Ultrasonic welding

It should be emphasized that ultrasonic welding is totally unlike the better-known fusion, diffusion and deformation welding processes. Because of certain similarities in equipment and in application of ultrasonic and resistance welding, it is sometimes difficult to appreciate that the welds are actually very dissimilar and cannot always be evaluated by the same yardstick.

The ultrasonic weld is devoid of cast structure, even though some heat is known to be generated during the welding process. The metallurgical bond is between the cladding layers, while the substrate layers appear unaffected. There is not sheet separation at the edges of the bond zone, and thickness deformation is negligible.

Vibratory welds in the aluminium alloys show slightly different characteristics. Depending on the alloy there may be marked disturbance and disruption at the interfacial plane, or grain growth or crystallization may occur across the surfaces.

Review of tensile strengths for aluminium alloys indicates ultrasonic welds to be superior to resistance spot welds within the range of presently weldable gases, and it appears that extension of the process to heavier material depends only on increasing the power-handling capacity of the equipment.

A further advantage of ultrasonic welding over other types of metallurgical joining is that surface preparation is less exacting. For aluminium alloys, it is necessary only to remove surface grease and oils.

The equipment for ultrasonic welding differs from resistance units in several fundamental respects. The controls are comparatively simple. Once the equipment is turned on, any type of aluminium alloy may be welded by adjustment of only three settings – power, clamping force and pulse time. Thus, in a productive setup, the equipment may be easily operated by inexperienced personnel. In contrast, a resistance welding maсhine may have 25 or more controls that require adjustment and must be handled by skilled operator. Furthermore, the power requirements for ultrasonic welding of aluminium are substantially less than for resistance welding. Thus expensive power installations are not required for ultrasonic welding equipment.

Exercises

1. Learn the following words and word – combinations:

cladding layer -вкритий шар

substrate layer -нижній шар

plate -площина

bond zone -зона з’єднання

sheet separation -розділення листа

disturbance -викривлення

Дата добавления: 2015-11-16