Steel wires are made by passing wire rods through conically converging dies made of sintered tungsten carbide (TC). As a result of the pulling force on the wire rods through the converging section, the diameter of the wire is reduced. This reduction in diameter of the wires is a gradual process and it takes place by passing the wires through a sequence of dies with gradually decreasing converging sections. The typical area reduction achieved in a die range from 25 % to 14 %. For the purpose of lubrication, dry lubricants consisting of calcium and sodium stearate soap powders are used which forms a thin layer between the wire and die surface to prevent direct contact between them to reduce friction.
Lubrication failure results in direct metal to metal contact (die-wire), which increases friction. This lubrication failure can be caused by many factors such as carbide die cracking, insufficient lubricant flow inside die, moisture in lubricants, poor quality of input wire rod used for drawing, poor die cooling etc. This lubrication failure results in the generation of surface defects on wires during drawing, breakage of carbide dies and subsequent loss of productivity.
Currently, lubrication effectiveness is judged by the operator through visual inspection of the wire surface, when the wires are coiled on drawing drum, as depicted in the video. Delay in the identification of lubrication failures results in defects and loss of productivity. The challenge is to develop a real-time mechanism for detecting & indicating abnormalities in lubrication and condition of the dies during the process of steel wire drawing.