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ABSTRACT
This paper describes the effect of extrusion ratio, die land length and lubrication on the mechanical property and surface quality of the extruded products in a multi-hole extrusion process. Different multi-hole dies with different extrusion ratios are used. The micro hardness and surface roughness of the extruded products from centre hole as well as peripheral holes are studied thoroughly. The variations in micro hardness of the extruded products exist with different die land lengths. The lubrication also has significant effect on the surface roughness of the extruded products.
Keywords: Multi-hole extrusion; micro hardness; surface roughness
1. INTRODUCTION
The production of small-sized component with desired mechanical properties and accuracy has become a challenging task for the manufacturers in the recent years. The demand of high productivity along with better mechanical properties can be fulfilled by forming processes like multi-hole extrusion process. Multi-hole extrusion process is the process in which a die with more than one hole is used. This process is used to produce the products of small length and cross-section. The effect of different extrusion parameters such as extrusion ratio, die land length, lubrication, extrusion speed and extrusion temperature on the quality of the extruded products has been studied for both single-hole and multi-hole extrusion processes.
In earlier research work, more importance was given to die design for minimizing the extrusion load (Dodeja and Johnson, 1957; Johnson et al., 1958; Chen and Ling, 1968). In multi-hole extrusion, the number of holes and their locations on the die is an important process parameter in determining the extrusion load and quality of the extruded products. Other process parameters like die land length, die pockets and their geometry, extrusion speed, billet dimensions and lubrication conditions also affect the extrusion load as well as the quality of the extruded products.
Peng and Sheppard (2004) studied the influence of the number and distribution of the holes on extrusion parameters in multi-hole extrusion. Finite element simulations using FORGE3® were carried out to study flow pattern, pressure requirement and the temperature developed during extrusion. The peak extrusion load was found to increase with increase in number of holes for a given reduction ratio. The optimum value of eccentricity of hole helps in reducing the extrusion load. Chen et al. (2008)...