1、STD-BSI BS EN IS0 14744-3-ENGL ZOO - present to the responsible internalional/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; - monitor related international and European developments and promulgate them in the UK. A list of organh
2、ations represented on this committee can be obtained on request to its secretary. Cross-references Attention is drawn to the fact that CEN and CENELEC Standards normally include an annex which lists normative references to international publications with their corresponding European publications. Th
3、e British Standards which implement these international or European publications may be found in the BSI Standards Catalogue under the section entitled “Internationai Standards Correspondence Index”, or by using the “Find” facility of the BSI Stankds Electronic Catalogue. A British Standard does not
4、 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 fro
5、nt cover, the EN IS0 title page, pages 2 to 8, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN IS0 14744-3 April 2000 ICs 2
6、5.1 60.00 English version Welding - Acceptance inspection of electron beam welding machines - Part 3: Measurement of beam current characteristics (IS0 14744-3:2000) Soudage - Essais de rception des machines de soudage par faisceau dlectrons - Partie 3: Mesure des caractristiques de lintensit du fais
7、ceau (IS0 14744- 3:2000) Schweien - Abnahmeprfung von Elektronenstrahl- Schweimaschinen - Teil 3: Messen des Strahlstrom- Kenngren (IS0 14744-3:2000) This European Standard was approved by CEN on 3 January 2000. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate
8、 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 obtained on application to the Central Secretariat or to any CEN member. This European Standard exists
9、 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 Secretariat has the same status as the officiai versions. CEN members are the national standards bodie
10、s of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMEE FOR STANDARDIZATION EUROPISCHES KOMITEE FOR NORMUNG COMITE EUROPEEN DE NORMALISATION Ce
11、ntral Secretariat: rue de Stassart, 36 B-1050 Brussels Q 2000 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN IS0 14744-3:2000 E STDeBSI BS EN IS0 14744-3-ENGL 2001 3624669 0902867 043 M Page 2 EN-IS0 14744-3:2000 Contents Page For
12、eword . : . 3 1 Scope 4 2 Normative references . 4 3 Termsand definitions 4 4 Testarrangement 4 4.1 General . 4 4.2 Faraday cup and electrical connections . 6 5 Measurement procedure 7 General . 7 5.1 5.2 Currentlosses . 7 5.3 Measuring the ripple 7 5.4 Measuring the stability . 7 5.5 Measuring the
13、reproducibility 7 6 Problems in measurement . 8 7 Evaluation . 8 Page 3 STD-BSI BS EN IS0 1,4744-3-ENGL 2001, = 3b24669 0902868 TBT m EN IS0 14744-3:2000 Foreword The text of EN IS0 14744-3:2000 has been prepared by Technical Committee CEN/TC 121 “Welding“, the secretariat of which is held by DS, in
14、 collaboration with Technical Committee ISOTTC 44 “Welding and allied processes“. 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 2000, and conflicting national standards shall be withdraw
15、n at the latest by October 2000. According to the CEWCENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxe
16、mbourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. This draft European Standard is composed of the six following parts: - Part 1 : Principles and acceptance conditions; - Part 2: Measurement of accelerating voltage characteristics; - Part 3: Measurement of beam
17、 current characteristics; - Part 4: Measurement of welding speed; - Part 5: Measurement of run-out accuracy; - Part 6: Measurement of stability of spot position. Page 4 EN IS0 14744-32000 Lb24bb9 0902b Lb 1 Scope This standard is intended for use when the beam current of electron beam welding machin
18、es complying with EN IS0 14744-1:2000 is to be measured in connection with an acceptance inspection. It provides essential information on the procedure and apparatus to be used for making the measurements. The beam current is one of the significant parameters in electron beam welding. When the beam
19、current impinges on the workpiece, it should be stable and reproducible within given short-term and long-term limits. The purpose of the measurement is thus to check whether the variations in beam current are within these limits. 2 Normative references This European Standard incorporates by dated or
20、 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 references, subsequent amendments to or revisions of any of these publications apply to this European Standard only
21、when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN IS0 14744-1 :2000 Welding - Acceptance inspection of electron beam welding machines - Part 1: Principles and acceptance conditions (IS0 14744-1 : 2000) 3 Terms and d
22、efinitions For the purposes of this European Standard, the following term and definition applies, 3.1 Beam current current produced by the sum of the accelerated electrons before these impinge on the workpiece, measured at a distance roughly corresponding to the work distance NOTE Although this curr
23、ent is somewhat lower than the electron current emitted from the cathode, it is the factor crucial to the welding procedure. 4 Test arrangement 4.1 General The beam current is to be measured at specified levels covering the entire power range of the welding machine. As there is no solid conductor, a
24、 Faraday cup shall be used that, as far as possible, collects all the electrons emitted from the cathode and causes them to flow to earth through a resistor of given rating (see figure 1). The Faraday cup shall be designed so that it: a) sustains the thermal load even at high beam powers over a peri
25、od equal to several times the measurement period; b) prevents, as far as possible, the escape of primary and secondary electrons and charged vapour. Page 5 STD-BSI BS EN IS0 L4744-3-ENGL 2001 = Lb24bb9 0902870 638 m EN IS0 14744-3:2000 Key 1 Electron beam 2 Faraday cup 3 Faraday cup orifice 4 Insula
26、tion 5 Work table 6 Resistor 7 Screened cable to oscilloscope 8 Feedthrough to pass cable through work chamber wall Figure i - Diagrammatic representation of beam current measurement using a Faraday cup STD-BSI BS EN IS0 l14744-3-ENGL 2OOL m Lb24bb9 0702871 574 m Page 6 Maximum Maximum accelerating
27、voltage, beam power, in kV in kW dl 60 15 6 60 30 10 150 6 6 EN-IS0 14744-3:2000 D 1 O0 170 1 O0 4.2 Faraday cup and electrical connections Figure 2 and table 1 provide recommended dimensions on the design of Faraday cups of copper for various beam powers up to 30 kW which may be adapted to meet pra
28、ctical requirements. For beam powers above 15 kW, water cooling is necessaty. 300 Table 1 - Faraday cup. Recommended dimensions (see figure 2) 500 10 x 10 I 150 I 30 I 10 I 100 values in mm 10 x 10 10 x 6 NOTE 1 Dimension d, should be kept small enough just to accommodate a focused electron beam inc
29、luding fringe beam, while preventing the escape of electrons. Ke 1 dectron beam 2 Copper 3 Ceramic insulator NOTE 2 The bores around the escape of electrons. 2 3 Figure 2 - Faraday cup assembly Faraday cup barrel allow a rapid escape of metal vapour whilst avoiding The Faraday cup shall be insulated
30、 electrically from the work table by means of a ceramic insulator. A resistor shall be connected between the Faraday cup and earth at a sufficient distance to prevent it being thennally influenced. As shown in figure 1, a screened cable shall be passed to the measuring instrument via a feed- through
31、 in the work chamber wall. 5 Measurement procedure 5.1 General The measurements shall be carried out with the welding machine set as specified in 6.2 of EN IS0 14744-1:2000. 5.2 Current losses The beam current entering the Faraday cup shall be measured and compared with the emission current (.e. the
32、 rated beam current). Excessive deviations indicate inaccurate positioning of the electron beam with respect to the diameter of the Faraday cup orifice, d, or adjustment errors in the beam source which are to be corrected. For all operations, when using the Faraday cup, the electron beam shall be fo
33、cused on the centre of the orifice (see figure 2). Beam parameters and position of the Faraday cup shall be adjusted to obtain maximum monitored voltage prior to testing. 5.3 Measuring the ripple An oscilloscope shall be used to determine the maximum range (peak-to-peak value) in the instantaneous v
34、alue U; of the monitored voltage, U,. The percentage deviation shall be calculated as follows: where U, max, U, ,“ and U, are maximum, minimum and average values observed during the period of observation (see figure 3). 5.4 Measuring the stability The average voltage shall be recorded continuously f
35、or a given operating period, using an instrument eliminating ripple. The percentage deviation shall be calculated as follows: whichever is the largest and where U, max and U, min are maximum and minimum observed values and U, is the initial value. 5.5 Measuring the reproducibility The beam current s
36、hall be switched on and the average monitored voltage shall be measured, using an instrument eliminating ripple. The specified beam current shall subsequently be switched off and on several times and the corresponding average monitored voltages shall be recorded. The reproducibility shall be calcula
37、ted as follows: whichever is the greater where U, mBy and U, min are maximum and minimum average values observed and U, is the initial value. STDmBSI BS EN IS0 14744-3-ENGL Page 8 EN IS0 14744-312000 2001 162LObb7 0902873 347 a) Measurement of U, b) Measurement of peak-to-peak value (greater sensiti
38、vity of indication in the Y direction than for item a) Figure 3 - Screen indications for measuring the beam current ripple 6 Problems in measurement The problem most frequently met with, particularly when measuring high beam currents, is a high frequency fluctuation of the beam current on the displa
39、y, which is associated with an over-large fusion area in the bottom of the Faraday cup. Such problems are best overcome by keeping to short measurement times and providing for long cooling intervals, or if possible using a water cooled Faraday cup. 7 Evaluation The measured values of ripple, stabili
40、ty and reproducibility shall be assessed by comparing them with the limit deviations specified in EN IS0 14744-1:2000. BS EN IS0 14744-3:2001 BSI 389 Chiswick High Road London w4 4AL BSI - British Standards Institution BSI is the independent nationai body responsible for preparing British standards.
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