Three-dimensional analysis of the modified sloping cooling/shearing process Three-dimensional analysis of the modified sloping cooling/shearing process

Three-dimensional analysis of the modified sloping cooling/shearing process

  • 期刊名字:北京科技大学学报(英文版)
  • 文件大小:102kb
  • 论文作者:Renguo Guan,Luolian Zhang,Chao
  • 作者单位:College of Materials and Metallurgy,Key Laboratory for Electromagnetic Processing of Materials
  • 更新时间:2020-11-11
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论文简介

Journal of University of Science and Technology BejingMaterialsVolume 14, Number 2, April 2007, Page 146Three- dimensional analysis of the modified sloping cooling/shearing processRenguo Guan), Luolian Thang"), Chao Wang,", Jinglin Wen", and Jianzhong Cui2)1) College of Materials and Matallurgy, Northeastern University, Shenyang 10004, China2) Key Laboratory for Electromagnetic Processing of Materials, Northeasterm University, Shenyang 10004, China(Received 2006-05-28)Abstract: A self- designed setup of modified sloping cooling/shearing process was made to prepare the semisolid Al-3wt%Mg alloy. Athree dimensional simulation model was established for the analysis of preparing the semisolid Al-3wt%Mg alloy. Through simulationand experiment, it is shown that the sloping angle of the plate greatly afects temperature and velocity distributions, and the temperatureand velocity of the alloy at the exit of the sloping plate increase with the increase of the sloping angle. The alloy temperature decreaseslinearly from the pouring mouth to the exit. The alloy temperature at the exit increases obviously with the increase of pouringtemperature. To prepare the semisolid Al-3wt%Mg alloy with good quality, the sloping angle 0=45° is reasonable, and the pouringtemperature is suggested to be designed above 650-660°C but under 700eC.Key words: semisolid aloy; modified sloping cooling/shearing process; simulation; temperature; velocity[This work was financially supported by the National Natural Science Foundation of China (No.50604007) and the Natural ScienceFoundation of Liaoning Province, China (No.20062016).]1. Introductionlated by the finite element software of ANSYS pro-gram. Through simulation and experiment, pouringSemisolid forming has been studied for more thantemperature and sloping angle were optimized.thirty years,' and now it has been applied in automobile,electronic, and many other fields [1-9]. As a relative2. Modelnovel metal forming process, semisolid forming has2.1. Study objectbecome sophisticated in many western countries, butThe sketch of the modified sloping cooling/shearingits application in other countries is not successful [1-process is shown in Fig. 1. Molten alloy is poured on a13]. One of the problems is that semisolid forming issloping plate with wavelike surface, and is cooled andmore complicated than conventional forming processes,sheared by the plate and evolves to semisolid alloy.and the solidification process is not easy to accuratelyFlowing alloy in a steady state in the process was thecontrol. So it is more difficult to apply in industry.research object. Because heat dissipates rapidly fromSloping cooling/shearing process have been used toAl-3wt%Mg alloy to the sloping plate and the air, themanufacture finer grain materials in the past, but it hasalloy temperature decreases gradually. Material ther-been considered to be a new way of semisolid formingmal properties change gradually along with tempera-proposed in recent years [10-13]. It is simple for pre-ture decreasing. The specific heat capacity and thermalparing the semisolid alloy, and can be easily applied inconductivity of the alloy were considered to changeindustry. Nowadays, it has already been used to preparewith nonlinear style. The size of the research object is 2semisolid slabs of aluminum and magnesium basedmmx10 mmx60 mm, and the curvature radius of thealloys, but the microstructure formation and its relatedwaves is 0.5 mm. The three-dimensional object meshedthermal/fluid fields have not been studied yet [10-13].by FI中国煤化工Fig. 2.These problems are very important factors for pre-paring semisolid slabs. In this article, the sloping plate2.2.THCNMHGwas modified to be a new one with wavelike surfaceA constant pourng temperature on the pouring[14]. A modified sloping cooling/shearing process formouth of the sloping plate was set and was equal topreparing the semisolid Al-3wt%Mg alloy was simu-pouring temperature T:T(x,y,z,t)=To. Heat ex-Corre啊嗍数塘hor: Renguo Guan, E-mail: guanrenguo@ 126.comAlso available online at www sciencedirect.comRG. Guan et al, Three dimensional analysis of the modifhed sloping cooling/shearing process147change on the contact surface between the alloy and thelarger, the alloy can easily flow down on the slopingsloping plate was considered by heat flux along theplate, and then the flow velocity of the alloy at the exitboundary. Heat flux was obtained from the transientincreases with the increase of the sloping angle. At theanalysis of contact heat exchange: qi.j = K.jSTI.s,same time, because the alloy flows quickly down thewhere K,j is the thermal conductivity and OTrj is thesloping plate with a bigger sloping angle, the coolingdifference in temperature. Convection was set at thetime of the alloy on the sloping plate is shorter and theboundary between the alloy and the air. A constant ve-alloy temperature at the exit of the plate is higher. Tolocity at the boundary of the contact surface betweenobtain good quality semisolid slabs, a suitable tem-he alloy and the sloping plate was set asperature range on the sloping plate should be controlled.zero:Vx =Vym =Vzu =0. Other positions were set asThe first requirement for this purpose is that the semi-free boundaries.solid zone on the plate should be as large as possible;secondly, the exit temperature should be suitable forfilling the casting mould, because the alloy temperatureinfluences the flow ability of the alloy. So it is impor-tant to control the sloping angle for preparing semisolidslabs. Through analysis by simulation and experiment,it is considered that the sloping angle θ =459 is reason-able. The related experimental results were describedelsewhere [13].Fig. 1. Sketch of the modified sloping cooling/shearing proc-3.2. Effect of pouring temperature on the tempera-ess.ture and velocity fieldsFig. 6 shows the temperature distribution at differentpouring temperatures. It shows that the temperaturealong the central line of the alloy decreases linearlyfrom the pouring mouth to the exit (along the arrow inFig. 7); this rule is almost the same for different pour-ing temperatures, as shown in Fig. 7. But it can be seenthat when the pouring temperature is relatively higher,the temperature decrease is sharper. The reason is thatwhen the pouring temperature is higher, the heat fluxfrom the alloy to the circumstance is larger, and theheat dissipation is faster, so the temperature changesFig. 2. Meshed three -dimensional object.rapidly. It also can be seen that the pouring temperaturegreatly affects the exit temperature of the alloy. The3. Results and analysisexit temperature obviously increases with the increas-3.1. Effeet of sloping angle on temperature and ve-ing of the pouring temperature. So it is important tolocity fieldscontrol the pouring temperature for preparing the semi-The sloping angle θ greatly influences the tempera-solid alloy. A reasonable semisolid temperature fieldture and velocity distributions. Figs. 3 and 4 are thecan be obtained on the sloping plate surface by con-temperature and velocity fields obtained by simulation.trolling the pouring temperature. Also, to manufactureAs shown in Fig. 3, because the cooling ability of thethe semisolid slabs without defects such as pores andsloping plate is stronger than that of the air, the alloyinclusions, the alloy flow ability should be controlledtemperature close to the sloping plate is lower than thatby controlling the pouring temperature and the slopingon the upper surface of the alloy. So the isothermal lineangle.deviates from the sloping plate to the surface of the al-The alloy flow velocity along the central line of theloy. In addition, the alloy temperature at the exit in-alloy increases from zero to the maximum corre-creases obviously with the increase of the sloping anglespon中国煤化工from the pouringθ. The reason is that the alloy flow velocity on themout. in Fig. 8). This rulesloping plate depends on the component of gravity ac-is theMYHC N M H Gmperatures, whichisceleration along the direction parallel to the plate, whi-shown in Fig. 8. But the pouring temperature obviouslych is shown in Fig. 5. So if the sloping angle Ois bigger,influences the values of the alloy flow velocity at thethe component of gravity acceleration gsinθ is alsoexit. It is seen that the alloy flow velocity at the exit148J. Univ. Sci. Technol Bejing, VoL.14, No.2, Apr 2007increases with the increase of the pouring temperature,lows: Va K-, where V is the flow velocity of thewhich is shown in Fig. 9. It is because the apparent vis-n'cosity of the alloy which determines the flow ability ofalloy, K is the parameter related to the solid fraction ofthe alloy mainly depends on the alloy temperature. Thethe alloy and the shape factor of solid particles in theapproximate relationship between the alloy flow ve-slurry, and η is the apparent viscosity of the alloy.locity and apparent viscosity can be described as fol-9029.s660454.631(a)(bFig. 3. Temperature distributions (°C) when pouring at 700C: (a) <-30*; (b) -45°; (c) θ=60°.a)b)Fig. 4. Velocity distributions (m/s) at the exit when pouring at 700°C: (a) C-30°; (b) 0-45.by about 10°C than the solidus of the alloy 600°C, andthe solid fraction of the alloy at the exit is high. Fromthe results of the experiment for preparing semisolidcos0 ',g sin0slabs, it is also found that if the pouring temperature islower than 650°C, the alloy flow ability is not good andcan not easily fill the casting mould [13]. So the pour-ing temperature is suggested to be designed above650-660°C. However, when the pouring temperature isFig. 5. Components of gravity acceleration.higher than 700°C, the semisolid zone of Al-3wt%MgIf the pouring temperature is higher, the alloy tem-alloy (between 600 and 640°C) on the plate is very lit-perature on the sloping plate is also higher, and so thetle, which is not favorable for preparing semisolid slabs.apparent viscosity of the alloy is smaller, thus the alloySo the pouring temperature should be set lower thancan flow easily from the pouring mouth to the bottom.700°C.As mentioned above, because the pouring temperaturecan greatly affect the apparent viscosity of the alloy, it4. Conclusionsis important to control the pouring temperature for pre-(1)During nreparing the semisnlid Al- 3wt%Mg al-paring semisolid slabs with fine good microstructuresloy中国煤化工gshearing process,and without defects.the sC N M H Ghe temperature andIt is shown that when the sloping angle θis 45° andvelocnty uisurlbutuns or une alloy, and the temperaturethe pouring temperature is 660°C, as shown in Fig. 6and velocity at the exit of the sloping plate increasethe exit temperature is about 612°C which is just higherwith the increase of the sloping angle.R.G. Guan et al, Three _dimensional analysis of the modifned sloping cooling/shearing process149Aa)329sA494032675767、 025.2449.63Fig. 6. Temperature distribution (°C) when the sloping angle 0-45° and pouring at: (a) 660C; (b) 680PC; (c) 700°C.700.7-690。680- o- 660C).6 F十680C- - 660C0.5-670660.4 t650640).2 t6306200.1|6100.00.1 0.20.30.40.5~ 0.0.0 0.10.2 0.30.4 0.5~ 0.6 0.7Distance 1 mDistance/ mFig. 7. Temperature decreasing along the centralFig. 8. Velocity increasing along the central line ofline of the alloy from the pouring mouth to the exitthe alloy from the pouring mouth to the exit whenwhen A=45°.0=45*..619270b)(eFig. 9. Alloy f0ow velocity at the exit when the sloping angle 0-45° at dfferent pouring temperatures: (a) 660C; 6) 680°C; (C)700°C.(2) It is shown that the alloy temperature decreasesand the pouring temperature is suggested to be des-linearly from the pouring mouth to the exit. The pour-igned above 650-660°C but under 700°C.中国煤化工ing temperature greatly affects the exit temperature ofRefthe alloy, and it increases obviously with the increaseCNMHGl] M.C.remmung, Denaviur u1 meual and alloys in the semi-of the pouring temperature.solid state, Metall. Trans., 5(1991), No.5, p.957.(3) To prepare the semisolid Al-3wt%Mg alloy with2] Z. Fan, Semisolid metal processing, Int. Mater. Rev,good quality, the sloping angle 0-45° is reasonable,2(2002), No.2, p.149.150J. Univ. Sci Technol. Beijing, VoL14, No.2, Apr 2007[3] SJ. Luo and W.T. Tian, Structure evolution ofLC4 alloy inSRS process, Rare Met, 12(2002), No.4, p.271.making thixotropic bllet by SIMA method, Trans. Nonfer-9] H. Kaufmann, A. Mundi, and P.J. Uggowitzer, An updaterous Mer. Soc. China, 8(2001), No.8, p.547.on the new theocasting development work for Al- and Mg-[4] W.M. Mao, A.M. Zhao, D. Yun, et al, Preparation study ofalloys, Die Cast. Eng., 4(2002), No.4, p.16.semisolid 60Si2Mn spring steel slurry, Acta Metall. Sin,[10] T. Motegi, E. Yano, and N. Nishikawa, New semisolid6(2003), No.6, p.483.process of magnesium aloys, [in] Proc. 2th Int. Conf. on[5] X.M. Xu, HX. Zheng, S. Yuan, et al, Recrystallization ofLight Materials for Transporation Systems, Pusan, 2001,preformed AZ91D magnesium aloys in the semisolid state,p.185Mater. Des, 6(2005), No.4, p.343.[1] T. Haga, Semisolid strip casting using a twin roll caster[6] Z.H. Chen, H. Zhang, ZT. Kang, et al, Thixoforming ofwith a cooling slope, J. Mater. Proc. Technol, 12(2002),6066 aluminum alloy by multi- layer spray deposition,No.12, p.558.Trans. Nonferrous Met. Soc. China, 1(2001), No.1, p.108.[12] T. Haga, T. Kenta, and I. Masaaki, Twin roll casting alumi-[7] Y. Chino, M. Kobata, H Iwasaki, et al, An investigation ofnum alloy strips, J. Mater. Proc. Technol, 10(2004), No.10,compressive deformation behavior for AZ91 Mg alloyp.42.containing a small volume of liquid, Acta Mater., 6(2003),[13] R.G. Guan, J.P. Li, L. Shi, and JL. Wen, ManufacturingNo.11, p.3309.semisolid Al-Mg based alloy by sloping cooling and8] R.G. Guan, JL. Wen, X.H. Liu, et al, Continuously ex-shearing, J. Northeast. Univ. (Nat. Sci) (in Chinese),tending extrusion forming of semisolid A2017 alloy by5(2005), No.5, p.448.中国煤化工MYHCNMHG

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