精密铸钛技术在义齿类铸件上的应用

简述了医用纯钛和钛合金在口腔医学中应用研究的历史、现状和发展前景，论述了牙科应用精密铸钛技术的意义，以及牙科专用铸钛机、包埋材料、焊接和抛光器材的现状，精密铸造工艺对牙科铸钛性能的影响，旨在提高我国牙科精密铸钛技术。     

口腔科铸钛系统的研究进展

钛具有优异的力学性能,良好的耐蚀性和生物相容性,已成为口腔医学中最有发展前途的金属材料.近年来,口腔科精密铸钛技术和理论迅速发展.从牙科铸钛用钛材、铸钛机、包埋料等方面综述了牙科铸钛技术的现状及发展.     

牙科专用铸钛机

介绍开发研制牙科专用铸钛机的意义，牙科铸钛技术的发展历程，牙科铸钛机的一般结构，几种常用机器的性能特点、使用方法和应用情况。     

牙科钛铸件缺陷的起因和预防

牙科钛铸件都采用失错铸造技术制成，铸件有缺陷是铸造加工中常遇到的问题．铸件缺陷包括变形、铸入不足、铸巢、气孔、铸件质地疏松等，景致命的铸造缺陷为铸入不足．造成牙科铸件有缺陷的起因有：①金属或合金凝固收缩所致的收缩孔；②熔化的金属或合金放出气体所致的缺损或铸巢；③铸入时空气卷入所致的缺损；④铸型内空气没有充分排出所致的缺损；⑤包埋材料与铸到反应或凝固时体积变化过大、铸型胶有缺损、包埋材料与熔化的金属或合金反应、铸型变形；⑤铸造用的合金或金属本身有质量问题．牙秆铸件缺损以收缩孔最常见．由于钛本身固有…     

牙科铸钛技术的研究现状

对目前牙科铸钛系统,包埋材料、铸件表面反应层结构以及铸造工艺如铸模温度、铸造压力等的研究及发展现状进行了综合介绍。     

牙科用钛系合金的现状

过去高K值的金合金以其易加工、耐蚀性和生物相容性优良等优点，居牙科用合金的第五位。然而，近年来，随着加工技术的进步，钛合金和Co-Cr-Ni系合金已在临床上普遍使用。以下简单介绍牙科用钛系合金的现状。 牙科铸造用钛及钛合金 20世纪70年代后半期开始试验的钛的牙科铸造合金是Ti-Cu合金。但后来发现纯钛铸件具有与金合金相媲美的机械性能，因此其后的铸造装置、材料、铸造方法等的研究主要以纯钛为中心而展开。80年代开发了真空装置和氩气保护电弧熔炼相组合方式的钛专用铸造装置，其后又不断改进和开发了多种铸造装置，如氩气保护…     

日本大原公司的牙科铸钛设备

日本大原有限公司注意到钛村在口腔医学中的应用前景，故也从事牙科设备生产．已开发出的新型氩气电弧无氧铸钛机（TutaniumerVF）可用于铸造种植体、假牙冠桥和义齿钛基托等各种修复体，设备已商品化，现已进入临床实用阶段．ITitaniumeVF结构和性能特点（l）熔化方式：采用钨电极，用氯气电弧熔化置于瓷材涡中的钛材．（2）铸入方式：利用发条的复原力，采用离心铸造法．该方法比较成熟，通过马达上紧发条，铸入时的起初速度大，是牙科常用的铸造方式．（3）T彻m——W各型号特点见表1．2具备牙科铸造机的所需条件体积小，不需选择特别…     

牙用Ti—75合金铸造性能研究

采用国产牙科专用铸钛机对Ｔｉ－７５合金做为牙科修复材料的可行性进行了研究结果表明：Ｔｉ－７５合金铸流率可达９８％;铸造抗拉强度为８５０ＭＰａ,屈服强度为７７５ＭＰａ,延伸率为７％;铸件金属相组织呈板条状α加少量β。     

新型牙科铸钛专用包埋料的研制

研究了自制磷酸盐包埋料焙烧温度与膨胀率及膨胀系数之间,焙烧温度、固化时间与抗拉强度之间的关系,以及室温条件下一次包埋时包埋料与纯钛的界面反应情况.结果表明:包埋料的最大凝固膨胀率为0.1%,800℃的热膨胀率为0.46%,总膨胀率为0.56%,完全可以满足实际义齿铸造的要求.焙烧后抗拉强度在0.3～0.35MPa之间,正常固化24h后,包埋料的抗拉强度为2.35MPa,已经能够满足铸造过程的需要.Zr、P元素在纯钛中的扩散很小,可以忽略不计.金属元素Mg的扩散深度约为6μm,Al的扩散深度约为20μm,Si的扩散深度约为15μm,可以通过表面处理来保证铸件质量.     

日本牙科专用钛铸造机

日本岩谷(Iwatani)产业公司是最早致力于牙科专用钛铸造机开发研究的厂家。早在1978年该公司就发现牙科是钛材应用的一个潜在大户,市场前景广阔。于1981年率先推出CASTMATIC-SS型CM-330号牙科专用钛铸造机。在以后的试用中不断地对该机进行改进,陆续推出S型CM-230号、CM-130号和T型钛铸造机。     

钛合金熔模精密铸件表面质量提升工艺性研究

研究并优化了钛合金熔模精密铸件工艺,解决了钛合金熔模精密铸件表面质量差的问题。分析了钛合金熔模精密铸件表面缺陷的类型,研究了缺陷产生的机理,并进行了实验验证。结果表明,浆液温度对型壳质量及钛合金熔模精密铸件表面质量具有重要影响。其它工艺参数不变的情况下,浆液温度为20~23℃时能获得表面质量较好的钛合金熔模铸件。     

Contraction of Investment Cast H13 Tool Steel Real Time Measurement

This paper presents the results of an investigation into the dimensional changes and variability of investment cast H13 tool steel. An experimental apparatus has been developed to measure the dimensional changes during the casting process. Investigating the dynamics of mould expansion and alloy contraction during investment casting, it has been possible to determine in greater detail the contributions of the cast alloy and the mould to the final contraction of unconstrained castings. Contraction and dimensional variability of the final cast product is defined and experimental estimations of the contributions of each stage of investment casting are made. A technique for combining the variability of sequential stages is discussed. The measured contraction appears to be non-uniform and dependent on the position along the casting.     

钛及钛合金熔模的感应凝壳铸造法

本文回顾了钛及钛合金熔模铸造的历史,通过对传统的真空电弧凝壳铸造法与新型的感应凝壳铸造法的比较,指出了该方法无需制作电极即可得到成分均匀的高质量铸件,并且消除了坩埚材料对炉料的污染,有助于产品获得理想的成分均匀性和准确性.     

用于铸造金属功能件的快速原型模样的特点分析

介绍几种快速成型系统，并对用于铸造金属功能件的几种快速原型模样进行归纳，总结，针对熔模铸造和陶瓷型铸造对成型模样的特定要求，考察一次性模样使用的几种原型模样的精度、表面粗糙度、热膨胀率、残余灰分等工艺参数，对实际铸造的影响。     

熔融沉积式燃机叶片快速熔模铸造技术研究与试验

针对某燃机叶片叶型部分形状复杂和轮廓度精度要求高的特点,提出了一种基于熔融沉积技术的燃机叶片快速熔模铸造方法,通过基于NURBS曲线的分层截面生成算法对燃机叶片STL(stereolithography)模型进行分层,提高燃机叶片模样的轮廓度精度,制订了燃机叶片快速熔模铸造工艺流程,采用三坐标测量机对燃机叶片铸件进行测量,对其两个关键截面进行型线轮廓度偏差分析与评价,结果表明:基于熔融沉积技术的快速熔模铸造燃机叶片铸件在轮廓精度方面满足要求,快速熔模铸造工艺流程合理、可行。     

Development and evaluation of a novel inclusion seeding methodology for Ti−6Al−4V castings

Hard alpha inclusions in titanium (Ti) investment castings are generally known to have detrimental effects on the mechanical properties of these castings. However, actual inclusions are infrequent and occur in random locations in castings. As a result, it is difficult to obtain tensile or fatigue test specimens of titanium castings with inclusions in the gage section. Quantifying the adverse influence of inclusions on the mechanical properties of castings is, therefore, extremely challenging. To address this problem, a novel artificial inclusion seeding methodology was developed to emulate actual Ti investment casting inclusions. Prefabricated inclusions were seeded into machined holes in cast Ti−6Al−4V plates, the holes were back-filled with plugs of the same Ti alloy and were then electron-beam (EB) welded closed. Hot isostatic pressing (HIP) was utilized to incorporate the inclusions fully into the cast titanium material. Finally, the plates were machined to create mechanical test specimens with inclusions centered in the gage region. Test specimens created by means of this novel artificial seeding methodology were evaluated and found to be equivalent to Ti casting specimens containing actual cast-in inclusions.     

Protective coatings for induction casting of titanium

Commercially pure titanium is among the most biocompatible metals available for dental uses: it combines good mechanical properties with high corrosion resistance in simulated body fluids. However, titanium casting shows some problems mainly related to its high melting temperature and chemical reactivity with oxygen at T > 600 °C; as a consequence, molten titanium reacts with crucibles and mould components during casting. In this research, new Y₂O₃-based slurry was used to produce yttria coated mullitic crucibles and wax pattern coatings for induction melting of titanium; furthermore, a detailed comparison among 4 different investment materials (one silica-based, one ZrSiO₄-based and two MgO-based) was performed. The titanium surface after casting was investigated with optical and electron microscopy (SEM) and energy dispersion spectroscopy (EDS). A reaction zone was observed on Ti when cast in an uncoated crucible, while a clean, pure Ti surface was obtained by using yttria coated crucibles and yttria coated wax patterns before investing with silica-based and zircon-based investment.     

钛合金安装座熔模铸造工艺设计研究

根据飞机安装座铸件的结构特点和使用要求，结合钛合金的铸造特性，分析和探讨了以硅溶胶作为型壳粘结剂的钛合金熔模铸造工艺，设计了熔模工艺方案和离心浇注系统，并对工艺方案进行工艺实验，讨论了生产中所面临的质量问题。     

液钛与氧化锆陶瓷型壳的相互作用

借助于Ｘ射线衍射、电子探针和扫描电镜等测试手段,研究了液钛与氧化锆陶瓷型壳的相互作用。结果表明,界面反应一方面基于型壳中的ＺｒＯ２分解和Ｚｒ,Ｏ原子向钛基体的扩散,形成ＣａＺｒＴｉ２Ｏ７相;另一方面液钛也向氧化锆型壳中扩散,形成Ｃａ２Ｚｒ５Ｔｉ２Ｏ１６相。阐述了液钛与氧化锆陶瓷型壳相互作用的双向扩散机制。指出降低浇注温度可减弱钛与型壳的界面反应。     

Titanium composite materials for transportation applications

Discontinuously reinforced titanium alloys containing in-situ formed TiB needles are emerging as candidate materials for advanced applications. This new family of titanium composites presents technical advantages, and it can be less expensive and easily amenable for net-shape manufacturing relative to titanium metal-matrix composites developed to date. The production of a master compound by a novel and cost-effective process called self-propagating high-temperature synthesis (SHS) has been studied. This master compound could be subsequently used in an investment casting process to obtain TiB-reinforced net-shape titanium-matrix composites. The SHS technique and its features were investigated in depth before a suitable master compound was defined and produced. Cast samples obtained from the addition of the master compound have been produced and the most important issues concerning the processing, microstructure, and mechanical properties are highlighted in this paper.