Zinc phosphate-free cold bulk metal forming

Zinc phosphate-free cold bulk metal forming

 

Motivation

Cold bulk metal processes provide high dimensional accuracy and good material utilization. Due to the high tribological loads, which occur during forming, complex separation and lubrication layers e.g. zinc phosphate coatings as separation layers and soap as a lubricant, are used to prevent wear and failure of expensive forming tools. The application and use of zinc phosphate coatings come along with several environmentally drawbacks.

Figure 1: Possible process chain with lubrication in time of the press
Figure 1: Possible process chain with lubrication in time of the press

Aim

Objective of this project is to gather basic knowledge for the zinc phosphate-free, multistage cold forging of billets. Within this project new single layer lubricants are developed and used for cold bulk metal forming of steel. In the long term, forming manufacturers are to dispense with chemical applied conversion layers and to use environmentally benign lubricants. Furthermore, within this project an Inline-surface treatment interlinked with a multistage forming process of billets will be realized. In combination with a more environmentally benign manufacturing, shorter treatment times, lower buffer volumes and a higher grad of flexibility will be achieved.

 

Methodical approach

A central aspect of this project is the development of novel single layer lubricants, which are adapted to the tribological loads of a multi-stage process. The application and adherence of these lubricants on the billets will be ensured by means of a variation of the composition and a specific setting of the lubricants’ viscosity. The lubricants’ application will be carried out with a novel lubrication test stand, which will enable an inline cleansing and lubrication of the billets. A knowledge base of the load capacity during the forming operation will be achieved by the detection of changes in the lubricant layers during the process chain as well as the development of a phenomenological model. The newly developed single layer lubricants will be investigated with the Sliding Compression Test in order to determine the limits of the tribological system with regard to the occurring temperature, contact normal pressure, surface enlargement and relative sliding distance.