tailieunhanh - Advanced Welding Processes Episode 2 Part 6

Tham khảo tài liệu 'advanced welding processes episode 2 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Narrow-gap Welding Techniques 225 d Applications The process has been in use in many commercial applications since the early 1980s 170 . Some of these are summarized in table they range from nuclear reactor containment vessels in 600 mm thick Ni Cr Mo alloy steels to the welding of 60 mm material for offshore tubulars. Table Applications of narrow-gap submerged arc welding. Weld type _ 7 Application Circumferential rotated pipe. Offshore oil platform tubular fabrication Circumferential rotated shafts Power generation turbine components. Propeller shafts. Rotated thick wall vessels Nuclear reactor containment vessels Summary and Implications The use of narrower joint gaps and reduced preparation angles can result in significant improvements in productivity. The use of processes which involve the inherent use of a narrow gap EBW laser plasma friction automatically exploit these advantages whilst systems have been developed to allow narrow gaps to be used with GT AW GMAW and SAW processes. The potential reduction in running costs must be evaluated against the capital cost of the equipment although it is reported 171 that sophisticated narrowgap submerged arc systems costing as much as 250 000 have been justified for welding 350 mm thick high-pressure feedwater heater shells. The minimum economic thickness for narrow-gap technology varies with the process and operating mode. Narrow-gap GT AW welding may be justified on thicknesses down to 15 mm. Narrow-gap type configurations have been used for GMAW in thicknesses from 15-22 mm upwards. Narrow-gap SAW is normally considered to be viable at thicknesses above 60-70 mm but if conventional equipment is used this lower economic limit may be reduced until it overlaps conventional square butt SAW procedures 226 Advanced Welding Processes in thicknesses down to 12 mm. Optimization of welding parameters and in-process control are essential to avoid defects in narrow-gap applications the restricted access of the gap