基于数值模拟的负重轮挤压铸造工艺研究

发布时间：2018-02-28 13:08

  本文关键词： 负重轮 挤压铸造 数值模拟 复合加压　出处：《中北大学》2017年硕士论文　论文类型：学位论文

【摘要】：科技时代的到来,使高精度、轻量化和高性能的武器装备成为各个国家发展的重点。而负重轮是装甲车辆行走系统的关键部件,直接影响着整个装甲车的重量和性能。使用铝合金替代原有钢质材料可大大减轻装甲车重量,实现轻量化,提高装甲车作战机动性。压铸、模锻和挤压铸造工艺是目前负重轮生产的主要方法。其中,挤压铸造是一种介于铸锻之间综合了铸锻加工优点、少切削或无切削的近终形成型技术,适合于补缩困难、壁厚不均匀的铸件。该工艺一次成型获得晶粒细小、组织均匀、力学性能优良的铸件且机加工量小、节省材料,不仅能保证产品的使用性能,而且具有良好的经济性能。因此,在负重轮的生产工艺中,首选挤压铸造。在学习掌握挤压铸造工艺原理及特点、凝固过程的传热学规律以及压力下凝固过程的力学成形过程等相关知识后,采用Pro CAST三维模拟软件,成功的模拟出负重轮挤压铸造工艺的凝固过程,得到了不同压力下的温度场变化和缩松、缩孔缺陷的预测结果。在结合国内挤压铸造设备情况和铸件补缩特点的基础上,根据模拟结果改进了工艺方案并优化模具设计。本文主要有以下结论:(1)根据凝固传热学的基本理论,建立负重轮的温度场数学传热模型并给出求解,成功应运于温度场模拟,进而预测缺陷。(2)不同比压下的温度场模拟结果表明:负重轮在压力下由表到里逐渐凝固,但各部位的凝固速度有明显区别。负重轮比较厚大的拐角部位,凝固最慢;而负重轮的表面,凝固最快。负重轮的凝固速度随压力的增大而加快。(3)负重轮的凝固时间随压力的增大而减小。(4)在研究压力对缩松、缩孔的影响时,发现压力的增大可以有效的减少缩孔和缩松,而当压力增大到100MPa后缩松和缩孔消失。(5)挤压铸造加载方式,由常规简单加压调整为复合加压。对复合加压的挤压铸造工艺数值模拟,发现较低的压力下缩松缩孔就大大减少甚至消失。实验验证,复合加压的负重轮件,抗拉强度和伸长率已达标,即力学性能已符合科研项目的要求。(6)文中在补缩量为4mm的复合加压挤压铸造工艺中,采用浇注温度730℃、模具预热温度300℃,保压时间32S的主要工艺参数获得的负重轮件,其整体抗拉强度σ_b为361.5MPa,伸长率δ为8.18%,满足项目σ_b360MPa、δ6%的力学要求。(7)在复合加压挤压铸造工艺可行的基础上,优化负重轮的成形模具,研发成形模具的控温系统并介绍其组成设备如加热装置、冷却装置、定位装置的工作原理。
[Abstract]:With the advent of the era of science and technology, high-precision, lightweight and high-performance weapons and equipment have become the focus of each country's development. And the load-bearing wheel is the key component of the armored vehicle's walking system. It has a direct impact on the weight and performance of the whole armored vehicle. Using aluminum alloy to replace the original steel material can greatly reduce the weight of the armored vehicle, achieve lightweight, and improve the operational mobility of the armored vehicle. Die forging and squeeze casting are the main methods in the production of load-bearing wheels at present. Among them, squeeze casting is a kind of near-end forming technology which combines the advantages of casting and forging with less cutting or no cutting, and is suitable for the difficulty of feeding. Casting with uneven wall thickness. The casting with fine grain size, uniform microstructure, good mechanical properties and low machining quantity can not only guarantee the performance of the product, but also have good economic performance. In the production process of load bearing wheel, the first choice is squeeze casting. After studying and mastering the principle and characteristics of squeeze casting process, the law of heat transfer in solidification process and the mechanical forming process of solidification process under pressure, and so on, The solidification process of weight bearing wheel squeeze casting process was successfully simulated by using Pro CAST 3D simulation software, and the temperature field and shrinkage were obtained under different pressure. Prediction results of shrinkage defects. On the basis of combining the situation of squeeze casting equipment in China and the characteristics of casting shrinkage, According to the simulation results, the technological scheme is improved and the die design is optimized. In this paper, the following conclusions are drawn: 1) according to the basic theory of solidification heat transfer, the mathematical heat transfer model of the temperature field of the load-bearing wheel is established and solved, which should be successfully applied to the simulation of the temperature field. The simulation results of temperature field under different specific pressures show that the weight bearing wheel solidifies gradually from surface to interior under pressure, but the solidification speed of each part is obviously different. The thickest corner is the slowest solidification. The solidification rate of the load wheel increases with the increase of pressure, and the solidification time decreases with the increase of pressure. 4) in the study of the influence of pressure on shrinkage and shrinkage, the solidification rate of the bearing wheel is quickened with the increase of the pressure, and the solidification time of the wheel decreases with the increase of the pressure, and the solidification time decreases with the increase of the pressure. It is found that the increase of pressure can effectively reduce the shrinkage and porosity, but when the pressure increases to 100 MPA, the shrinkage and shrinkage disappear. By adjusting the conventional simple pressure to the compound pressure, the numerical simulation of the squeeze casting process shows that the shrinkage shrinkage holes are reduced or even disappeared at lower pressure. The experimental results show that the composite pressure bearing wheel parts, The tensile strength and elongation have reached the standard, that is, the mechanical properties have met the requirements of the scientific research project. In this paper, the casting temperature is 730 鈩，

本文编号：1547422