oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Development of vacuum die-casting process  [PDF]
Masashi Uchida
China Foundry , 2009,
Abstract: The vacuum die-casting process, started 25 years ago in Japan, has been widely applied. This technology contributes very much to improvement of castings quality. The main factor causing the defects of die castings is the trapped air in the mold cavity, while the key technology of vacuum die-casting process is to avoid the trapped air effectively by evacuating the cavity before casting. At the same time, due to the shot speed and the casting pressure reduced in half, the service life of the die is prolonged and the productivity is enhanced, as well. Vacuum die-casting process is of great signifi cance in improving the die castings quality and making up the shortcomings of super-high-speed shot casting.
Effect of Injection Velocity on Structure Part Characteristic in AZ50 Die Casting Process with High Vacuum System

SMLee,PKSeo,CGKang,

材料科学技术学报 , 2008,
Abstract: When diecasting large and thin Mg alloy parts, material defects occur, which include porosity, nonuniform mechanical properties, irregular surfaces, and incomplete filling. To resolve these problems, it is necessary to have uniform injection velocities and temperatures as well as control the melt. This study investigated the feasibility of producing large and thin components using a die caster by attaching a high vacuum system. In particular, the effects of injection velocity on surface quality and the mechanical properties of the products were investigated. Hence, an injection velocity scheme and a die structure capable of casting in a vacuum were proposed. As a result, it was found that the critical low injection velocity was 0.2 m/s to produce large thin Mg alloy structures having good mechanical properties.
The ‘full sleeve’ application in the horizontal cold-chamber machine for pressure die casting of aluminium alloys  [PDF]
Z. Konopka,A. Zyska,M. ??giewka,A. Bielecka
Archives of Foundry Engineering , 2008,
Abstract: The ‘full sleeve’ construction has been designed and accomplished in the horizontal cold-chamber pressure die casting machine. Main part of this solution is a counter plunger placed in a movable die half which allows for full filling of the shot sleeve and precisely fixes the metal quantity needed for casting. The purpose of this new construction solution is mainly the reduction of the casting porosity caused by air entrapment and the improvement of both castability and accuracy of the die cavity reproduction. For such a redesigned machine there have been performed examinations consisting in pressure casting of AlSi9Cu alloy (EN AC-46000) at varying plunger velocity in the second stage of injection and varying intensification pressure. The alloy castability (the die filling ability) has been measured for each parameter setting. For the purpose of comparison, similar measurements have been performed also for the conventional system without a counter plunger. The castability examination has been done by means of a specially designed die with an impression of a trial casting of variable wall thickness. The experiments have been held according to the assumed factor design 22, what allowed for determining the mathematical models describing the influence of die filling parameters on the castability and the die cavity reproduction level. Both alternatives of the experiment confirmed the positive influence of plunger velocity and intensification pressure increase on the improvement of castability, the measure of the latter being the filled length of the impression. Applying of the new ‘full sleeve’ solution has improved castability for each experiment by about 20% as compared with conventional alternative. Castability in the ‘full sleeve’ system has been increased even for low values of plunger velocity and intensification pressure. For both alternative systems the influence of plunger velocity has been found, as an average, by four times greater than the influence of intensification pressure. The possibility of applying lower pressure values has been noticed for the shot sleeve construction with the counter plunger. This can influence favourably both the die and the machine durability. The obtained results have been explained and it has been pointed out that the ‘full sleeve’ construction can be widely adopted in pressure die casting of metal alloys.
The Efficacy of Botulinum Toxin Type a Injection in the Hamstring and Calf Muscles With and Without Serial Foot Casting in Gait Improvement in Children With Cerebral Palsy
Amirsalari S,Dalvand H,Dehghan L,Feizy A
Tehran University Medical Journal , 2011,
Abstract: Background: The goal of this study was to compare the efficacy of botulinum toxin type A (BTX-A) injection in the hamstring and calf muscles with and without ankle serial casting in the improvement of gait in children with cerebral palsy (CP).Methods : This double-blind prospective clinical trial was performed on 25, 2 to 8-year-old children with hemiplegic or diplegic CP in Tehran, Iran in 2010. The participants were chosen by simple randomized sampling and were matched for age, gross motor function classification system (GMFCS) and type of CP and were randomly divided into two groups: children in the first group (13) only received BTX-A injection, but the second group (12) received BTX-A and serial foot casting starting one week after the injection.Results : Comparison of the gross motor function, right and left knee spasticities and passive ROM of both knees between the two groups before and 1, 3, 6 and 12 months after the injections were not statistically significant (P>0.1). Furthermore, comparison of the right and left ankle spasticities and passive ROM before the injections and in1 and 3-month follow-ups did not show a statistically significant difference (P>0.1), but the differences were significant in 6 and 12-month follow-ups (P<0.05).Conclusion: BTX-A injection with serial foot casting vs. BTX-A alone was more effective in decreasing spasticity and improving passive ROM in the ankle of children with CP, but such injections in the hamstrings were not useful in these regards.
Improvement of quality of a gravity die casting made from aluminum bronze be application of numerical simulation  [PDF]
A. Fajkiel,P. Dudek,W. Walczak,P. Zawadzki
Archives of Foundry Engineering , 2007,
Abstract: The paper describes the possibility of improving the quality of gravity die cast connectors for overhead power transmission lines. The castings were made from aluminum bronze, grade CuAl9Fe1Ni1. A MAGMAsoft computer programme was used for simulation of the process of die filling and casting solidification to avoid defects, like shrinkage depression and gas porosities. The results of the simulation have finally led to redesigning of the metal feeding and cooling system and to reduced level of defects in castings.
Assessment of effectiveness of water mist cooling of casting die  [PDF]
R. W?adysiak
Archives of Foundry Engineering , 2007,
Abstract: At work research findings of the process of cooling the research casting die in the range of the 600-100°C temperature were presented and of the research-production casting die while pouring the cycle out cooled with compressed air about the pressure 0.6 MPa and the water mist about the pressure of air and water appropriately 0.3/0.35 MPa. The character and the speed of the temperature changes in the die and being formed of gradient of the temperature on the thickness partition walls were shown the die with the help of thermal and derivative curves. A course of changes was presented to the density of the thermal stream during cooling and in function of the temperature as well as results were shown a computer simulation of the process of pouring the production casting die. A scheme of the device for generating the water mist cooling the die and an image of spraying water were shown with the help of the designed rotary sprayer. They showed that applying the water mist for cooling dies is increasing the intensity of casting process and is accelerating it.
Heat Transfer between Casting and Die during High Pressure Die Casting Process of AM50 Alloy-Modeling and Experimental Results

Zhipeng GUO,Shoumei XIONG,Sang-Hyun Cho,Jeong-Kil Choi,

材料科学技术学报 , 2008,
Abstract: A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density (HFD) and interfacial heat transfer coefficient (IHTC) during the high pressure die casting (HPDC) process. Experiments were carried out using step shape casting and a commercial magnesium alloy, AM50. Temperature profiles were measured and recorded using thermocouples embedded inside the die.Based on these temperature readings, the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values, after which their values decrease to a much lower level until the dies are opened. Different patterns of heat transler behavior were found between the die and the castingat different thicknesses. The thinner the casting was, the more quickly the HFD and IHTC reached their steady states. Also, the values for both the HFD and IHTC values were different between die and casting at different thicknesses.
Structure of Water Mist Stream and its Impact on Cooling Efficiency of Casting Die  [PDF]
R. W?adysiak,P. Budzyński
Archives of Foundry Engineering , 2012,
Abstract: The work is a continuation of research on the use water mist cooling in order to increase efficiency of die-casting aluminum alloys. The paper presents results of research and analysis process, spraying water and generated a stream of water mist, the effect of the type of nozzle, the nozzle size and shape of the emitting of the water mist on the wall surface of casting die on the microstructure and geometry of water mist stream and cooling efficiency. Tests were used to perform high-speed camera to record video in the visible and infrared camera. Results were used to develop a computerized image analysis and statistical analysis. The study showed that there are statistical relationships between water and air flow and geometry of the nozzle and nozzle emitting a stream of microstructure parameters of water mist and heat the incoming stream. These relationships are described mathematical models that allow you to control the generating of adequate stream of water mist and a further consequence, the cooling efficiency of casting die.
Water mist effect on cooling process of casting die and microstructure of AlSi9 alloy  [PDF]
R. W?adysiak
Archives of Foundry Engineering , 2010,
Abstract: The paper presents the results of crystallization and cooling process of silumin AlSi9 and temperature distribution in the wall of research casting dies made of cast iron and steel in the temperature range 650100C during casting of silumin using water mist cooling consisting with air compressed (0,30,4 MPa) and water (0,350,45 MPa). It’s shown the nature and rate of change of casting die temperature and the formation of the temperature gradient at the wall thickness in the axis of the nozzle cooling the outer surface of the wall of casting die. Using derivative curves and regression models were compared to the temporary and average speed of crystallization and cooling of the casting in the 75÷200C temperature range. The differences of microstructure resulting from a change in the type of casting die, wall thickness of casting and the use of cooling water mist. It has been shown that the use of water mist and the changing wall thickness of die and the casting cooled pointwise lets you control the crystallization process, microstructure and quality of the silumin casting.
Materials on dies for pressure die casting  [PDF]
E. Ragan,J. Dobránsky,P. Baron,T. Olejár
Metalurgija , 2012,
Abstract: In the contribution the stress of die materials of thermal fatigue is defi ned and material life is derived theoretically and compared with the measured values. The important properties of the die materials as thermal conductivity, coeffi cient of thermal expansivity, modulus of elasticity and mechanical properties are described. Binding to it single die materials as carbon steels and chrome-tungsten steels are analyzed. As the perspective die material for pressure die casting of ferrous metals appears molybdenum with regard to advantageous properties.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.