tailieunhanh - The Welding of Aluminum & Its Alloys Part 10

Tham khảo tài liệu 'the welding of aluminum & its alloys part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Resistance welding processes 175 surface indentation can be readily identified. These features may be used to assess the quality of production batches. Seam welding Seam welding uses a wheel-shaped electrode Fig. to make either a series of overlapping spot welds to form a continuously welded and leak tight seam or a number of spot welds spaced apart - roll-spot welding. The requirements on electrodes and surface finish are the same as for spot welding. The shunt effect of the closely spaced nuggets and the short weld times mean that higher currents are necessary than for spot welds. Typical welding parameters are given in Table . Higher welding forces will be needed for harder alloys and lower values for softer alloys. Welding parameters for three phase frequency converter Typical resistance seam welder showing the copper wheel electrodes. Courtesy of British Federal. 176 The welding of aluminium and its alloys Table Seam welding conditions. Single phase AC units. Hardened 5XXX series alloy Sheet thickness mm Travel speed m min Spots metre On plus off time cycles On time cycles Welding current kA Welding force kN Weld 625 5 550 7 395 10 355 315 18 275 24 units are similar to those in Table except that welding current needs to be increased by between and times the higher values for the thicker materials. Pick-up on the electrode wheel can be a problem and may require the wheel to be cleaned after only one revolution. Mechanised cleaning systems that remove the contamination in-process by wire brushing or abrasive means have been successful in maintaining continuous production. Flash butt welding Process principles As the name suggests flash butt welding is capable of making butt joints in bar-like or tubular components L T and X-shaped extrusions etc. The weld is a .