The welding of aluminium and its alloys

Seam welding

Seam welding uses a wheel-shaped electrode (Fig. 9.4) 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 9.4.

Higher welding forces will be needed for harder alloys and lower values for softer alloys. Welding parameters for three phase frequency converter

9.4 Typical resistance seam welder showing the copper wheel electrodes. Courtesy of British Federal.

Table 9.4 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

0.9

1.02

625

5

1.0

29.0

3.1

3.2

1.0

0.88

550

7

2.0

32.0

3.4

3.5

1.6

0.79

395

10

3.0

38.5

4.3

4.8

2.0

0.64

355

12.5

4.0

41.0

4.8

5.5

2.5

0.55

315

18

5.5

43.0

5.5

6.5

3.2

0.45

275

24

7.0

45.0

6.0

8.0

units are similar to those in Table 9.4 except that welding current needs to be increased by between 0.5 and 2.5 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.

The welding of aluminium and its alloys

Alloy designations: wrought products

Table A.4 BS EN BS EN Old BS/DTD Temperature (°C) numerical chemical number designation designation Liquidus Solidus IVIdUng range Al 99.99 1 660 660 0 AW-1080A Al 99.8 1A AW-1070A …

Principal alloy designations: cast products

Table A.3 BS EN numerical designation BS EN chemical designation Old BS number ANSI designation Temperature (°C) Liquidus Solidus Melting range Al 99.5 LM0 640 658 18 AC-46100 Al Si10Cu2Fe …

Physical, mechanical and chemical properties at 20°C

Table A.2 Property Aluminium Iron Nickel Copper Titanium Crystal structure FCC BCC FCC FCC HCP Density (gm/cm3) 2.7 7.85 8.9 8.93 4.5 Melting point (°C) 660 1536 1455 1083 1670 …

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