Browsing by Author "Tseng, KH"

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Effect of nitrogen addition to shielding gas on residual stress of stainless steel weldments
(2002-02-01)
Tseng, KH
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
The objective of the present study, was to investigate the effect of nitrogen additions to the shielding gels Oil the ferrite content and residual stress in austenitic stainless steels. Autogenous gas tungsten arc (GTA) welding was applied on austenitic stain less steels 304 and 310 to produce a bead on plate weld, The delta ferrite content of the weld metals was measured using a Ferritscope. The residual stress in the weldments was determined using the hole drilling strain gauge method. The present results indicated that the retained delta ferrite content in type 304 stainless steel weld metals decreased rapid v as nitrogen addition to the argon shielding gas was increased. The welding residual stress increased with increasing quantity, of added nitrogen in the shielding gas. It was also found that the tensile residual stress zone in austenitic stainless steel weldments was exteneded as the quantity of added nitrogen gas in the argon shielding gas was increased. (C) 2002 IoM Commuications Ltd.
Effect of pulsed gas tungsten arc welding on angular distortion in austenitic stainless steel weldments
(2001)
Tseng, KH
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
The effect of the parameters of the pulsed gas tungsten arc welding (GTAW) process on the angular distortion in austenitic stainless steel weldments was investigated. Autogenous GTAW was conducted on types 304 and 310 stainless steels to produce a bead on plate weld. The weldment thermal cycle was recorded during pulsed GTAW to investigate the influence of thermal stress. Angular distortion was determined by using the mean vertical displacement method. The experimental results indicate that higher pulse frequency, smaller pulse spacing, greater amplitude ratio, and greater duration ratio can reduce the angular distortion. The angular distortion of type 310 stainless steel weldments was greater than that of type 304 weldments under the same welding conditions because of the lower thermal conductivity and thermal diffusivity of type 310. (C) 2001 IoM Communications Ltd.
Effects of the process parameters on austenitic stainless steel by TIG-flux welding
(2006-05-01)
Huang, HY
;
Shyu, SW
;
Tseng, KH
;
Chou, CP
;
機械工程學系
The effects of the process parameters of TIG (tungsten inset gas)-flux welding on the welds morphology, angular distortion, ferrite content and hot cracking in austenitic stainless steel were investigated. Autogenous TIG welding process was applied to the type 304 stainless steel through a thin layer of activating flux to produce a bead on plate welded joint. TiO2, SiO2, Fe2O3, Cr2O3, ZnO and MnO2 were used as the activating fluxes. The experimental results indicated that the TIG-flux welding can increase the weld depth/width ratio and reduce the HAZ (heat affected zone) range, and therefore the angular distortion of the weldment can be reduced. It was also found that the retained ferrite content within the TIG-flux welds is increased, and has a beneficial effect in reducing hot cracking tendency for stainless steels of the austenitic type weld metals. A plasma column constriction increases the current density at the anode spot and then a substantial increase in penetration of the TIG-flux welds can be obtained.
Evaluation of TIG flux welding on the characteristics of stainless steel
(2005-09-01)
Huang, HY
;
Shyu, SW
;
Tseng, KH
;
Chou, CP
;
機械工程學系
The aim of the present study was to investigate the effect of specific oxide fluxes on the surface appearance, weld morphology, retained delta ferrite content, hot cracking susceptibility, angular distortion and mechanical properties obtained with the tungsten inert gas (TIG) process applied to the welding of 5 mm thick austenitic stainless steel plates. An autogenous gas tungsten arc welding process was applied to stainless steels through a thin layer of activating flux to produce a bead on plate welded joint. The MnO2 and ZnO fluxes used were packed in powdered form. The experimental results indicated that the 80% MnO2 - 20% ZnO mixture can give full penetration and also a satisfactory surface appearance for type 304 stainless steel TIG flux welds. TIG welding with MnO2 and/or ZnO can increase the measured ferrite number in welds, and tends to reduce hot cracking susceptibility in as welded structures. It was also found that TIG flux welding can significantly reduce the angular distortion of stainless steel weldments.
The effect of pulsed GTA welding on the residual stress of a stainless steel weldment
(2002-05-10)
Tseng, KH
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
The objective of this study was to investigate the effect of pulsed GTA welding parameters on the residual stress of the weldment. Autogenous gas tungsten arc welding was applied on SUS 304 and SUS 3 10 stainless steels to produce a bead-on-plate weld. The residual stress was determined by using the hole-drilling strain-gage method of ASTM standard E837. The experimental results show that a greater pulse frequency, a larger pulse spacing, a greater amplitude ratio, and a greater duration ratio can reduce the magnitude of the residual stress in the austenitic stainless steel weldment. The residual stress of the 3 10 stainless steel weldment is greater than that of the 304 stainless steel weldment under the same welding conditions because of its lower thermal conductivity and thermal diffusivity. The experimental results also showed that pulsed current welding has a smaller range of the tensile residual stress zone as compared to that of constant current welding because of its lesser amount of heat input. (C) 2002 Elsevier Science B.V All rights reserved.
The study of nitrogen in argon gas on the angular distortion of austenitic stainless steel weldments
(2003-11-10)
Tseng, KH
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
The objective of this study was to investigate the effect of nitrogen added in argon shielding gas on the angular distortion of austenitic stainless steels. An autogenous gas tungsten arc welding was conducted on austenitic stainless steels 304 and 3 10 to produce a bead-on-plate weld. The delta-ferrite content of welds was measured by using Ferritscope. The angular distortion of weldments was determined by using the mean vertical displacement method (MVDM). The present results indicate that the retained ferrite content in Type 304 stainless steel weld metals was rapidly reduced as the nitrogen addition in argon shielding gas was increased. The welding angular distortion was raised with the increase of the amount of nitrogen added in the shielding gas. This experimental result also found that the existence of retained ferrite microstructure within the austenitic matrix has a beneficial effect in reducing welding distortion tendency of austenitic stainless steel weldment. (C) 2003 Elsevier Science B.V. All rights reserved.