Технические науки
Металлургия
Zhiguts Yu.Yu., Legeta Ya.P., Laptyev Yu.Yu.
(
PROBLEM OF THE SYNTHESIS
MATERIALS BY METALLOTHERMY AND SHS PROCESSES
Creation of alloys on the basis of combined processes makes it possible
to synthesize cast alloys, which are being obtained now by other technologies.
The investigation of the properties and structures of such alloys is a primary
task that will allow detecting strictly the field of their application. At the
same time non-ordinary method of obtaining the alloys leads to creation of
materials with features different from obtained by industrial methods.
The given thesis is denoted the development scientific bases shaping
phase and structured condition of cast alloys with improved official and
technological characteristics and development on their base of competitive
technologies of their syntheses by way dedicated to investigating of alloys
synthesized by metallothermy and by selfpropagating high-temperature synthesis (SHS); to making
up of theoretical principles of synthesis, to establishing of connection
between the structure of fluid state of cast iron with the characteristics of metallothermit burden and to putting of synthesized
materials into practice of cast industry.
Theoretical calculations of burden compositions are founded on
establishing the dependence between component activities in systems from the
third while using Hillert equation. The usage of Screinemaker coordinates instead of ordinary coordinates
for geometric interpretation of the equations gives a unique possibility to
simplify and solve them with the reduction of quantity of approximations only
to two, both of which are being fully confirmed in most of the cases in
concrete examples of calculating of Fe–C–Si and Fe–C–S
systems.
Different carbon iron thermite alloys the
analogues of industrial alloys, their mechanical and service features, chemical
composition are investigated in the article, and the composition of metallothermic burden and the regimes of heat treatment are
optimized. Synthesized thermite steels (carbon,
spring, stainless, scale and high-manganese and bearing), special cast irons
(white and gray, high-temperature thermite and
high-duty) where under investigation, besides synthesized tool materials has
been investigated: tool thermite carbon steels,
high-speed steels, alloyed hard wolfram-cobalt alloys and carbide steels.
Microstructures of above mentioned alloys have been analyzed, mechanical, and
technological and service features.
The
investigations allowed detecting the peculiarities of these materials, in the
first turn, heightened viscosity (connected, obviously, with deoxidization by
aluminum which is in the composition of the burden), as well as fine-grained
structure.
While using
high-overheated alloys for heating of metallothermite
addition of large cast iron moldings and high-alloy steels in serial and mass
production improved method of burden calculating has been proposed. Synthesized
high-overheated iron-carbon alloys are fit to thermite
welding of blanks and instrumental alloys-for metallurgic welding together of
instrumental plates to the base of the tool.
Colored thermite metals (bronze and brass) are also investigated in
the article, the usage of thermite color alloys for
improvement of feeding of bronze moldings on fluid metal. Experimental
investigations on layout in strengthening of cast iron moldings by exothermic
doping mixtures as well as the results of modifying within the inner cavity of
the form have been analyzed.
Foundry thermite
alloys are used limitedly in machine-building though the given method may due
to some preferences give an essential economical and technical effect in
solving of separate tasks in heavy branches of techniques. First of all it is
high speed of burning process and simultaneously of technological melding the
absence of necessity of complex technological equipment (foundry furnaces,
autoclave with temperature control, pressure and composition of medium); the
absence of necessity of huge courses of electrical energy (thermite
methods of melding demand energy only for initiating of the reaction),
universality of the method. Besides, the given methods permite
to use waste materials of metallurgical thermic and
metal cutting industries (iron scale, grist of aluminum and manganese chip,
grist of waste materials of graphite electrodes, riddling of alloying
composition, modificators, dust out of the filters in
metallurgical industry, etc.). Its worth noting that this methods become
economically useful while it is necessary: to obtain cast blanks of spare parts
urgently under conditions for away from industrial centers, making of blanks of
conditions of experimental production; besides exothermic mixtures made for
methods mentioned above may be applied for technology of exothermic founding
editions of high temperature gradient which allow not only to economize fluid
metal but to improve metal properties of subadditional
zone (in the first turn mechanical) and to improve microstructure with odificatothe help of microdoping by aluminum
and alloying composition or mrs.
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