F. Shehata

Computer aided foundry die-design

Abstract In the design of die casting dies, the object is to produce sound casting as cheaply and rapidly as possible. At the same time consideration must be given to suitable die size, locations of gating system, and selection of an appropriate die casting machine. Foundries in many cases encounter difficulties to ensure shortened lead-time in designing a new die for new product. A lot of estimations have to be done which use fundamentally based on previous experience and application of various mathematical and empirical equations. In this work, main die design procedures and related equations are presented in a logical way. A computer program is developed to estimate main die elements based on the geometry input of casting shape. After initial inputs have been given, the system does full calculations, optimizes selections, and lists main die element sizes. The program can present die characteristics and casting machine characteristics. From both characteristics the optimum die elements were optimized. Optimum filling time and gating dimensions among other elements of die are estimated. Cooling time, cooling channel locations, and flow rates relations are estimated and presented.

Fabrication of Copper-Alumina Nanocomposites by Mechanochemical Routes

Nanostructure composites of Copper-Alumina were successfully produced by new mechanochemical method using two different routes. First, route A was carried out by addition of coarse copper to aqueous solution of aluminum nitrate, and second, route B was also carried out by addition of coarse copper to aqueous solution of aluminum nitrate and ammonium hydroxide. In both routes, the mixtures were heated in air and milled mechanically to get the oxides powders of CuO and Al2O3. The CuO was reduced in preferential hydrogen atmosphere into fine copper. The composite powders have been cold pressed into briquettes and sintered in hydrogen atmosphere. The structure and characteristics of powders as well as sintered composites produced from both routes were examined by XRD, SEM, EDS, TEM and metallographic techniques. The results showed that, in both routes, nano-sized particles of alumina were formed and dispersed within the copper matrix. The structure revealed the formation of CuAlO2 spinel structure at copper alumina interface. Nanocomposites produced by route-B showed finer alumina particles of 30 nm compared to 50 nm produced by route-A resulting in improved properties in terms of relative density, macro and microhardness values.

Effect of plate thickness on mechanical properties of steel arc welded joints

Abstract Specimens of various plate thicknesses (10–32 mm) were fabricated from thick plate of plain carbon steel and butt welded, using the shield metal arc welding process. The mechanical properties were examined and discussed in terms of changes in cooling rates. The hardness of welded joints was correlated to hardness and cooling rates were extracted from the Jomeny end bar of the same welded material. The welding procedure and the so-called Jomeny weld correlation are presented and discussed. The results showed that welding strengths vary according to plate thickness and to the distance from the weld root. The microstructures across and along the welded joints showed significant changes. The cooling rates of the welded joint can be easily determined from the corresponding cooling rates of the Jomeny end bar test.

Computer aided die-design

Die is very expensive items and every effort is required to improve die design to get sound cast with an efficient die. Most selection and estimations are basically based on previous experience and empirical equations. The wrong choice usually means costly and time-consuming. In this paper, a die-design computer program has been developed that can be used efficiently and friendly to estimate the die overall dimensions including sizes of sprue, runners and ingates. The system can be used to select casting machine characteristics and display its main capabilities and specifications. The program could also used to estimate the casting process characteristics, which include melt velocity and pressure, injection flow rate and die filling and cooling times. Finally, procedures for drawing die-casting die were attempted, which allows us to build die geometry from part drawings, without needing any additional CAD software. The die-design program can be used for virtually any alloy, cast in die and permanent mould processes.