tailieunhanh - Advanced Welding Processes Episode 1 Part 11

Tham khảo tài liệu 'advanced welding processes episode 1 part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 194 Advanced Welding Processes T - kW - kW - kW 10kw - kW X 5kW Figure Thickness versus travel speed for laser keyhole welding at various power levels and for a range of materials. Multimode Single mode Figure Effect of secondary variables on weld quality for a butt weld by CƠ2 laser in mm steel . After Shinmi et al 144 . High Energy Density Processes 195 Applications The range of materials which can be successfully welded by laser techniques is in the first instance determined by their physical properties including reflectivity and thermal diffusivity and secondly by metallurgical considerations. In the keyhole mode once coupling and cavity formation has occurred even metals with high reflectivity . nickel may be successfully welded but copper with high reflectivity and high thermal diffusivity can at present only be welded with difficulty. Most of the metallurgical problems experienced with laser welding are common to other fusion welding processes for example cold cracking in high-carbon and alloy steels solidification cracking in aluminium alloys but with suitable precautions these problems may be restricted. Some common application areas are described below. a Austenitic stainless steel Austenitic stainless steels have been laser welded in a range of thicknesses. Typical conditions for mm keyhole welds are given in the figures above but speeds of up to 1 mmin-1 can be achieved with a CƠ2 laser at 11 kw. b Low-carbon steel Low-carbon steel is readily joined with a range of common welding processes including GMAW and GTAW. The primary reasons for using high-capital-cost processes such as lasers is to increase productivity and to improve quality. There are no specific problems with the laser welding of uncoated plain carbon steels and both CO2 and YAG systems have been used successfully as the following applications confirm. In thin-section sheet material laser welding has been used for fabrication of