Английский для сварщиков. Гричин С.В. - 54 стр.

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54
thin materials up to 0.5 mm (0.02 inch) have, however, been very successful.
The process is useful in the joining of miniaturized electrical circuitry.
Diffusion bonding
This type of bonding relies on the effect of applied pressure at an
elevated temperature for an appreciable period of time. Generally, the
pressure applied must be less than that necessary to cause 5 percent
deformation so that the process can be applied to finished machine parts. The
process has been used most extensively in the aerospace industries for joining
materials and shapes that otherwise could not be made—for example,
multiple-finned channels and honeycomb construction. Steel can be
diffusion bonded at above 1,000° C (1,800° F) in a few minutes.
Ultrasonic welding
Ultrasonic joining is achieved by clamping the two pieces to be welded
between an anvil and a vibrating probe or sonotrode. The vibration raises the
temperature at the interface and produces the weld. The main variables are
the clamping force, power input, and welding time. A weld can be made in
0.005 second on thin wires and up to 1 second with material 1.3 mm (0.05
inch) thick. Spot welds and continuous seam welds are made with good
reliability. Applications include extensive use on lead bonding to integrated
circuitry, transistor canning, and aluminum can bodies.
Explosive welding
Explosive welding takes place when two plates are impacted together
under an explosive force at high velocity. The lower plate is laid on a firm
surface, such as a heavier steel plate. The upper plate is placed carefully at an
angle of approximately 5° to the lower plate with a sheet of explosive
material on top. The charge is detonated from the hinge of the two plates, and
a weld takes place in microseconds by very rapid plastic deformation of the
material at the interface. A completed weld has the appearance of waves at
the joint caused by a jetting action of metal between the plates.
After-reading activity
Match a welding type with its description
1. Cold welding A. Light energy is used to weld parts together.
2. Friction welding B. The weld is formed at the expense of the applied
pressure at a high temperature for a long period of
time.

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