Method of manufacturing zinc-coated electrode wire for electric discharge processors using hot dip galvanizing process

A method of manufacturing a zinc-coated electrode wire for electro discharge machining using a hot dip galvanizing process, the method comprising the following steps of:

• firstly surface-forming a wire so that a terminal end of the wire is tapered while the wire is drawn through a first die;
• pre-coating the firstly surface-processed wire with zinc by passing the wire through a molten zinc bath at a relatively slow speed;
• main-coating the pre-coated wire with zinc, wherein the pre-coated wire is immersed in the molten zinc bath for a predetermined time to maintain the temperature of zinc pre-coated on the wire at a predetermined level, and is removed from the molten zinc bath and then passed through a sizing die preheated to 400° C. before zinc coated on the wire is hardened, so that zinc coated on the wire has a predetermined thickness;
• secondly surface-forming the main-coated wire by passing the wire through a heated pipe at a constant speed to raise a surface temperature of the wire to a predetermined level, and then passing the wire through a second die having a diameter of 5˜10 μm smaller than that of the wire so that zinc is coated around the wire at a uniform thickness;
• homogeneously heat-treating the secondly surface-processed wire in a closed space by hot air circulating therein;
• and
• drawing the homogeneously heat-treated wire with a drawing ratio of 4˜80 or higher by passing the wire through a third die made of natural diamond and having an inlet portion of 5 μm across, a middle portion of 3 μm across and an outlet portion of 1˜3 μm across to make the surface of the wire smooth, provided that the homogeneously heat-treated wire has a sectional area of 0.3˜3 mm2.