tailieunhanh - Laser Welding Part 2

Tham khảo tài liệu 'laser welding part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 14 Laser Welding produced around it. As the heat source moves forward the hole is filled with the molten metal from the reservoir and this solidifies to form the weld bead. Baba et al 2004 The presence of cracks on the fracture surfaces of the specimans were evident in several studies made on laser-welded Co-Cr-Co while they were not reported on the fracture surface of the laser-welded titanium. Watanabe et al 2002 This is due to the different values of thermal conductivity among metals that of CoCrMo is higher than of the titanium. After welding the solidification of the molten CoCrMo alloy may occur more quickly if compared with titanium in fact the heat generated by the laser energy rapidly diffuses to the surrounding solid metal. This rapid solidification causes a drastic constriction of the welded region at the same time. Thus a concentration of stress occurs at the laser-welded region and so cracks are created. Duhamel and Banas 1983 Also in the samples analysed in this study fissurations and cracks were observed into the welded zone. The greater differences between the plates welded by laboratory laser and these welded by dental office laser regarded the group without filler where these belonging to the second group had a greater number of cracks than these of the first group. This difference was significantly reduced by the use of filler metal and this is an important indication for our clinical practice where we decided to use always a filler metal. The mechanical tests of this study hold an importance by the clinical point of view in fact in all the tests with all the samples the elastic module of the orthodontic wires was very high and this means that our technique may be used intraorally as an aid to the orthodontic therapy. We must emphasize that dental laboratory laser operates under an atmosphere of shielding gas in this particular case argon and this might be an important aspect regarding to the differences of the without filler welded samples two .