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Wire & Cable ASIA – September/October 2007

90

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