Strengthening technology and mechanism for semi-solid die casting of aluminum alloy

Combined with theoretical evaluation,an optimized strengthening process for the semi-solid die castings of A356 aluminum alloy was obtained by studying the mechanical properties of castings solution treated and aged under different conditions in detail,then,the semi-solid die castings and liquid die castings were heat treated with the optimized process.The results show that the mechanical properties of semi-solid die castings of aluminum alloy are superior to those of the liquid die castings,especially the strengthening degree of heat treated semi-solid die castingsis much greater than that of liquid die castings with the tensile strength more than 330 MPa and the elongation more than 10％,and this is mainly contributed to the non-dendritic and more compact microstructure of semi-solid die castings.The strengthening mechanism of heat treatment for the semi-solid die castings of A356 aluminum alloy is due to the dispersive precipitation of the second phase(Mg2 Si) and formation of GP Zone.     

锡磷青铜合金水平连铸工艺参数的优化

铸造锡磷青铜合金组织中存在显微缩松、枝晶偏析和反偏析是冷加工报废的主要原因.通过连铸工艺参数的正交实验,建立了轧制成材率与主要工艺参数之间的神经网络描述,网络模型与遗传算法结合对工艺参数的组合进行了优化,改善了铸坯的组织,提高了轧制带材成材率.     

有机酯水玻璃砂在特大型铸钢件上的应用

以有机酯水玻璃砂替代CO2水玻璃砂,应用于特大型铸钢件的生产中。介绍了有机酯水玻璃砂的硬化机理。选用福建平潭20/40目原砂、模数为2.0~2.3的改性水玻璃、12%~16%的有机酯进行有机酯水玻璃砂配比。给出了混砂和造型操作过程中的注意事项。通过对油压机横梁、汽轮机缸体、油轮挂舵臂和宽厚板轧机机架等一些特大型铸钢件的生产,实践表明:采用有机酯水玻璃砂后,铸件质量明显提高,铸件气孔、裂纹减少,表面光洁,尺寸精度提高。     

EPS模陶瓷型精密铸造失模工艺研究

针对EPS陶瓷壳型精铸失模时容易裂壳的现象,对EPS消失模精密铸造工艺进行了研究。利用自制的膨胀率检测设备对不同密度的EPS模试样在不同加热温度下的最大膨胀率进行了测试,研究了壳型膨胀与失模温度之间的关系;对陶瓷壳型中EPS模失模时的温度场分布进行测量,发现EPS模试样的密度大小对失模时温度场有着很重要的影响。在试验和分析的基础上,对EPS模失模机制进行了探讨,提出了高温失模机制。高温失模有利于降低失模时对壳型的膨胀作用力,为获得洁净而健全的陶瓷型壳提供了可靠保证。     

Analysis of chill-cast NiAl intermetallic compound with copper additions

This study carried out a characterization of chill-cast NiAl alloys with copper additions, which were added to NiAl, such that the resulting alloy composition occurred in the β-field of the ternary NiAlCu phase diagram. The alloys were vacuum induction melted and casted in copper chill molds to produce ingots 0.002 m thick, 0.020 m wide, and 0.050 m long. X-ray diffractometry (XRD) and transmission electron microscopy (TEM) performed in chill-cast ingots identified mainly the presence of the β-(Ni,Cu)Al phase. As-cast ingots showed essentially no ductility at room temperature except for the Ni₅₀Al₄₀Cu₁₀ alloy, which showed 1.79% of elongation at room temperature. Ingots with this alloy composition were then heat treated under a high-purity argon atmosphere at 550 °C (24 h) and cooled either in the furnace or in air, until room temperature was reached. β-(Ni,Cu)Al and γ′(Ni,Cu)₃Al were present in specimens cooled in the furnace and β-(Ni,Cu)Al, γ′(Ni,Cu)₃Al plus martensite-(Ni,Cu)Al were present in specimens cooled in air. Thermogravimetric analysis indicated that martensite transformation was the result of a solid-state reaction with M _s ∼ 470 and M _f ∼ 430 °C. Tensile tests performed on bulk heat-treated ingots showed room-temperature ductility between 3 and 6%, depending on the cooling media.     

304不锈钢精铸件点缺陷的形成与控制

针对典型304不锈钢精密铸件内出现的黑色点缺陷,对其表面形貌、成分进行了分析,并在此基础上总结了缺陷的形成机制,确定了相应的防止措施。研究结果表明,铸件内的点缺陷可以划分为两类:一类具有不规则截面,为脱蜡过程中剩余腊料的燃烧残留物;另一类为熔炼过程中,由于脱氧剂和除渣剂的去除不彻底而引入的夹杂。通过优化脱蜡和熔炼工艺,使得铸件内的点缺陷得到了很好的控制。     

艺术铸件冷冻冰模制模方法的研究

艺术铸件是艺术创作和铸造技术的完美组合，铸造工艺是艺术思想的重要保证。从古至今，艺术家和铸造工作者进行了不懈的探索。本文通过试验，分析了冷冻铸造方法用于艺术铸造的一些优势，探讨了用硅橡胶模具制作冰模的工艺方法，并将用此工艺成功制作的一些冰模展示出来。     

Airslip结晶器内凝固壳形成特性分析

根据Airslip结晶器的传热特性,建立了凝固壳厚度和临界凝固壳厚度的数学模型.理论分析和实验结果表明,凝固壳厚度与铸造速度的乘积为常数,铸造速度增大,凝固壳厚度减小,铸锭表面质量提高;铸造速度的波动引起凝固壳厚度的波动,降低了铸锭的表面质量;铸锭直径和铸造速度的乘积也为常数,铸锭直径增大,铸造速度相应减小.     

铸造工艺远程设计系统的实现

探索一种基于Internet的铸造工艺远程设计系统的开发方法。采用大口出流理论和均衡凝固理论作为浇冒口设计理论;以ASP．NET作为系统的开发工具,使用Access作为后台数据源,并用ADO．NET技术连接数据库;介绍实现系统主要功能的关键技术。将铸造工艺设计系统从单机平台转向Internet,提高了系统的共享度及升级维护的方便性,避免了系统的孤立和老化,并能实现多用户同时对系统的不间断使用。     

Analysis of Intermetallic Phases Formed on Surface Vapor Oxidized H13 Hot Work Steels in Molten Aluminum

In this paper, the author dipped surface vapor oxidized H13 steel specimens into 700℃ molten aluminum liquid for a certain period of time. Analyze the intermetallic phases formed on the H13 samples surface with optical microscope and X-ray diffraction method. The observation of immersion test sample's cross-section shows that Fe3O4 film will protect die substrate from molten aluminum erosion. The identification of the intermetallic phases reveals that they consist of 2parts, which is named as the composite layer and the compact layer. Further investigations are made in order to know the phase constituents of the 2 layers, they are Al8Fe2Si (outer composite layer), (AlCuMg) and Al5Fe2 (compact layer),respectively. The experimental results show that on the same specimen, a convex surface with bigger radius of curvature is more likely to be molten and the melting loss speed is also faster than a flat and smooth surface. The thickness of compact layer on a smooth surface is much bigger than that of the convex surface. Therefore, the author supposes the compact layer is favorable in stabilizing the die surface material from further melting loss, as their formation on the die surface, the melting loss speed will decrease.