THE STUDY OF INFLUENCE CORE MATERIALS ON TECHNOLOGICAL PROPERTIES OF UNIVERSAL BENTONITE MOULDING MATERIALS Mtej BEZNÁK, Vldimír HANZEN, Ján VRABEC Authors: Mtej Beznák, Assoc. Prof. PhD., Vldimír Hnzen, MSc. Eng. Ján Vrec, MSc. Eng. Workplce: Deprtment of Csting, Institute of Production Technologies, Fculty of Mterils Science nd Technology in Trnv, Slovk University of Technology Brtislv Address: J. Bottu 23, 917 24 Trnv, Slovk Repulic Phone: +421 918646051 Emil: mtej.eznk@stu.sk, vldimir.hnzen@stu.sk, jn.vrec@stu.sk Astrct The pper dels with influence of core mterils on universl moulding mteril with entonite used for mouldmking. The experiments evluted the influence of core snd content (10, 20, 30, 50%) in universl entonite moulding mteril. The influence ws estimted y mesurement of technologicl properties of moulding mteril. The results proved tht these contents influence technologicl properties of universl entonite moulding mteril. Key words core mterils, universl moulding mterils, entonite Introduction The development in foundry production improves mny used methods. Their improvement increses cstings qulity nd decreses proility of defects. So the qulity of moulding mteril is very importnt. The Dis mouldmking method uses universl entonite moulding mteril, which is continuously recycled during production cycle. The new entonite must e dded fter its use in certin numer of cycles or fter chieving certin level of wer. Also new snd is dded into mopulding mteril. There is need of technologicl properties (humidity, permeility) mesurements to use the inder nd snd economiclly. These cn e mesured during production process y testers plced in moulding mteril processing workshop ner muller to control the necessry djustments. After lrge numer of production cycles the technologicl properties of universl moulding mteril re influenced y some core mteril content. The core mteril is dmixed into universl moulding mteril t high-frequency shkeout tles, virtion devices, etc.. Core mteril remins in moulding mteril s deris of cores. These deris cn cuse decresing of some technologicl properties especilly t mss production of ox type cstings. The mesurements of humidity 1
nd permeility re insufficient for such production nd mesurements of mechnicl properties of universl entonite moulding mteril re lso necessry. The properties of moulding mteril re chrcterized y physicl, chemicl nd technologicl prmeters. Bentonite moulding mterils The entonite moulding mterils re most used moulding mterils for moulds used for cst iron cstings production. Their sic composition is snd (usully silic snd), inder ( entonite) nd dditives (cron contining, strch, grphite), wter. Using these moulding mterils in tch production cuses progressive decresing of their qulity (chnge of technologicl properties) nd ecuse of this fct they must e improved y new inder ddition nd lso wter ddition to chieve required humidity. The humidity of moulding mteril is djusted for optiml comptiility 30-40 %. The optiml wter content is determined from curves of compression strength nd permeility (humidity). The properties of moulding mteril like mouldility, flowility nd comptiility re very sensitive even on smll chnge of wter content. [3] Experimentl Universl entonite moulding mteril (its components shown in Tle 1) ws used for experimentl mesurements. BASIC COMPONENTS OF UNIVERSAL BENTONITE MOULDING MATERIAL Tle 1 Universl entonite moulding mteril Binder Snd KERIBENT C30 Šjdíkové Humence SH34 (d 50 =0,22 mm ) (mixed entonite) +Grudzeň Ls (d 50 =0,16mm) (pure entonite 7% + grphite 3%) Moulding mteril ws prepred y intensive mixer TECHNICAL SPM 70. The moulding mteril ws smpled during its trnsport (y conveyor elt) efore moulding. For its finl conditioning lortory verticl wheel tch type muller MK ws used. The humidity of moulding mteril ws djusted efore experimentl mesurements to chieve required compctiility 35 % for experiments. One tch in lortory verticl wheel tch type muller ws 10 kg of moulding mteril. Core mteril with vrious inding processes ws used. Cores were mde from snd Šjdíkové Humence SH33 (d 50 =0,27 mm) from Kerkosnd.s.. Vrious content of core mteril ws dmixed into moulding mteril (10, 20, 30, 50 %). After ddition of core mteril wter ws dded moulding mteril to chieve required compctiility 35 %. 2
Fig. 1. Devices for moulding mteril strength properties mesurement LRU-D nd permeility mesurement LPiR-D [2] Fig. 1 shows universl device for moulding mteril strength properties mesurement LRU-D nd device for permeility mesurement LPiR-D for experimentl mesurements. The test specimens were cylinders with dimeter 50 nd height 50 mm. They were mde y snd rmmer HVD-1 with impct energy 9,81 J. They were used to determine the moulding mteril technologicl properties (specimens were mde with vrious contents of core mteril). Experiments mesured mechnicl properties like compression strength, splitting strength nd permeility. Fig. 2 shows compression strength of moulding mteril influenced y incresing content of core mteril nd Fig. 2 compression strength of moulding mteril influenced y incresing content of core mteril with ddition of new entonite. The ddition of new entonite ws 7 % of core mteril content. Simultneously lso cron ddition (fine grphite powder 3%) ws dmixed to improve technologicl properties of moulding mteril. 220 220 Compression strength [ kp ] 200 180 160 140 Compression strength [ kp ] 200 180 160 with ddition of new entonite 140 Fig. 2. The dependence of moulding mteril compression strength on core mteril content ) ) with ddition of new entonite 3
On fig.2 cn e seen influence of core mteril content on moulding mteril compression strength. The splitting strength tests were lso crried out. This test is good indictor of moulding mteril qulity. Fig. 3 shows grphs of splitting strength nd 3) shows curves of moulding mteril splitting strength influenced y incresing content of core mteril without ddition of new inder (entonite). Fig. 3) shows curves of moulding mteril splitting strength influenced y incresing content of core mteril with ddition of new inder. 50 50 Splitting strength [ kp ] 30 Splitting strength [ kp ] 30 10 with ddition of new entonite 10 Fig. 3. The dependence of moulding mteril splitting strength on core mteril content ) ) with ddition of new entonite Fig. 4 shows influence of incresing core mteril content on moulding mteril permeility. Fig. 4 shows influence of core mteril content on moulding mteril permeility nd Fig. 4 with ddition of new entonite. 170 Permeility [ j.p.si ] 150 130 110 90 Fig. 4. The dependence of moulding mteril permeility on core mteril content c) d) with ddition of new entonite 4
Discussion The strength properties of moulding mteril depend on its humidity nd comptiility. The mesurement of compression strength shows tht incresing content of core mteril cuse decresing of compression strength. The content of 50 % core mteril in moulding mteril decrese the compression strength out 50 kp s cn e seen on Fig. 2. The ddition of new inder (mixed entonite with 10 % content) did not chnged compression strength significntly s cn e seen on Fig. 2. Fig. 3 shows dependence of splitting strength on core mteril content. From the splitting strength mesurements cn e concluded tht incresing core mteril content decreses splitting strength. 50 % core mteril content in moulding mteril decreses splitting strength y 13,4 kp. This decresing cn e eliminted y 10 % new entonite ddition when the decresing is stopped nd originl vlues re reched. Thus cn e concluded tht core mteril content influences mechnicl properties of moulding mteril. The decresing of mechnicl properties cn e cused y lower inder content in moulding mteril. Permeility is chrcteristics of moulding mteril tht permits gses nd vpour to pss through them. These re generted during pouring of molten metl into mould. Mesurements of moulding mteril permeility estlished tht ddition of core mteril increses its permeility, due to decresing inder content s cn e seen on Fig. 4. The ddtion of 10 % new mixed entonite cused smller incresing t sme core mteril content. Thus cn e concluded tht inder content hs gret influence on moulding mteril permeility. Conclusion The otined results enle to conclude, tht presence of core snds significntly influence properties of universl entonite moulding mteril. This influence cn e oserved on strength properties of moulding mteril (compression strength, splitting strength). The incresing content of core mteril decreses strength properties of moulding mteril. The incresing content of core mteril increses permeility of moulding mteril y inder content decresing nd men grin size incresing ecuse of using snd with higher d 50 vlue for coremking. It ws lso estlished tht ddition of new inder (mixed entonite) into moulding mteril did not chnge moulding mteril`s mechnicl properties nd permeility significntly. From this cn e concluded tht it is necessry to monitor of technologicl properties during mouldmking. It cn e crried out y mechnicl properties nd permeility mesurements. Susequently the new inder nd wter is dded into moulding mteril ccording to previously mesured vlues. References: [1] JELÍNEK, P. Pojivové soustvy slévárenských formovcích směsí. Ostrv, 2004. [2] Mercie zrideni, Formservis, dostupné n internete: http://www.formservis.cz/pge5.php [3] NEUDERT, A. Řízení jednotných formovcích směsí. In Slévárenství, 2000, č. 2 3, s. 90-99. 5