球墨鑄鐵與不銹鋼摩擦攪拌點銲接合性質之研究

Abstract

摩擦攪拌點銲是摩擦攪拌銲接所衍生的另一種固態接合技術，其製程溫度皆於母材熔點以下，可避免因熔化而產生的缺陷，適合異質材質或是難銲材料之接合。球狀石墨鑄鐵由於機械性質優良、鑄造性良好且價格低廉，所以在許多工程結構件上已被廣泛使用。肥粒鐵系不銹鋼因為其抗蝕性比麻田散鐵與沃斯田鐵系不鏽鋼更加優越，常被應用在一些腐蝕嚴重的環境中。本研究利用1615 rpm的主軸轉速，在10-240秒的持溫時間下，探討SUS 444不銹鋼、球墨鑄鐵、SUS 304不銹鋼三種異質材料之試片，經摩擦攪拌點銲搭接接合後之微觀組織與機械性質之影響。 實驗結果顯示，透過本研究設計的參數能使不銹鋼與球墨鑄鐵板材產生接合，攪拌時間愈長，接合效果愈明顯，在進給邊成功接合的區域比退出邊大。此外，在攪拌接合區域未發現因重熔凝固所產生的碳化物，然而，由於攪拌所產生的熱及外力作用，不銹鋼產生晶粒細化現象，而球墨鑄鐵部份則在攪拌區形成麻田散鐵組織，而熱機影響區則為類似變韌鐵組織。而越靠近攪拌區由於晶粒細化的作用，其微硬度值也有明顯提升。拉伸試驗結果顯示保持時間越長，其接合強度越好，尤其同材質之接合優於異質接合。

Friction stir spot welding is another solid-statebonding technique deri- ved from friction stir welding, the process temperature which is below the melting point of the base material can be avoided defects resulting from melting, it is suitable for joining dissimilar materials and difficu- lt materials. Ductile iron has been widely used in many engineering structures, due to excellent mechanical properties, good casting and low-cost. Ferrite stainless steels have been used in some severe corrosion environment for its corrosion resistance which is mo- re superior than Martensitic stainless steel and austenitic stainless steel. In this study, the effect for microstructure and mechanical properties of SUS 304 stainless steel, SUS444 stainless steel and cast iron joining by friction stir spot welding with 1615 rpm spindle speed and 10-240 seconds hold time was investigate. The experimental results show that the parameters design in this study can produce stainless steel and cast iron plates joining together,. The stirring time is longer, bonding success area in the advancing side is larger than the retreating side. In addition, cementite structure generated by remelting and solidifying has not been found in the joints. Furthermore, the phenomenon of grain refinement has been observed in the stainless steel, due to the heat and external force produced by stirring. On the other hand, martensite structure appeared in the stir zone of ductile iron and bainite structure appeared in the thermo-mechanical affected zone, resulting in the increase of microhardness. Tensile test results present that the holding time is longer, the bonding strength is better, especially joint the same material material is superior to bonding dissimilar material.