tailieunhanh - Advanced Welding Processes Episode 1 Part 12

Tham khảo tài liệu 'advanced welding processes episode 1 part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 214 Advanced Welding Processes Figure Additional gas-shielding facilities. The process has been used for welding thicknesses of up to 200 mm particularly for circumferential welds and pipework. b Hot wire GTAW The hot wire GTAW process described in Chapter 6 is particularly suitable for narrow-gap welding since it allows the deposition rate of the process to be increased to levels comparable with those of GM AW. Many commercial applications of narrow-gap GT AW employ hot wire addition and an interesting example is the Roboweld system shown in figure which was designed for welding transmission pipelines both on land and on pipe lay barges. Seam tracking and accurate positioning of the electrode may be achieved by one of the methods described in Chapter 10 but some systems also include facilities for video monitoring of the arc and torch position with the ability for the operator to override the automatic control to correct the torch position. To improve the sidewall fusion the electrode may be oscillated or alternatively the arc may be deflected magnetically. Narrow-gap Welding Techniques 215 Figure Multihead narrow-gap and hot wire GTAW system for line pipe welding Saipem Roboweld . Courtesy EMC UK. GMAW The potential for using narrower weld preparations and smaller included angles for GMAW has often been claimed as an advantage of the process when compared with SMAW. But although some concessions are allowed in the construction standards this advantage has not been fully exploited in manual welding probably due to the difficulty of maintaining consistent fusion with reduced access. Reduced preparation widths are however used in automatic welding where improved control is possible. The developments in narrow-gap GM AW fall into two categories i the use of conventional automatic systems and narrower gaps ii the use of special narrow-gap GMAW systems and narrow gaps. a Reduced gap I angle GMAW A major application in the first category are the .