- 學位論文
應用氣體鎢極電弧硬銲碳化鎢與不銹鋼之研究
Gas Tungsten Arc Brazing Tungsten Carbides and Stainless Steel
摘要
本研究目的主要是在探討以電弧做為能量來源並藉由硬銲的方式對異種材料進行銲接，同時探討其銲後性質與結構改變。使用以氬氣做為保護氣體的氣體鎢極電弧銲(Gas Tungsten Arc Welding, GTAW)來進行實驗，實驗材料選用420麻田散鐵型不銹鋼及碳化鎢，銲料選擇銀基膏狀銲料。在銲接過程中，在420不銹鋼與碳化鎢接合處均勻塗佈填料，將兩者緊密堆疊後進行接合。由微觀組織觀察結果顯示，420不銹鋼晶粒尺寸並沒有受到熱量輸入的影響，而產生明顯的尺寸變化，但在晶粒邊界處發現圓形與不規則團聚物，可能為合金碳化物聚集。再經由SEM與EDS確認後，發現團聚物為MxCyx類之鉻碳化物，其中M代表合金元素。隨著溫度升高在高鉻鋼中常發現這類碳化物存在，隨著溫度升高碳化物生成順序為基地→(Fe,Cr)3C→ Cr7C3→Cr23C6。由於碳化物存在會造成母材耐蝕性下降等問題，故將接合後的銲件進行電化學腐蝕，觀察腐蝕後銲件金相組織與極化曲線，來判斷碳化物是否造成耐腐蝕性下降。
並列摘要
The main purpose of this study is to investigate using arc as the energy source, welding dissimilar materials by brazing and probing the change of nature and structure after being welded. In this research, Gas Tungsten Arc Welding (GTAW) with argon as protective gas is used to conduct experiment. We select 420 Martensite stainless steel and tungsten carbide as experimental materials and silver-based solder paste as solder. During welding, apply packing materials at the junction of 420 stainless steel and tungsten carbide, making them connected and stacked.The microstructural observation showed that the size of 420 stainless steel grain doesn’t change significantly by the heat; however, there is circular and irregular aggregation around its boundary and it could be alloy carbides gathering.After confirmed through SEM and EDS, we found that the aggregation is chromium carbide, MxCy, and the M represents alloy elements. With the increasing temperature, this kind of carbide is often found existing in high chromium steel and the order of its appearance is base →(Fe,Cr)3C→ Cr7C3→Cr23C6. Since the presence of carbide will decrease the corrosion resistance of the base metal, the jointed weldment will conduct electrochemical corrosion. We observe the metallographic structure and the polarization curve of corroded weldment to see if the carbide causes the decrease of the corrosion resistance.