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Wire & Cable ASIA – September/October 2007
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March/April 2011
This will lower the coefficient of friction and
improve the adhesion of the coating to the
metal surface. The fine crystal structure
also increases the available surface area for
the subsequent lubrication process.
4 A new type of lubricant as
an alternative to soaps
and MoS
2
The new lubricants are high performance
polymer systems. Applied by immersion
in an aqueous solution they produce thin
organic coatings.
For
maximum
performance
results
this lubricant is best used on top of a
conversion coating. Application on bare
material is possible but must be examined
on a case-by-case basis and thus cannot
be generalised.
The chart above shows the coating thickness as compared
to the conventional lubricants used so far.
4.1 Objectives of the new development
The general target was to develop a coating that
allows net shape forming without any negative impact on
the tool life.
This means that the forming accuracy should be
appreciably better than that obtained when using soap,
and should be at least equivalent to that obtained with
MoS
2
.
Moreover, the goal was to achieve a coating that is
substantially cleaner and easier to remove. The lubricant
concentrate should be classified in the lowest water
hazard class and no additives were to be used that may
present a potential corrosion risk.
4.2 Chemical principles of
the new coating
The newly developed polymer coating is a mix of
high-molecular compounds that are free from heavy
metals, boron compounds, mineral oil, chlorine or sulphur-
containing lubricant additives (such as molybdenum
disulfide and tungsten disulfide) or compounds based
upon fluorine, for example, Teflon
®
.
4.3 Benefits for the customer
4.3.1 Benefits of a polymer coating for the wire
manufacturer or the pre-treater of rod sections.
Using a
polymer bath instead of a soap bath will provide the wire
manufacturing plant with the following benefits:
Polymer coatings need no soap powder in the drawing
•
die. This avoids the problem of dust formation affecting
the operators. It reduces costs, as there is no need to
purchase soap powder or to provide for its disposal. It
also improves the reliability of the drawing machines
because less soap dust settles on the machines and
drives
Improved forming means improved productivity
•
Clean wire is beneficial for subsequent processing
•
operations
Improved corrosion protection helps the product store
•
for longer, providing customers with a better product
4.3.2 Benefits of a polymer coating for manufacturers of
fasteners or cold extruders
For wire processors, such as fastener manufacturers, this
coating offers the following benefits:
Improved extrusion accuracy due to cleaner material
•
Higher speed of the bolt heading machines
•
Longer tool life
•
Manufacture of parts with complex geometry that were
•
not possible before
Mechanical
Calibration draw
of cold
heading wire
Polymer
Cleaning
Chemical
Continuous line treatment of cold heading wire or solid parts
Calcium
phosphate
Cold
Extrusion
Figure 5
❍
❍
: Diagram of a continuous line treatment plant
Calcium phosphate coat prior
to forming
Calcium phosphate coat after
forming
Cold
Extrusion
Figure 4
❍
❍
: Cold heading wire prior to and after forming