The Study on the Distortion and Residual Stress in Stainless Steel Weldments
|Keywords:||銲接;變形;殘留應力;脈衝參數;氮氣含量;殘留肥粒相;沃斯田鐵不□鋼;welding;distortion;residual stress;pulse parameter;nitrogen content;retained ferrite;austenitic stainless steel|
The objective of this study was to investigate the effect of pulse parameters and nitrogen contents on the angular distortion and residual stress in austenitic stainless steel weldments. An autogenous gas tungsten arc welding was conducted on austenitic stainless steels 304 and 310 to produce a bead-on-plate weld. The retained delta-ferrite content of welds was measured by using the Ferritscope. The welding angular distortion was determined by using the mean vertical displacement method. The welding residual stress was determined by using the hole-drilling strain-gage method of ASTM standard E837. The thermal cycles of weldment were recorded during welding process to investigate the influence of thermal stresses. The experimental results indicate that the higher pulse frequency, smaller pulse spacing, greater amplitude ratio, and greater duration ratio can reduce the angular distortion and residual stress in stainless steel weldments. The retained delta-ferrite content in 304 stainless steel weld metals was rapidly reduced as the nitrogen addition in argon shielding gas was increased. The welding angular distortion and residual stress were raised with the increase of the amount of nitrogen gas added in the shielding gas. This experiment result found that the existence of retained ferrite microstructure within the austenitic matrix has a beneficial effect in reducing angular distortion and residual stress tendency in stainless steel weldments. The angular distortion and residual stress of 310 stainless steels are greater than that of 304 stainless steels under the same welding conditions because its higher yield stress, lower thermal conductivity and thermal diffusivity.
|Appears in Collections:||Thesis|