Before a finished product, such as a screw, is born by massive forming, a zinc phosphate coat is applied to the wire. This method known as phosphating, which allows mass production by cold massive forming, is old but is still state-of-the-art. It is the subject of criticism because of its high use of energy and chemicals. A new BECHEM product is taking completely new directions.

Today and in the future, wire products continue to be important industrial semi-finished products which are used broadly for example in the automotive sector with its supplier businesses, in mechanical engineering, and in the electrical and construction industries. Cold massive forming will turn semi-finished steel products into ready-to-use components. This process allows forming in single or multi-stage processes without pre-heating of the semi-finished steel product. In the process, high relative speeds, high material compression and considerable surface enlargements take place between tool and material. The slug can easily heat up to 500°C during the forming process.

In the cold massive forming process, these conditions require elaborate lubrication systems, the purposes of which are to reduce direct metallic contact between tool and material, and so their wear, and wear of the forming tools. In the 1930s, Fritz Singer had the phosphating method he developed patented. After the Second World War, it established itself worldwide in the industry. It has been state-of-the-art to this day. Only when this method was introduced was affordable cold massive forming and its use for mass production of cold form parts for industry rendered possible. In the process, a lubricant carrier layer is applied (zinc phosphate) which secures the actual lubricant to the workpiece.

Nowadays, phosphating is deemed severely detrimental because applying the individual layers requires high levels of energy and large quantities of chem-icals. Once used, the chemicals (including large quantities of phosphate sludge) must be disposed of properly. The system technology in question, and its use, are subjected to stringent official regulations with regular checks by environmental authorities.

Global competition and cost pressure, and requirements pertaining to environmental protection, are increasingly calling for alternative industrial production processes which are efficient in terms of energy and raw materials. Against this background, it is the use of a phosphate layer as a conversion layer on semi-finished products which is being called into question in articular. The requirements made of alternatives are strict.

Replacing phosphating layers for cold massive forming is not without complications.
The requirements made of processes are strict. An alternative system must guarantee good separation of tool and semi-finished product, and a resistance to surface enlargements of up to 80%. Good fail-safe running properties and high load-bearing capacity belong in the continued requirement profile. Suitability for use includes being able to use existing press techniques for alternatively coated semi-finished products, and easily being able to remove lubricant from the formed parts. Switching to such a system free of phosphate coating has high economic and ecological potential.

As part of a joint project, BECHEM has tested multiple lubricant systems for these criteria. The end of the project finally saw a new product range which, according to the developers, is unrivalled by all previous phosphate-free systems. The Beruforge 150 product range enables for the first time full redundancy of phosphatic compounds on semi-finished wire products, also for complex forming operations. The dispersion is suitable for use on all non-phosphatic wire surfaces and products, as well as rust-proof steel and aluminium, and its simple application is a stand-out feature.

Reports from wire manufacturers and end-users are also positive. Wire fabricators and manufacturers exchanged opinions in a discussion session at BECHEM. In light of good experiences, project partner and manufacturer of precision cold forming parts Schrauben Betzer from Lüdenscheid has already switched major parts of its production, smaller screw diameters in particular, to phosphate-free wire coating. Zinc phosphate and the associated production costs are eliminated. Wire manufacturers Max W. Claas and Brüninghaus Draht from Altena also provided positive feedback.

According to the lubricant experts, switching from the conventional multi-layer method to the single-layer method brings about much less entry of solid matter in the forming process, and so consequently much improved cleanliness within the machine. “The considerably lower dirt level in the forming oil results in prolonged oil life and considerable prolonging of the lives of the forming tools”, explains Dr. Jens Ostrowski, Head of R&D for Oil / Forming Technology, and adds: “Tool lives can be prolonged by more than 20% in practise”. Machine manufacturer and development partner Jankowski in Horhausen confirms these figures.

The products are now being used with great success in different industrial applications – be it in wire rod production or in the production of screws, bolts or other cold form parts. Flexibility in application also features here. The new medium can be applied by means of single part coating, such as single wire sections, by immersing complete wire rod coils or by drawing cold heading wires. In the area of the wire cable, the tempered wire is drawn closed with the lubricant. The special mix of organic and inorganic components gives rise to excellent corrosion protection, which enables long storage times with no impacting of quality. But the process is also possible without intermediate storage. “Inline production with process reliability is also conceivable for the first time”, says Dr. Jens Ostrowski. In this process, semi-finished products are cleaned mechanically and, after a calibration pass, transferred to the forming process using the new Beruforge 150 coating system. The lubricant residue can be removed easily after the forming process.

Associated with this in many cases is a considerable reduction in disposal costs which require declaration. The enormous market potential becomes clear when considering the high market volume of semi-finished steel wire products in the different industries, and the efforts of the industry as regards sustainability and resource efficiency. We are still at the beginning in terms of the applications of this lubricant in forming. But the dimensions of this new technology are clearly evident now and point towards potentially major changes – not only on wire production technology.