Технические науки
Металлургия
Zhiguts Yu.Yu., Dragula E.Yu., Tcsiganin Yu.B.
THE WORKABILITY AND
RELATIVE WEAR RESISTANCE THERMITE SPECIAL CAST IRONS
Abstract
The given paper
deals with the problems of the synthesis of cast iron by metallothermy.
On the basis of investigated method of calculations structures of charges have
been arranged and cast iron has been synthesized further. Peculiarities
metallothermic smelting were found, mechanical properties and structure of
received cast iron were investigated and different technologies for cast iron
receiving were worked out.
1
Introduction
Metallothermic reactions further and further
become of great appliance in science and technology. Under the lack of
energetic and raw basis, of special melting and cast equipment such
technological processes of creating the materials become economically
expedient, and their usage in already existed methods of casting production e.
g. in technique of producing steel and cast iron castings with thermite
addition greatly rises the efficiency of production.
2.
The methods of experiment
While
organizing the process of synthesis of steels and cast irons classic [1]
thermite reactions based on oxidation of aluminum and renovation of iron are
used Fe3O4+Al→Fe+Al2O3. The
task was to work up the method of calculating of burden composition on the
basis of stechiometric relationship of reaction components with the
introduction of suitable coefficients taking into account the component
activity and the coefficients of its adoption by metal. The method allows to
establish the composition of metalthermic burdens and to calculate adiabatic
temperature of its combustion. The main condition of the process is the
necessity to have real temperature of burden combustion higher then the
temperature of slag melting [2-6].
Introducing additionally into
the burden even a small quantity of chromium in powder state or in the state of
low carbon ferrochromium using breakage of graphite electrodes increase greatly
wear resistance of mentioned cast iron. Using roengenostructural analysis
method in the structures of these cast irons carbides Fe3C and (Fe,Cr)3C as well as carbides (Fe,Cr)C3
and others were detected, that provides the hardness of ~ 15000MPa.
Microhardness of carbides (FeCr)3C – HV
10000–10500 MPa, (FeCr)7C3 and (Fe, Cr)23C6
14500–17500 MPa. The workability and relative wear resistance of synthesized termite alloyed cast irons are shown in tables 1 and 2.
Table 1
Termite alloyed cast iron workability
|
№ |
Mark |
HRC |
Velocity of cutting***,
m/min |
|
1 |
ИЧХ28Н2* |
57–59 |
9,2 |
|
2 |
ИЧХ12М** |
38–40 |
24,8 |
|
3 |
ИЧХ2Н4* |
58–62 |
10,1 |
|
1 |
ИЧХ28Н2* |
57–59 |
9,2 |
*Tempering at 350 oC, 3 hours.
**Unnealing.
***Cutting velocity at 90 minute resistance of
cutting tool at S=0,3 mm/rev; t=2mm.
Table 2
Relative wear resistance of termite alloyed
cast irons
|
№ |
Mark |
Relative wear
resistance coefficient* |
|
1 |
ИЧХ28Н2 |
7,8–8,3 |
|
2 |
ИЧХ12М |
14–16 |
|
3 |
ИЧХ2Н4 |
6,9–7,2 |
*The probation was conducted under grinding with
cup wheel, cutting velocity being 7 m/sec, pulp, quartz sand and water
(correlation 1:2 by volume), wear resistance of steel of mark «Сталь10» after normalization was adopted as 1,0.
4 Conclusion
Thus we may make a conclusion that aluminothermic
ways can be used for producing of special thermite alloyed cast irons expect
for high-chromium cast irons during the synthesis of those the problems of
technological character appear. Other types of special cast irons have in some
cases even better properties than in cast irons produced by ordinary methods.
Designed compositions of thermite mixtures are
also suitable for technology of thermite casting additives of high-temperature
gradient. The work that has been carried out allows making a conclusion that
for their mechanical properties synthesized specialized cast irons don't yield
to "common" and the methods themselves are available for synthesis in
principle of any black alloy.
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