RU1789576C - Device for supplying electroplating bath with pulse current - Google Patents

Description

cathodic and anodic pulses with switching off the current between the cathodic pulses.

Highlighted by the switch 3 and adjustable bursts of pulses are fed to the matching elements 12 and 13. An even positive pulse opens the thyristors 7 and 8, forming a recharge circuit of the capacitors 10 through the galvanic bath 16 and the inductive toroidal coil 9. In this case, the group of capacitors 10 is recharged from voltage + V s to -V s (diagram q), equal to twice the rectified rectified voltage of the regulated rectifier 1 (resonance mode of the LC circuit). The recharge current flows through the plating bath 16, forming a polarizing impulse (diagram e). The pulse duration is determined by the frequency of free oscillations f0 of the L-C circuit. When the magnetic flux of the inductive toroidal coil 9 changes, a pulsed symmetrical electromagnetic field is generated in the electrolyte volume of the interelectrode space during the passage of the polarizing current. At the end of the transient, the current becomes zero, and thyristors 7 and 8 are closed.

Thyristors 5 and 6 open upon receipt of an even trigger pulse (diagram c). This facilitates the reverse recharging of the capacitors 10 through the plating bath 16 and the toroidal inductor 9.

In this case, the capacitors 10 are recharged from -Vc to + V s (diagram), and the recharging current passes through the bath in the same direction as with the operation of thyristors 7 and 8 - diagram e.

After the time determined by the adjustable delay unit 15, the unlocking pulse (diagram d) is supplied to the short-circuit thyristor 11, which shunts the galvanic bath 16 and forms the trailing edge of the polarizing current pulse.

In the proposed device, polarizing current flows through an inductive toroidal coil 9, forming an asymmetric electromagnetic field of the interelectrode space. Due to this, the distribution of current densities on the cathode surface is equalized, eliminating the edge effect, which consists in a significantly faster increase in the deposit at the edges and protrusions of the cathode surface. Ultimately, it is possible to achieve a significant increase in the uniformity of coatings not only for parts with a simple surface (shafts, cylinders), but also for profiled surfaces.

0

5

5

0

5

0

5

0

The parameters of the toroidal coil 9 are selected from the resonance condition of the L-C circuit at a given frequency of free vibrations.

The frequency of free vibrations f0 is selected from the condition

,

where T 2 tn is the period of free oscillations of the L-C circuit;

ti - duration of current pulses, ms.

Since a polarizing current pulse is formed overcharging the resonance circuit L-C-R, where R is the ohmic resistance of the bath, in order to maintain the aperiodic course of the transient processes, it is necessary to fulfill the conditions

R 2vT7C

From the condition of the resonant mode of operation of the L-C circuit, the duration of polarizing pulses:

1 and 2 L2 C D (I / D + 0.44) -OIK1

where C is the capacitance of the switching capacitors, microfarads;

D is the diameter of the inductive coil, m;

I is the length of the coil winding, m;

W is the number of turns of the inductive coil,

K-empirical coefficient depending on winding pitch.

The introduction of a toroidal inductor into the device allows you to really increase the power factor of the device (cos (p) to 0.99, and improves the secondary distribution of metal on the cathode 91 against 78%. A real increase in power factor is achieved by reducing the reactive power of the device to zero. along the surface profile it is possible to increase the average working current densities by 2–3 times, i.e., it is possible to intensify the process.

The direction of the magnetic axis of the toroidal coil with respect to the direction of the polarizing electrolysis current is determined from the expression

V -. e j B2

U2

where e is the charge of the electron;

B - magnetic induction; j is the mobility of ions.

As a result, under the influence of a magnetic field at the edges and edges of the part, the effect of discarding polarizing

ions in the middle part of the surface, i.e. surface leveling occurs.

Claims (1)

The proposed method, in comparison with the basic method, allows to increase the uniformity of the coating in thickness up to 91%, reduce the porosity of the coating by 45-50%, simplify the process of machining parts due to the partial elimination of the grinding operation that occurs with significant unevenness in the thickness of the coating, and reduce the complexity, which will make it possible to use the proposed method in various sectors of the national economy to obtain wear-resistant chromium plating. SUMMARY OF THE INVENTION A device for supplying galvanic baths with pulsed current, comprising an alternating current source, an adjustable rectifier, a gate pulse generator, a switch, matching elements, an adjustable delay unit, a short-circuit transistor and a single-phase thyristor bridge, the diagonal of which includes switching capacitors and inductance in series with them, while the inputs of two matching elements are connected to the output of the switch, the outputs of each of them are connected to the control electrodes of the corresponding pair of thyristors of a single-phase bridge, and the third matching element is connected between the control electrode of the short-circuit thyristor and the adjustable delay unit, the input which is connected to the switch, characterized in that, in order to intensify the galvanic process, reduce energy consumption and increase the uniformity of the coating on parts having complex surface geometry by conducting the process in an asymmetric pulsed magnetic field, it is equipped with three decade-long finders with graduation scales in milliseconds, and the inductor is made in the form of an open toroid, and its magnetic axis is directed at an angle of 45 ° to the direction of the polarizing current in the galvanic bath. S st Uuuli Time to Sound & Rzhkh Fm.2