Question

10- In a welding operation carried out on a eutectoid steel (C =0.8wt%), the selection of welding travel speed, applied voltage and current and application of blowing air and wrapping of the work piece into insulating cloth was as such that the following cooling schedules obtained. You are required to specify the most likely microstructure of the weld metal. Once identified the most likely microstructure, then discuss the ductility and toughness of the weld joint. Rc (Hardness) Eutectoid temperature Temperature Bowite M 200 M50 MO 100 1 104 104 10102 Time (s) TTT diagram of eutectoid steel Cooling curves are marked as 1,2,3,4 from left to right on the diagram. (20 Marks)

Answer 1

- At we get Mastenisite we get Banite ③ we get pearlite + Mastenisite ® we get Bainite. Ductility of weld joint in increasing orde Toughness = 6 7 Ô > ③ > 0.