Технические науки/3. Отраслевое машиностроение
Zhiguts Yu.Yu.1, Hom’ak B.Y.2, Maioroshi Z.-R.L.1
1Uzhhorod National University, Ukraine
2Mukachevo State University, Ukraine
THE THERMITE CASTING STAINLESS STEELS
Introduction. Now
using in industry the chromium-nickel steels content a low nickel for the
manufacture of products resistant to corrosion are used. Examples of such
steels are the most common industrial grades “Х22Н5Т”, “Х21Н5Т”, “Х21Н6М2Т”, “Н18Н2Г8Т”,
etc. We know that the phase ratio in steels of the dual austenitic-ferritic class depends on the chemical composition of the
steel, on the heat treatment conditions, on the temperature pouring in the mold and can fluctuate in significant limits.
The metallothermic methods are developed for
the synthesis of materials, which differ from industrial methods, first of all,
by a number of advantages when applied in specialized conditions show many
works [1-3]. This is give possibility to synthesize materials by high speed and
productivity of the process, simplicity of technological introduction into
industrial production of a certain chemical composition in the absence of
powerful electric power sources, complex foundry equipment (furnaces and
ladles) and apparatuses for chemical synthesis (autoclaves).
The purpose of the work. The
main possibility of synthesis materials by metallothermic
methods of stainless steels of austenitic-ferritic
class, to reveal the features of their properties for subsequent use in the
production of castings is established.
Materials and methods of
conducting experiments. The essence of the metallothermic reactions consists in the reduction from the
oxide of a metal with a higher chemical activity of a metal with less activity.
Exothermic interaction of elements occurs in the case when as a result of the
reaction oxides with higher thermodynamic stability are formed. The aluminothermic reduction of metals and alloys is
significantly affected by the properties of the components contained in the metallothermic charge, their aggregate state, the
relationship between the components, the ignition circuits, etc. The mechanism
of the aluminothermic interaction is mainly described
in [1, 3].
Experimental research. The
feature of the thermite steels of the double austenitic-ferritic
class is the high value of the yield strength and strength, while maintaining
plasticity and resistance to impact by impact. These termite steels can
successfully replace industrial stainless high-alloy steels “Х18Н9Т”, “Х18Н10Т”,
“Х17Н13М2Т”. This research is comparative of the corrosion resistance of
thermite and industrial corrosion steels is shown in fig. 1.
Fig. 1. Dependence of corrosion of termite steels on
the action of nitric acid heated to 60°C during testing for 100 hours for a
thermite analogue: 1 ˗ “Х18Н9Т”;
2 ˗ “Х22Н5Т”, 3 ˗ “Х21Н5Т”
The stability was achieved by mechanical properties of thermite biphasic
steels only with a clear observance of the chemical composition, because in
them even deviations that are unimportant for steels of other classes lead to a
significant change in the phase composition. This influence is especially felt
when the content of alloying elements such as Ni and Ti
changes in steel. The experimental work was conducted on the study of thermite
two-phase stainless steels of austenitic-ferritic
grade, their tendency to embrittlement at 350 to 700°C was observed.
These thermal stainless steels improved their technological properties
in direct proportion to the temperature of steel heating during plastic
deformation, which is associated with an increase in the ferrite content in the
structure to 90% (by volume) at 800°C (for example, for the thermite steel “Х18Г8Н2Т”).
This is improvement in technological properties is limited by the possibility
of structural changes in steel. In addition, high temperatures lead to an
increase in the grain score and, as a consequence, to a decrease in plasticity
in the range of 350-700°C.
Conclusions. 1.
Authors has been established that the metallothermic
method can be successfully used for the production of thermite two-phase
stainless steels of austenitic-ferritic grade. 2. The
research has revealed mechanical
properties of thermit steels, analogs of industrial
grades “Х22Н5Т”, “Х21Н5Т”, “Н18Н2Г8Т”, namely, an, σв,
σ0,2, δ, have been revealed and their variation has been
studied depending on the nickel content in the alloy. 3. The increased in the
nickel content leads to an increase in the toughness of the alloy, and this is
most likely due not only to an increase in the content of doped ferrite and
austenite, but also to an increase in the volume of the doped austenite phase.
Literature:
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alloys synthesized by combined processes [Text] / Yu. Yu. Zhiguz,
VF Lazar. - Uzhhorod: Invasor,
2014. - 388 p.
2. Zhigus, Yu. Method of calculation of composition of
exothermic charges on the basis of thermochemical analysis [Text] / Zhiguz Yu., Shirokov V. //
Machine Science. - 2005. - No. 4. - P. 48 - 50.
3. Zhiguts, Yu. Yu. Technology of obtaining termite
high-temperature alloys on a nickel basis [Text] / Yu.Yu.
Zhiguz, D.F. Chernega, V.F.
Lazar // Scientific Bulletin of the Mukachevo State
University. Journal of scientific works. - 2012. - No. 12 (7). - pp. 5 - 12.