On materials flow using different lubricants in upsetting process
Authors: Misirli Cenk 
Published: August 2014

Purpose
– The purpose of this paper is to apply the upsetting process to cylindrical specimens using flat end dies in which three types of lubricants were used. In many industrial processes, friction and lubrication have major advantages and are key during the metal forming process. Upset forging is a process which increases the diameter of the work-piece by compressing its length.

Design/methodology/approach
– The materials flow for various materials using different lubricants in upsetting was investigated in this study. AISI 304 austenitic-stainless steel and commercially pure aluminium (Al99.7) were used as the test materials. The upsetting process was applied to the cylindrical specimens using flat end dies. Three types of lubricants, namely, grease, graphite and SAE 40 oil, were used in this study. Experiments were performed using a hydraulic press, which has 5 mm/s ram speed, with a capacity of 150 metric tons. On the other hand, finite element methods (FEMs) have been carried out to analyse the forming performance for displacement prediction in the barrelling process.

Findings
– The results showed that the measured radius of the curvature of the barrel seemed to confirm the calculation values used before the initiation of the experimental process. It has been observed that the surface roughness had no considerable effect on the barrelling contour changes on the free surfaces, as it showed an increasing deformation ratio for all materials and lubricant types. However, minimum friction at the interface seems to occur with the grease lubricant. The present analyses show that FEMs, which can be used in the rapid prediction of required barrelling process displacements, are more suitable for use in a pressure distribution analysis for the development of the barrelling radius.

Research limitations/implications
– It would be interesting to search the material flow for more different materials and lubricants. It could be a good idea if future work could be concentrated on the material flow on upsetting by using different lubricants.

Practical implications
– Open-die forging, which is also known as the upsetting process, is one of the simplest forging operations used in bulk deformation processes. This operation can be explained as a solid work-piece which is positioned between two flat dies, and then with the aid of compression, the height of the work-piece is reduced under controlled working parameters during the upsetting process, in which friction and surface roughness are the major parameters playing an important role on the material flow. In a cold upsetting process, one of the undesirable conditions is that barrelling occurs as a consequence of friction between the work-piece and the die surfaces. The existence of this frictional constraint directly affects the plastic deformation of the work-piece, as friction causes barrelling in upsetting processes. However, it has been observed that the use of lubricants reduces the degree of bulging.

Social implications
– This paper will be useful for industrial applications.

Originality/value
– The main value of this paper is to contribute and fulfil in detail the material flow of various materials using different lubricants that are being studied so far in the literature.