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H. DYJA et al.: THE ANALYSIS OF THE INFLUENCE OF VARYING TYPES OF SHAPE GROOVES ON THE BEHAVIOUR... Figure 4 Distributions of discontinuities on the strip crosssections after rolling in: a,a’,b,b’ ) slitting grooves; c,c’) bending grooves; d,d’) shaping grooves prox. 2,7 in the fi rst stand), as compared to strips rolled according to Variant I (approx. 1,5). The greater strains caused by the groove shape used resulted in an increase in the magnitudes of maximum stresses in the metal deformed following to Variant II, which contributed to the acceleration of the discontinuity closing process. – The process of discontinuity closing is largely affected by deformed metal temperature and strip cooling rate in the rolling process. The higher rolled strip temperature, the better internal discontinuities are welded. As a result of strip overcooling in surface regions, the yield stress value increases there (the surface becomes less plastic). This results in an increase in strains within the sample and, as a consequence, an accelerated process of closing of discontinuities is observed in those regions. – The groove shape used for rolling fl at bars following to Variant II caused better closing of internal material discontinuities compared to the shapes made according to Variant I. REFERENCES [1] Sobczak K., Dyja H.: The infl uence of rolling process parameters and lengthening grooves shape on closing internal material discontinuities. The 7th International Conference Mechatronic Systems And Materials MSM 2011. Kaunas University of technology. 7-9 July, Kaunas, Lithuania (2011), p. 192. [2] Woźniak D.: Wpływ kształtu wykroju na stany naprężenia i odkształcenia w kotlinie walcowniczej oraz na inten sywność zamykania osiowych nieciągłości materiałowych w układzie owal – kwadrat. The Institute for Ferrous <strong>Metallurgy</strong> in Gliwice, Rolling Engineering 2005, October 19- 21, Ustroń (2005), p. 82-90. [3] Woźniak D., Tkocz M., Cyganek Z.: Zmiany stanów termomechanicznych w pobliżu pęknięć w strefach przypowierzchniowej i środkowej ciągłego wlewka płaskiego w procesie walcowania na gorąco blach. Hutnik- Wiadomości Hutnicze, No. 8 / 2009, p. 670/673. [4] Woźniak D., Grosman F., Tkocz M.: Analiza stanów mecha nicznych towarzyszących zamykaniu i spajaniu nieciągłości materiału w procesach przeróbki plastycznej. Prace IMŻ nr 1, Gliwice (2010), p. 68/72. [5] Radecki J., Łabuda E.: Symulacja zmian objętości nieciągłości materiałowych podczas wal cowania wyrobów płaskich w zmiennych warunkach odkształcenia, Materiały Konferencji Walcownictwo, Procesy – Narzędzia –Wyroby, Ustroń (1999), p. 126-129. [6] Wang A., Thompson P.F., Hodgson P.D.: A study of Pore Closure and Welding in Hot Rolling Process, In: Proc. Metal Forming’96, eds, Pietrzyk M., Kusiak J., Hartley P., Pilinger I., Mat. Proc. Techn., Kraków 60 (1996), p. 95- 102. Note: The responsible translator for English language is Czesław Grochowina, Poland 38 METALURGIJA 52 (2013) 1, 35-38
K. LABER, S. MRÓZ, P. SYGUT, H. DYJA ANALYSIS OF THE TEMPERATURE CHANGE OVER THE CONTINUOUS INGOT LENGTH ON THE PARAMETERS OF ROUND BAR ROLLING PROCESS K. Laber, S. Mróz, P. Sygut, H. Dyja, Częstochowa University of Technology, Czestochowa, Poland METALURGIJA 52 (2013) 1, 39-42 ISSN 0543-5846 METABK 52(1) 39-42 (2013) UDC – UDK 621.77:669.71:669.3=111 Received – Prispjelo: 2012-03-29 Accepted – Prihvaćeno: 2012-07-20 Original Scientifi c Paper – Izvorni znanstveni rad The paper presents results of theoretical and experimental studies on the eff ect of feedstock end overcooling before the fi rst rolling stand on the plastic fl ow of metal and on the energy and force parameters during bar rolling process. From the obtained investigation results it has been found that the uniform heating of the feedstock in the stepped furnace does not insure the uniform plastic fl ow of metal over the rolled band length. Therefore, it is necessary to modify the method of feedstock heating in the stepper furnace in order to obtain a uniform temperature over the length of the feedstock before the fi rst rolling stand. Key words: groove rolling, heat exchange, metal plastic fl ow, energy and force parameters, thermovision investigation INTRODUCTION The accuracy of Shape Mill products is defi ned by their deviations of the actual cross-sectional dimensions of band from the nominal values. The principal dimensions of Shape Mill products is their height and width of fi nished product and the mass of one running metre. For round bars, their ovality is also determined as the difference between the horizontal and vertical diameters, while for square bars, the difference between the diagonals is determined. The manufacture of rolled products within negative deviations of dimensional tolerance arouses increasingly great interest among purchasers. Newly built Shape Mills [1] and existing Shape Mills that have been modernized in recent years [2] manufacture products with a dimensional accuracy tighter than the 1 / 4 of that of the DIN Standard. Introducing new solutions to the rolling technology and Rolling Mill machinery and equipment assures the manufacture of rolled products within a narrow range of dimensional tolerance, which results in considerable metal savings, as well as a reduction in the mass of structures, equipment and machine parts [3]. Contemporarily constructed heating furnaces allow the end of feedstock to be heated up to a temperature higher than that of its beginning. It must be determined, however, how much the feedstock end temperature will have to be higher relative to the feedstock beginning temperature so that a uniform temperature distribution over the feedstock length be obtained before the fi rst rolling stand. The main objective of the investigations carried out was to examine the effect of feedstock end overcooling before the fi rst rolling stand on the metal plastic fl ow and on the energy and force parameters during bar rolling process. EXPERIMENTAL CONDITIONS AND SIMULATIONS The studies were carried out for one of Poland’s continuous bar Rolling Mill. The study analyzed the effect of the change in the temperature of the heated feedstock beginning and end on the plastic fl ow of metal during rolling of 20 mmdiameter bars. Round bars were rolled in 17 stands (17 rolling passes). The theoretical and experimental studies were carried out for the starting and end regions of the feedstock and the band and for the end region of the feedstock and the band heated to a temperature higher that the nominal temperature which was 1 150 °C for the entire volume of the continuous casting. The mill feedstock was a 14 000 mm-long 160×160 mm continuous casting. The use of that long feedstock caused the duration of cooling the feedstock end prior to the process of rolling in the fi rst rolling stand to be much longer than that of cooling the feedstock beginning. This resulted in an uneven temperature distribution over the length of the feedstock and then the rolled band (overcooling of the end the feedstock, compared to its beginning). The theoretical and experimental study was divided into two stages. In the fi rst stage of the study, a uniform temperature of 1 150°C within the entire continuous casting volume was assumed. Whereas, in the second stage of the study, to minimize the unevenness 39
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Figure 5 Process of rolling with up
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guarantees effi cient application o
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