S15C/SUS304 異種金屬銲接之溫度與殘留應力研究

Abstract

本研究目的主要在探討同種與異種金屬銲接之溫度場與殘留應力之差異，以了解材料係數對於銲接殘留應力之影響程度。 為模擬分析銲接過程中溫度與應力之變化情形，本研究採用熱彈塑性理論，並考慮非線性材料特性等來進行銲接平板之有限元素數值分析。在模擬分析過程中，主要可區分為熱學與力學模式兩種分析理論。實驗材料選用SUS 304不□鋼與S15C碳鋼兩種，進行同種與異種金屬銲接模擬分析。銲接方法則採用自生氣護鎢極電弧銲，並以鑽孔應變計法來量測銲件殘留應力值。 本研究結果顯示使用54 %的GTAW電弧效率可準確模擬銲件溫度場的分佈狀況。在相同的銲接參數下，最大拉伸殘留應力會隨熱膨脹係數增加、熱傳導係數減少與降伏應力增加而呈線性增加。拉伸殘留應力區則隨楊氏係數的增加、熱膨脹係數的增加、熱傳導係數的減少、與降伏應力的增加而呈線性增加。本研究最後根據材料係數與銲接殘留應力之關係，推導出頗具實用性的銲接殘留應力預測公式，此公式可快速且準確的預測出平板對接銲之殘留應力分佈情形。

This study explored the difference in the distribution of the temperature and residual stresses of both the similar and dissimilar weld metal joints. Autogenous GTA welding process was conducted on stainless steel 304 and structural steels S15C. The hole-drilling method was used to experimentally measure the residual stress. The thermo-elastic-plastic theory was employed in the finite element model with temperature dependent material properties. The results showed that using 54% thermal efficiency of GTA welding can accurately simulate the welding temperature distributions. Under the same welding parameters, results showed that the maximum longitudinal tensile residual stresses increase linearly with the increase of the thermal expansion coefficient and the increase of the yield stress. The length of the tensile residual stress zone linearly decreases with the increase of the thermal conductivity. Finally, based on the relationship between material properties and welding residual stresses, a very useful and effective prediction equation is developed and verified in this study.