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Effect of Different Metalurgical Phases on the Welding Residual Stresses of Base Metal

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This report is related to Welding Metallurgy.
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    EFFECT OF DIFFERENT METALLURGICAL PHASES ON THE WELDING RESIDUAL STRESSES OF BASE METAL S355 GROUP NO. 09 Batch: 2009-2010 Name Seat No. Salman Zafar MY-015 Sadia Abro MY-025 Mohammad Tehmas Khan MY-053 Iqbal Ahmed Alvi MY-054 Supervisor: Engr. Bilal Ahmed Co-Supervisor: Engr. M. Ali Siddiqui DEPARTMENT OF METALLURGICAL ENGINEERING NED UNIVERSITY OF ENGINEERING & TECHNOLOGY    CERTIFICATE   Submitted in partial fulfilment of the requirement of the degree of Bachelors of Engineering (Metallurgical Engineering).   Effect of Different Metallurgical Phases on the Welding Residual Stresses of Base Metal S355 Group No. 09 Batch: 2009-2010 Name Seat No. Salman Zafar (G.L) MY-015 Sadia Abro MY-025 Mohammad Tehmas Khan MY-053 Iqbal Ahmed Alvi MY-054  __________________ __________________ Supervisor Co-Supervisor  __________________ __________________ Examiner-1 Examiner-2 DEPARTMENT OF METALLURGICAL ENGINEERING NED UNIVERSITY OF ENGINEERING & TECHNOLOGY  i ABSTRACT Welding technology and design has been acknowledged as an essential feature of industries involving heavy fabrication. It plays an important role in productivity and quality of the manufactured products. Despite its advantages, welding can lead to structural problems such as distortion and residual stresses in the weldment as a result of rapid heating and cooling. Therefore actual prediction and reduction of residual stresses are critical in improving the quality of weldments. One of the critical factors that influence the formation of residual stresses is the metallurgical phase transformations in base metal and weld metal. This research aimed to investigate the effect of different metallurgical phases on the welding residual stresses of base metal (S355). In this study, Finite Element Method was utilized to predict the residual stresses, while S355, low manganese carbon steel, was selected as a base metal, which is specific to Tungsten Inert Gas (TIG). Goldak’s double ellipsoidal model was used to simulate the TIG heat source. Simulations for two different cases were conducted using software, namely Visual Mesh and SYSWELD. The first case involved the analysis without the employment of any filler metal whereas in the second case 316L was used as a filler metal. The effect of martensite and austenite on welding residual stresses was observed. In first case, the proportion of martensite phase was much higher than the austenite i.e. 31% which led to the generation of tensile residual stresses in the weld area and compressive residual stresses away from the weld area. This stress generation was attributed to martensitic transformation in the weld area which caused volumetric expansion. In second case, maximum proportion of austenite in weld area, about 88%, was obtained, due to the much lesser specific volume of austenite than that of martensite. Hence, compressive residual stresses were observed in the vicinity of the weld and tensile residual stresses were generated away from the weld area. Keywords:  Welding, FEM, SYSWELD, Visual Mesh, Phase Transformation, Residual Stresses.  ii ACKNOWLEDGEMENT All Praise is for Almighty Allah, Who granted us the will and ability to work on this  project and bring it to completion. We would like to express the highest gratitude towards our project supervisor Engr. Bilal Ahmed, for his kind supervision and encouragement without which we would not have accomplished our objectives. We would like to warmly thank our co-supervisor, Engr. Muhammad Ali Siddiqui, for his immense support and encouragement. His helpful nature and constant help in this  project deserves great appreciation. We would also like to express our appreciation towards Engr. Faisal Nadeem for his cooperation and guidance. We would extend a thank you to Engr. Kashif Iqbal, who helped us with his intellectual suggestions. We would also like to thank all the faculty members and technical staff of Metallurgical Engineering Department who helped us throughout our project, sparing time for us from their busy schedules, listening to our problems and suggesting solutions thus making this project a success for us. Our thanks and appreciations also go to our colleagues in developing the project and  people who have willingly helped us out with their abilities.
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