Browsing by Author "Tseng, K. H."

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Enhancement of mechanical properties of electron beam-welded D6ac steel tube
(2015-04-01)
Wu, S. C.
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Tseng, K. H.
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Wen, H. C.
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機械工程學系
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Department of Mechanical Engineering
A forward flow-formed D6ac steel tube was joined through the electron beam welding process and was then subjected to post-weld heat treatment. The mechanical properties and hardness profiles of the as-welded (without heat treatment after welding) steel and different post-weld heat treatment weldments were investigated. The results show that the as-welded D6ac steel exhibited very poor mechanical strength and elongation. After post-weld heat treatment, a large improvement in the mechanical properties of the weldment was achieved. Forward flow-formed D6ac electron beam weldment subjected to post-weld heat treatment at 350 degrees C reached the largest yield strength and ultimate tensile strength values (approximately 1359.2 and 1494.3 MPa, respectively). Forward flowformed D6ac electron beam weldment subjected to post-weld heat treatment at a temperature of 650 degrees C exhibited an overtempered state, which led to mechanical strength and hardness deteriorations of the weldment. This study found that the forward flow-formed D6ac electron beam weldment heat-treated at 350-450 degrees C and held at this temperature range for 2 h exhibits high mechanical strength, sufficient elongation and a yield strength/ultimate tensile strength ratio of 0.91.
Study of the performance of stainless steel A-TIG welds
(2008-04-01)
Shyu, S. W.
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Huang, H. Y.
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Tseng, K. H.
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Chou, C. P.
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機械工程學系
The purpose of the present work was to investigate the effect of oxide fluxes on weld morphology, arc voltage, mechanical properties, angular distortion and hot cracking susceptibility obtained with TIG welding, which applied to the welding of 5 mm thick austenitic stainless steel plates. A novel variant of the autogenous TIG welding process, oxide powders (Al2O3, Cr2O3, TiO2, SiO2 and CaO) was applied on a type 304 stainless steel through a thin layer of the flux to produce a bead on plate welds. The experimental results indicated that the increase in the penetration is significant with the use of Cr2O3, TiO2, and SiO2. A-TIG welding can increase the weld depth to bead-width ratio, and tends to reduce the angular distortion of the weldment. It was also found that A-TIG welding can increase the retained delta-ferrite content of stainless steel 304 welds and, in consequence, the hot-cracking susceptibility of as-welded is reduced. Physically constricting the plasma column and reducing the anode spot are the possible mechanism for the effect of certain flux on A-TIG penetration.