修復管件之熱裂紋行為：實驗研究AISI304L 不銹鋼之GTAW 被覆Inconel 52M

Repair of Hot Cracking in Piping: Experimental Investigation into GTAW Clad Welding of AISI 304l Stainless Steel Using Inconel 52M

AISI304L 不銹鋼為目前核電廠管路最常使用之材料，惟在銲接修補過程，最常產生熱裂 （hot cracking） 現象，為沃斯田鐵型不銹鋼被覆銲接過程最容易產生問題。本研究針對AISI304L 不銹鋼，以GTAW 進行Inconel 52M 被覆，並進行可調應變試驗裂紋敏感性量測。研究結果顯示，被覆層最適參數為電流90 A，被覆速度100 mm/min、送線速度400 mm/min，入熱量約810 J/mm及用氬氣為保護氣體，流量為15 L/min；SUS 304L 不銹鋼界面層區金相組織為樹枝晶狀結構，而無明顯之熱影響區，d-ferrite 於母材部份熔融區成長；因多道次被覆，故下被覆層，在經過多次熱循環後，因再熱使得晶粒細化硬度增加；同時該被覆層界面硬度值為Hv 210，較被覆材Inconel 52M 硬度及AISI 304L 硬度為高。在成份分析，被覆材Inconel 52M 被覆至第三層時，其成分已趨近於Inconel 52M 原材，其硬度值亦隨被覆層增加而降低，惟仍較原素材為高。另外被覆層並無凝固熱裂紋及延性降低裂紋產生之發現。

This study investigated the cladding of AISI 304L stainless steel (SS)with four layers of Inconel 52M using gas tungsten arc welding (GTAW).Our results revealed an increase in the hardness of the SS substrate at theinterface with the first cladding layer. However, the hardness of the Inconel52M region within the weld decreased with the number of claddinglayers, due to the effects of dilution. This had the effect of altering thethermal efficiency during the solidification process, resulting in the formationof various solidification structures. In addition, the cladding processshowed to increase the susceptibility of the 304L SS substrate to hot crackingdue to an increase in the precipitation of d-ferrite phase at the interfacebetween the substrate and the first Inconel 52M cladding layer, the effectsof which appear to increased susceptibility.