氮氣添加於TIG-Flux銲接製程對不□鋼銲件之影響

Abstract

本研究目的主要係針對自行研發出之活性助銲劑來探討氮氣添加對沃斯田鐵型不□鋼銲道外觀與形態、銲件變形、銲道殘留肥粒相含量、微觀組織及機械性質等之影響行為與作用機制。實驗材料選用AISI 304沃斯田鐵型不□鋼，活性助銲添加劑選用MnO2與ZnO混合成份，銲接方法採用不加填料金屬的惰氣保護鎢極電弧銲來進行Bead-On-Plate實驗，並且架設CCD影像擷取系統並以同步方式擷取銲接電弧影像與電弧電壓值變化。 實驗結果顯示當添加活性助銲劑或添加氬-氮混合氣時銲道熔透深度與機械強度明顯提昇且有效降低銲件角變形，其中以添加活性助銲劑效果最佳。當以氬-氮混合氣為保護氣體時，不論TIG-Flux製程或傳統氬銲製程其電弧穩定性差，形成較不平整的銲道外觀；此外，添加少許比例的氮氣對銲道肥粒相含量會急劇下降。本實驗亦發現，電弧電壓值變化、電漿電弧收縮及熔融銲池緊縮等現象的共同作用應是可有效提高銲道穿深能力的主要因素。

The purpose of this research was to study the effect of specific oxide fluxes and nitrogen additions to the shielding gas on the surface appearance, weld morphology, retained delta ferrite content, angular distortion, and mechanical properties of TIG process applied to the welding of 5 mm thick austenitic stainless steel plates. Autogenous gas tungsten arc welding process through a thin layer of activating flux was applied on stainless steels to produce a bead on plate welded joint. A CCD camera was used to record the real time shape of plasma arc during welding. The MnO2 and ZnO fluxes used are packed in powdered form. The experimental results indicated that TIG welding with the oxide fluxes or Ar-N2 mixed gas can effectively enhance the penetration, better mechanical properties, and lower welding distortion in austenitic stainless steel. It was found that electrode erosion in excessive spatter and arc instability. A few nitrogen gases added to the argon shielding gas, a rapid reduction in measured ferrite number was obtained. Additionally, increase in nitrogen content, the retained delta ferrite content in Type 304 stainless steel welds can be reduced to near zero. The increase in arc voltage, retraction of the plasma arc, and contraction of the molten weld pool are the primary factors that effectively enhance the weld penetration.