RU2714574C1 - Method of chemical removal of defect layer from surface of parts after electroerosion cutting - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to chemical methods of removing a defect layer from surface of parts after electroerosion cutting and can be used in engineering related to cleaning parts made of alloyed steels, alloyed tool steels, precision alloys, as well as sintered alloys. Method involves treatment of parts after electroerosion cutting in solution at temperature of 18–30 °C until complete removal of defect layer, wherein solution is used, having following composition, wt%: citric acid 5.0–7.0, tartaric acid 5.0–7.0, disodium salt of ethylenediamine-N,N,N',N'-tetraacetate 0.5–0.7, surfactant OP-7 0.25–0.7, distilled water – the rest. To increase efficiency, treatment is performed with superposition of ultrasonic vibrations.

EFFECT: method provides removal of defective layer from surface after erosion cutting directly in mechanical shops at section of parts washing, at the same time it allows increasing ecological compatibility of production.

1 cl, 1 ex

Description

The invention relates to chemical methods for removing a defective layer of the surface of the processed material after EDM cutting, and can be used in technical fields related to the operation of cleaning parts made from alloy steels, alloyed tool steels, precision alloys, and also sintered alloys.

During electrical discharge cutting, the surface layer of the material of the workpiece is exposed to local and short-term, but very intense thermal and chemical effects. As a result, a layer forms on the surface of the part, which differs from the main material in its physicomechanical properties (structure, hardness, etc. change). Due to the decrease in hardness and the appearance of inhomogeneity of the material, in most cases the surface layer is defective, which reduces the strength properties of the metal. In the manufacture of critical parts, it is removed. However, it is not always possible to remove the defective layer mechanically (using sandpaper, file, etc.), due to the overall dimensions and complex geometry of the parts.

There is the possibility of cleaning metal surfaces from contaminants, in particular from scale, oxides, by treating the parts to be cleaned in multicomponent solutions based on inorganic acids.

A known method of removing glass grease from the surface of metal products, such as hot-pressed pipes, including hydrofluoric acid, sulfuric acid, ammonium persulfate and organic acid, such as tartaric, oxalic (AS USSR No. 747908, IPC C23F 1/02, C03C 15/00 A solution for removing glass grease from the surface of metal products / V. A. Bogomazov, V. Kh. Kasyan, B. A. Mlinarich, Yu., I. Vashchenko, L. M. Komaretskaya, N. V. Makhankov, O. V. Donskoy - No. 2587086 / 22-02; claimed 01.03.78; publ. 15.07.80). The disadvantage of this method is the limited use due to the presence in it of such strong (aggressive) acids, hydrofluoric and sulfuric and is intended mainly for lubricants.

A known method of removing scale and metal oxides and their alloys in a bath for etching with ferric iron (CS 8800287, IPC C23G 1/02; C23G 1/08; C23G 1/10; C23G 1/12; C23G. Method of scale and metal oxides and their alloys removal of trivalent iron pickling bath / Bordas Zoltan, Mihaleczku Jozsef, Toereki Ernoe, Humenyanszky Pal, Ersek Barnabas, Nyitray Istvan. - No. 1,988,000,287; claimed Jan. 15, 1988), in which the solution consists of an aqueous solution of ferric chloride-sulfate and (or) iron (III) chloride and (or) iron (III) sulfate, which may contain up to 5% mineral acid. The concentration of Fe (III) in the etching solution is 15-200 g / L. Etching is carried out for 3-40 minutes at a temperature of 20-80 ° C. The spent pickling solution can be regenerated with chlorine and reused. This process avoids working with highly concentrated acids and does not leave spent pickling baths that pollute the environment. No etching additives are required. The disadvantage of this method is the inability to completely remove the defective layer in hard to reach places. The saturation of the solution with chlorine during the regeneration process, significantly complicates its use in mechanical shops, because requires certified specialized equipment and facilities for working with gaseous chlorine.

A known method of cleaning metal surfaces of parts from scale, rust oxides during the production of semiconductor devices, radio products (RF Patent No. 2079930, IPC H01L 21/306, C23G 1/02. Method of cleaning metal surfaces of parts from scale, rust oxides / Deryugin V. N., Ezhov A.A., Korovin S.K., Komarova N.V., Galaev A.A., Usov N.N., Semenov L.L., Lapygin A.V. - No. 96103333/25; Declared on February 22, 1996; published on May 20, 1997). The method consists in processing the cleaned metal surfaces with an aqueous solution of sulfomaleic anhydride, the concentration of which is 10-30 wt. %, for 10-20 minutes at a temperature of 50-80 ° C. The disadvantage of this method is the low efficiency - the inability to completely remove the defective layer from the surface of any parts.

One of the ways to reduce the aggressive effect and increase the efficiency of the solutions used to remove scale, defective layer, and other deposits is to use complexones (complexing agents) in them, which bind the metal cations that make up the defective layer, scale and other deposits, such as ethylenediaminetetraacetic acid and salts thereof, diethylenetetramine pentaacetic, hydroxyethylidene diphosphonic acid and the like.

The closest in technical essence is a solution for chemical cleaning of equipment from scale, rust, scale (AS USSR No. 283772, IPC C23F 14/02. Solution for chemical cleaning of equipment / AA Cat - No. 917753 / 22-1; Dec. 20.08.64; publ. 06.10.70). The solution contains the following ratio of components: containing Trilon B (complexone) 0.5-1.2%, citric acid 0.5-1.5%, hydrazine hydrate 0.1-0.2%, ammonia to pH 7-9 and water rest. This composition, which is the closest to the claimed method, is relatively effective, but due to the presence of hydrazine hydrate and ammonia in its composition, it is quite toxic and, in addition, when it is used, high dissolution rates of the above materials are observed.

Common disadvantages of these methods are: significant environmental pollution by reaction products, toxicity of the cleaning process, pronounced erosion of the surface of the processed material, the need and complexity of disposal of used chemical reagents.

The objective of the invention is to develop a method that allows you to efficiently and guaranteedly remove deposits and a defective layer from the surface of parts after electrical discharge cutting, to ensure the toxicity of the process.

The problem is solved as follows. Parts after electrical discharge cutting are treated in a solution having the following composition (in wt.%):

Citric Acid 5.0-7.0 Wine acid 5.0-7.0 Ethylenediamine-N, N, N ', N'-tetraacetic disodium salt 0.5-0.7 Surfactant OP-7 0.25-0.7 Distilled water Rest

at a temperature of 18-30 ° C until the defective layer is completely removed. To increase efficiency, the treatment is carried out using ultrasound.

The solution is obtained by successive dissolution of the components in distilled water, the presence of an incompletely dissolved complexon in the solution (in the form of a suspension) is allowed. The solution is poured into a working container in which the workpiece is placed.

Example. The tests were carried out on parts made of 44NKhTYu material obtained after EDM cutting. Details in metal sects are placed in a solution containing (in wt.%):

Lemon acid 6.5 Wine acid 6.5 Ethylenediamine-N, N, N ', N'-tetraacetic disodium salt 0.7 Surfactant OP-7 0.5 Distilled water 85.8

The treatment is carried out at a temperature of 18-25 ° C with the application of ultrasound until the defective layer is completely removed (12-18 min). Then the parts are washed in water and dried with compressed air. After processing in the above solution on the part, in the places of electroerosive cutting, the defective layer is completely absent, “etching” of the surface is not observed.

The inventive method allows you to:

- effectively remove the defective layer from the surface of parts made of alloy steels, alloy tool steels, precision alloys, as well as sintered alloys;

- remove the defective layer in hard to reach parts;

- use it directly in the mechanical workshops on the parts washing section, without requiring powerful supply and exhaust ventilation;

- increase the environmental friendliness of production.

Claims (3)

1. The method of chemical removal of the defective layer after electrical discharge cutting from the surface of parts made of alloy steels, alloyed tool steels, precision alloys and sintered alloys, comprising treating the part in a solution, characterized in that the removal of the defective layer is carried out at a temperature of 18-30 ° C until it is completely removed in a solution containing, wt.%: lemon acid 5.0-7.0 wine acid 5.0-7.0 ethylenediamine-N, N, N ', N'-tetraacetic disodium salt 0.5-0.7 surfactant OP-7 0.25-0.7 distilled water rest 2. The method according to p. 1, characterized in that the removal of the defective layer is carried out with the imposition of ultrasonic vibrations.