Papers by Keyword: Investment Casting

Abstract: The present study was undertaken to investigate the effect of different metallurgical parameters such as casting techniques, wall thickness, inoculant technique, carbon equivalent, nodule count, ferrite and pearlite percent on the mechanical properties of thin wall ductile iron castings (TWDI). Understanding of the effect of chemistry, casting techniques, melting and molten treatment on the mechanical properties and microstructural features of TWDI castings would help in selecting conditions required to achieve optimum mechanical properties and alloy high strength to weight ratio. The use of the design of experiment (DOE) and the analysis of variance (ANOVA) can be a useful methodology to reach this objective. The analysis of the effects of each variable and their interaction on the mechanical properties of TWDI castings using green sand, green sand with insulation and investment casting techniques plays a key role in improved materials performance.The results indicate that nodule count, pearlite content and the interaction between carbon equivalent, nodule count and pearlite content have a significant effect on the tensile strength of TWDI castings. The impact toughness values decrease with smaller section thickness and increased nodule count. Using investment casting technique, decreasing the pearlite percent and nodule count, and increasing the wall thickness and ferrite percent reduce the values of ultimate tensile strength and yield strength. The results of percent elongation and impact toughness show a reverse trend compared with those of ultimate tensile strength and yield strength in terms with different metallurgical parameters.

Abstract: For cost reduction of the molds manufacturing, as well as environmental load in foundries sodium silicate binder is often used. However, without treatment with special compositions that accelerate curing and improve their properties, sodium silicate molds have insufficient thermal spalling resistance and often cause the rejection of castings made of heat-resistant alloys. As a result of the research, there was developed a technology of chemical drying of the sodium silicate cover layers in investment casting with the use of aluminoborbophosphate concentrate. It allows to reduce the production time of ceramic molds by 2...3 times, as well as to increase their strength either before baking or after it by 20...25 %. At the same time, as a result of softening effect of aluminoborbophosphate concentrate after baking and cooling of the specimens there has been observed a significant reduction of their retained strength and, as a consequence, better knockout of fire-resistant shells. Industrial tests of the sodium silicate cover chemical drying showed a significant reduction of the investment castings rejection due to the insufficient thermal spalling resistance and the reduction of the cleaning processing time of casting made of heat-resistant alloys.

Abstract: As a result of the research, the technology of accelerated forming on the sol-silicate binder in precision casting has been developed. It is based on granular materials cladding by the gel-processing catalysts of the sol-silicate binder and on the use of the clad granular materials as the stucco of ceramic coating layers. That allows to achieve a reduction of ceramic molds product cycle of more than 2...2.5 times and strength improvement of 1.4...1.5 times at the temperature of baking. The developed technology allows to improve the quality of ceramic molds and significantly shorten the forming cycle. Production tests of the gel-processing clad stucco in the investment casting showed a significant reduction of the reject precision castings, acceleration of ceramic molds production and a reduction of the working hours on removing "wedged" ceramic from less-accessible cast section cavities of the pump parts from complex alloyed steels.

Abstract: In order to reduce the defects of investment casting and improve its casting quality, vibration technology and casting technology are combined effectively and the effect of vibration degree of freedom, frequency and amplitude on the filling ability of liquid metal are studied by means of EDEM-FLUENT solid liquid coupling visualization. With the use of orthogonal test method, the sensitivity of the particles towards each parameter index is obtained. Optimal vibration parameters are chosen and then the best variable cell vibration casting solution is obtained.

Abstract: In order to solve production defects such as shrinkage and porosity inside a certain train coupler casting in Anhui Xinhong Machinery Co.,Ltd., the main reasons of defects are found through the process of CAE simulation analysis and physical X ray detection to determine the location and morphology of casting defects and to reflect the actual situation of coupler filling and solidification process. The main reasons are found as follows: uneven thickness of casting structure, insufficient original gating and feeding system and etc. Through the process optimization and apply multidimensional vibration, then test validation, the train coupler casting which meets the technical requirements has been successfully produced, ensuring the smooth mass production of the company. ProCAST numerical simulation results have confirmed the rationality of the proposed work in optimization process measures in reducing and eliminating the shrinkage defects.

Abstract: Malocclusion or improper teeth arrangement is the most common problem in the field of orthodontics. If the malocclusion is not corrected, it will promote more serious problems, such as bleeding gums, tooth decay, cavities, difficulty breathing and other problems. Currently, the most common technique used to cure the malocclusion is using treatment of orthodontic brackets. Normally, orthodontic brackets can be produced by machining, metal injection molding and investment casting processes. In the previous research, orthodontic brackets have been successfully produced using investment casting process. The investment casting is selected, since the technology was developed well in Indonesia which is shown by existing number of investment casting industries. However, surface roughness of the bracket produced by investment casting is still high, valued at 0.91 μm. On the other hand, surface roughness of the commercial orthodontic bracket is 0.53 μm. In this current work is focused on surface modification of investment casting brackets by using electropolishing. The best result shows that the surface roughness of cast brackets achieve up to 0.44 μm. It shows that opportunity to fabricate orthodontic brackets domestically is applicable.

Abstract: Centrifugal pouring is often used in investment casting of large thin-wall Ti castings to promote filling. Shrinkage defects often appear in a Ti casting produced by centrifugal casting. Numerical simulation indicate that shrinkage is caused by these reasons: improper pouring system and thin-wall structure limited feeding of liquid metal from pouring system, and centrifugal force enlarged the shrinkage defects by strengthen feeding of liquid within the casting. Thus centrifugal casting is replaced by gravity casting and a new pouring system is adopted. Obvious shrinkage defects disappear in the new casting process.

Abstract: Ceramic corundum molds on hydrolysed ethyl silicate solution which have insufficient inertness to poured alloys are widely used in the production of castings from reactive metals alloys. This is due to the presence of free silica, which is a strong oxidant of such alloy components as aluminium and titanium in vacuum conditions, in the form of a high content. To solve the indicated problem using aluminium-borophosphate concentrate, chemically cured with periclase, as a silica free binder of ceramic corundum molds was suggested. The use of the combination of the indicated mold materials allows not only enabling chemical inertness of the molds, but also operating the process of mold forming. The developed technology provides the acceleration of the mold manufacturing cycle in 4...6 times, the increase the strength of the mold covers, the reduction in the heat-resistant alloy casting cost. It enables significant improvement of the quality and increase of the economic efficiency of manufacturing of precision casting from reactive metals and alloys.

Abstract: Protective coatings are used today in many applications for reducing friction and wear of tools in hot-working process e.g. metal die casting, hot forging, metal die plastics injection. The main goal of undertaken investigation was to evaluate usability of those coatings for improving wear resistance of metal die applied in investment casting process for wax injection. The (Ti,Al)N and (Al,Cr)N PVD coatings were deposited onto X37CrMoV5-1 hot-work tool steel and their mechanical and tribological properties are characterized in the paper. Based on the results of microscope examinations, scratch test, hardness measurement the similar properties of (Ti,Al)N and (Al,Cr)N coatings were found. Moreover it was established that type of steel surface machining before coating deposition, i.e. grinding, electrical discharge machining (EDM) and milling, did not affect coating properties. Thin coatings replicate steel base roughness parameters as Ra, Rz and Rmax with over 95% of correlation. Based on tensile test results of wax/coated steel samples and wax/uncoated steel samples the lowest wax adhesion to (Ti,Al)N coating was confirmed.

Abstract: The research presents methods for modern design and processing tools to be used in manufacturing process of castings in the aviation industry. In the study it is described how to use a computer simulation software and rapid prototyping / rapid tooling methods for manufacturing of drone’s micro-engine turbine rotor. The computer simulation of flow and solidification process and the investment casting technology were applied for manufactured elements.