臺灣博碩士論文加值系統

本研究是探討雷射焊接電壓對於不同厚度商業級鑄造純鈦（Cp Ti）金屬熔接點機械性質的影響。將商業用二級純鈦鑄成厚度分別為1、1.5、2、2.5及3 mm的試片，再利用不同電壓（290、300、310、320、340、360及400V）進行雷射焊接。利用Vickers微硬度機及光學顯微鏡量測焊件微硬度及觀察微結構；利用四點彎曲測試進行焊件機械性質（包括破斷負荷、破斷強度及延性）之評估；利用掃描式電子顯微鏡及光學顯微鏡觀察破斷面形態。利用Two-way ANOVA分析焊接電壓及焊件厚度兩因子對焊件機械性質的影響。本研究結果顯示，鑄造純鈦焊道結構均呈現出層狀/針狀混合組織，此組織隨焊接電壓的增加而有粗化現象；與母材交接處並未發現有明顯的熱影響區。鑄造純鈦經雷射焊接後，焊道微硬度均高於母材，但隨焊接電壓的增加而有下降的趨勢。焊件破斷負荷及延性均隨焊接電壓的增加而增加，但破斷強度則減小。破斷面觀察顯示，所有焊件斷裂均發生在焊接點（即焊道），且呈現劈裂狀之脆性斷裂。增加焊接電壓及減少焊件厚度可降低鑄造純鈦焊件的破斷敏感度。

In this study, we assayed the effect of welding voltage on the mechanical properties of laser-welded commercial cast Ti joint with various thicknesses. According to the dental clinical applications, the various thicknesses chosen in this study included 1.0, 1.5, 2.0, 2.5, and 3.0 mm. Different laser welding voltages, including 290, 300, 310, 320, 340, 360, and 400 V, were used for welding. A Vickers microhardness tester and an optical microscope were used to measure the microhardness and to observe the microstructure, respectively. A four-point bending test was conducted on the laser-welded Ti joint specimen by a universal testing machine to evaluate the mechanical properties, including breaking load, breaking strength, and ductility. A scanning electron microscope and an optical microscope were used to observe the breaking morphology. The mechanical properties were analyzed by two-way ANOVA for analyzing the factors of welding voltage and specimen thickness. The results showed that the weld metal exhibited a mixed lamellar/acicular structure which became coarsening on increasing the welding voltage; no significant heat-affected zone was observed in the vicinity of Ti joint. The microhardness of the weld metal of Ti joint was higher than that of the base metal, but decreased gradually on increasing the welding voltage. The breaking load and ductility of Ti joint increased on increasing the welding voltage, but the breaking strength decreased. The breaking, if existed, occurred only at the weld metal of Ti joint, and revealed a brittle cleavage morphology. Increasing the welding voltage and decreasing the specimen thickness led to a decrease in the breaking susceptibility of cast Ti joint.

中文摘要………………………………………………………………I
英文摘要………………………………………………………………II
總目錄…………………………………………………………………III
表目錄…………………………………………………………………V
圖目錄…………………………………………………………………VI
第一章 前言…………………………………………………………..1
第二章 材料與方法…………………………………………………..5
2-1 試片備製…………………………………………………….5
2-2 雷射焊接…………………………………………………….6
2-3 焊件顯微組織觀察………………………………………….7
2-4 焊件機械性質試驗………………………………………….7
2-4-1 硬度測試………………………………………………….7
2-4-2 四點彎曲測試…………………………………………….8
2-5 焊件破斷面觀察…………………………………………….8
2-6 統計分析…………………………………………………….8
第三章 結果…………………………………………………………..9
3-1 焊件顯微組織……………………………………………….9
3-2 焊件硬度…………………………………………………….9
3-3 焊件破斷敏感度…………………………………………….9
3-4 焊件破斷負荷……………………………………………...10
3-5 焊件位移量………………………………………………...10
3-6 焊道熔合面積………………………………………………11
3-7 焊件破斷強度……………………………………………...12
第四章 討論…………………………………………………………13
4-1 焊接電壓及焊件厚度對焊道硬度的影響………………...13
4-2 焊接電壓及焊件厚度對焊件破斷行為…………………...14
第五章 結論…………………………………………………………16
第六章 參考文獻……………………………………………………17

Berg E, Wagner WC, Davik G, Dootz ER. Mechanical properties of laser-welded cast and wrought titanium. J Prosthent Dent 1995;74:250-257.
Chai T, Chou CK. Mechanical properties of laser-welded cast titanium joints under different conditions. J Prosthet Dent 1998;79:477-483
Hruska AR, Borelli P. Quality criteria for pure titanium casting, laboratory soldering,intraoral welding, and a device to aud in making uncontaminated castings. J Prosthet Dent 1991;66:561-565.
Jang KS, Youn SJ, Kim YS. Comparison of castability and surface roughness of commercially pure titanium and cobalt-chrpmium denture fameworks. J Prosthet Dent 2001;86:93-98.
Li Z, Gobbi SL, Norris I, Zolotovsky S, Richter KH. Laser welding techniques for titanium alloy sheet. J Mater Process Technol 1997;65:203-208.
Liu J, Watanabe I, Yoshida K, Atsuta M. Joint strength of laser-
welded titanium. Dent Mater 2001;18:143-148.
Neo TK, Chai J, Gilbert JL, Wozniak WT, Engelman MJ. Mechanical Properties of Titanium Connectors. Int J Prosthodont 1996;9: 379-393.
Qi Y, Deng J, Hong Q, Zeng L. Electron beam welding, laser beam welding and gas tungsten arc welding sheet. Mater Sci Eng 2001; A280:177-181.
Roggensack M, Walter MH, W.Böning K. Studies on laser-and pasma-welded titanium. Dent Mater 1993;9:104-107.
Sjögen G, Andersson M, Bergman M. Laser welding of titanium
in dentustry. Acta Odontol Scand 1998;46:247-253.
Sun Z, Annergren I, Pan D, Mai TA. Effect of laser surface remelting on the corrosion behavior of commercially pure titanium sheet. Mater Sci Eng 2003;A345:293-300.
Wang RR, Welsch GE. Joining titanium materials with tungsten inert gas welding, laser welding, and, and infrared brazing. J Prosthet Dent 1995;74:521-530.
Wang RR, Chang CT. Thermal modeling of laser weding for titanium dental restorations.J Prosthet Dent 1998;79:335-342.
Wiskott HWA, Doumas T, Scherrer SS, Susz C, Belser UC, Microstructures of brazings and welds using grade 2 commercially pure titanium. Int J Prosthodont 2001;14:40-47.
.
Wiskott HWA, Doumas T, Scherrer SS, Belser UC. Mechanucal and structural characteristics of commercially pure grade 2 Ti welds and solder joints. J Mater Sci. Mater Med 2001;12:719-725.
Yamagishi T, Ito M, Fujimura Y. Mechianical properties of laser welds of titanium in dentistry by pulsed Nd:YAG laser apparatus. J Prosthet Dent 1993;70:264-273.
Yung WKC, Ralph B, Lee W B, Fenn R. An investugation into welding parameters the tensile properties of titanium welds. J Mater Process Technol 1997;63:759-764.