Method of electrochemical machining of materials

Abstract

The invention relates to electrochemical pulse machining (ECM) of high alloy steel, alloys and conducting composite materials that include components with substantially different electrochemical properties. In particular, the invention can be used to perform various copy-piercing operations when producing intricately shaped surfaces of machines and tools made of WC—Co, WC—TiC—Co alloys. The method comprises machining at low interelectrode gaps using anode or bipolar high-frequency current pulses supplied in bursts which are synchronized with the moments of maximum convergence between an oscillating tool electrode and a workpiece, and additional singular pulses of opposite polarity supplied during pauses between pulse bursts, wherein a ratio of parameters for the pulses of normal and opposite polarity is adjusted based on the initial electrolyte acidic value. The method is carried out in a way that a transitional bend is formed at a peak of an additional pulse, said bend being caused by the change in electrical resistance of the interelectrode gap up to a steady value, the duration of additional pulse sections before and after the bend point being set depending on the machining mode and the composition of the material subjected to machining. The invention allows to carry out electrochemical machining of composite conducting materials comprising components with substantially different electrochemical properties providing a surface layer of predetermined chemical composition, as well as surface quality, by operatively adjusting and controlling the machining process parameters to provide control over component anode dissolution intensity.

We claim: 
     
         1 . A method of electrochemical machining of composite materials comprising components with substantially different electrochemical properties, at short interelectrode gaps using anode or bipolar high-frequency current pulses supplied in bursts which are synchronized with the moments of maximum convergence between an oscillating tool electrode and a workpiece, and additional singular pulses of opposite polarity supplied during pauses between the bursts of pulses, wherein a ratio of parameters for the pulses of normal and opposite polarity is adjusted based on the initial electrolyte acidic value, the method further comprising a step of regulating the said machining process to form a transitional bend at the maximum of the additional pulse in response to the change in electrical resistance of the interelectrode gap up to a steady value, wherein the duration of the additional pulse sections before and after the bend are adjusted depending on the machining mode and the composition of the material subjected to machining. 
     
     
         2 . The method according to  claim 1 , wherein the process regulation is carried out as follows: when the initial electrolyte acidic value is increased, the duration of the additional pulse section after the transitional bend point characterizing the steady process, is decreased, and when the initial electrolyte acidic value is decreased, said duration is increased. 
     
     
         3 . The method according to  claim 1 , wherein the process regulation is carried out as follows: when the number of pulses in a burst is increased, the duration of the additional pulse section after the transitional bend point characterizing the steady process, is increased, and when the number of pulses in a burst is decreased, said duration is decreased. 
     
     
         4 . The method according to  claim 1 , wherein the process regulation is carried out as follows: when the duration of anode pulses in a burst is increased, the duration of the additional pulse section after the transitional bend point characterizing the steady process, is increased, and when the duration of anode pulses in a burst is decreased, said duration is decreased. 
     
     
         5 . The method according to  claim 1 , wherein the process regulation is carried out as follows: when amplitude of anode pulses in a burst is increased, the duration of the additional pulse section after the transitional bend point characterizing the steady process, is increased, and when the amplitude of anode pulses in a burst is decreased, said duration is decreased. 
     
     
         6 . The method according to  claim 1 , wherein the process regulation is carried out as follows: when the amount of a binding component (for example cobalt) in a workpiece composite material is increased, the duration of the additional pulse section after the transitional bend point characterizing the steady process, is decreased, and when the amount of the binding component in the workpiece composite material is decreased, said duration is increased. 
     
     
         7 . The method according to  claim 1 , wherein the process regulation is carried out in a way that the duration ratio of the additional pulse sections before and after the transitional bend point is adjusted by changing the amplitude of the additional pulse. 
     
     
         8 . The method according to  claim 1 , wherein the process regulation is carried out in a way that the duration ratio of the additional pulse sections before and after the transitional bend point is adjusted by changing the amplitude of the pulses of opposite polarity in the burst of bipolar pulses. 
     
     
         9 . An apparatus for electrochemical machining of composite materials with components having substantially different electrochemical properties, using an oscillating tool electrode and a workpiece at short interelectrode gaps, the apparatus comprising
 a current pulse generator, generating anode or bipolar high-frequency current pulses supplied in bursts, and generating additional singular pulses of opposite polarity supplied during pauses between the bursts of pulses, wherein a ratio of parameters for the pulses of normal and opposite polarity is adjusted based on the initial electrolyte acidic value,   a synchronizing unit for synchronizing the said current pulses with the moments of maximum approach between the oscillating tool electrode and workpiece, and   a pulse regulator, the pulse regulator adjusting the pulses so that a transitional bend is formed at a peak of an additional pulse in response to the change in electrical resistance of the interelectrode gap to a preset value, wherein the duration of additional pulse sections before and after the bend point are preset depending on the machining mode and the composition of the material subjected to machining.   
     
     
         10 . An article of manufacture obtained by a process of  claim 1 , characterized by having a surface layer having a predetermined chemical composition and surface roughness. 
     
     
         11 . The article of manufacture of  claim 10 , wherein the article is selected from workpieces and tools made of WC—Co, WC—TiC—Co or other transitional metal of IV-VI group and alloys thereof.