High-voltage electric pulse welding of magnetic cores made of rings of magnetic soft alloy 49K2FA

Transcription

1 IOP Conference Series: Mterils Science nd Engineering PAPER OPEN ACCESS High-voltge electric pulse welding of mgnetic cores mde of rings of mgnetic soft lloy 49K2FA To cite this rticle: A V Yudin et l 2017 IOP Conf. Ser.: Mter. Sci. Eng View the rticle online for updtes nd enhncements. This content ws downloded from IP ddress on 14/10/2018 t 17:53

2 IOP Conf. Series: Mterils Science nd Engineering (2017) doi: / x/218/1/ High-voltge electric pulse welding of mgnetic cores mde of rings of mgnetic soft lloy 49K2FA A V Yudin, E G Grigoryev, S S Bshlykov nd V I Goltsev The lortory of dvnced technologies for cretion of new mterils, Ntionl Reserch Nucler University MEPhI, Kshirskoe shosse, 31, Moscow, Russi, E-mil: Artem.Yudin@icloud.com Astrct. This reserch nlyses the influence of the prmeters of high-voltge electric pulse welding on microstructure of weld sems nd mechnicl prmeters of smples. Specil tooling ws developed for the process of high-voltge electric pulse welding, llowing welding of ring smples. The method of determintion of mechnicl chrcteristics of toroidl smples ws developed. An influence is estlished of prmeters of high-voltge electric pulse welding, such s current density nd pplied pressure, on microstructure of weld sem nd density of weld joint. The study of mgnetic prmeters of smples is conducted. 1. Introduction Vrious types of welded joints nd welding processes re currently used for production of solid devices. Conventionl welding methods cn not lwys meet the requirements of the welding joints. Consequently, the moderniztion is required, s well s development of new methods with wider potentil [1]. One of the promising directions of welding is the high-voltge electric pulse welding. A high-voltge electricl pulse pssing through the welded prts cuses significnt chnge in the stte of the contcting surfces. Intense lternting mgnetic field nd the pplied pressure ffect the lnk detils simultneously with the ohmic heting in the zone of contct of detils. This leds to firm joint (good qulity of welding) of detils. Depending on the initil stte of the contcting surfces, current pulse prmeters nd the pplied pressure, oth forming of firm joint (t the optiml prmeters vlues) nd explosive destruction of the contct zone re possile [1]. Erlier studies [2] discovered tht initil roughness of surfces of welded prts hs sustntil effect on the welding process. Experiments showed tht the mximum strength of the T-type welding joints (core - disk) in the nlyzed rnge is otined t the vlue of roughness of surfce (R z ) 20 µ to 40 µ. This chieves the mximum energy relese nd the mximum heting of the contct surfces of the welded prts. The high-voltge pulse welding method uses specil high-voltge process equipment, which llows providing controlled pulse electric power impct on the joined prts. This equipment hs een designed nd creted in the Interdeprtmentl lortory of dvnced technologies for cretion of new mterils of Ntionl Reserch Nucler University MEPhI for implementing dvnced electric pulse technologies of development of new mterils nd products mde them, with unique structure nd properties unttinle y other methods. A more detiled description of the equipment cn e found in rticles [3-5]. Modern mechnic engineering widely use vrious systems of electromgnetic energy conversion. The technicl nd opertionl chrcteristics of such systems re determined y the mgnetic Content from this work my e used under the terms of the Cretive Commons Attriution 3.0 licence. Any further distriution of this work must mintin ttriution to the uthor(s) nd the title of the work, journl cittion nd DOI. Pulished under licence y Ltd 1

3 IOP Conf. Series: Mterils Science nd Engineering (2017) doi: / x/218/1/ prmeters of the permnent mgnets nd mgnetic cores, mde of soft mgnetic mteril, in which cpcity the 49K2FA precision lloy is used in Russin instrumenttion engineering. The improvement of mgnetic properties: n increse of sturtion induction nd the mximum mgnetic permeility nd decrese of coercive force significntly ffect the qulity of the products, which use detils mde of this precision lloy. The ojective of this pper is to investigte the influence of technologicl prmeters of the highvoltge electric pulse welding (the current pulse mplitude nd the pplied pressure) on the joint efficiency of the elements in the reference smples, compre the chrcteristics of mgnetic circuits mde of thin rings of soft mgnetic lloy 49K2FA to the chrcteristics of the glued mgnetic cores. 2. Experiment A specil tooling hs een developed to crry out the high-voltge electric pulse welding process. The welding of toroidl smples of the lloy 49K2FA ws conducted on the system shown in Figure 1, with the tooling shown in Figure 1. The high-voltge electric pulse welding system consists of high-frequency pulse genertor (1) nd executive unit (2). The technologicl tooling includes rss rod (1), centrl lminte liner (2) nd rss electrode punch (3). Figure 1. Used equipment () nd tooling (). Toroidl smples of 10 mm height were produced y welding t different technologicl modes of thin rings with thickness of 0,2 mm cut out of sheet of 49K2FA precision lloy. In high-voltge electric pulse welding process the min vriles re the vlue of the ring (disks) compression force nd the vlue of current density through the lnk smple, s well s the numer of pulses pssed through the lnk. Chnging the current density ws crried out y chnging the voltge on the cpcitor nk, nd chnging the compression force ws crried out y chnging the pressure in the pneumtic system. The testing is proposed of the ring smples y compression in ring plne. Compression testing of ring smple llows simplify the process of loding the smple nd its destruction s fully s possile nd determining not only the mechnicl chrcteristics of the mteril, ut lso the qulity nd reliility of the joints of elements in cses when the produced smple is mde of thin ring elements y the method of high-voltge welding. Essentilly this relizes lterl ending of em plceв on two supports (Fig. 2). 2

4 IOP Conf. Series: Mterils Science nd Engineering (2017) doi: / x/218/1/ Figure 2. Schemtic digrm of compression test of the reference smples Considered re three possile types of smple filure under compressive loding y the scheme presented in Figure 2: rittle frcture on the plne of lod ppliction plstic deformtion of the ring up to its flttening (without frcture or with formtion of crcks in the externl side surfces or internl long plne coinciding with the plne of the loding); delmintion of the produced ring on seprte elements (exposed to weld joint) followed y loss of stility of these thin elements. If the mteril of finished product is rittle, thn the smple filure occurs long the plne of lod ppliction, where the mximum ending moment pplies, ending strength is determined y the formul: и 3P k D d В 2 2h (1) where P k recorded loding t the smple filure; D ср verge ring dimeter; ring width; h ring thickness. Expected significnt vrition of the test results is typicl for rittle frcture nd my require sttisticl processing. If the mteril is plstic, grdul flttening of the ring occurs with possile formtion of crcks on the externl or on the internl surfces of the ring. In this cse the deformtion (the deflection of the smple) t the moment of the crck ppernce is determined s well chrcteristic of the strength of the mteril resistnce to the initil ppernce of plstic deformtion the yield ending strength, determined y the formul: и 3P T D d Т 2 2h (2) where P Т the vlue of loding, corresponding to lod corresponding to the mximum reltive deformtion of the smple 0,002 (determined y the digrm of loding-deflection of the smple); D d verge ring dimeter; ring width; h ring thickness. If during the loding of the ring smple delmintion nd susequent loss of stility of the individul elements occurs, it does not men tht the strength of mteril joint in the weld is insufficient. It is importnt to estlish t which stge of loding the delmintion occurs. Ensuring the 3

5 IOP Conf. Series: Mterils Science nd Engineering (2017) doi: / x/218/1/ strength of the smple nd the reliility of the element joint is chieved under optiml conditions of high-voltge welding. 3. Experimentl results nd discussion A study of microstructure of the smple produced y single pulse of 2 kv nd the pressure of 88.5 MP, reveled rther lrge gps etween the rings. The weld sem is spot weld of size out 50 µm (see Fig. 3 ). Conducting mechnicl test llowed determining tht the smple is degrding y delmintion of the finished product into the seprte elements with consequent loss of stility of these thin elements. The delmintion of rings occurs t the pressure equl 43.2 MP nd the displcement vlue equl 0.17 mm (Fig. 3 ). Figure 3. Chrcteristics of the smple produced y single pulse of 2.0 kv The microstructure of the smple welded y single pulse of 3.5 kv t the pressure equl 88.5 MP is chrcterized y smller gps etween the disks, t the sme time the size of the weld sem remined nerly the sme (out 50 µm). Mechnicl tests showed tht the pressure vlue t the smple filure mounts to 67.5 MP, nd deformtion equls 1.1 mm. The chrcter of the destruction lso chnged with no delmintion of the rings nd it proceeded y the scheme of plstic deformtion of the ring. Next smples were mde y two high-voltge pulses of 3.0 kv t the pressure of 88.5 MP. At these prmeters of the high-voltge electric pulse welding the gps etween the disks re prcticlly nonexistent nd the size of the weld sem mounts to 70 µm to 100 µm (Fig.4, ), nd the filure pressure incresed to MP, with the mximum deformtion equl 2.6 mm. The filure lso proceeded y the scheme of plstic deformtion of the ring, with no shrp declines of lod vlue leding to the delmintion of the rings from the smple (Fig.4, ). Figure 4. Chrcteristics of the smple produced y two pulses of 3,0 kv Next set of smples ws produced y pssing two high-voltge pulses of with n mplitude of 4.0 kv t the pressure equl 88.5 MP. 4

6 IOP Conf. Series: Mterils Science nd Engineering (2017) doi: / x/218/1/ Figure 5. Chrcteristics of the smple produced y two pulses of 4.0 kv As is evident from the photogrph of the microstructure there re no gps etween the discs nd the size of the weld sem mounts to more thn 100 µm (Fig. 5 ). Concurrently the ultimte strength mounts to 351 MP, the deformtion equls 0.77 mm, ut the chrcter of the filure hs chnged. In this set of smples the rittle filure is prevlent (Fig. 5 ). Consequently, the overll nlysis of smple loding digrms nd recorded stepwise imges of the process leds to the conclusion tht the delmintion of ring smples strts outside of the elstic initil loding zone nd is reflected in the digrm in the form of steps. The study of mgnetic properties of the smples showed tht with this method of joining rings into the mgnetic core there is no deteriortion of the mgnetic chrcteristics of the mteril. E.g. for the smple produced y two pulses of the mplitude 4.0 kv, the following mgnetic chrcteristics were otined: B = 2.26 T, H c = 50 A/m, μ = G/Oe. 4. Conclusions The reserch proposes method of strength testing of weld sem qulity. Such strength testing llows simplifying the process of loding the ring smple nd its filure s fully s possile nd determining not only the mechnicl chrcteristics of the mteril, ut lso the qulity nd reliility of the joints of elements. The comprison of the microstructure nd strength properties of welded joints showed the following: the strength the weld joint depends on the distnce etween the pltes in the smple, the shorter the distnce the greter the strength; the use of two high-voltge pulses increses the weld zone (weld sems), which lso increse the strength of joint; the loction of weld sems etween the pltes depends on the roughness of the welded surfces, which define the contct zone An optiml mode of otining qulity weld sem is suggested: two high-voltge pulses with voltge vlue of 4,0 kv. References [1] Grigoryev E G 2011 High voltge electric pulse welding of titnium with stinless steel Interntionl Scientific Journl Mchines. Technologies. Mterils [2] Gurevich S M 1990 Reference ook on welding of nonferrous metls (Kiev, Nukov Dumk) [3] Grigoryev E G, Bznov V N 2008 Electric current pulse welding of titnium VT1-0 with stinless steel 12Х18Н10Т Moscow Stte University of Eduction J.: Nturl Sciences [4] Grigoryev E G, Bznov V N 2010 Electric current pulse welding of titnium with STAINLESS STEEL Advnced Mterils Reserch [5] Grigoryev E G 2011 Welding of titnium with stinless steel y high-voltge electric-current pulse Proceedings of the 2011 Interntionl Conference on Powder Metllurgy nd Prticulte Mterils, PowderMet