DE2338242A1 - Electrolytic surface boriding - in direct A.C. heated electrolyte - Google Patents

Abstract

Electrolytic boriding of workpiece surfaces is carried out in a crucible with a boriding electrolyte which is directly resistance heated by a.c. passed between electrodes projecting into the electrolyte and spaced at a distance from the d.c. anodes and the cathodic workpieces such as to ensure that the d.c. current density on the workpiece surfaces is greater than the a.c. current density. Direct resistance heating of the electrolyte greatly increases the service life of the crucible compared with heating by means of a heating element surrounding the crucible.

Description

P-

Pr. ^ - tanwälto

'üiLLLä ·:. "H-Iu. LUYKEN

8U00 Munich 22
Zweibrückonstr. 6th

naucno-issledovatel'skiJ

proektno-Konstruktorskiö Institut P 4-8 4-87 / 2

elektrotermiceskogo oborudovanija July 27, 1973

Moscow / USSR ^L / HD

APPLICATION FOR THE ELECTBOLYT BOY OF WORKPIECES

The present invention relates to equipment that can be used for the chemical-thermal treatment, and in particular for boronizing, of workpieces.

Are known 'Vorrichtun @ * E represents the Elektrolytborieren with äuBerer heating of the melt.

They represent an electrothermal crucible furnace that consists of a welded metallic housing, lined with fire-resistant material.

The metallic crucible made of chrome-nickel steel is arranged in the furnace. In it is the melt of the boron-containing Medium.

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Between the melt of the boron-containing medium and the electrical equipment, open resistance heating elements, which serve as a heat source, is the metallic one Crucible wall.

To carry out the electrolysis, anodes are arranged in the melt inside the crucible, which are connected to the positive Pole of the DC power source are connected.

The negative pole of this source is attached to that to be treated Connected workpiece, which is immersed in the melt.

In the known device, the average life of the crucible is about 2000 hours, which is a The main disadvantage is that if the crucible fails, the resistance heating elements and the lining are destroyed, which leads to the need for a complete overhaul of the entire device.

The present invention aims to avoid the disadvantage mentioned.

The invention 1αά ~ the object; '. one Developing a device with such a device for the electrical heating of the melt, which extends the service life of the entire device * for electrolyte boring extended-

To solve the problem, a device for the electrolyte boring of workpieces is proposed,

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which consists of a crucible with the melt of the boron-containing medium, with anodes and workpieces arranged in it, which are connected accordingly to the position and negative pole of the DC power source. When letting the current pass the workpiece to be treated and the heating of the melt of the medium result in the formation of a borated one Diffusion layer. According to the invention, the device is for the electrical heating of the melt of the boron-containing medium within the crucible is arranged directly in the melt and has electrodes connected to an AC power source; the electrodes are in such an ab-. stood by the anodes and the workpieces to be treated arranged that the density of the direct current on the surface the latter is greater than the density of the alternating current. In the device according to the invention, the distance is between the anodes, electrodes and the workpieces to be treated according to the following formulas, calculated:

Alternating current

arctg

fTi-) ² -

Direct current

^R altern.

2Jl h

here means:

* ^ider stood, in chain, (Ohm);

AC electrodes

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^R direct current «Resistance in the electrolysis chain, (Ohm); ^ specific electrical resistance of the medium containing boron (ohms, cm);

H - working length of the alternating current electrodes,

d - diameter (side of the square) of the

AC electrodes, (in);

1 - distance between the alternating current electrodes,

h - length of the workpiece to be treated, (m);

X * - current coordinate showing the position of the

Workpiece in the working area of the device

considered;

Γη, - radius of the direct current anode (m); ? 2 - Inner radius of the cathode (cassette with

the workpieces to be treated) (m);

The greatest benefit of the present invention is that it is more as a five-fold increase in the average life of the crucible associated with the arrangement of the facility for the electr ο heat directly in the melt of the boron-containing Medium, which leads to a reduction in the temperature of the crucible walls and an increase in the service life of the Crucible leads.

Determining the distance between the anodes, electrodes and the workpieces to be treated according to the above

509808 /.0 427

The aforementioned formulas ensure such conditions for each workpiece to be treated, at which the direct current density increases its surface area is greater than the alternating current density.

The development and application of the present device allows the specific consumption of electricity such as also reduce the cost of electrolyte borating, what results in a significant economic efficiency.

To illustrate the essence of the invention, the description of an embodiment of FIG Device brought as well as a drawing on which the view of the device for the electrolyte borating is shown is.

The device contains one made of chrome Mckel steel Cast crucible 1. Inside the crucible, which is filled with a melt of the boron-containing medium, an electrical Device, designed in the form of two electrodes 2 made of nichrome, arranged. The electrodes 2 are connected to an alternating current source (not shown) connected. In the boron-containing medium, the to be treated are in a special cassette 2 Workpieces 4 arranged, which serve as a cathode and are connected to the negative pole of the direct current source (not shown) are connected. The graphite anodes immersed in the melt are connected to the positive pole of the same source 5 connected.

The crucible 1 is set up in the lined housing 6. The temperature of the melt is controlled with the help of the

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Thermocouple 7 measured.

The system works as follows:

After the melt of the boron-containing medium has been prepared, the electrodes 2 are connected to the alternating current source and intended for the heating of the melt, switched on. The temperature of the melt is using of the Chroxael-Alumel-'eiements 7 measured, which is in a protective cover made of stainless steel.

The introduction and removal of the workpieces 4 in the cassette 3 is mechanized. The workpieces are immersed in the melt at a temperature of the melt equal to 95O ⁰ C.

Furthermore, the direct current source is switched on to accomplish the electrolysis process and the desired one Current density set on the surface of the workpieces 4 to be treated, which leads to the electrolysis of the melt of the boron-containing medium, the decomposition of the melt with the formation of boron ions and the precipitation of the same takes place on the surface of the treated workpieces 4

When the electrode method is used to heat the melt of the boron-containing medium, the to be treated workpieces 4 under the action of the direct current of the electrolysis and the sinusoidal alternating current of the Electrodes 2. Considering that the process of electrochemical dissociation of the melt of the boron-containing Medium and the supply of boron ions to the surface of the

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workpiece 4 to be treated only in the cathode half-cycle occurs, the presence of an anode component of the alternating current slows down the electrochemical reactions and under certain conditions <fes zur The result is that the reactions run in the opposite direction.

In those cases where the amplitude density of the alternating current is less than the direct current density, it flows over the surface of the workpieces to be treated, a cumulative current that has no anode component and that is continuous The course of the electrochemical! Reactions with the elimination of the required electrolysis products is guaranteed.

In the device according to the invention, the arrangement of the workpieces, the anodes and electrodes, the elec-

cLic

tric device for ^ heating of the melt in the working volume as well as the energy characteristics (voltage in the chain of the heating electrodes and in the electrolysis chain) conditions for each workpiece to be treated, under which the direct current density at its. Surface area is greater than the alternating current density. This mutual arrangement and the energy characteristics are determined from the dependencies to be calculated, which connect the geometric parameters of the device according to the invention and which ultimately result from the known resistance in the chain of alternating current electrodes and from the resistance in the electrolysis chain as described above

5 0 9 8 0 8/0 A 2 7

specified formulas can be determined.

below we give an example of the arrangement of AC electrodes, anodes and the workpieces to be treated, which are determined from the above-mentioned formulas and ensure conditions under which the alternating current density at the surface of any to be treated Workpiece less? Is than the DC current density.

Example'

For boronizing cylindrical workpieces with a diameter of 16 'mm and a length of *> 10 mm made of carbonaceous, with chrome and silicon low-alloy steel in a boron-containing medium with a specific electrical Resistance 1.86 ohms. cm. has the device for electrolyte boring the following geometric parameters listed in the table below.

Tabel

GEOMETRIC PARAMETERS OF THE DEVICE FOR ELECTRICAL ROLYTHBORING

Serial Designation of the geo-calibration dimension no. metric parameter is called size

1 distance between the
Yellular current electrodes 1 m 0.060

2 diameters of alternating currents! ekt rode d m 0.060

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Serial Designation of the geometric designation no. see parameters

Unit of measurement large

Working length of the electrodes

Running coordinate showing the position of the workpiece in the work area the device taken into account

Inner radius of the cassette

Radius of the DC motion

0.5

0.1 0.2 0.0275

The application of the device for electrolyte boring of the workpieces mentioned ensures the production of a uniformly borated layer with a depth of 0.12-0.20 mm at a temperature of the process 940-950 ° C, the density of the direct current on the surface of the workpieces to be treated 0.10-0.15 A / cm and a duration of the process equal 2 hours.

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Claims (1)

F 43 437/2 July 27, 1973 PATENT CLAIMS: _{L / KD} M.) Device for the electrolyte boring of workpieces, consisting of a crucible with the melt of a boron-containing medium and anodes and workpieces arranged in it, which are connected to the positive and negative pole of the direct current source, w <? when passing the direct current '. . "-_ *. /.! ·. J. '.; ./ ,.'. On the workpieces to be treated and when the melt of the / medium is heated with an electrical device, the formation of a borated diffusion layer takes place t _t ^s that the device for the electrical heating of the melt of the boron-containing medium is arranged within the crucible (1) directly in the melt and has electrodes (2) which are connected to an alternating current source, the electrodes (2) in one Distance from the anodes (5) and the workpieces (4) to be treated are arranged so that the direct current density is greater than the alternating current density on the surface of the latter. 2 · Device according to claim 1, characterized in that the distance between the Anodes (5) »the electrodes (2) and the workpieces to be treated (4-) is determined according to the following formulas: 509808/0427 21 γ. jji ι- β. 1 * Γ- Alternating current "_. H arcts 2 | - ^R direct current ^ 'echselstr. Resistance in the chain of AC electrodes (2), JjDhnfj ι— ^R direct current resistance in the electrolysis chain, _ ^ specific electrical resistance of the boron-containing medium lOhms. cm.I H working length of the alternating current electrodes (2), H-, d diameter (side of the square) of the alternation current electrodes (2), Distance between the AC electrodes (2), & Q. h Length of the workpieces to be treated ( ¹ O * ΓπΠ X Current coordinate showing the location of the plant taken into account piece in the working space of the device; r- radius of the direct current anode (5), Inner radius of the cathode (cassette with the workpieces to be treated) (4), [ml - Π ι) 9 8 O * '' i A η. Blank page