不同铸造条件对纯钛铸件表面粗糙度的影响

目的：探讨包埋料及铸造温度等铸造条件对纯钛铸件表面粗糙度的影响。方法：铸型用氧化锆包埋料内包埋后再用磷酸盐包埋料包埋或只用磷酸盐包埋料包埋片状蜡型，用ＬＺ型牙科铸钛机分别在室温、３００℃和９００℃条件下铸造Ｇｒ２型纯钛，并分别用磷酸盐和硅酸乙酯包埋料常规包埋铸造钴铬（Ｃｏ－Ｃｒ）合金作比较，使用表面粗糙度仪对铸件的表面粗糙度（Ｒａ）进行测定。结果：铸造纯钛时，使用氧化锆内包埋且铸型温度在３００℃或室温铸造的纯钛铸件Ｒａ值无显著差别（Ｐ＞０．０５），且低于其它条件下铸造的纯钛铸件和常规铸造的（Ｃｏ－Ｃｒ）合金的表面粗糙度（Ｐ＜０．０１）。结论：使用氧化锆内包埋且铸型温度在３００℃以下铸造Ｇｒ２型纯钛，其铸件表面粗糙度较小。     

铸模温度对牙用Ti-Zr合金铸造后力学性能影响的研究

目的　观察铸模温度对牙用Ti-Zr合金铸造后力学性能的影响。方法　在3种铸模温度下,对牙用Ti-Zr 合金铸造后的抗拉强度、屈服强度和延伸率3种力学性能指标进行测试;同时采用金相显微镜观察3种铸模温度下 的铸件的显微组织结构。结果　随着铸模温度的升高,Ti-Zr合金的抗拉强度及屈服强度均增高而延伸率下降。Ti- Zr合金的显微金相组织结构显示,随着铸模温度的升高,表面污染层逐渐增厚,室温时约为35.5μm、300℃时约为 55.0μm、600℃时约为65.5μm;铸件边部与中心部的显微结构不同,铸件边部从表面向基体形成粗大的树枝状α 片,而中心部为等轴的α晶粒。结论　铸模温度影响Ti-Zr合金铸件的显微结构,从而使Ti-Zr合金铸造后的力学性 能发生改变;Ti-Zr合金铸造后的力学性能,能够满足临床义齿支架合金的性能要求。     

国产LZ型牙科铸钛机铸造性能的初步观察

钛作为口腔修复的新型材料具有广阔的应用前景，但由于其熔点高，极易氧化，钛铁铸造十分困难。笔者依靠医工结合研制出第一台国产离心－真空－压力铸钛机，经铸造纯钛测试结果表明：钛铸件外观完整，Ｘ线显示内部有少量微小气孔Ｋｎｏｏｐ氏显微硬度从表层到内部逐渐减小，硬化层厚７５μｍ，０．６８ｍｍ厚度蜡网钛的铸流率为１００％。     

高铌钛合金铸流率的探讨

目的以钛铌锆锡（Ti—Nb—Zr—Sn）合金为研究对象,通过对其铸流率的研究,探讨高铌钛合金用于牙科铸造加工的可行性．并为牙科应用提供合理的铸造参数。方法采用网状试样法。检测钛铌锆锡合金在3种铸模温度（室温、300℃、600℃）下的铸流率,并以纯钛（Ti）、钛铝钒（Ti－6A1－4V）合金做对照,结果做统计学分析。结果在室温及300℃铸造时钛铌锆锡合金铸流率明显低于纯钛及钛铝钒合金;在600℃铸造时三种合金铸流率没有明显差别。该合金室温及300℃组铸流率明显低于600℃组。结论高铌钛合金在室温铸造时铸流率不佳,钛铌锆锡合金在铸模温度高于600℃以上铸造时可以获得完整铸件。     

低弹性模量钛铌锆锡合金铸件表面反应层结构的研究

目的:观察铸模温度对钛铌锆锡(Ti-Nb-Zr-Sn)合金铸件表面反应层结构的影响。方法:在两种铸模温度下(室温,300°C)进行合金的铸造。对铸件表面反应层的结构及显微硬度进行测试;采用SEM下的能谱分析(EDS)对铸件抛光前后的表面元素成份进行对比研究。结果:随着铸模温度的提高,Ti-Nb-Zr-Sn合金铸件表面反应层的厚度增加,表面硬度值增大。组织金相显示铸件表面反应层结构可分为3层。铸件表面抛光前元素Si、A1含量较高,抛光后则明显减少。且随着铸模温度的提高,Si的扩散深度及渗透量均有所增加。结论:为了减少Ti-Nb-Zr-Sn合金铸件表面反应层的厚度,应尽量降低铸模温度,同时应选择无Si的包埋材料。     

铸造方式对纯钛铸件表面性状及流铸率的影响

本研究通过改变石英粒度和调整磷酸盐结合剂的成份配制三种铸钛实验包埋料，观察铸造方式及铸造温度对纯钛铸件表面性状及流铸率的影响。实验结果证明加压铸造和３００℃铸造的铸件表面粗试明显高于离心铸造。室温铸造时两种铸造方式的铸件表明硬度明显低于３００℃铸宾结果。     

牙科精密铸钛技术的研究进展

钛制冠桥，可摘义齿支架已应用于临床，但钛的铸造技术尚待改进。本文回顾了国内外对牙科铸钛技术的研究；介绍国外对牙科铸钛机，包埋料，铸造工艺等方面的研究；对各种牙科铸钛机的可铸性能，包埋料的理化性能对钛铸件质量的影响，铸模温度对钛铸伯质量的影响，以及铸道的设计对钛铸件质量的影响等进行了综述。     

铸模温度对牙科用钛铌锆锡合金铸流率影响的研究

目的:通过对钛铌锆锡(Ti-Nb-Zr-Sn)合金铸流率的研究,为钛铌锆锡合金临床应用提供合理的铸造参数。方法:采用网状试样法,评价钛铌锆锡合金、纯钛、钛铝钒(Ti-6A l-4V)合金分别在3种铸模温度(室温、300℃、600℃)下的铸流率,做统计学分析。结果:在室温及300℃铸造时钛铌锆锡合金铸流率明显低于纯钛及钛铝钒合金;在600℃铸造时3种合金铸流率没有明显差别。该合金室温及300℃组铸流率明显低于600℃组。结论:为保证临床义齿铸造的完整性,钛铌锆锡合金铸造时铸模温度应在600℃以上。     

牙科用Ti-Zr合金铸造收缩性的研究

目的：通过研究Ti-Zr合金铸造收缩率,为临床选择最佳的铸模温度提供参考依据。方法 采用马蹄形试样,对Ti-Zr合金、钝钛及Ti6A14V合金在三种铸模温度下的铸造收缩率进行评价。结果 Ti-Zr合金在三种温度下与纯钛的铸造收缩率无显著差异,而明显低于Ti6A14V合金;室温铸造时,其收缩率明显高于300℃及600℃组,而300℃组与600℃组之间无显著差异。结论 为保证临床义齿铸造精度,铸造Ti-Zr合金时铸模温度应在300℃以上。     

ZrP99铸钛包埋材料的铸模温度对铸造精度的影响

目的：研究ZrP99铸钛包埋材料的铸模温度对铸造精度的影响。方法：利用代型模具，制作30个超硬石膏全冠预备体代型．并制作相应的全冠蜡型，随机分为5组，每组6个样本，其中4组为实验组，采用ZrP99铸钛包埋材料进行包埋，分别在铸模温度为600℃、450℃、300℃、150℃条件下进行铸造；另外一组为对照组，采用Titavest—CB包埋材料进行包埋．在铸模温度为600℃条件下进行铸造。利用显微图像分析技术．在实体显微镜下分别测量蜡型及相应的铸件边缘与代型肩台之间在标志点处的间隙，两者差值即代表铸造精度。采用t检验及单因素方差分析进行统计学处理。结果：Titavest—CB包埋材料组的铸造精度显著优于在不同铸模温度下ZrP99包埋材料组：当ZrP99包埋材料的铸模温度低于450℃时，随着温度升高，铸造精度显著提高。结论：ZrP99铸钛包埋材料的铸模温度必须高于300℃．才有可能满足临床精度要求。     

牙用Ti-Zr合金铸件表面反应层结构的研究

目的：观察铸模温度对牙用Ｔｉ－Ｚｒ合金铸件表面反应层结构的影响。方法：在３种铸模温度下（室温,３００℃,６００℃）进行牙用Ｔｉ－Ｚｒ合金的铸造。对牙用Ｔｉ－Ｚｒ合金的铸件表面粗糙度以及表面反应层的厚度及显微硬度进行测试;采用ＳＥＭ观察及元素线分析对铸件的表面反应层结构进行分析。结果：随着铸模温度的提高,Ｔｉ－Ｚｒ合金铸件表面粗糙度明显增加,表面反应层的厚度增加,硬度值增大。Ｔｉ－Ｚｒ合金铸件表面反     

Titanium casting: the surface reaction layer of castings obtained using ultra-low-temperature molds

To examine whether the surface reaction layer of titanium castings can be reduced by lowering the mold temperature during casting, we cast titanium at three mold temperatures, including an ultra-low temperature produced by cooling the mold with liquid nitrogen, then measured the tensile strength and elongation of the castings. The titanium was cast using a centrifugal casting machine, and the molds were incinerated according to the manufacturers' instructions. Castings were then made with the molds at 200 degrees C, 600 degrees C, and an ultra-low temperature (-196 degrees C). The castability of titanium cast in the mold at the ultra-low temperature was good. The Vickers hardness near the surface layer of castings decreased as the mold temperature decreased.     

Studies on titanium casting. (1) Influence of the mold temperature on titanium castings

Pure titanium and titanium alloys have excellent biocompatibility, excellent corrosion tarnish resistance, a quarter of the specific gravity of gold base alloys and suitable mechanical properties for dental clinical use. However, titanium has some undesirable characteristics. For example, it has a high melting temperature and chemical reactivity at high temperatures. The investigate influence of the mold temperature on castability and mechanical properties of the titanium castings was study. The castability was found to be good at various mold temperatures, but the higher the mold temperature during casting, the greater the adhesive phenomenon between titanium surface and the investment. From the EPMA observation of the surface layer on the titanium castings, an Si- rich layer whose thickness increased considerably with increasing temperature was observed. The Vickers hardness in the surface layer was greater than that in the inner part. At a higher mold temperature during casting the thickness of the high Vickers hardness layer was increased. There was a relationship between the Vickers hardness value and the thickness of Si rich layer. In the tensile strength test of titanium castings, elongation values decrease and tensile strength values increased with the rise in mold temperature.     

Study of resin-bonded calcia investment. Part 3: Hardness of titanium castings

The Vickers hardness of the cross-sectioned area of titanium castings made from an experimental resin-bonded calcia investment and three commercial investments was evaluated. The microstructure and element distribution of the surface zone were analyzed using an EPMA. The results showed that the high hardness of the casting surface could be decreased using the experimental investment. The hardness of the castings made from the experimental investment at a 25-50 microm depth was lower than those from the other investments, and the thickness of the hardened casting surface was 125 microm. Layered structures with fewer layers were formed on the surfaces of the castings made from the experimental investment. The layered structures were influenced by both the investment components and the mold temperature at casting. The less contaminating nature of the experimental investment components and the technology of the room temperature mold contributed to the improved surface properties of the resulting castings.     

Studies on application of pure titanium for cast plate

Pure titanium produced by a commercial pure titanium casting system was studied for use as a cast plate for clinical application. The mechanical properties, elemental analysis, castability, adaptability of pure titanium and adhesion to denture base resin were investigated. The interfacial zone of the pure titanium castings was composed of a layered structure obtained by reaction with phosphate bonded Al2O3/SiO2 investment material. Vicher's hardness at 100 microns thick from the surface was higher than that in the inner part by oxidation. Cast pure titanium showed tensile strength, elongation and hardness close to those of the type III or IV dental gold alloy. The castability of pure titanium was lower than that of Co-Cr alloy and pure titanium castings also had large casting defects. Adaptability between pure titanium cast plate and the working model was satisfactory when reversible hydrocolloid impression material was used with heating-bath treatment in the refractory model. The tensile and compressive shear bonding strength of pure titanium to heat-curing or self-curing resin were similar to that of the Co-Cr alloy, and surface treatment using a solution containing 2-vol% 3-methacryloxypropyltrimethoxysilane produced a higher bonding strength than non-treatment, MKV treatment and 4-META treatment. These findings suggest that pure titanium castings produced by this system have suitable mechanical properties, adaptability and adhesion to denture base resin, and is available for cast plate in clinical application.     

铸模温度对牙科用Ti-Zr合金铸流率影响的研究

目的：通过对Ti-Zr合金铸流率的研究,为Ti-Zr合金临床应用提供合理的铸造参数,方法：采用网状试样法, 测量Ti-Zr合金,纯钛及Ti-6Al-4V合金在3种铸模温度（室温,300度,600度）下的铸流率,结果：Ti-Zr合金在室温铸造时其铸流率明显低于纯钛及T-6A-4V合金,并且Ti-Zr合金的铸流率也明显低于300度及600度组,结论：为保证 临床义齿铸造的完整性,Ti-Zr合金铸造时模温度应在300度以上。     

改良型FUS-invest锆系铸钛冠桥专用包埋材料对钛铸件表面反应层影响的研究

目的研究改良型FUS- invest锆系铸钛冠桥专用包埋材料对包埋铸造的纯钛铸件表面反应层的影响。方法制备10 mm×10 mm×1 mm的纯钛铸件,对其表面反应层进行能谱分析、金相观察及显微维氏硬度的测量。结果金相观察可见反应层不明显,富Si层难以分辨,针状结晶层散在分布于表面钛基体之间,其进入深度约55 μm;能谱分析显示Si、Zr等元素含量随深度增加逐渐减少;显微维氏硬度从表面至基体由高到低下降趋势明显,距表面约75 μm以后与钛基体硬度值接近。结论改良型FUS- invest锆系铸钛冠桥专用包埋材料铸造的纯钛铸件表面反应层由改良前85 μm降低为55 μm。     

纯钛冠桥铸造包埋料对铸件反应层的影响

目的探讨自行研制包埋材料（FUS-invest）中各组分对纯钛铸件反应层的影响。方法使用FUS-invest包埋并铸造10 mm×10 mm×1 mm的纯钛试样3片,观察反应层的金相,对反应层进行X射线衍射（XRD）及扫描电镜能谱分析（EDS）,测量显微维氏硬度。结果反应层的金相主要为粗大的片状α晶内结构,显微维氏硬度值在距表面105 μm后较为恒定,范围为243～314 MPa。XRD显示反应层中除了钛基体外,主要由ZrO2、SiO2、Mg2TiO4及TiO2组成。EDS检测到的元素除了钛元素外,主要为Al、Si、Zr和Cl。结论使用FUS-invest包埋材料铸造的纯钛铸件产生的反应层较薄,金相结构没有显著改变,适合作为纯钛铸造的专用包埋材料。     

Modeling the investment casting of a titanium crown.

OBJECTIVE: The objective of this study was to apply computational modeling tools to assist in the design of titanium dental castings. The tools developed should incorporate state-of-the-art micromodels to predict the depth to which the mechanical properties of the crown are affected by contamination from the mold. The model should also be validated by comparison of macro- and micro-defects found in a typical investment cast titanium tooth crown. METHODS: Crowns were hand-waxed and investment cast in commercial purity grade 1 (CP-1) titanium by a commercial dental laboratory. The castings were analyzed using X-ray microtomography (XMT). Following sectioning, analysis continued with optical and scanning electron microscopy, and microhardness testing. An in-house cellular-automata solidification and finite-difference diffusion program was coupled with a commercial casting program to model the investment casting process. A three-dimensional (3D) digital image generated by X-ray tomography was used to generate an accurate geometric representation of a molar crown casting. Previously reported work was significantly expanded upon by including transport of dissolved oxygen and impurity sources upon the arbitrarily shaped surface of the crown, and improved coupling of micro- and macro-scale simulations. RESULTS: Macroscale modeling was found to be sufficient to accurately predict the location of the large internal porosity. These are shrinkage pores located in the thick sections of the cusp. The model was used to determine the influence of sprue design on the size and location of these pores. Combining microscale with macroscale modeling allowed the microstructure and depth of contamination to be predicted qualitatively. This combined model predicted a surprising result--the dissolution of silicon from the mold into the molten titanium is sufficient to depress the freezing point of the liquid metal such that the crown solidifies the subsurface. Solidification then progresses inwards and back out to the surface through the silicon-enriched near-surface layer. The microstructure and compositional analysis of the near-surface region are consistent with this prediction. SIGNIFICANCE: A multiscale model was developed and validated, which can be used to design CP-Ti dental castings to minimize both macro- and micro-defects, including shrinkage porosity, grain size and the extent of surface contamination due to reaction with the mold material. The model predicted the surprising result that the extent of Si contamination from the mold was sufficient to suppress the liquidus temperature to the extent that the surface (to a depth of approximately 100 microm) of the casting solidifies after the bulk. This significantly increases the oxygen pickup, thereby increasing the depth of formation of alpha casing. The trend towards mold materials with reduced Si in order to produce easier-to-finish titanium castings is a correct approach.