Abstract: While switching polarity of an electrode, a voltage is applied between the electrode and a workpiece hard metal with the electrode used as a negative-electrode such that tungsten carbide (WC; component of the hard metal) is anodized to form a tungsten oxide (WO3), and a voltage is supplied therebetween with the electrode used as a positive-electrode such that cobalt (Co) that is a component of the workpiece is electrolytically-eluted and at the same time the WO3 generated by anodization is dissolved in the machining fluid, a saline solution (NaCl) or an aqueous solution of nitrate of soda (Na(No3)) is used as an machining fluid; a calcium salt is added beforehand to the machining fluid to react tungstate soda (Na2WO4) generated in the machining with the calcium salt whereby calcium tungstate (CaWO4) is produced; and a calcium compound is separated and recovered using a difference in specific gravity.

Abstract: To simultaneously machine a plurality of workpieces, 6, 6a a continuous wire electrode 2 supplied by a feed unit 1 is reversed by a pulley 21 below the movable mounting table 7 after passing down through one of the workpieces, and led back up through the other workpiece to a tensioning takeup unit 11. The wire electrode runs 2, 2a are maintained parallel by upper guides 3, 3a secured to a common mounting plate 20, and relative movement between the electrodes and workpieces is controlled to discharge machine identical configurations in both of them.

Abstract: A workpiece consisting essentially of sintered tungsten carbide alloy having added thereto titanium carbide and/or tantalum carbide is electrolytically machined using an aqueous electrolyte solution consisting essentially of 5% to saturated value by weight of an alkali metal chloride selected from the group consisting of sodium chloride and potassium chloride, and an alkali metal compound selected from the group consisting of 3.6%-5.3% by weight of sodium hydroxide, up to 7.5% by weight of potassium hydroxide, up to 7.1% by weight of sodium carbonate, up to 9.2% by weight of potassium carbonate, up to 11.2% by weight of sodium bicarbonate, and up to 13.3% by weight of potassium bicarbonate.