Massive cold forming
Experiences with massive cold forming
(extrusion of mass products on double and multi-stage presses)
Concerning massive cold forming operations on double and multi-stage presses with the use of wires suitable for cold-heading, is a still more and more an up-coming need for suitable extrusion oils, in order to reduce pollution of environment and wires caused by dry metal soaps and post-saponification of extrusion oils
Wire industry and manufacturers of extrusion oils discussed in the past intensively (gestrichen weil unnötige Woederholung) the condition of wire surfaces after massive cold forming. These discussions resulted in better surfaces using new lubricant carriers capable to achieve performance improvement at massive cold forming.
There are cold-headed wires in use – blasted and slightly passivated with Rotex® KS V 1767-1 as corrosion protection. This passivation medium Rotex® KS V 1767-1 anchors itself on the blasted surface and is suitable for following processes with oil, so that high performance extrusion oils hardly saponify.
Wire surfaces coated with thick phosphate and soap layers are pre-cleaned before actual massive cold forming by scrapers, in order to reduce post-saponification of high performance extrusion oils. The better way would be the application of thin phosphate layers combined with thin soap layers. Wires should be drawn to the required dimension using an extrusion oil even in a high performance extrusion oil before transferred to the forming machine.
In this case the wire has an appropriate surface which can be preserved for a longer period without further saponification when using a high performance extrusion oil. Thus good tool performance can be achieved.
Compromises made by many screw manufacturers today are:
Thick layers of zinc phosphate neutralized with a thick layer of soap using normal extrusion oils, being cheaper of course. The result is a considerable additional consumption of extrusion oil followed by more frequent oil changes caused by oil pollution with soaps and abrasives. This results again in additional costs for waste disposal.
Thin layer phosphating with a thin neutralizing soap layer are better for high performance extrusion oils. There are also other possibilities in certain circumstances.
If pre-drawn wires are adhered with relevant drawing or forming oils used before to achieve dimensional accuracy, a good surface adhesion of the extrusion oil with a very low post saponification can be obtained also in the high performance section.
In this case very high tool performances are achieved. That is also an improved cost-effectiveness. Change times of high performance extrusion oils of a year and even longer are achieved in practice.
Extrusion oils for this applications are highly loaded with additives partly demulsifying, according to operation procedure.
MKU-Chemie GmbH produces drawing and forming oils as Putrol® NW V-line, used for pre-drawing at wire production. These oils contain an adequate corrosion protection suitable for interim storage of wires
Drawing oils are
- line Putrol® NW V 1679
- line Putrol® NW V 1442
High performance extrusion oils are
- line Dionol® ST V 1260
- line Dionol® ST V 1724
- line Dionol® ST V 1885
- line Dionol® ST V 1605
Multi-functional extrusion and lubrication oils are
- line Dionol® ST V 1955 (ISO VG 68)
- line Dionol® ST V 1112 (ISO VG 100)
- line Dionol® ST V 1162 (ISO VG 150)
- line Dionol® ST V 1620 (ISO VG 220)
These oils have different characteristics adapted to lubricating procedure and production basis. Complexity and type of parts play a major role for the application of high performance extrusion oils because temperatures produced by forming operation must be carried by the extrusion oil. It is desired and necessary to obtain a thin surface layer of the oil. Thin layers of extrusion oil avoid post carbonization residues on hot parts to a largest possible extent.
Shear surfaces are without lubricant carrier. In this area extrusion oil takes the entire lubrication of tool.
Of course, there are after-treatments, like parts falling from forming stations into aqueous cleaning agents with corrosion protection. Extrusion oil demulsifies and can be removed from cleaning agent.
MKU-Chemie GmbH offers process combinations which cover the entire process sector, beginning from drawing of wire rod to pre-drawn wire until to the finish of extrusion process and cleaning.
After-treatment machines for example for thread rolling, thread forming and thread cutting are also covered with appropriate oils:
- Dionol® Cutting oil
- Dionol® Forming oil
- Dionol® Tempering oil.
Finally it is necessary, to use appropriate cleaning agents, to achieve a clean production piece, which has also to provide suitable corrosion protection.