铝合金轮毂低压铸造工艺的数值模拟
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摘要
本文采用ProCAST软件模拟了铝合金轮毂低压铸造充型及凝固过程,优化铸造工艺,消除铸件缺陷,使模具的设计和铸造工艺更合理,从而大大缩短开发周期,降低生产成本。
在本论文中,采用Pro/E创建模型。对金属型低压铸造,由于至少包括金属型及铸件,必须使用装配方式。Pro/E输出默认的实体格式文件对装配为.asm。这种格式文件不能被ProCAST接受,因而只能通过标准接口格式文件与ProCAST进行数据传递,主要有三种方式:在MeshCAST中划分面网格和体网格;在Pro/E中划分面网格,在MeshCAST中划分体网格;在Pro/E划分面网格和体网格。在实验中发现这三种方式在处理铸件/铸型接触面时(尤其是对于复杂件来说)会产生问题,导致体网格生成困难甚至无法生成。在此引入了HyperMesh软件来划分网格,经过测试,通过HyperMesh软件划分网格后能够读入MeshCAST,从而进行单元检测,得到符合要求的有限元网格。
在铸件充型过程中发现在充型初期和充型后期金属液面前沿出现参差不齐的现象,经过模拟验证,这种现象主要是由模具结构设计不合理造成的。在铸件凝固完成后发现在轮辐与轮辋相交处,浇口处产生了收缩缺陷,从轮毂切片图中可以看出是由于补缩通道的较早断开造成的。在相应位置增加了风冷,消除了收缩缺陷。
The automobile industry of China has taken shape after several decades’development, the output of automobile increases greatly. The development of Al automobile hub industry is promoted by the fast developing of automobile industry, especially the passenger car industry. Nowadays, Al hub is applied in almost all types of new passenger car. The domestic light alloy hub industry starts relatively late, but develops rapidly. Now China has become a production country of Al automobile hub, while a majority of companies depends mainly on the experiential mode of production, there is a repeated process from mould development to trial production, then modifying mould and process scheme. During the designing process of casting process, there are many complicated calculations and lookup work. Technological design personnel resorts on personal experience and manual operation, which is time consuming, moreover, the results are always with low precision, reliability, unsatisfied casting quality. Repeated experiments also increase the production cost, development cycle and reduce the yield.
The effective method for the prior problems is developing advanced casting numerical simulation technology. The whole process of mold filling and solidification of castings can be observed by computer visualization technology to predict and analyze the defect and its position in the cast product, then judge whether the technique is reasonable and the casting structure meets the use requirement. According to the above results, which provide theoretical basis for obtaining cast with less defect and high quality, the casting process and structure can be improved. Meanwhile, the development cycle can shorten, and the production cost decreases, production efficiency improves.
We take one type of Al hub for example, simulate the process of mold filling and solidification of castings, predict defect during the process. The main conclusions are as follows:
(1) The mould was established using Pro/E in this study. Metal-mould low pressure casting has to use assembly mode because it at least includes metal-mould and casting. Acquiescent Entity format file of Pro/E for assembly is .asm, which is unacceptable by ProCAST, therefore, the data can only be transferred through standard interface format file, which contains dividing surface cell and volume mesh in MeshCAST, dividing surface cell in Pro/E, dividing volume mesh in MeshCAST, dividing surface cell and volume mesh in Pro/E. We found there were some problems when dealing with the casting and mold interfaces by these methods. So it was difficult to form volume mesh. The HyperMesh software was introduced to divide mesh. After testing, it is found that the mesh divided by HyperMesh software can be read-in MeshCAST, and obtain finite element mesh meeting the requirement after units detection.
(2) Mould structure has great influence on the process of mold filling. In this study, the liquid metal flow was hindered by the five salient cylinders in the bottom die during the process of molten aluminum filling, which caused different filling speeds of initial liquid metal in seven wheel spokes. This situation was relieved at the intersection of wheel spoke and wheel rim, but the irregularity of metal level was discovered at the late stage of filling. After removing the salient cylinders in the bottom die, the filling process became stable. Therefore, it should ensure unblocked flow channel and avoid structural obstruction when designing mould.
(3) The shrinkage porosity was discovered at the intersection of wheel spoke and wheel rim and the central part of hub after the simulating of casting solidification. The shrinkage porosity was attributed to the disconnection of feeding channel for the intersection structure. The isolated liquid can’t be compensated by metal liquid during the solidification process, which led to generate of defect. The shrinkage defect can be eliminated by increasing air cooling at corresponding position and improving the cooling speed at the two positions, which proved that the cooling system of low pressure casting played an important role in the realization of sequence solidification.
(4) The variation of pressure speed has an obvious effect on the temperature distribution of wheel rim when the pouring temperature is constant. The faster the pressure speed is, the higher the average temperature of wheel rim is, but the change of wheel spoke isn’t obvious. The best pressure speed is pouring 0.0017 MPa/s,best pouring temperature is 700℃,in this experiment.
在本论文中,采用Pro/E创建模型。对金属型低压铸造,由于至少包括金属型及铸件,必须使用装配方式。Pro/E输出默认的实体格式文件对装配为.asm。这种格式文件不能被ProCAST接受,因而只能通过标准接口格式文件与ProCAST进行数据传递,主要有三种方式:在MeshCAST中划分面网格和体网格;在Pro/E中划分面网格,在MeshCAST中划分体网格;在Pro/E划分面网格和体网格。在实验中发现这三种方式在处理铸件/铸型接触面时(尤其是对于复杂件来说)会产生问题,导致体网格生成困难甚至无法生成。在此引入了HyperMesh软件来划分网格,经过测试,通过HyperMesh软件划分网格后能够读入MeshCAST,从而进行单元检测,得到符合要求的有限元网格。
在铸件充型过程中发现在充型初期和充型后期金属液面前沿出现参差不齐的现象,经过模拟验证,这种现象主要是由模具结构设计不合理造成的。在铸件凝固完成后发现在轮辐与轮辋相交处,浇口处产生了收缩缺陷,从轮毂切片图中可以看出是由于补缩通道的较早断开造成的。在相应位置增加了风冷,消除了收缩缺陷。
The automobile industry of China has taken shape after several decades’development, the output of automobile increases greatly. The development of Al automobile hub industry is promoted by the fast developing of automobile industry, especially the passenger car industry. Nowadays, Al hub is applied in almost all types of new passenger car. The domestic light alloy hub industry starts relatively late, but develops rapidly. Now China has become a production country of Al automobile hub, while a majority of companies depends mainly on the experiential mode of production, there is a repeated process from mould development to trial production, then modifying mould and process scheme. During the designing process of casting process, there are many complicated calculations and lookup work. Technological design personnel resorts on personal experience and manual operation, which is time consuming, moreover, the results are always with low precision, reliability, unsatisfied casting quality. Repeated experiments also increase the production cost, development cycle and reduce the yield.
The effective method for the prior problems is developing advanced casting numerical simulation technology. The whole process of mold filling and solidification of castings can be observed by computer visualization technology to predict and analyze the defect and its position in the cast product, then judge whether the technique is reasonable and the casting structure meets the use requirement. According to the above results, which provide theoretical basis for obtaining cast with less defect and high quality, the casting process and structure can be improved. Meanwhile, the development cycle can shorten, and the production cost decreases, production efficiency improves.
We take one type of Al hub for example, simulate the process of mold filling and solidification of castings, predict defect during the process. The main conclusions are as follows:
(1) The mould was established using Pro/E in this study. Metal-mould low pressure casting has to use assembly mode because it at least includes metal-mould and casting. Acquiescent Entity format file of Pro/E for assembly is .asm, which is unacceptable by ProCAST, therefore, the data can only be transferred through standard interface format file, which contains dividing surface cell and volume mesh in MeshCAST, dividing surface cell in Pro/E, dividing volume mesh in MeshCAST, dividing surface cell and volume mesh in Pro/E. We found there were some problems when dealing with the casting and mold interfaces by these methods. So it was difficult to form volume mesh. The HyperMesh software was introduced to divide mesh. After testing, it is found that the mesh divided by HyperMesh software can be read-in MeshCAST, and obtain finite element mesh meeting the requirement after units detection.
(2) Mould structure has great influence on the process of mold filling. In this study, the liquid metal flow was hindered by the five salient cylinders in the bottom die during the process of molten aluminum filling, which caused different filling speeds of initial liquid metal in seven wheel spokes. This situation was relieved at the intersection of wheel spoke and wheel rim, but the irregularity of metal level was discovered at the late stage of filling. After removing the salient cylinders in the bottom die, the filling process became stable. Therefore, it should ensure unblocked flow channel and avoid structural obstruction when designing mould.
(3) The shrinkage porosity was discovered at the intersection of wheel spoke and wheel rim and the central part of hub after the simulating of casting solidification. The shrinkage porosity was attributed to the disconnection of feeding channel for the intersection structure. The isolated liquid can’t be compensated by metal liquid during the solidification process, which led to generate of defect. The shrinkage defect can be eliminated by increasing air cooling at corresponding position and improving the cooling speed at the two positions, which proved that the cooling system of low pressure casting played an important role in the realization of sequence solidification.
(4) The variation of pressure speed has an obvious effect on the temperature distribution of wheel rim when the pouring temperature is constant. The faster the pressure speed is, the higher the average temperature of wheel rim is, but the change of wheel spoke isn’t obvious. The best pressure speed is pouring 0.0017 MPa/s,best pouring temperature is 700℃,in this experiment.
引文
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[4] Shoumei XIONG, Baicheng LIU, Liangrong JIA. Study on Numerical Simulation of Mold Filling and Solidfication Processes under Perssure Condition[J]. J.Mater. Sci. Technol. 2002,(5):413-416.
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[8]刘致远.铸造CAE技术的应用[J].中国铸造装备与技术,2003,6:26-29.
[9]安阁英,苏仕方,等.铸件充型凝固过程数值模拟发展现状[J].铸造,2000,(2):84-86.
[10]李晨曦,吴春京,郭鸿志,等.铸造充型过程流场计算机模拟技术述评[J].铸造,1997,(2):47-50.
[11] Shea Chen, David B Johnson, Peter E Raad. Simulated filling of dies with cores,in: Transactions of the NADCA Congress and Exposition [C]. Detroit, USA,1991,275.
[12] Thomas B C, Beckerman C. Modeling of Casting, Welding and Advanced Solidification ProcessesⅧ: Proceedings of the Eighth International Conference,1998[C].San Diego, USA:The Minerals&Metals&Materials Society,1998.
[13] Wang Wei, Shen Houfa, Liu Beicheng. Effect of electromagnetic field on fluid flow in continuous casting mold: Proc.of MCSP6,2004[C].Taiwan:Kaohsiung,2004,13.
[14]袁浩扬,林汉同.铸造充型流动过程的三维数值模拟[J].力学与实践,1996,(5):24-27.
[15]麻向军,侯骏,赵立信.充型过程中自由表面的数值模拟[J].特种铸造及有色合金,2001,(4):34-37.
[16]荆涛,闻星火,等.微机在铸造工艺与设备中的应用[J].中国铸造设备与技术,1997,(2):50-53.
[17]蒋永,张云鹏.铸件充型数值模拟的研究进展[J].热加工工艺,2006,(1):70-74.
[18]刘瑞祥,杜锋,等.铸钢件流动与传热耦合计算数值模拟[J].铸造,1998,(6):8-12.
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