Cold pressure welding at ambient temperature

1. Cold Pressure welding
Basel Raafat Radwan Saleh Selim
Port Said University
Faculty of engineering
Baselr.saleh@gmail.com

2. Introduction
All metals are surrounded by surface layers (oxide)
which must be disrupted if they are to be welded.
Cold pressure welding, carried out at
ambient(surrounding) temperature, relies upon
the use of high compressive pressure 1400-
2800N/mm2 for Aluminium and at least double
that value for copper). This provides interfacial
deformations of 60% to 80% that break the oxide
layers to expose fresh, uncontaminated metal
that makes contact. In this state, take over to
interatomic forces produce the weld.

3. Definition And History
• Cold pressure welding is a form of solid phase
welding, which is unique because it is carried out
at ambient temperatures. Other forms of solid
phase welding are conducted at elevated
temperatures
• As early as 3,000 BC, the Egyptians prepared iron
by hammering a metal sponge in order to weld
the red-hot particles together. Blacksmiths have
also hammer welded wrought iron for centuries.
This type of welding was always carried out at
high temperatures.

4. • The first known example in Britain of hammer
welding at ambient temperatures (therefore
true cold pressure welding) dates back to the
late Bronze Age, around 700 BC. The material
used was gold, and gold boxes made by this
process have been found during excavations.

5. :In Cold pressure welding
• Join metal together using no heat or flux
• Pressure brings surfaces together , disrupts
surface films and allows chemical bonding of
clean surfaces
• Applicable to soft ductile metals , e.g. aluminium
• Mainly used for welds in a circular wire section
• Used for joining components where heating is
not possible:
-Magnets
-Butt welding of wires

7. How are the two pieces of metal
joined?
• There have been several explanations as to the actual
mechanism by which a cold pressure weld is obtained
(with no flux , heat or electricity). For example, it has
been suggested that it happens via recrystallisation,
but most explanations have been either experimentally
disproved or refuted on theoretical grounds.
• The currently accepted accounts for a cold pressure
weld taking place involves the atoms of metals being
held together by the metallic 'bond’. The bond can be
described as a 'cloud' of free, negatively charged atoms
into a unit as a result of attractive forces

8. Joint types
Lap Joint Butt Joint

9. • Lap Joint :Where the
application demands
the joining of lapped
sheets to themselves
or bars, a series of
small welds can be
used. When
calculating strength,
the designer should
consider that at least
half the thickness of
one of the sheets will
be lost due to the
applied pressure.

10. • Butt joints: Are
primarily used
for joining
wires and rods
in diameters
from ~0.5mm
up to 12mm

11. THE ROLE OF DIES
• The dies play an important role in the cold butt
weld process. Firstly, they must grip the material
firmly and, therefore, the inside of the cavity is
either etched or made with an electric pencil
• The gap between the two faces, or noses, of the
die is also extremely important. If it is too large,
the material will just collapse or bend away. This
dimension is taken care of during manufacture
and cannot be changed.

12. • Dies can also
be
manufactured
to suit various
profiles, as
long as the
profile allows
the die to be
made in two
halves.

13. Advantages
• As the process is performed at ambient
temperature, there are no thermal effects on the
parts being joined
• The process is fast
• It is simple and inexpensive to operate once dies
have been produced.
• The ends of the wire or rod need no preparation
to welding and the alignment of the two butt
ends is automatic as the material is placed in the
die

14. Disadvantages
• Highly specialized with respect to joint design
and materials to be welded (soft iron that has
no carbon content)
• welds are made in the 'solid state' they are
difficult to inspect
• With the exception of butt welds, or welds
where the contact surfaces are sheared
together, the thickness of the parts is reduced.

15. Thank
youCaution
For scientific integrity …
This Information was only combinated and collected by me and I’m not it’s
author .