الفهرس 
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Abstract
An experimental the investigation was carried out to compare the mechanical properties of welded joint in that valid seamless tubes made of low carbon steel SA 210 grade Al .The welds were made using three types of welding processes; manual metal arc welding MMA; tungsten inert gas TIG and flash welding FW.
Tensile tests were carried out at room temperature and at elevated temperatures, Micro structural variations along the welded joint were studied for the different welding conditions. Hardness transverse measurements giving hardness profiles for the different welding condition were made.
Impact shelf energies and transition temperatures ware measured for the different conditions. The effect of post weld heat treatment on the mechanical properties was investigated.
The investigation indicated that the MMAW with a TIG root pass gave superior properties regarding strength and ductility for room temperature applications. For relatively high temperature applications; 200 and 400 °C TIG give the best results of strength and ductility measurements. Although Flash welding gave satisfactorily and competitive results, it provides a fast and low cost process.
Post weld heat treatment is found to be of great importance for high temperature applications in order to restore ductility although it may reduce strength.
The hardness profiles of TIG welded joints were slightly affected by post weld heat treatment and its yield strength values were also slightly affected by it for both room temperature and relatively high temperature tests. Shelf energy and transition temperatures obtained from impact tests indicated that all weld types tested in the present investigation performed satisfactorily. Post weld heat treatment did not show any significant effect on impact results. Slightly higher shelf energy values were observed for the MMAW
with TIG root passes compared to other conditions tested.