Electrochemical machining method, electrochemical machining apparatus and electrochemical machining fluid

An electrochemical machining method, in which electrochemical machining is performed by applying a voltage to pass a current between an electrode and a hard metal that is a workpiece with the electrode used as a negative electrode such that tungsten carbide (WC) that is a component of the hard metal workpiece is anodized to form a tungsten oxide (WO3) and, at the same time, cobalt (Co) is electrolytically eluted, and by chemically dissolving the tungsten oxide (WO3) generated by the anodization, the method comprising:

• using a saline solution (aqueous solution of NaCl) or an aqueous solution of nitrate of soda (Na(No3)) as an electrochemical machining fluid;
• and
• adding sodium hydroxide (NaOH) to the electrochemical machining fluid while measuring a pH of the electrochemical machining fluid so as to make the electrochemical machining fluid to be alkaline, in order to facilitate dissolving in the electrochemical machining fluid the tungsten oxide (WO3) produced by anodizing the tungsten carbide (WC).

An electrochemical machining method, in which electrochemical machining is performed by applying a voltage to pass a current between an electrode and a hard metal that is a workpiece with the electrode used as a negative electrode such that tungsten carbide (WC) that is a component of the hard metal workpiece is anodized to form a tungsten oxide (WO3) and, at the same time, cobalt (Co) is electrolytically eluted, and by chemically dissolving the tungsten oxide (WO3) generated by the anodization, the method comprising:

• dissolving, in an electrochemical machining fluid, cobalt (Co), which is a metal component of the hard metal, and TiO2, which is produced in a chemical reaction of titanium carbide (TiC) added as a component of the hard metal, when a polarity of the hard metal that is a workpiece is positive;
• and
• applying a voltage to the electrochemical machining fluid within approximately ten hours to make electrodeposition and recovery.

An electrochemical machining method, in which electrochemical machining is performed by applying a voltage to pass a current between an electrode and a hard metal that is a workpiece with the electrode used as a negative electrode such that tungsten carbide (WC) that is a component of the hard metal workpiece is anodized to form a tungsten oxide (WO3) and, at the same time, cobalt (Co) is electrolytically eluted, and by chemically dissolving the tungsten oxide (WO3) generated by the anodization, the method comprising:

• using an electrochemical machining fluid containing sodium carbonate (Na2CO3) or sodium hydrogen carbonate (NaHCO3) to supply the electrochemical machining fluid with sodium hydroxide (NaOH) needed to chemically dissolve the tungsten oxide (WO3) produced by the anodization;
• heating the machining fluid to a temperature of 63° C. or higher to thereby release CO2 and produce NaOH when the electrochemical machining is executed;
• and making CO2 to pass through the electrochemical machining fluid to restore sodium carbonate (Na2CO3) or sodium hydrogen carbonate (NaHCO3) when the electrochemical machining is not executed.

An electrochemical machining fluid for use in electrochemical machining of a hard metal, the fluid comprising a saline solution (aqueous solution of NaCl) or an aqueous solution of nitrate of soda (aqueous solution of NaNo3) to which calcium salt is added.

An electrochemical machining apparatus comprising:

• a power source to apply an AC voltage between an electrode and a workpiece that is a hard metal;
• and
• a machining tank that stores therein an electrochemical machining fluid containing a saline solution (aqueous solution of NaCl) or an aqueous solution of nitrate of soda (aqueous solution of NaNo3) to which a calcium salt is added.