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1 Journal Journal o Cemical o Cemical Tecnology and and Metallurgy, 5, 3, 5, 25, 3, STUD OF BROADENING IN A COMBINED PROCESS ROLLING - PRESSING USING AN EQUAL-CHANNEL STEP DIE Adrakman Naizaekov, Sergey Leznev, Evgeniy Panin, Tonco Koinov 2 Karaganda state industrial University, Temirtau, Repulic o Kazakstan, sergey_legnev@mail.ru 2 Department o Pysical Metallurgy and Termal Equipment, University o Cemical Tecnology and Metallurgy, 8 Kliment Oridski, Soia 756, Bulgaria, toni39@koinov.com Received 5 Decemer 24 Accepted 6 April 25 ABSTRACT Tis article is devoted to studying o roadening in a comined process rolling - pressing, using an equal-cannel step die. In laoratory conditions an experiment or lementation o tis process, using smoot rolls and tree dies wit dierent values o angle o te cannels junction was done. A ormula, wic allows inding te value o roadening in te comined process rolling-pressing, using an equal-cannel step die was otained. Tis ormula is applicale or any value o te angle o te cannel s junction. Keywords: comined process, rolling-pressing, equal-cannel step die roadening. INTRODUCTION Te comined process rolling-pressing is one o te most promising ways to otain ig-strengt metal, wic is ased on te use o reserve orces and riction on te contact surace o te metal wit rotating rolls []. At te Metal orming department o te Karaganda state industrial university a new comined metod o rolling and pressing using equal-cannel step die was developed and proposed. It, in comparison wit conventional pressing in tis die [2], provides continuity o te process and removes restrictions on te illets size (Fig. ). Te essence o te proposed metod o deormation is descried ereunder. Te illet, pre-eated to te temperature o te eginning o deormation, is ed to te rolling rolls, wic due to te contact riction orces, take it into te mout o te rolls, and on te exit pus troug cannels o te equal-cannel step die. Wen te illet is completely out o equal-cannel step die, it is captured y a second pair o rolls, wic also due to te contact riction orces, grip te workpiece into te mout o te second pair o rolls and completely pull te illet rom te equal-cannel step die. Te advantage o tis metod is tat te lementation o tis comined process wit te proposed sceme, ensures te continuity o te process, and removes restrictions on te illets size. In [3] a comparative analysis o te process o rolling-pressing wit an equal-cannel step die using grooved and smoot rolls was done. It was ound tat te use o grooved rolls at a similar source o data allowed realizing te process o rolling-pressing wit an equal-cannel step die wit a smaller angle o intersection, at a muc lower compression. Tis will allow to get te metal wit an ultraine-grained structure in lower 38

2 Adrakman Naizaekov, Sergey Leznev, Evgeniy Panin, Tonco Koinov Fig.. Te comined process rolling - pressing using an equal-cannel step die. Fig. 2. Pressing out o illet. numer o cycles, due to greater intensiication o sear deormation in te wole volume o te deormed illet in a single pass. Anoter undouted advantage o using grooved rolls instead o te smoot ones is te opportunity to control te roadening o te illet during its deormation in te rolls. However, ecause o te circumstances, a situation migt arise wen te use o grooved rolls, or one reason or anoter, will not e possile. For example, wen one wants to deorm te illets wit dierent values o te initial widt. Ten, it using smoot rolls, one as to take into account te roadening o te workpiece, as y rolling in smoot rollers lateral metal low is not limited to te walls o te calier. Tis work is devoted to te study o tis actor. RESEARCH METHODS Because ater rolling in te rolls, te illet enters into te matrix cannel, it is necessary tat its widt does not exceed te widt o te input matrix cannel. Oterwise te illet would e stuck at te input o matrix (Fig. 2). Usually, or calculating o te roadening in rolling empirical ormulas are used. Te most well known ormulas o Cekmarev, Celikov, Gukin and Batinov are [4]: Formula o Cekmarev: 2 AV = n AV + ( + ) + ( + α ) Rα 2 ( + Rα / AV ) () were:, - te initial and inal tickness o illet, mm; - average widt o illet, mm; AV (it assumes tat AV ); - reduction, mm; α - angle o capture, rad; R - radius o rolls, mm; n = wen < R α ; n =2 wen > R α ; - riction coeicient. ormula o Celikov: 2 = l 2 ln 2 d + (2) 2 were = R - lengt o deormation zone, mm. l d ormula o Gukin: = + ld (3) 2 ormula o Batinov: =,5 ld 2 2 (4) Because in all o tese ormulas tere are dierent components, te calculation results can e very dierent rom eac oter. In tis regard, a comparative analysis o te calculation o te roadening wit all 4 ormulas or te ollowing initial data: R = mm; = 2 mm; = 2 mm; = 7 mm; =,5 was perormed. Te radius o te rolls and te coeicient riction 39

3 Journal o Cemical Tecnology and Metallurgy, 5, 3, 25 Tale. Teoretical determination o te roadening. Constant initial Variale parameter parameters Initial parameters: R = mm; =2 mm; =2 mm; ; =,5 Cekmarev Celikov Gukin Batinov 4,,76,2,59 R =2 mm R =4 mm R =8 mm R =6 mm =2 mm =,5 4,26 4,47 3,7 3,32,37,94,8 -,69,37,53,2 -,8,8,53,6 -,54 = l d =26,457 mm < l d =8 mm > l d =3 mm >> l d =4 mm << l d =2 mm =5 mm =3 mm = mm =5 mm =,5 =, =,2 =,25 R = mm =,5 R = mm =2 mm =,5 R = mm =2 mm 4,46 3,83 4,3 3,74 3,2 2,59,23 6,33 9,9 3,77 3,89 4,2 4,22,96,72 -,62-6,77 -,6-2,8 2,8 3,4,25,8 -,8-2,7 -,96 -,38,79,38,78,62 -,46-4,63-8,34 -,64,72 2,38 * means tat in tese ormulas it is ossile to use value o initial widt. were taken in relation to mill DUO, located in our university laoratories. In addition to te calculation o te roadening wit te aove initial data varying o te various geometrical and tecnological actors: radius o te rolls, coeicient riction, initial widt o te illets and asolute value o reduction, was conducted. Te variation was perormed y increasing or decreasing one o te input parameters wit te rest o te parameters kept at te same. Te results o te calculations are given in Tale. As can e seen rom Tale, te calculation results or all 4 ormulas wen variation o te main actors aects te roadening is conducted, are very dierent rom eac oter, suggesting te need or identiying ormulas, calculation results o wic will e close to te experimental values. LABORATOR EXPERIMENT For studying te roadening in te comined process rolling-pressing a laoratory experiment, wit tree equal-cannel step dies was done (Fig. 3). All tree dies ave a similar structure and dier only in te angle o intersection o te cannels (angle X in Fig. 3). In te irst die cannels intersect at an angle o 35 degrees, in te second - at an angle o 45 degrees, in te tird - at an angle o 55 degrees. Te lead samples were made wit sizes: Group : l =, mm Group 2: l =,5 6 5 mm Group 3: l = 9, mm Group 4: l = 9,5 6 5 mm Group 5: l = 7, mm Group 6: l = 7,5 6 5 mm Te numer o samples in eac group was equal to 2 pcs. Te small range o initial tickness is due to te act tat te mill, on wic te experiment was conducted ad rolls wit a diameter o mm, wic did not allow to deorm lanks wit a larger tickness, ecause o limitations on te angle o grip. Beore te experiment, or eac sample in ive points measurements o te initial tickness and widt 3

4 Adrakman Naizaekov, Sergey Leznev, Evgeniy Panin, Tonco Koinov Fig. 3. An equal-cannel step die. were made, ten teir average values or eac group were determined. Te deormation o te samples was produced in two stages. At te irst stage, tree samples rom eac group were sly rolled, and ater rolling measurements were made in ive points o te tickness and widt. Ten te averaged values were ound. At te second stage, te die was set at te exit o te rolls and rolled te oter tree samples so tat te metal, ater leaving te rolls, came into te die cannel. Rolling was carried out as eore, until tere was no slipping o te workpiece in te rolls. Ater tat, te rolls were separated, te die was removed rom te mill and te deormed workpiece was removed rom te die. Next, measurements o te tickness and widt in ive points were made and teir average values were ound. RESULTS AND DISCUSSION To identiy te ormula, wic as calculation results o te roadening close to experimental values, calculation y all 4 ormulas or samples o eac group was done. For tis purpose, te radius o te rolls was set to mm, te coeicient o riction during rolling was adopted asequal to.5. Ten te deviation o te experimental values o te widt ater rolling rom te teoretical values was calculated using te ormula: BEXP.ROLLING B THEOR = (5) B EXP.ROLLING were: BEXP.ROLLING - experimental value o widt ater rolling, mm; BTHEOR - teoretical value o widt, calculated y te ormula, mm. Te results o te calculation are given in Tale 2. As can e seen rom Tale 2, or calculation o te roadening we need to use ormula o Gukin, ecause it gives a minimum deviation o te experimental values rom te teoretical ones. However, or te calculation Tale 2. Teoretical and experimental values o te widt o te samples. Teoretical and experimental values o te widt o te samples, mm Deviation o experimental values rom teoretical, % Parameters Cek Cel Gu Bak EXP ΔCek ΔCel ΔGu ΔBak Group 26,8 25,96 25,32 25,73 25,24 3,73 2,85,33,95 Group 2 6,9 7,4 6,56 6,8 6,62,7 3,8,4,4 Group 3 25,84 26,6 25,53 25,94 25,58,99 2,24,22,38 Group 4 7,38 7,43 6,9 7,25 6,85 3, 3,4,257 2,33 Group 5 =5 mm 26,47 26,9 25,76 25,9 25,73 2,86,77,3,68 Group 6 =5 mm 7,8 7,73 7,2 7,65 6,92 5,8 4,76,63 4,29 3

5 Journal o Cemical Tecnology and Metallurgy, 5, 3, 25 Tale 3. Experimental values or te widt in mm o te samples ater rolling-pressing. Paramaters Angle 35 Angle 45 Angle 55 Group 27,7 27,6 27,9 27, , 26,5 26,8 26,9 Group 2 Group 3 Group 4 Group 5 =5 mm Group 6 =5 mm 7,4 7,4 7,5 27,4 27,2 27,5 8,2 8,4 8,5 27, ,8 8,9 8,7 8,9 6,9 6,7 6,8 26,7 26,5 26,8 7,9 7,6 8 26,8 26,5 26,7 7,9 8 8, 6,8 6,9 6,6 26,2 25,9 26 7,4 7,6 7, 25, ,8 7,3 6,9 6,9 o te roadening in te process o «rolling-pressing», tis ormula is unsuitale, ecause it does not take into account te inluence o te ack-pressure, created y te die. Tereore, it is necessary to include in tis ormula a coeicient tat takes into account te inluence o ack-pressure. In Tale 3 are presented te values o te widt o te samples ater te lementation o te comined process o «rolling - pressing» or all tree matrices. Tale 3 sows tat wit increasing o te angle o te cannels intersection te roadening or eac crosssection is reduced. Tis is ecause te larger angle o cannels intersection decreases te inluence o te ackpressure rom te die side, and te roadening o te metal goes down. Wit reducing te value o te angle o te cannels intersection, te ack-pressure rom te die side increases, and te value o te roadening increases. Fig. 4 presents a summary cart o te average values o te widt eore ( ) and ater ( ) rolling, and ater rolling-pressing or a die wit an angle o 35 degrees ( 2 ), wit an angle o 45 degrees ( 3 ), and wit angle o 55 degrees ( 4 ). In accordance wit tese values, or eac die coeicients o te inluence o te ack-pressure or eac group o samples were calculated according to te ormula: K RP =, (6) Fig. 4. Experimental values o widts o samples. 32

6 Adrakman Naizaekov, Sergey Leznev, Evgeniy Panin, Tonco Koinov Te average value o te coeicient: Fig. 5. Dependence o te ack-pressure coeicient on te angle o te cannels junction. were: RP - widt o te samples ater rolling-pressing, mm; - initial widt o te samples, mm. Based on ormula (6), te ollowing data were otained: or a die wit te angle o cannels intersection 35 degrees: К =,9; К 2 =,89; К 3 =,94; К 4 =,47, К 5 =,2; К 6 =,76. Te average value o te coeicient:,9 +,89 +,94 +,47 +,2 +,76 =,2 6 or a die wit te angle o cannels intersection 45 degrees: К =,84; К 2 =,5; К 3 =,67; К 4 =,4, К 5 =,67; К 6 =,25. Te average value o te coeicient:,84 +,5 +,67 +,4 +,67 +,25 =,84 6 or a die wit te angle o cannels intersection 55 degrees: К =,69; К 2 =,47; К 3 =,4; К 4 =,85, К 5 =,32; К 6 =,62.,69 +,47 +,4 +,85 +,32 +,62 =,56 6 Tus, te ormula o Gukin or calculation o te roadening in te process «rolling-pressing», will ave te ollowing orm: = Κ + ld (7) 2 were К - coeicient taking into account te inluence o ackpressure in te die (Fig. 5). CONCLUSIONS Te otained ormula (7) allows to ind te value o te roadening arising rom te lementation o te comined process rolling-pressing, wen using an equal-cannel step die. Moreover, tis ormula is applicale or any value o te angle o te cannels intersection. For tis purpose, it is necessary to sustitute in ormula (7), as coeicient K, te value deined in Fig. 5, depending on te desired angle o cannels intersection. In Fig. 5 one can ind te value o K or values o te angle o cannels intersection o degrees. Values o te coeicient K or angles o cannels intersection lying outside tis interval sould e ound using extrapolation. REFERENCES. А.R. Fastykovskiy, V.N. Peretyatko, Hig scools. Ferrous metallurgy, 2, 22, 5-7, (in Russian). 2. A.B. Naizaekov, S.N. Leznev, E.A. Panin, Hig scools. Ferrous metallurgy, 6, 28, 22-26, (in Russian). 3. A.B. Naizaekov, S.N. Leznev, E.A. Panin, Tecnology o production o metals and recycled materials,, 27, 6-22, (in Russian). 4. A.P. Grudev, Teory o rolling, М., Metallurgy, 2, pp , (in Russian). 33