Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9744
標題: 微量元素對AISI 309不銹鋼銲料金屬之熱龜裂敏感性研究
The Investigation on Hot Cracking Susceptibility of AISI Type 309 Filler Metal with Trace Elements
作者: 許秀菁
Hsu, Hsiu-Ching
關鍵字: AISI type 309 stainless steel;309不銹鋼;hot cracking susceptibility;Varestraint test;austenitic stainless steel;filler metal;BTR;brittle temperature range;熱龜裂敏感性;可調應變試驗;沃斯田鐵系不銹鋼;填料金屬;BTR;脆性溫度範圍
出版社: 材料工程學研究所
摘要: 
摘 要
本研究主要在評估304不銹鋼銲接母材與309不銹鋼填料金屬之銲接熱龜裂敏感性,實驗上藉由AISI 309不銹鋼填料金屬中不同微量組成元素(C、S、Si及Al等)的改變,以觀察銲件銲道金屬之金相顯微組織變化、銲道及熱影響區(HAZ)之硬度分佈,並利用可調應變試驗(Varestraint Test)進行銲件之熱龜裂敏感性評估。
實驗過程中分別選用四種微量組成不同的309不銹鋼作為銲接填料金屬,並利用自動銲接機施行GTAW開槽式多道次銲接,銲接後的試片,一方面縱向截取銲道面觀察銲道金屬肥粒相的顯微結構分佈情形,並在銲道熱影響區與熔融區間進行硬度試驗分析。另一方面則是將銲道金屬施行可調應變銲接性試驗及銲接熱循環的量測。試驗後,觀察試片表面龜裂情形及熱循環曲線的製作,並由掃瞄式電子顯微鏡(Scanning Electronic Microscope, SEM)觀察龜裂的型態及龜裂破斷面銲道及熱影響區之組成分佈。並記錄下最大龜裂長度(Maximum crack length, MCL)或最大龜裂距離(Maximum crack distance, MCD)及總龜裂長度(Total crack length, TCL)。進而根據這些銲接性數據,來預測材料歷經銲接熱循環過程後的脆性溫度範圍(Brittle Temperature Range, BTR)。
實驗結果顯示含碳量較高之銲件其熱龜裂敏感性較大,銲道流動性佳且表面氧化情形較為嚴重;而根據可調應變銲接性能試驗評估出其龜裂數目相較其他309不銹鋼填料金屬為多,總龜裂長度最長,脆性溫度範圍最為寬廣,故對熱龜裂最為敏感。但銲道的熱龜裂型態,以產生銲道凝固龜裂為最多,其次為熱影響區液化龜裂,再其次則為銲道與熱影響區之低延性龜裂,EDS分析銲道有無被覆液態薄膜之凝固晶粒的結果發現C、S、Si及Al等元素在熱影響區有增加的趨勢。

Abstract
In this thesis, there was estimated hot cracking susceptibility of AISI Type 309 stainless steel filler metal welded on AISI Type 304 stainless steel base metal. By controlling and adjusting elements (example: C, S, Si, Al etc.) to AISI Type 309 stainless steel filler metal, that could observe microstructure and hardness analysis on welded material, and estimate hot cracking properties by using Varestraint Test.
In the experiment procedure, an automatic welding machine executed multi-pass GTAW (Gas Tungsten Arc Weld). Further, by observed the welded samples, it would inspect the delta ferrite distribution in the weld metal and did the hardness analysis between the HAZ and fusion zone of the weld. On the other hand, there could execute the Varestraint Test and measure the welding thermal cycles. After tests, the cracks of weld were observed, the thermal cycle curve of welding was measured, and the cracking types and the crack fracture morphologies were analyzed. After serial experiments, the maximum crack length (MCL), maximum crack distance (MCD), and total crack length (TCL) were recorded. According to the data of weldability, it would predict the brittle temperature range (BTR) for the materials in terms of weld thermal cycle.
In the experimental results, it shows that the weld metal with higher carbon content has higher hot crack susceptibility, better welding fluid flow, serious oxidization, wider BTR. From SEM observation, most of the cracks showed solidification cracking, the next is liquid cracking in HAZ, and then is ductile-dip cracking between weld and HAZ. The EDS analyzed found that carbon, silicon, sulfur, and aluminum elements segregated in the solidified grain with liquid film covered.
URI: http://hdl.handle.net/11455/9744
Appears in Collections:材料科學與工程學系

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