الفهرس 
CHAPTER [1] INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Carbon steel is widely used in various applications in automotive industry. Boron is used as micro-alloying element to enhance the mechanical properties of carbon steel. The objective of the present work is to study the effect of boron on the mechanical properties of dual phase steels which are mainly used in the underbody suspension for automotives. The material used in the present study was a carbon steel (0.29 C %) with different boron contents: 0.0003 and 0.007wt. %. The steels were cast using an open air induction furnace. The molten steel had the form of Yblocks.The parts of Y-blocks of alloys 0.0003B and 0.007B steels were heated up to 1200ºC and then were hot forged producing bars. After hot forging, the bars were subjected to air cooling. In the hardening process, the different alloys(0.0003B, 0.007B) were heated up to the intercritical annealing temperatures
(between AC1 and AC3) for 15 minutes and then water quenched. The resultant
microstructures after quenching process were observed as ferrite plus islands of
martensite. After that, tempering was done at 300°C, 400°C and 500°C for
different interval times. The experimental results revealed that the mechanical
properties of the selective alloys were significantly changed by boron content and
tempering treatment. By increasing the boron content, hardness was gradually
increased (up to 46%) with small effect on ductility of alloys. By increasing the
tempering time and temperature, hardness was gradually decreased and ductility
was improved. Compression testing was carried out to determine the compressive
strength and work-hardening coefficient. Welding of dual phase steel containing
boron (0.007wt. %) using GTAW, SMAW and EBW was carried to obtain the
mechanical properties and microstructure of welded joints.