Plasma nitriding could improve the lifecycle of plastic mould steels by modifying the surface layers. In this study, the effects of time and temperature of plasma nitriding on plasma nitriding behavior of plastic Injection moulding steel P20 were studied. In this regard, pulsed plasma nitriding treatment was performed on P20 samples at different processing temperatures such as 450, 500 and 550oC for 2.5, 5, 7.5 and 10h at gas mixture of 75% N2 - 25% H2. Diffusion zone and compound layer were studied by optical and scanning electron microscopy and the crystallographic phases on surface were determined by X-ray diffraction analysis. Also, micro hardness changes from surface to core of the samples were determined. Results have shown that by increasing treatment temperature and time, nitrided layer thickness and hardness were increased respectively. The SEM results showed that the interface of the compound layer and the diffusion layer formed on the sample treated at higher temperatures were more uniform than those treated at lower temperatures. Regarding the results of EDS, during the ion nitriding of P20 upward diffusion of the carbon and the downward diffusion of the nitrogen have been occurred. XRD results have shown that in all the process parameters e-nitride was the most forming phase.

Master moulds are used to cast copper anode moulds. These moulds are made of grey or nodular castitons, because they posses the desired properties. It was expected that ductile cast iron moulds could have performed their nominal life but in service; these moulds have not performed their nominal life and they have experienced premature failures due to warping and cracking, Also grey cast iron moulds fail because of generalized surface cracks. In this paper, the failure of master moulds is investigated according to the metallographic and hardness measurement test. Then paralytic and austempered ductile iron alloys are proposed and tested through short time high temperature tensile and thermal shock test similar to working conditions of the moulds. Also master mould is modeled by Finite Element Method to evaluate the thermal conditions. Finally it is concluded that compared with paralytic ductile iron, austempered ductile iron has higher resistance to thermal shock.

Injection mould design is a complex task which consisits of different fields of knowledge such as solid modelling, polymer science and flow and solid mechanics.Therefore a comprehensive and efficient system of computer aided mould design, is still somehow far from reality. In this paper, an' attempt is made to determine the parting surfaces in Injection moulds by the use of "CAD" and "IGES"; a standard tool for graphics data exchange Besides a flowchart is developed to show a typical procedure for finding the set of definition points on the parting line of parts. Determining the parting lines and surfaces are the most critical elements in Injection mould design which have the most profound effects on the mould design and subsequent operation.

In this investigation for Expandable Pattern Casting (EPC) simulation, an algorithm was developed to calculate the gas pressure of the evaporated foam during mould filling. Also, the effect of backpressure evaporative foam on filling behavior was modeled with a new experimental function by adding a Volume of Fraction (VOF) function. The simulation of molten flow and track free surfaces is based on the (Solution Algorithm) SOLA-VOF numerical technique. To simulate the three-dimensional incompressible flow of melt in EPC moulds, the pressure boundary conditions, heat transfer and foam gas pressure effect were modified. In order to verify the computational results of simulation melt flow in EPC casting, a thin grey iron plate was poured into a transparent foam mould. mould .filling and foam depolymerization were recorded with a 16mm high-speed camera. The comparison of experimental and simulation results of the sequence filling of EPC casting showed a good consistency, which confirms the accuracy of the model.

In this paper, the heat transfer coefficient on the A356 alloy metal-mould interface for HI3 steel and Gray Iron moulds was measured and modeled. Conditions as same as the low-pressure casting conditions were imposed by adding a piston, into the sprue channel. In order to establish one dimensional heat transfer condition, a cylindrical chalky sleeve was placed around of the mould cavity, and then metallic chills (H13 and Gray Iron) are placed at the bottom and the top of the mould cavity. Once purring, the time-temperature (T-t) curves at the interface of chill-mould were saved and plotted by a data acquisition system. Then a mathematical model was introduced for the heat transfer coefficient of the metal mould interface based on the experimental data by utilizing of "inverse heat problems" method. A simulation code of heat transfer was developed by finite difference method (FDM) that it could simulated distribution of heat transfer into at the mold and the cast part. The results of this code showed a sufficient agreement between the simulation and the experimental data.