Технические науки

Металлургия

Zhiguts Yu.Yu., Legeta Ya.P., Lendel I.V., Marushka V.V.

Uzhgorod National University, Uzhgorod, Pidgirna str. 46, 88000, (Ukraine)

TERMITE HIGHLY ALLOYED CAST IRON

Abstract. The given paper deals with the problems of the synthesis of cast iron by metallotermy. On the basis of investigated method of calculations structures of charges have been arranged and cast iron has been synthesized further. Peculiarities metallotermic 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. Metallotermic 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 termite 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] termite reactions based on oxidation of aluminum and renovation of iron are used. 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 metaltermic 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 [2-4] (for Al₂O₃ 2400 K).

If we assume that synthesized termite cast irons of carbide class have one-type phase composition, then to determine its ware resistance will be possible using the scheme: the more is their hardness, the more is the wear resistance.

3. The directions of studies. Under the synthesis of white termite cast iron the necessity to get high temperature in the zone of reacting of burden components is considered, that is why Cr and Mn are introduced not in the shape of ferroalloys but like oxides Cr₂O₃, CrO₂, MnO, MnO₂. Pearlite matrix of such cast iron contains carbides Cr and Fe. Under considerable gradient of temperatures under termite conditions micromelting white cast iron is produced in large measure simply, simultaneously it is the cheapest among the cast irons mentioned above, but its wear resistance is less then that of the alloyed one. 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. Chemical composition of burden and composition of ingots, the properties of some marks of termite cast irons are shown in tables 1, 2 and 3.

Table 1

Chemical composition of burden for synthesis of special termite cast iron

Mark	Electrode powder , per cent	Ferrosilici-um (ФС 75)	Ferromagne-se (ФМн 75)	Powder Ni, B, Cu	Ferrochromium (ФХ 100А); Ferrotitanium (ФТи 055А)	Ferroalumi-nium termite
“OИ-1”	2,6–3,1	1,6–2,4	0,2	0,1–0,4	–	the rest
“OИ-3”	2,6–3,1	1,3–2,0	0,7–1,3	0,1–0,4	2,0–2,6 FeTi	the rest
“ИЧХ4Г7Д”	2,6–3,1	2,0–2,6	8,0–10,0	>0,8Ni, Cu	10,0–12,9 FeCr	the rest

Table 2

Chemical composition and the properties of medium alloyed termite cast irons

Mark

Element content, %

Mechanical properties

С

Si

Mn

S

P

Cr

Ni

Ti

Cu

sв, MPa

su, MPa

Hardness

“OИ-1”

2,5–3,0

1,2–1,8

>0,1

0,1

0,1

–

–

–

–

230

550–710

47–52 НRC

“OИ-3”

2,5–3,0

1,0–1,5

0,5–1,0

0,1

0,1

–

–

0,7–0,9

–

210–250

580–700

47–52 НRC

“ИЧХ4Г7Д”

3,0–3,5

1,5–2,0

6,0–7,5

0,05

0,1

3,5–4,5

>0,5

–

>0,7

175

370

500–550HB

Table 3

Mechanical properties of termite highly-alloyed cast irons

Mark^*	HRC	su, MPa
“И4Х12М”*	65–67	670
“ИЧХ12Г5”*	64–66	680
“ИЧХ28Н2”	53–57	620

^*After proper thermal treatment.

It is necessary to mention that mechanical properties of termite cast iron are better than the properties of highly-chromium cast iron because of additional microalloying by aluminum, which must be introduced into the burden composition. Within cast irons with a considerable content of manganese disregarding high temperatures of synthesis one can see the aggravation of fluidity under the keeping of shrinkage within the range of 1,6–2,2 %. Cast iron «ИЧX12M» are annealed (for getting the structure of grain perlite) with further hardening. Cast iron «ИЧX12Г5» with the structure of alloyed austenite are hardened in an open air and «ИЧX28H2» are treated under the medium-temperature tempering.

4. Conclusion. Thus we may make a conclusion that aluminotermic ways can be used for producing of special termite 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.

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