WCA March 2011

New technology for lubricating cold extrusion materials and cold heading wire By Jude Burke, Chemetall PLC, UK

technology, which offers benefits such as improved tool life, extension of the interval between oil changes in cold heading machinery and allowing the fabrication of parts with complex geometry. These polymer coatings are applied on top of conventional coatings as use on bare steel is restricted to a very few specific cases. Conventional coatings used are zinc phosphate or zinc- calcium phosphate. However, it is becoming increasingly difficult to deal with the sludge and heavy metal con- tamination of wastewater from these processes. The answer to these problems is given in this paper, which describes a conversion coating based on the electrolytic deposition of a calcium phosphate carrier coating. This process is highly efficient and free from heavy metals and sludge. The conversion coating is eminently suitable for wire drawing, cold heading and cold extrusion. This paper highlights the cost savings, environmental benefits and productivity improvements that can be achieved by using a combination of calcium phosphating with a polymer coating.

Abstract It is increasingly difficult to deal with the contamination of wastewater from zinc phosphate or zinc-calcium phosphate coatings. This paper describes a conversion coating process involving the electrolytic deposition of a calcium phosphate carrier coat. The process is efficient, free from heavy metals and sludge, and well suited to wire drawing, cold heading and extrusion. The paper highlights the cost savings, environmental benefits and productivity improvements that can be achieved by a combination of calcium phosphating with a polymer coating.

Synopsis

The lubricants currently used for drawing cold heading wire and for cold extrusion processes are soaps. In addition, molybdenum disulphide dispersions are used for cold extrusion processes. These lubricants are increasingly being replaced by ultra thin polymer

Figure 1 ❍ ❍ : State of the art workflow

Conversion coating

Activation

Rinsing

Neutrali- sation

Lubrica- tion

Rinsing

Pickling

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Wire & Cable ASIA – September/October 2007 March/April 2011