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Investigation of friction in warm forging of AA6082B. Buchner, A. Weber, B. BuchmayrChair of Metal Forming, University of Leoben – Franz-Josef-Strasse 18, 8700 Leoben, AustriaURL: www.metalforming.at e-mail: metalforming@unileoben.ac.atABSTRACT: This paper presents an experimental investigation of friction in hot forging of AA6082, whichis a standard forging alloy in automotive engineering, mechanical engineering and in naval architecture, byemploying a modified ring-on-disc test. The experiments were performed with three different commercialgraphite-based lubricants and at various loads, sliding velocities and specimen surface conditions. In addition,some tests were performed without lubrication.KEYWORDS: Friction, Warm Forging, Aluminium1 INTRODUCTIONForged parts made of aluminium play a significantrole as components of light weight structures in theautomotive and aerospace industry. The main parametersinfluencing forging processes are the flow curvesof the specimen material, the heat transfer at the contactarea and the friction in the die-workpiece interface[1, 2]. The exact knowledge of the latter is paidmuch attention to as it affects power requirements,material flow, die filling, tool life and workpiece quality.In order to understand the tribological processesand interactions in the tool-workpiece interface, theinfluences of the load collective and the surface conditionson friction were investigated systematically. Theexperiments were performed with a facility based onthe ring-on-disc test introduced by Schey [3].2 EXPERIMENTAL WORKforce is realised by another load cell, the rotationalspeed of the specimen is calculated from the speed ofthe servo motor. The specimen is brought to forgingtemperature by an inductive heating system, whereasthe tool is heated by a heating sleeve. The lubricantis sprayed onto the tool by an automatic applicationsystem that allows a reproducible dosing. The testingdevice is controlled by a programmable logic controlunit (PLC), the data acquisition is realised by a measurementamplifier that is connected to a commercialpersonal computer.The tribometer has a maximum upsetting force of approximately100 kN and provides a maximum torqueof more then 800 Nm on the rotary disc. The rotationalspeed can be up to 1.7 s −1 . The sliding distanceis not constrained by the testing device. Themaximum temperature of the specimen is 1200 °C,the maximum temperature of the tool is 450 °C. Thetemperatures can be kept constant in an interval of±2.5 °C.2.1 Testing deviceFigure 1 shows the Rotational Forging Tribometer.The circular motion is supplied from the bottom sideby means of a servo motor and a bevel gear system.The compression force is applied by a hydraulic cylinderfrom the top side. The specimen (workpiece)is mounted on a rotary disc and transmits the frictionaltorque to the pivot-mounted ring-shaped tool.The tool is supported by a load cell via a lever armwhich enables an accurate measurement of the frictionaltorque. The acquisition of the compressionFigure 1: Rotational Forging Tribometer.1