助銲劑對1020 碳鋼及304 不□鋼電漿銲接特性之研究

Abstract

本研究之主要目的在探討活性助銲劑對電漿銲接特性之影響研究。本 文除了對電漿銲接加入助銲劑所產生穿深能力之增加機制作探討外，亦針對惰氣鎢極電弧銲接的各種性質作一差異性之比較。為了瞭解活性助銲劑對不同材質的效應，實驗中分別採用AISI 1020 低碳鋼與AISI 304 沃斯田鐵型不□鋼以不填料方式來進行Bead-on-plate 實驗。使用之活性助銲劑有氧化物之MoO3、MnO2、TiO2、SiO2、Cr2O3、Fe2O3 及ZnO 等與碳酸鹽之NiCO3、MgCO3、MnCO3 等粉末，銲接過程中利用影像擷取系統即時記錄銲接過程，並採訊號同步接收方式來擷取銲接電弧動態影像。 銲接完成後，截取銲道之橫截面來觀察銲道型態與微觀組織、測定硬 度及量測不□鋼銲道殘留肥粒相含量，並做拉伸試驗來瞭解銲道機械性質。利用EDS 來分析銲道合金元素成份之變化，以平均垂直位移法來量測銲件角變形。 實驗結果顯示添加氧化物所組成之活性助銲劑將可有效提高低碳鋼與不□鋼銲接金屬熔深效率與銲接熱源之能量密度，而得到窄而深的銲道截面與較小的銲接熱影響區，亦可有效降低銲件變形。提高銲道穿透能力的主要作用機制是由於活性助銲劑能促使電漿電弧收縮並減少熔融銲池面積所致。添加活性助銲劑之銲接製程導致不□鋼在銲後會有較多的殘留肥粒相含量，因此可有助於降低金屬熱裂敏感性的效果。在電漿銲接中單一成分助銲劑以SiO2 對304 型不□鋼熔深效果改善最為顯著，與不使用助銲劑時比較約可提升200﹪。混合助銲劑則以SiO2 60%+ MnO2 40%較佳, 與不使用助銲劑時比較約可提升300﹪，熔深效果極為顯著。由本文實驗結果顯示，活性助銲劑添加後，在實際銲接工程應用上確實可大幅提高生產效率與降低生產成本，極具工業應用之潛力。

The purpose of this paper was to investigate the effects of activating flux on the characteristics of plasma arc welding process. This study compares plasma arc welding with TIG welding on the various properties of weldment, and also explores the mechanism of how activating flux improves weld penetration. In order to evaluate the effect of activating flux on the different materials, AISI 1020 low carbon steel and AISI 304 austenitic stainless steel were used to produce a bead-on-plate welded joint. The activating fluxes were oxides (MoO3, MnO2, TiO2, SiO2, CrO3, Fe2O3 and ZnO) and carbonates (NiCO3,MgCO3 and MnCO3) powders. During welding, a CCD camera system was used to observe and record images of the arc profiles. The microstructure and morphology of the welds obtained were examined by means of an optical microscope using transverse weld cross-sections prepared by cutting. The retained ferrite content of welds was measured by using the Ferritscope. Transverse tensile and Vickers hardness tests were used to determine on the mechanical properties of weldments. EDS were employed for studying the elemental analysis of the welds. The mean vertical displacement method was utilized for calculating the welding angular distortion. The experimental results indicate that higher penetration depth and narrower HAZ range are the results of the increased energy density of the welding heat source, and therefore the angular distortion of carbon steel and austenitic stainless steel weldments can be reduced, while using a certain oxide flux. Physically constricting the plasma column and reducing the anode spot are the possible mechanisms for the main contribution to the augmented weld penetration capability. The number of ferrite in stainless steel welds was increased due to the flux additions, and thus helps reduce hot cracking susceptibility in welded structures. The penetration capability up to 200% can be obtained in plasma welds that use SiO2 flux when compared with the non-flux addition welds. The SiO2 60%+ MnO2 40% mixture flux can greatly increase penetration depth up to around 300%. TIG and plasma welding with activating flux could bring about large benefits in terms of productivity and cost-effect and achieve practical use.