镁合金及其铸造成形技术

镁合金是目前最轻的结构材料,在汽车、电子等诸多领域的应用日益增加。本文介绍了铸造镁舍金的性能及强化方法、镁合金熔炼的阻燃、镁合金的铸造成形技术和铸造缺陷及改进方法。     

基于数值模拟缸体浇注系统的设计与优化

针对镁合金发动机缸体的结构特点设计了浇注系统,并用铸造分析软件对其充型和凝固过程进行了模拟。通过观察分析模拟结果,预测了充型时间、凝固时间以及铸件中可能存在的缩孔缩松缺陷的分布与尺寸,并设计了优化浇注系统。     

原镁直接熔炼生产镁合金压铸件的工艺进展

简述了我国镁合金压铸件生产现状，分析了从原镁到镁合金压铸件的工艺过程及存在的问题；讨论了全封闭式熔化及浇注集成化方法、合金化阻燃技术和半固态成形技术等三种工艺优化方法。     

Die Casting for High Performance—Focus on Alloy Development

Development of magnesium die casting alloys is the art of combining a thorough understanding of thermodynamic aspects of alloy composition and phase formation with the solidification kinetics as experienced in the die casting process. The microstructures obtained will determine The Alloy Property profile, which must be in line with the targeted application requirements. Successful development of an industrial alloy means that also The Diecasting Performance profile as well as the Alloy Production and Recycling profile must be fulfilled. In the present paper, a summary of current alloy development efforts will be given. Results from alloy development work by Hydro Magnesium will be presented, focusing mainly on creep resistant alloys. Specifically, alloys within the Mg‐Al‐RE system are highlighted.     

Influences of Casting Pressure Conditions on the Quality and Properties of a Magnesium Cylinder Head Cover Die Casting

Casting pressure conditions have great influences on the casting defects, such as gas porosity, shrinkage porosity and gas holes. A Mg cylinder head cover die casting was used to experimentally study the influences of casting pressure, the loading time and the piston position of pressure intensification on the variation of pressure and the quality of casting. The results show that casting pressure, the loading time and the piston position of pressure intensification have great influences on the pressure variations in the mold, the quality and performance of casting. The external quality, the density and the tensile strength of casting were improved with the increase of casting pressure and the piston position of pressure intensification and the decrease of the loading time of pressure intensification.     

镁合金挤压铸造凝固过程数值模拟

利用有限元法对镁合金挤压铸造凝固过程进行数值模拟,分析了铸件的凝固收缩和凝固时间,预测铸件可能发生缺陷的位置,对比挤压压力对铸件缺陷的影响。 结果发现,与重力铸造相比,挤压铸造的凝固收缩小,铸件在挤压铸造的压力作用下可缩短凝固时间;缺陷模拟结果与实验相符,加大挤压铸造压力有助于减少缺陷的产生。     

铝合金风扇叶片压铸模具设计

目的采用铝合金代替传统塑料风扇叶片,适应节能减排、绿色铸造发展的趋势。方法采用UG建模和Anycasting软件,对铝合金风扇叶片的压铸模具进行设计,包括分型面设计、型芯型腔结构设计、浇注系统设计、溢流槽设计、排气系统设计、推出机构设计、冷却系统设计等,并对其压铸成形过程进行了数值模拟。结果风扇扇叶部分最后凝固且容易产生缩松和气孔,将溢流槽向扇叶方向移动,收集扇叶和扇叶之间的气体和夹杂,加强对缺陷处的排气,缺陷基本消失。结论设计的压铸模具满足铝合金风扇叶片的生产要求,符合节能减排、绿色铸造发展的趋势。     

压铸AZ91D镁合金TIG焊接气孔研究

对压铸AZ91D镁合金进行TIG自熔焊接,研究焊接电流对压铸镁合金气孔的影响,探讨焊缝中不同区域的气孔形貌特点及形成机理。结果表明:焊接气孔主要集中在焊缝近表面和熔合线附近;焊接接头的凸起面积、熔化区面积以及气孔率均随着焊接电流的增大而增加。在焊缝近表面主要是氢致气孔,其H主要来自母材;在焊缝中心,气泡受向上的流体力和浮力作用,气孔问题并不严重;在半熔化区,气泡受阻碍其上浮运动的流体力作用,且液态金属黏度较大,气泡很难上浮逸出到熔池表面,从而滞留在半熔化区成为大气孔。     

铸旋铝合金车轮旋压模具的优化设计

目的 保证铸旋车轮短流程制造工艺的实现,提高旋压模具与同一轮型不同铸造毛坯的配合能力,防止因旋压后毛坯尺寸变化过大,造成车轮机加成品率下降的现象。方法 以某款车轮旋压模具为研究对象,对其旋压模具结构进行重新设计,增加定位滑块、垫板等设计,提高毛坯与模具的定位与配合,增强模具对毛坯的自适应性。结果 对改进后的旋压模具进行试验验证,新结构的旋压模具能够满足不同铸造毛坯的旋压,且控制上模压力在4.5 MPa内,毛坯尺寸合格,性能无影响。结论 该旋压模具设计的方法已经应用到了其他铸旋车轮的设计中。     

镁合金消失模铸件表面膜成分及其结构

采用X射线光电子能谱技术(XPS)对消失模镁合金铸件的表面成分进行了测定,结果表明消失模镁合金铸件表面元素成分为Mg、Al、C、O、Si;结合对镁合金液和消失模样界面间的化学反应分析,揭示了消失模镁合金铸件表面是由MgO、Al2O3、SiO2和无定型C等组成的一层薄膜,即消失模镁合金铸件表面的Al2O3-SiO2-MgO-C复合膜;该复合膜对提高镁合金表面的防腐蚀性有很好的作用;提出了镁合金消失模表面膜的结构模型.这些结果表明,消失模技术作为镁合金零件的成形方法具有独特的优势.     

Optimization of Processing Parameters During Laser Cladding of ZE41A-T5 Magnesium Alloy Castings Using Taguchi Method

A continuous wave 4 kW Nd:YAG laser welding system was employed to clad single beads on machined 6.2-mm thick ZE41A-T5 aerospace magnesium alloy sand castings using nominal 1.6-mm filler rods of the parent metal. Based on the quality criterion of minimum dilution ratio, the Taguchi experimental method was used to optimize different process parameters and to identify the dominating factors. It was found that, for the process window investigated in this work, the optimal levels were 5.0 m/min for wire feed rate, 2.25 kW for laser power, and 2.5 m/min for cladding speed, with a minimum dilution ratio of 0.155. With 95% confidence, the wire feed rate is the dominating factor with the most significant influence on the dilution ratio. The dilution ratio usually decreases with increased wire feed rate while it increases with increased laser power. By contrast, the cladding speed appears to have insignificant influence on the dilution ratio over the cladding speed range used in this study.     

Selection of Welding Process Parameters for the Optimum Butt-Joint Strength of an Aluminum Alloy

In this paper, the selection of welding process parameters for obtaining the optimum weld butt-joint ultimate tensile strength (UTS) of aluminum alloy (6061-T6) is presented. Considering weld-joint UTS as the quality characteristic in the selection of process parameters, the Taguchi method is used to analyze the effect of each individual process parameter and of their interaction and then to determine process parameters for the optimum weld-joint UTS. Analysis of variance (ANOVA) technique is applied to investigate which welding process parameter has significant effect on the weld-joint UTS. Experimental results are provided to illustrate the proposed approach.     

Selection of Welding Process Parameters for the Optimum Butt-Joint Strength of an Aluminum Alloy

In this paper, the selection of welding process parameters for obtaining the optimum weld butt-joint ultimate tensile strength (UTS) of aluminum alloy (6061-T6) is presented. Considering weld-joint UTS as the quality characteristic in the selection of process parameters, the Taguchi method is used to analyze the effect of each individual process parameter and of their interaction and then to determine process parameters for the optimum weld-joint UTS. Analysis of variance (ANOVA) technique is applied to investigate which welding process parameter has significant effect on the weld-joint UTS. Experimental results are provided to illustrate the proposed approach.     

钛合金阀体件“一模多件”铸造工艺优化设计

目的 对钛合金阀体件“一模多件”铸造工艺进行优化研究,达到降低成本、保证铸件产品质量的目的。方法 以ZTA2钛合金阀体件为研究对象,基于零件壁厚范围较宽的结构特点、零件的技术要求与生产实际现状,结合经验分析及数值模拟仿真技术进行铸造工艺设计。结果 确定分型面和浇冒口的设计,在热节点及孤立液相区域设置补缩冒口,通过数值模拟对铸件模拟结果的缩孔缩松情况进行分析,优化冒口的设计,增加补缩通道,最终确定合理的“一模多件”开放式浇注系统。对于“一模多件”铸造工艺,通过合理设计浇注系统,可以有效保证浇注过程中各层铸件的平稳浇注。浇注系统宜采用开放式的浇注系统,直浇道、横浇道、内浇口的截面积比例为1∶2∶4。结论 采用机加工石墨型铸造,在真空凝壳炉完成熔炼,在浇注温度为1 770 ℃、模壳预热温度为200 ℃的情况下,采用重力浇注的形式在真空凝壳炉中铸造生产出钛合金阀体件,所获得的铸件无铸造缺陷,其成分和力学性能均满足质量要求。研究结果表明,在铸造过程中使用数值模拟技术可以优化铸造工艺设计,缩短产品试制周期,大大提高生产效率。     

Understanding Magnesium Corrosion—A Framework for Improved Alloy Performance

The purpose of this paper is to provide a succinct but nevertheless complete mechanistic overview of the various types of magnesium corrosion. The understanding of the corrosion processes of magnesium alloys builds upon our understanding of the corrosion of pure magnesium. This provides an understanding of the types of corrosion exhibited by magnesium alloys, and also of the environmental factors of most importance. This deep understanding is required as a foundation if we are to produce magnesium alloys much more resistant to corrosion than the present alloys. Much has already been achieved, but there is vast scope for improvement. This present analysis can provide a foundation and a theoretical framework for further, much needed research. There is still vast scope both for better fundamental understanding of corrosion processes, engineering usage of magnesium, and also on the corrosion protection of magnesium alloys in service.     

铝合金车轮低压铸造充型工艺设计

目的运用科学计算的方法对铝合金车轮低压铸造充型工艺进行优化设计。方法通过对铸造铝合金车轮充型过程进行研究,分析在充型过程中各部位尤其是截面较小的浇冒口部位的铝液流动状态。结果运用数学计算的方法对充型工艺进行优化设计,既提高了铸造效率,又使铸造过程充型平稳,缩短了新产品的试制周期,使铸造工艺由通过试生产阶段的工艺摸索变为试生产阶段的工艺验证。结论经过科学计算可以使液态铝合金的充型按每个阶段预期效果进行,为优化铸造工艺、改进模具设计提供了有效的手段。     

焊前热处理对压铸镁合金GTAW焊气孔的影响

在不同温度下对压铸AM60B母材进行焊前热处理,待冷至室温后对其实施不填丝GTAW重熔焊接。焊后用扫描电镜对焊缝截面的气孔分布及形貌进行观察,并用粒径分析软件Nano measurer 1.2测量焊缝中气孔尺寸,用基于Matlab二次开发的图像分析程序识别和计算焊缝气孔率。结果表明:焊缝气孔主要分布在焊缝熔融区及熔合线附近;与未经焊前热处理母材对应的焊缝相比,经焊前热处理后所得焊缝中的气孔率及气孔尺寸均降低;随着焊前热处理温度升高,焊后气孔率及气孔尺寸均逐渐增加。     

铝合金压铸工艺数值模拟分析

采用压铸工艺成形铝合金薄壁长轴类零件。首先根据压铸模具浇注系统的设计原则,对铝合金件压铸模的浇注系统进行了设计计算;其次运用procast软件对铝合金压铸成形工艺进行数值模拟,根据压铸过程中的温度场云图,进行了压铸模具的热平衡分析和压铸件的充型凝固分析;最后针对模拟的结果进行了压铸模具的设计。     

提高铝合金压铸模使用寿命的途径

针对3Cr2W8V钢制铝合金压铸模,采用真空亚温淬火加浅层氮碳共渗改进的热处理工艺,并找出了适宜的工艺参数.结果表明,该工艺能明显提高模具的抗热疲劳性能和使用寿命.