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STANDARD
SIST EN 3976:2009
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 3976December 2006ICS 49.025.30 English VersionAerospace series - Titanium and titanium alloys - Test method -Chemical analysis for the determination of hydrogen contentSérie aérospatiale - Titane et alliages de titane - Méthoded'essai - Analyse chimique pour détermination de la teneuren hydrogèneLuft- und Raumfahrt - Titan und Titanlegierungen -Versuchsmethode - Chemische Analyse zur Bestimmungdes WasserstoffanteilsThis European Standard was approved by CEN on 18 October 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards 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 translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2006 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 3976:2006: ESIST EN 3976:2009
EN 3976:2006 (E) 2 Contents Page Foreword.3 Introduction.4 1 Scope.4 2 Normative references.4 3 Terms and definitions.5 4 Health and safety.5 5 Principle.5 6 Testing requirements.6 7 Test report.10 Annex A (informative)
Solid State Hot Extraction under Vacuum Method.11
SIST EN 3976:2009
EN 3976:2006 (E) 3 Foreword This document (EN 3976:2006) has been prepared by the Aerospace and Defence Industries Association of Europe - Standardization (ASD-STAN). After enquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the National Associations and the Official Services of the member countries of ASD, prior to its presentation to CEN. 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 June 2007, and conflicting national standards shall be withdrawn at the latest by June 2007. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. SIST EN 3976:2009
EN 3976:2006 (E) 4 Introduction This standard is part of the series of EN metallic material standards for aerospace applications. The general organization of this series is described in EN 4258. 1 Scope This standard specifies the requirements for chemical analysis using Inert Gas Fusion Thermal Conductivity Method for the determination of the hydrogen content of titanium and titanium alloys for aerospace applications. The method applies to hydrogen contents ranging from several micrograms per gram to several hundreds of micrograms per gram. It shall be applied when referred to in the EN technical specification or material standard unless otherwise specified on the drawing, order or inspection schedule. NOTE The absolute method not used in routine inspection is solid state hot extraction under vacuum followed by measurement of volume and pressure. Due to its complexity, it is only summarized in Annex A. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO Guide 30:1992, Terms and definitions used in connection with reference materials. ISO Guide 31, Reference materials — Contents of certificates and labels. ISO Guide 35, Reference materials — General and statistical principles for certification. EN 2003-10, Aerospace series — Titanium and titanium alloys — Test methods — Part 10: Sampling for determination of hydrogen content. 1) EN 4258, Aerospace series — Metallic materials — General organization of standardization — Links between types of EN standards and their use. EN 4259, Aerospace series — Metallic materials — Definition of general terms. 1)
1) Published as ASD Prestandard at the date of publication of this standard. SIST EN 3976:2009
EN 3976:2006 (E) 5 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 general terms definition, see EN 4259 3.2 certified reference material (C.R.M.) definition, see ISO Guide 30 4 Health and safety Resources, test pieces, test samples, test materials, test equipment and test procedures shall comply with the current health and safety regulations/laws of the countries where the test is to be carried out. Where materials and/or reagents which may be hazardous to health are specified, appropriate precautions in conformity with local regulations and/or laws shall be taken. 5 Principle 5.1 General The test consists of thermally decomposing the hydrogenated compounds (mostly as metallic hydrides) present in the titanium or titanium alloys. The degassed hydrogen is sent, in a stream of supporting inert gas, into the detection system (thermal conductivity cell) which allows a quantitative measurement of hydrogen content (comparative). Two extraction modes are considered, with respect to the use (or not) of a melting flux. (Table 1). Table 1 Method Extraction Mode Temperature Supporting Gas 1 With flux 1 800 °C Nitrogen or Argon 2 Without flux 2 100 °C Argon
5.2 Method 1 The role of melting flux is to liquefy the mixture (thus facilitating the gas extraction) and to avoid an eventual formation of nitrides. Fusion is performed in a graphite crucible at a temperature of around 1 800 °C: either in a nitrogen supporting gas which allows the nitrogen in the sample to be disregarded with the carbon monoxide which, with the nitrogen, has a very small difference in conductivity. (The excess of carbon and the temperature at which melting is performed prevents any carbon dioxide from forming; it is necessary, however, to foresee a way of trapping small quantities of this gas eventually present by using, for example, a molecular sieve); or in an argon supporting gas which prevents nitrides forming and results in a better sensitivity since argon has a greater difference in conductivity compared to hydrogen. A separation of nitrogen and carbon oxides is necessary as well as, in the case of using a high frequency furnace, an adapted frequency to avoid discharges by ionization. SIST EN 3976:2009
EN 3976:2006 (E) 6 5.3 Method 2 Fusion is performed in a graphite crucible at a temperature of around 2 100 °C and shall be carried out in an argon supporting gas (nitrogen in this case would cause formation of nitrides). 6 Testing requirements 6.1 Resources 6.1.1 Equipment There are numerous models of apparatus but they all generally include the following elements: Device for introducing samples; Heating device (induction furnace or resistance furnace); Sweeping system using supporting gas; System for separating gases (if necessary); Thermal conductivity cell. Where a high frequency furnace is used with an argon supporting gas, the frequency shall be adapted to avoid discharges by ionization. 6.1.2 Materials/Reagents 6.1.2.1 Certified Reference Materials (titanium base alloys with certified hydrogen content) According to ISO Guides 31 and 35 these C.R.Ms. should be produced by a certifying body, traceable to S.I. Units by demonstrated methods and accompanied by a certificate. The certified hydrogen content value shall be accompanied by an uncertainty at a stated level of confidence. 6.1.2.2 Reagents During the analysis only reagents of recognised analytical quality shall be used. Nitric acid
ρ 20 = 1,38 g/ml Hydrofluoric acid
Aqueous solution at 40 %, ρ 20 = 1,13 g/ml 95 % or 96 % (v/v) ethanol Melting flux tin granules Absorbing reagents, separating columns as specified by the manufacturer of the equipment Carbon tetrachloride Diethyl oxide Acetone SIST EN 3976:2009
EN 3976:2006 (E) 7 6.1.2.3 Compressed gases 6.1.2.3.1 Supporting gases Nitrogen of a purity > 99,
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