Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1990-06-15
1991-07-02
Valentine, Donald R.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
20412995, 2041415, 204146, B23H 308, C25F 316, C25F 500
Patent
active
050283049
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to methods of electrochemical and electrophysical machining, and more particularly it relates to methods of electrochemical machining of articles made of electrically conducting materials.
BACKGROUND OF THE INVENTION
There is known a method of electrolytic anodic polishing of steel articles by direct current in a chromium-phosphorus-sulfuric acid electrolyte (A.M. Yampolski "Travleniye metallov", 1980, Metallurgiya/Moscow/, p. 51) performed by submerging articles in the electrolyte containing, % by weight:
______________________________________ orthophosphoric acid
65-85
chromic anhydride 6-12
sulfuric acid 5-15
______________________________________
30.degree.-70.degree. C. The electrolytic polishing is conducted with the
anodic current density of 50-60 A/dm.sup.2 for 3-15 mn.
There is also known a method of electrolytic polishing of articles made of copper and its alloys by way of electrolysis in an aqueous solution of phosphoric acid (the density of the solution being .rho.=1.6 g/cm.sup.3) (A.M. Yampolski "Travleniye metallov", 1980, Metallurgiya (Moscow/, p. 99), or else in an electrolyte containing 385 g of potassium pyrophosphate and 853 g of water, at 20.degree.-50.degree. C. for 1.5-3 mn (SU, A, 177732).
There is still further known a method of electrolytic polishing of articles made of aluminium and its alloys, in an electrolyte containing 20-25% by weight of sulfuric acid, at 18.degree.-20.degree. C. and under a voltage of 6-12 V (Witt C., "Galvanotechnik", 1981, V.72, No. 10, pp.1073-1075).
The abovementioned methods are based on the use of high-concentration solutions of expensive and toxic substances; they are characterized by relatively long duration of the polishing operation and require prolonged pretreatment of the surface of an article prior to the electrolytic polishing operation, including degreasing, etching (pickling), flushing, etc., which adversely affects the overall productivity and efficiency, to say nothing of the considerable input of power and labour.
There is also known a method of electrochemical machining of articles made of electrically conducting materials, including treating the articles at 220-380 V in an electrolyte containing 20% aqueous solution of ammonium chloride at 35.degree. C. (V. N. Duradzhi et al. "Elektronnaya obrabotka materialov"/Electronic Machining of Materials/, 1978, No. 5, pp.13-17).
However, this last-mentioned process fails to produce a surface finish of the articles finer than R.sub.a =0.28 . . . 0.32 .mu.m, with the reflection factor of the machined surface within 30-40%. Furthermore, the process requires the use of an electrolyte of a relatively high concentration (20%), which increases the machining cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problem of creating a method of electrochemical machining of articles of conducting materials, wherein the selection of the machining duties and concentrations of the electrolyte should step up the productivity of the machining operation and enhance the quality of polishing, with low-concentration, inexpensive and non-toxic electrolytes employed and operations of pretreatment of the surfaces of articles avoided.
The problem is solved by a method of electrochemical machining of articles of conducting materials, including applying to a machined article a positive electric potential and submerging the article in a heated aqueous electrolyte solution. In the method, in accordance with the present invention, the potential applied to the article equals 200-400 V, with the temperature of the electrolyte which is an aqueous solution of a concentration of 2-12% by weight being 40.degree.-95.degree. C.
To enhance still further the quality of polishing by upgrading the surface finish and raising the reflectivity of articles made of corrosion-proof chromium-nickel steel grades, it is expedient that the electric potential applied to the articles should be 240-320 V, the aqueous electrolyte solution being an
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Khlebtsevich Vsevolod A.
Kosobutsky Alexandr A.
Parshuto Alexandr E.
Semchenko Alexei A.
Semenenko Leonid M.
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