Технические науки

Металлургия

Zhiguts Yu.Yu., Skyba Yu.Yu., Shubert V.V., Pylypko P.V.

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

CHILLED 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.

1 Introduction

The important problem for modern production is not only making up new materials and improving the properties of traditional ones but also supplying of the production with spare parts and tools of non-common applying, the need of selfproviding of those appears at small enterprises and in the shops where required base is absent. Deep studying of the question makes it possible to consider that the problems mentioned above can be solved successfully when using as machine-building alloys the materials got by the process of burning of exothermic powder mixtures. This method can be successfully used also for metal economy at the plants of large scale and mass production of machine-building parts and tools.

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 [2-4]. The main structure components in thermite cast irons that influence greatly the wear resistance are the carbides. First of all these are cementite and more wear resistanceable carbides Cr, W, Mo, Ti and others.

Wear resistance of synthesized cast irons under abrasive wear resistance depends on microhardness, form, replacement and quantity of structural components.

3. The directions of studies

Synthesized thermite wear resistant cast irons in analogy with the cast irons dot by ordinary methods, can be divided into the following groups: grey, white, including non-alloyed, low-alloyed, nickel-chromium-plated; martensite and high chromium-plated.

The burden composition for synthesis, chemical composition and components of the burden for getting wear resistant thermite cast iron are shown in table 1 and 2.

Chilled cast has increased wear resistance and is easy to get under conditions of micromelting.

Table 1

Chemical composition of chilled termite wear resistant cast iron

№	Element content, %							HB
	С	Si	Mn	Cr	Ni	S	P
1	3,4–3,5	1,5–1,9	0,5–0,8	0,5	0,5	<0,1	<0,2	–
2	3,5	1,1	0,8	0,5	0,5	<0,1	<0,2	–
3	3,5	0,9	0,5	1,0	–	<0,1	<0,3	440–470

The analysis shows that in the surface layer of termite cast irons the content of cementite is not less than 50 % that leads to microhardness from 1000 to 1050 HV.

Table 2

Burden composition for synthesis of chilled termite wear-resistant cast iron

№	Electrode power, %	Ferrosilicium (ФС 75)	Ferromanganese (ФМн 75)	Powder Ni	Ferrochromium (ФХ 100А); Ferromolibdenum (ФМ 055А)	Ferroaluminium termite
1	4,2–4,4	2,0–2,6	0,7–1,1	0,5	0,7	the rest
2	4,4	1,5	1,1	0,5	0,7	the rest
3	4,4	1,5	0,7	–	1,4	the rest

With the increasing of alloying element content consecutive changes in the structure, which comes from perlite to martensite take place, which in its turn leads to increasing of hardness as well as to the increasing of wear resistance.

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.

References

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