1、AECMA STANDARD NORME AECMA AECMA NORM Edition approved for publication 1999-04-30 prEN 3976 Edition P 1 April 1999 Comments should be sent within six months after the date of publication to AECMA Gu!ledelle 94 8-1200 BRUXELLES PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES (AECMA) Gul
2、ledelle 94 - 8-1200 BRUXELLES - Tel. (+32) 2 775 81 1 O - Fax. (+32) 2 775 81 11 ICs: Descriptors: ENGLISH VERSION Aerospace series Titanium and titanium alloys Test method Chemical analysis for the determination of hydrogen content Srie arospatiale Titane et alliages de titane Mthode dessai Analyse
3、 chimique pour dtermination de la teneur en hydrogne Luft- und Raumfahrt Titan und Titanlegierungen Versuchsmethode Chemische Analyse zur Bestimmung des Wasserstoffanteils This “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA (The European Association of Aerospace I
4、ndustries). It is published on green paper for the needs of AECMA-Members. It has been technically approved by the experts of the concerned Technical Committee following comment by the Member countries. Subsequent to the publication of this Prestandard, the technical content shall not be changed to
5、an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and signature of the AECMA Standard Checking Centre (NPS) and formal agreement of the Official Services of the Member countries it will be submitted as a draft Euro
6、pean Standard to CEN (European Committee for Standardization) for formal vote. Nota - Extra cooies can be suoolied bv B.N.A.E. - TechnoDolic 54 - 199. rue Jean-Jacques Rousseau - 92138 ISSY-LES-MOULINEAUX CEDEX C5 Chairman Mr Evetts aecma 1999 STD-AECMA PREFI 377b-ENGL 1799 S LO123Ll OOLbL04 IT3 S P
7、age 2 prEN 3976: 1999 Contents Page O Introduction I Scope 2 Normative references 3 Definitions 4 Health and safety 5 Principle 6 Testing requirements 7 Test report Annex A (informative) STD-AECMA PREN 397b-ENGL 1999 LOL23Ll 001bL05 D3T I Page 3 prEN 3976: 1999 O Introduction This standard is part o
8、f 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
9、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 otherwis
10、e specified on the drawing, order or inspection schedule. The absolute method not used in routine inspection is solid state hot extraction under vacuum NOTE 1 followed by measurement of volume and pressure. Due to its complexity, it is only summarized in Annex A. 2 Normative references This European
11、 standard incorporates by dated or undated 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 reference, subsequent amendments to or revisions of any of these publications apply
12、 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. IS0 Guide 30: 1992 IS0 Guide 31: 1981 IS0 Guide 35: 1989 EN 2003-1 O EN 4258 EN 4259 Terms and Definitions Used in Connection with Refer
13、ence Materials Contents of certificates of reference materials Certification of reference materials - General and statistical principles Aerospace series - Titanium and titanium alloys - Test methods - Part IO: Sampling for determination of hydrogen content 1) Aerospace series - Metallic materials -
14、 General organization of standardization - Links between types of EN standards and their use Aerospace series - Metallic materials - Definition of general terms 2) 3 Definitions For the purposes of this standard, the following definitions apply: Definition of general terms: see EN 4259. Definition o
15、f certified reference material (C.R.M.): see IS0 Guide 30. 1) Published as AECMA Prestandard at the date of publication of this standard 2) In preparation at the date of publication of this standard Page 4 prEN 3976: 1999 Method 1 2 4 Health and safety Extraction Mode Temperatu re Supporting Gas Wit
16、h flux 1800 “C Nitrogen or Argon 2 100 “C Argon Without flux 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
17、 which may be hazardous to health are specified, appropriate precautions in conformity with local regulations and/or laws shall be taken. 5 Principle The test consists of thermally decomposing the hydrogenated compounds (mostly as metallic hydrides) present in the titanium or titanium alloys. The de
18、gassed 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). 5.1 Metho
19、d 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 OC: - either in a nitrogen supporting gas which allows the nitrogen in the sample
20、to be disregarded with the carbon monoxyde 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 dioxyde from forming; it is necessary, however, to foresee a way of trapping small quantities
21、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 neces
22、sary as well as, in the case of using a high frequency furnace, an adapted frequency to avoid discharges by ionization. 5.2 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 f
23、ormation 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 g
24、as; Page 5 prEN 3976: 1999 - 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 MateriaMReagents 6.1.2.1 According to IS0 Guides 31 and 3
25、5 these C.R.Ms. should be produced by a certifying body, traceable to S.l. 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. Certified Reference Materials (titanium base alloys
26、with certified hydrogen content) 6.1.2.2 Reagents During the analysis only reagents of recognised analytical quality shall be used. - Nitric acid pz0 = 1,38 g/ml - Hydrofluoric acid Aqueous solution at 40 %, p20 = 1,13 glml - 95 % or 96 % (v/v) ethanol - Melting flux tin granules - Absorbing reagent
27、s, separating columns as specified by the manufacturer of the equipment - Carbon tetrachloride - Diethyl oxide - Acetone 6.1.2.3 Compressed gases 6.1.2.3.1 Supporting gases - Nitrogen of a purity 99,995 Oh (N + rare gases) with H2 99,995 % with N 99,9999 % - Helium of a purity 99,9999 % 6.1.2.3.3 Ga
28、s for pneumatic devices Compressed air “for laboratory use“. 6.1.3 Qualification of personnel Testing to the requirements of this test method shall only be undertaken and/or supervised by personnel who have demonstrated their competence by a suitable education and appropriate training and experience
29、. 6.2 Test samplesltest pieces 6.2.1 Location of samples In the case of semi-finished products: as per EN 2003-10. In the case of finished products: as per special agreement and availability. Page 6 prEN 3976: 1999 6.2.2 Sampling is carried out by machining, in dry conditions, with no lubricant, usi
30、ng tools cleaned with solvents (sawing with a blade, the protecting paint of which has previously been removed by cleaning with solvents and abrasive paper, drilling, pelleting, excluding hot cropping) in conditions whereby any heating of the metal is avoided as far as possible. Sampling method and
31、preparation of test portion NOTE 2 Titanium is easily hydrogenated by the humidity in the air at temperatures above 300 “C. Sampling in the form of chips shall only be envisaged in the case of absolute necessity (due to the risks of heating the sample for analysis and the difficulties in introducing
32、 it in the analyser). Whatever its surface appearance, the sample for analysis shall be thorougly cleaned with solvents to eliminate any potential pollutants such as paint, grease, etc. The procedure is as follows: - clean at ambient temperature with a solvent such as carbon tetrachloride, diethyl o
33、xide (ether), acetone ., - if trichlorethylene is used, it shall be followed by one of the above solvents, - drying in the air at about 60 “C or at ambient temperature under a slight vacuum. Furthermore, on certain semi-finished industrial products, but never on finished products, cleaning may be co
34、mpleted by pickling at ambient temperature for several minutes using the following acid mixture as recommended by work carried out by the European Community Bureau of References: - 4 volumes of nitric acid; - I volume of hydrofluoric acid; then rinsed three times in water, three times in ethanol and
35、 dried in the air at about 60 “C or at room temperature in a slight vacuum. 6.2.3 The necessary mass of the sample for analysis may vary according to the apparatus, but is generally about 250 mg. It may be necessary to reduce sampling accordingly depending on the size of the crucibles Mass of the sa
36、mple for analysis NOTE 3 compatible with certain types of apparatus. Where the method 1 is used, the quantity of melting flux shall be about 15 times greater than that of the titanium alloy. 6.3 Testing proced we 6.3.1 General instructions The detailed procedure depending on the apparatus used is sp
37、ecified on the manufacturers instruction sheet and cannot be described in this standard. Certain general considerations shall nevertheless be recalled. According to the individual characteristics of each type of analyser, the following should be checked: - the cleanness and the absence of deposits i
38、n the different circuits by obtaining correct and constant values for the various gas deliveries (in the case of apparatus with a supporting gas), - the cleanness and effectiveness of the different filters, traps and absorbing systems. It is absolutely necessary to maintain the same values for the d
39、elivery of the supporting gas, for the temperature of the measuring cell and for the intensity applied on the filament of the thermal conductivity cell in the analysing sequence as in the calibration sequence. STD-AECMA PREN 397b-ENGL 1999 lU12311 110lb1;07 785 m Page 7 prEN 3976: 1999 6.3.2 Cali br
40、ation The various apparatuses generally include a calibrating device by injecting one or several known volumes of pure hydrogen (adjusted according to variations in temperature and pressure). These known volumes are delivered from a compressed hydrogen cylinder by a pneumatic system (calibrated “cav
41、ities“ and gas slide valves .). This procedure effectively calibrates the measuring system but does not enable the effectiveness of extraction and the eventual separation of degassed chemical substances to be evaluated. It is therefore essential to complete this procedure by analysing the Certified
42、Reference Materials. If the result differs considerably ( relative 5 %) , the analytical conditions shall be changed: quantity of flux powder, setting of the power applied to the furnace, heating time . The use of the result obtained with the Certified Reference Material for an arithmetical correcti
43、on of the value obtained with the sample to be analysed is to be avoided. In the case where the analytical equipment is not fitted with gas-calibration system, it is only possible to calibrate with CRMs for routine analysis; several CRMs shall be analysed in order to ensure the linearity of the resp
44、onse of the detector. The analytic conditions: power of the furnace, heating times, quantity of melting flux _._, should be set according to the manufacturer recommendations. In the case where calibration by injecting known volumes of hydrogen is substituted by calibration with injections of known v
45、olumes of helium it is necessary to take into account the difference in sensitivity of the catharometer between the calibration process and the analysing process. Where a same system for injecting volumes of gas is used, the calibration value for the delivery of identical supporting gases obtained w
46、hen using hydrogen shall be multiplied by a corrective coefficient. This coefficient which depends on the properties of these two gases (thermal conductivity, mass per unit volume .) is also influenced by the nature of the supporting gas (thermal conductivity .) and the apparatus (in particular the
47、temperature of the catharometers filaments). In practice, it may, however, be considered constant and equal to: k = 0,60 k 0,Ol It may also be determined experimentally by the ratio of values obtained with the catharometer by successively injecting the same volumes of hydrogen or helium. Since the c
48、alibration procedure with helium introduces a supplementary factor likely to influence the reproducibility criteria of the analysing method, laboratories using it should periodically carry out calibration with hydrogen. 6.3.3 Analysis 6.3.3.1 Method I The test is performed in two stages in the analy
49、ser: - during a first phase the graphite crucible, filled with melting flux, is totally emptied of its hydrogen by heating in the supporting gas flow; - during a second phase the sample for analysis is placed in the crucible, now degassed, and submitted to the thermal analysis cycle under the supporting gas flow. Measuring is carried out using the thermal conductivity cell. Depending on the apparatus, the sample for analysis may be introduced by a lock chamber or manually through a “curtain“ of supporting gas after opening the analyser; in this case it is essential to allow the cruci
