الفهرس 
Chapter One IntroductionOnly 14 pages are availabe for public view
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Abstract
The improvements of production methods of leaded brass alloy (CuZn40Pb2) used for gas valves were studied to prevent the cracking phenomena. This alloy was prepared according to European Standards (EN), with controlling the addition of lead (Pb) element for modified alloy structure. Two batches of leaded brass alloy have been produced during casting process by using two production parameters and raw materials. The first batch of casting alloy has been produced from 100% recycle and without change in casting parameters, while, the second one has been produced after adding 30% of pure materials (Cu, Zn and Pb) to alloy charge and some improvements for casting parameters were performed. Both batches of billet castings of (Ø180×300) mm dimensions which already produced have been hot extruded before and after change the extrusion parameters to produce two extruded leaded brass rods (Ø 32.2±0.2) mm in each extrusion action. Then, these extruded rods have been cold drawn by hydraulic draw bench to produce (Ø 30±0.1) mm diameter. Hot forging process has been adopted for leaded brass alloy (CuZn40Pb2) rods in two different preheating temperatures (720 and 680) °C to produce the gas valves, and then finally machined. Fourteen samples of leaded brass alloy (CuZn40Pb2) during the casting, extrusion, cold drawing, hot forging and machining processes have been selected and prepared. Mechanical tests such as (tensile strength, hardness and elongation) have been performed. X-ray and scanning electron microscope SEM inspections were examined using optical microscope, radiographic test by X-ray device and the micrographic investigations also performed with elemental analysis by SEM/EDS device. The hardness recorded high values after casting process due to some impurities such as iron with silicon and the effect of cooling rate through solidification process. The hardness values are decreased during extrusion process and then, increased again by cold drawing and with 30% of pure materials added to material charge. Micro-hardness values for the fractured tensile test samples are appeared higher than others due to work hardening effect. The ultimate tensile strength of CuZn40Pb2 alloy products are appeared into cold forming sample with pure material used. The detecting inspections by using the ultrasonic and X-ray tests for cracks and other defects appeared that, most of leaded brass samples have been improved by using new production parameters and pure material added.The morphological structure and the elemental micro-analysis of most samples by using SEM and EDS device are revealed as α-β dual phase with distributed lead elements. The structure and elemental analysis have been improved from the casting step towards to the cold drawing process which has the best specifications.The conclusions of the study explained that; the microstructure, elements with phase homogeneity and grain size of the cold drawn leaded brass samples were improved when, pure materials adding and casting with extrusion parameters changing and improving. Also, the mechanical properties of these samples as ultimate tensile strength and hardness were improved and the samples’ defects were minimized.The suggested of some future works were included by the recommendation of this study as increasing of pure material addition to 50% of alloy charge, using Abaqus Software to creating a simulation model for the detection of defects during the casting, hot extrusion and hot forging processes.