17-4析出硬化型不鏽鋼具有麻田散鐵型不鏽鋼的強度與沃斯田鐵型不鏽鋼的耐腐蝕性，可藉由固溶及時效處理，達到析出強化效果。且因其具有良好的強度、韌性、耐蝕性、與焊接性，已被廣泛應用於航太等工業之零組件。 17-4PH不繡鋼作為焊接材時，鑄錠一般是經均質化、固溶後，才進行焊接作業，焊後再施以時效處理。本研究擬藉由探討真空鑄造及大氣鑄造之17-4PH不繡鋼焊接處理前、焊接後微結構及機械性質，以評估鑄造製程（真空鑄造及大氣鑄造）對於17-4PH不鏽鋼焊件性質之影響。另一方面，實驗中也進行了模擬焊接熱處理實驗，期能藉由熱處理來呈現焊件的微結構與機械性質。 鑄錠依照焊件不同區域（即母材、熱影響區及焊道）的狀況施以相對應的模擬焊件之熱處理，其程序分別如下，1.母材區之模擬：鑄錠施以均質化、固溶後空冷及時效處理。2.熱影響區之模擬：鑄錠施以均質化、固溶後，快速『重升溫』到800℃～1300℃、持溫5min後淬火再施以時效處理。3.焊道區模擬：鑄錠施以時效處理。 結果顯示鑄造製程（真空鑄造及大氣鑄造）對17-4PH不鏽鋼的微結構與機械性質影響極為微小，影響17-4不繡鋼焊件性質的主要因素是熱處理製程的差異。另外模擬焊接熱處理實驗能有效且真實的模擬實際焊件之微結構與機械性質。 17-4PH martensitic stainless steel can strength by solid solution and aging treatment , to precipitation hardening effect. And it has excellent strength, toughness, corrosion resistance and weldability. It has been widely used in aerospace and other industrial. This study intends to investigate the vacuum casting and atmosphere casting of 17-4PH stainless steel, two kind of process. What’s the different about microstructure and mechanical properties after and before welding. On the other hand , the experiment also simulated weld heat treatment experiments , can be heat-treated to render on the microstructure and mechanical properties of weldments. The results showed that the casting process ( vacuum casting and atmospheric casting ) microstructure and mechanical properties of the impact on the 17-4PH stainless steel is extremely small , the main factors are heat treatment processes. Another experiment simulated weld heat treatment can be effective and realistic simulation of the actual microstructure and mechanical properties of weldments .
