| Summary: | 碩士 === 國立虎尾科技大學 === 創意工程與精密科技研究所 === 99 === The process of forging is completed by impacting or extruding when the materials are put in different dies and tools undergoes the plastic deformation. This process will convert the shape without changing the actual composition and mass of the materials in order to obtain the required shape, size, and mechanical property of parts. Forging can control the metallic flow and structure of the grains in order to make forged parts with better mechanical strength and toughness which is needed to withstand highly overload resistant and frequent used mechanical parts. Single piece forging process is commonly adapted.
The low-carbon materials of steel after forging must go through carburizing and quenching in order to improve the hardness of steel surface. The study focuses on the of forging deformation percentage in accordance with different steel materials that undergoes different carburizing and quenching condition. More so, the microstructures observation on carburized cross-section and micro-hardness test can help understanding how forging type, forging deformation percentage, and carbon potential affect carburizing process. The study helps to look for the better resolve when carburizing different percentage of forging deformation from various steel materials, in which, might provide technical reference on the company of forging technology and heat treatment.
According to the results, forging deformation percentage affects the internal microstructure of carburized and non-carburized layer. Under the same forging process, the grain size after the carburizing – the greater, the hot forging is, secondly the warm forging is, the finer, the cold forging is. The carburizing depth and the surface hardness both increase as the forging deformation percentage increases. When carbon potential is at 0.4% or 0.8%, the transverse and longitudinal depth of carburization both decrease as the forging deformation rate increase. The hardness slightly increases as the forging deformation rate increase. When carbon potential is at 1.2%, the forging deformation rate has no effect on transverse and longitudinal depth of carburization, and hardness. When carbon potential is at 0.8%, transverse and longitudinal depths of the carburization are both similar. It is most likely to produce less excessive carburized to avoid quenching crack when harden.
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