ECONOMIC; TECHNOLOGICAL-MACHINE TOOLS, ELECTRIC-SPARK PROCESS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000700210082-3
• Release Decision: RIPPUB
• Original Classification: R
• Document Page Count: 4
• Document Creation Date: December 14, 2016
• Document Release Date: January 9, 2002
• Sequence Number: 82
• Publication Date: March 6, 1953
• Content Type: REPORT

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CLASSIFICATION RESIRICTrr
CENTRAL ME EOlfr REPORT NO.
INFORMATION FROM
FOREIGN DOCUMENTS OR RADIO BROADCASTS CD NO. --
COUNTRY USSR
HOW
PUBLISHED
WHERE
PUBLISHED
DATE
PUBLISHED
LANGUAGE
Economic; Technological - Machine tools,
electric-spark
process
Monthly periodical
Moscow
Sep 1952
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DATE OF
INFORMATION 1952
DATE DIST. 10 Mar 1953
NO. OF PAGES 4
SUPPLEMENT TO
REPORT NO.
THIS IS UNEVALUATED INFORMATION
Vestnik Mashinostroyeniya, No 9, 1952.
THE USE OF ALTERNATING CURRENT
FOR ELNTRIC HARDENING OF TOOLS AND MACHINE PARTS
(Russian Editor's Note: Recently a number of conflicting viewpoints
have been presented concerning the process of electric-spark haraening.
Snm. organizations and individuals express doubt concerning the effec-
tiveness of lectric-spark hardening; at the same time, a large number of
plants have successfully applied this method of hardening and have achieved
significant savings. The process of electric-spark hardening is being
accomplished by diverse enterprises in various ways and with differing
electrical and nt.b*r operating conditions. In view of the drive to save
metals, ^specially high-speed steel, the editorial office of Ver--tnik
Manhinostroyeniya considers it necessary to clarify the problem, and requests
workers in plants and scientific institutions engaged in electric-spark
hardening tc express their opinions regarding the means of developing and
the spheres of utilizing this method of hardening tools and machine parts.)
Surface hardening of iron and steel products, Including a variety of
tools, by means of an electrical discharge was discovered by Soviet
researchers relatively long ago, but this type of processing hac undergone
general industrial appliation only in recent years. As a result of numerous
research studies and practical observations, it has been established that the
process of surface hardening metal objects by impulse electrical. discharges
forms a wear-resis}aat layer of special. structure. This layer increases the
durability of steel tools and machine parts. (The poorer the qua] tty of heat
treatment of the tool, the greater is the increase in durability. With high-
quality tools, made of high-alloy steel, the increase In durability may be
insignificant.)
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The formation of the hardened layer is a part of the complex of
intricate physiocochemical phenomena occurring in the area of '.h. electrical
discharge. The nature of these phenomena has not been completely inves-
tigated. Of the many hypotheses advanced in explanation of the processes
taking place, two have received the widest circulatior. According to the
first, that of B. R. Lazarenko, hardening is achieved as a result of the
polar transfer of the electrode material (anode) to the surface being
hardened (cathode) by forces originating in the path of the spark discharge.
The hardness of the surface being hardened results from the deposit of one
or another hard alloy up on it. The process should be carried out with
direct current only; otherwise, as B. R. Lazarenko claims, no polar transfer
will occur.
According to the second hypothesis, hardening occurs as a result of an
intricate process. Special attention is called to the following factors in
the processing of steel:
1. The tempering of individual microscopic particles of the surface
being hardened, which have been heated and individually fused by the heat
given ff during the electrical discharge. The speed of tempering reaches
10-1-100 degrees per second, which is unusual in generally accu:pted heat
treatment and leads to deep structural changes in the surface layer.
2. The alloying of the molten steel with various elements through con-
tact of the fused particles at both electrodes.
3. The formation 9f carbides and nitrides by the contact of the molten
steel with carbon- and nitrogen-containing substances breaking down in the
zone of discharge (air, electrode material, impurities, fluxes, etc.).
4. A secondary increase in hardness due to the dispersed segregation
of the hardening. phase in the process of solidifying the fusion and to the
multiple teat effects of the subsequent discharges.
Present knowledge regarding these four processes does not permit
precise determination as to which of its constituent parts is the ma!n one.
The four enumerated processes can take place almost identically with
either direct current of alternating current feeding the unit, simultaneous
occurrence of all the processes not being compulsory for accomplishing the
hardening effect; the presence of one or some of them is sufficient. However,
because the phenomena associated with contact electrohardening have not been
studied sufficiently, a conviction that an electrohardening unit must perforce
be supplied with direct current has been widely held in technical circles
until recently.
The use of alternating current, from the point of view of existing con-
cepts concerning the polar transfer of metal, was considered inadmissible,
as not providing the necessary technical effect. Hence, a number of organizations
began to produce hardening units with built-in rectifiers which considerably
increase the cost of the unit.
Furthermore, an examination of the results obtained by industry in the
introduction of electrohardening, and an analysis of the theoretical conditions,
indicate that there are no bases for limiting electrohardening to the use of
diic.:t current, arl that the process can be a_complished on very simple units
supplied by alternating current.
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Some data from the numerous observations concerning the effectivenss of
electrohardening is given in the following table.
effectiveness of Electrohardened Tools
Durability of
Hardened Tool.
Type of Tool
as Compared With
Unhardened Tool,
in Percent
Type of
Current
Compiler
of Data
Cutters, 90 mm in diameter
160-205
alternating
I. G. Kosmachev
(B1262)
Pneumatic chisels
150-300
alternating
P
.
I. Morshrev
End mills, 70 mm in diameter
110-210
direct
I
.
G. Kosmachev
(FM)
Saws for marble (U8)
175
alterrating
L
.
A. Anagorakiy
Lathe tools (RF1)
180
direct
G
.
M. Kremerman
Through cutters (rezets
300
alternating
P
.
I. Morshnev
prokhodnoy) (RF1)
Profile milling cutters,
190
alternating
P
I. Morshnev
105 mm in diameter (E1262)
As can be seen from the table, there is virtually no difference between
the effectiveness of hardening with direct or alternating current, or the
difference is so slight as to be negligible.
The research work conducted by A. V. Alekseyev and others also shows
that the characteristics of hardened layers, "whether obtained by alternating
or direct current, are, for practical purposes, equal.
An analysis of the data presented by enterprises at the Leningrad con-
ference on electrohardening shc.rs that of 170 units studied, 30 operated on
alternating current.
The conclusion that alternating current is suitable can be based also on
an analysis of the phenomena occurring in electrohardening.
After the heat, given of as a result of the electrical impulse, fuses
the contacting particles at the rnnvergi.ng electr,deo, subsequent changes in
the metal do not depend on the type of current; they are determined only by
the composition (manna) and the thermophysical properties of the materials used.
Bre:'V.ing down of the gas medium, solution of the carbon and nitrogen in the
molten metal, or on the other hand, the decompositicn of the carbides and
nitrides, are purely thermochemical precesses and are determined solely by
heat factors, regardless of the type of current generating the heat.
The transfer of material from one electrode to the other, and the
diffusion phenomena associated with contact electrohardening, come about '+s
a result of the contact of the particles of the molten metal of both elec-
trodes under great specific pressure. This transfer also occurs regardless
of the type of current by which the metal is fused.
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Finally, in operating on direct current, the discharge of the condenser
has an oscillatory character in most cases, owing to the presence of an
inductance discharge in -Lbe circuit, whereby the inverse half wave attains
a significant magnitude. Thu,, even in this case, the process actually
taken place in part or alternating current.
From the above account it follows that if the some amount of heat is
given off as a result of the impulse effect of either direct or alternating
current, then both types of current must have an analogous effect on the
surface of the contacting electodea, i.e., the same hardening effect.
Proceeding from this premise, which has been verified experimentally,
it is possible substantially to simplify and reduce the cost of hardening
units, utilizing alternating current directly for this purpose without
first rectifying it.
As a result, the annual saving for a machine-building plant of medium
size, with 10-15 units in operation, would amount to 10,000-15,000 rubles in
the cost of the units alone. In addition, the use of alternating current
units, together with the simplicity of their manufacture, would considerably
facilitate and expedite the introduction of this method of hardening into
industry.
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