Although it depends on ingoing diameter, a wire that has undergone less than 10 percent reduction in its cross-sectional area is unlikely to receive uniform drawing around its circumference, unless proper care is taken. When reduction in area is low the payoff speed is similar to drawing speed and is, therefore, limited to 1.5 metres/sec. To pay off at higher speeds may cause the wire to snap. This means that throughput in such drawing is low and this results in the cost of drawing being too high. The maximum limit of drawing depends on: a) The number of passes available in the wire-drawing machine. Normally, the maximum number of passes in a dry-drawing machine is 12 and in a wet-drawing machine it is 20. b) The drawability of wire, ie the amount of cold reduction it can undergo. This depends on the quality and type of heat treatment and the wire's resulting microstructure. c) The soundness of wire rods, ie the amount and distribution of nonmetallic inclusions and segregation. d) The composition of the material - the higher the carbon, the lower the drawability. e) The quality of pickling and coating. f) The type and quality of lubrication g) The efficiency of the machine being used and its system for wire cooling during drawing, h) The die geometry and quality of die grinding - smoother dies are more conducive to drawability. i) The die pass schedule - a well-designed die pass schedule provides better drawability. j) The size of wire - thin wire can undergo a greater reduction in area than thick wire.
展开▼
