| Summary: | 碩士 === 國立臺灣師範大學 === 工業教育學系 === 97 === This research introduces S45C medium-carbon steel which commonly used as base material for V-groove welding in hydraulic turbine accessories, in which 3 domestic welding rods (specified as A, B, C, respectively) and one imported welding rod (specified as D) were selected to proceed stack welding, to take test strip on full welding bead and make tensile test bar as per ASTM E8M standard regulation, and to observe via metallographic microstructure, microhardness measurement, tensile test, observation of SEM cross-section and EDS analysis after welding, to explore the mechanical property and changes in microcosmic structure, in which this research is to be provided as a reference and application for the welding rod.
According to the experiment results : the medium-carbon steel is composed by A, B and C, to change from pearlite structure and become a bainite structure from the root of welding bead to weld-pool of welding bead; with Hv 245 microhardness value for cap area that is slightly higher than middle line; around 360MPa for yield strength (YS) and 460MPa for ultimate tensile strength; and to observe tensile cross-section via SEM, which belongs to ductile fracture.
In addition to Fe and C, welding rod D contains certain ratio of Cr, Ni, with shining cross-sectional welding bead after welding process, close to stainless nature and Austenitic-ferritic stainless steel structure, which is also named as two-phase stainless steel, with 50% hardness higher than welding rod A, B and C, and welding line exceeds around 100% while YS and UTS exceed 35% and 60% than welding rod A, B and C; tensile cross-section also belongs to ductile fracture with finer hole than above 3 welding rods.
|
|---|
