in hydrogen method, this method is more specific for the following reasons: The interfe
45、rence of moisture and adsorbed gases is prevented by pre-treatment at low temperature. With a slight modification of the procedure, it is possible to determine the water content of the sample. The interference of metalloids and of volatile metals is avoided. However, interference of carbon present i
46、n the sample may have to be taken into account. Some part of the metal oxides, which otherwise may have been reduced by hydrogen, are reduced by carbon, producing carbon monoxide or dioxide, which are not measured by water titration. Consequently a lower result will be obtained. Therefore two altern
47、ative methods are specified: Method 1: Oxygen content corresponding to hydrogen-reducible oxides, without taking into account carbon interference. This method is applicable in practice when the sampled powder is known to be almost free of carbon for example C 0,02% (m/m) or the carbon present is in
48、an unreactive form. Then the result represents the oxygen content from hydrogen-reducible oxides. Method 2: Oxygen content corresponding to hydrogen-reducible oxides, taking into account carbon interference. In this method the CO+CO 2gases released by carbon reduction of some of the oxides and conta
49、ined in the H 2carrier gas, are quantitatively converted to methane and water on a nickel catalyst at380 C. The total water determined represents the oxygen content emanating from hydrogen-reducible oxides, irrespective of whether the actual reduction has taken place by means of hydrogen or carbon.EN 24491-1:1993 BSI 11-1999 5 NOTEWith reference to4.1.2 d), certain oxides may be partially reduced by carbon, i.e.oxides which otherwise would not be reduced by hydrogen. In such a case, the test condition
