RU2550068C2 - Method for electrochemical polishing of metals and alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the electrochemical treatment of metals and alloys and can be used in machine and instrument building at finishing of inner and outer surfaces. The method involves cyclic polishing of a part in a neutral water solution of salts at the current density of 0.2-10.0 A/cm², electrolyte temperature equal to an ambient temperature, vibration of the treated part with the amplitude and frequency, which are specified based on electrochemical properties of the metal, and evaluation of roughness after each polishing cycle; with that, the time between the cycles is calculated depending on polishing parameters and electrochemical properties of the metal by the following formula: $${\tau }_{мц}\ge {\left(\frac{z\cdot F}{2i}\right)}^2\pi D{C}_S^2,$$

where z - charge of a potential-determining ion, F - faraday number, C·mol^-1, i - current density of anodic dissolution, A/cm², D - diffusion coefficient of ions of the treated metal, cm²/sec, C_S - concentration of ions on the surface of the polished part, mol/cm³, and the time of one polishing cycle is determined depending on $$\tau =\frac{K}{i\cdot D}$$

, where τ - time of the polishing cycle, sec, i - current density of anodic dissolution, A/cm², D - diffusion coefficient of ions of the treated metal, cm²/sec, K=10^-5 A.

EFFECT: invention allows calculating the accurate time of the polishing cycle at the best polishing quality and making the polishing process automatic.

3 ex

Description

The invention relates to the field of electrochemical processing of parts from metals and alloys and can be used in machine and instrument engineering, for example, when fine-tuning internal and external surfaces.

A known method of electrochemical polishing, which is anodic dissolution, leading to improved microgeometry of the treated surface [Application No. 49-38418, Japan, MKI S23B 3/00, NKI 12A63]. Electrochemical polishing is carried out both in stationary and in a moving electrolyte [Lipkin Y.N., Bershadskaya T.L. Chemical polishing of metals. - M.: Mechanical Engineering, 1982. - 112 p.].

The disadvantage of existing methods is the toxicity of the electrolyte, low productivity.

A known method of electrochemical polishing [RF patent No. 2451773, IPC C25F 3/16, B23H 3/00], which is adopted as a prototype. Electrochemical polishing is carried out in a neutral aqueous solution of salts at a current density of 0.2-10 A / cm ² , an electrolyte temperature equal to the ambient temperature, vibration of the workpiece with an amplitude and frequency specified based on the electrochemical properties of the material. Polishing is carried out in cycles, while the time of one polishing cycle is set no more than 2 s, and the time between cycles is calculated by the formula

where z is the charge of the potential-determining ion; F is the Faraday number, C · mol ^-1 ; i is the current density of the anodic dissolution, A / cm ² ; D is the diffusion coefficient of the ions of the treated metal, cm ² / s; C _S is the concentration of ions on the surface of the polished part, mol / cm ³ .

The surface roughness after each subsequent cycle is evaluated by the analytical dependence, taking into account the electrochemical properties of the processed material and polishing parameters

- шероховатость последующего цикла, мкм;

- шероховатость предыдущего цикла, мкм; n - порядковый номер цикла; k_ν - объемный электрохимический эквивалент обрабатываемого металла, см³/А·мин; χ - удельная проводимость электролита, см^-1·Ом^-1; η - выход по току обрабатываемого металла; U - напряжение на электродах, В; ΔU - падение напряжения в приэлектродных слоях, равное алгебраической сумме падений напряжения в прикатодном и прианодном слоях, В; δ_МЭ3 - величина межэлектродного зазора, см; τ - время цикла электрохимического полирования, мин.Where

- roughness of the subsequent cycle, microns;

- roughness of the previous cycle, microns; n is the sequence number of the cycle; k _ν - volumetric electrochemical equivalent of the treated metal, cm ³ / A · min; χ is the specific conductivity of the electrolyte, cm ^-1 · Ohm ^-1 ; η - current output of the treated metal; U is the voltage at the electrodes, V; ΔU is the voltage drop in the near-electrode layers, equal to the algebraic sum of the voltage drops in the near-cathode and anode layers, V; δ _ME3 - the value of the interelectrode gap, cm; τ is the cycle time of electrochemical polishing, min.

The disadvantage of the prototype is the complexity of automation of the technological process due to the fact that the exact duration of the cycle of electrochemical polishing is not specified.

The objective of the invention is to simplify the automation of the process.

The problem is achieved in that in the known method of electrochemical polishing of a metal part, including cyclic polishing of the part in a neutral aqueous solution of salts at a current density of 0.2-10 A / cm ² , an electrolyte temperature equal to the ambient temperature, vibration of the workpiece with amplitude and the frequency specified on the basis of the electrochemical properties of the material and the roughness assessment after each polishing cycle, while the time between cycles is calculated depending on the polishing parameters and electrochemical properties of the metal according to the formula

where z is the charge of the potential-determining ion; F is the Faraday number, C · mol ^-1 ; i is the current density of the anodic dissolution, A / cm ² ; D is the diffusion coefficient of the ions of the treated metal, cm ² / s; C _S - ion concentration on the surface of the polished part, mol / cm ³ , according to the technical solution, the time of one polishing cycle is determined from the dependence

where τ is the cycle time of electrochemical polishing, s; i is the current density of the anodic dissolution, A / cm ² ; D is the diffusion coefficient of the ions of the treated metal, cm ² / s; K = 10 ^-5 A.

The invention is illustrated by examples:

Example 1: Processing samples were made of steel 12X13. Initial roughness R _z 4.3 μm; volumetric electrochemical equivalent of the treated metal k _ν = 2.1 · 10 ^-3 cm ³ / A · min; specific electrolyte conductivity (15% NaCl in water); χ = 0.164 cm ^-1 · Ohm ^-1 ; current output of the treated metal η = 0.8; voltage at the electrodes U = 8V; voltage drop in the electrode layers ΔU = 2.3V; current density in the workpiece i = 1 A / cm ² ; vibration frequency of the anode (workpiece) f = 50 Hz; vibration amplitude A = 0.5 mm.

The time between cycles is calculated by the formula (1). Given that C _S = 0,48 · 10 ^-3 mol / cm ^3, the diffusion layer thickness δ = 0,4 · 10 ^-3 cm, τ _mfi ≥l, 45c.

The time of one cycle is calculated according to dependence (3) obtained by summarizing the experimental data and characterizing the time of saturation of the diffusion layer during one processing cycle:

K is a constant value, numerically equal to the current strength provided by the diffusion of ions of the treated metal, A. For a range of current densities of 0.2-10 A / cm ² K = 10 ^-5 A; D is the diffusion coefficient of the ions of the treated metal, D = 10 ^-5 cm ² / s

Moreover, after the first polishing cycle, using formula (2), we obtain the calculated parameter

The measured value of the roughness parameter

The second cycle of electrochemical polishing lasting 1 s was carried out after a pause of 1.45 s.

измеренное

After the second cycle, the calculated value of the surface roughness parameter

measured

The surface roughness is improved by carrying out the process in the optimal diffusion kinetics mode. Example 2:

Samples of steel 12X13 were processed. The current density of the workpiece i = 2A / cm ² . The rest of the initial data, the properties of the electrolyte, vibration parameters as in example 1.

The time between cycles is calculated by the formula (1). Given that C _S = 0.96 · 10 ^-3 mol / cm ^-3 ; the thickness of the diffusion layer δ = 0.4 · 10 ^-3 cm, received τ _mts ≥1.5 s.

The time of one cycle was calculated according to dependence (3):

K = 10 ^-5 A, D = 10 ^-5 cm ² / s.

Estimated Surface Roughness Parameter

В результате увеличения плотности тока, время цикла уменьшилось до 0,5 с. При этом режим диффузионной кинетики сохраняется, в результате чего характер изменения шероховатости не меняется.Measured value

As a result of the increase in current density, the cycle time decreased to 0.5 s. In this case, the regime of diffusion kinetics is maintained, as a result of which the nature of the change in roughness does not change.

Example 3:

Samples of steel 12X13 were processed. Initial data, electrolyte properties, vibration parameters as in example 1. The polishing cycle time was set arbitrarily equal to 3 s. The time between cycles was calculated according to the formula (1), τ _mfi ≥1,45 p.

At a time of one polishing cycle of 3 s, an undulation and dullness are formed on the surface of the workpiece.

Thus, during electrochemical polishing with a time of one cycle calculated by the formula (3), the pattern of reducing the surface roughness at its best quality is preserved. In subsequent processing cycles, this pattern is observed.

временем цикла полирования дает возможность автоматизировать процесс электрохимического полирования, не проводя экспериментальных исследований.The inventive method of electrochemical polishing with calculated according to

polishing cycle time makes it possible to automate the process of electrochemical polishing without conducting experimental studies.

Claims (1)

The method of electrochemical polishing of a metal part, including cyclic polishing of the part in a neutral aqueous solution of salts at a current density of 0.2-10.0 A / cm ² , an electrolyte temperature equal to the ambient temperature, vibration of the workpiece with an amplitude and frequency specified based on electrochemical properties of the metal, and the roughness assessment after each polishing cycle, while the time between cycles is calculated depending on the polishing parameters and the electrochemical properties of the metal according to the formula
$${\tau }_{mc}\ge {\left(\frac{z\cdot F}{2i}\right)}^2\pi D{C}_S^2,$$

where z is the charge of the potential-determining ion, F is the Faraday number, Cl · mol ^-1 , i is the current density of the anodic dissolution, A / cm ² , D is the diffusion coefficient of the ions of the treated metal, cm ² / s, C _S is the concentration of ions on the surface polished parts, mol / cm ³ , characterized in that the time of one polishing cycle is determined from the dependence
$$\tau =\frac{K}{i\cdot D}$$

where τ is the polishing cycle time, s, i is the current density of the anodic dissolution, A / cm ² , D is the diffusion coefficient of the ions of the treated metal, cm ² / s, K = 10 ^-5 A.