Технические науки

Металлургия

Zhiguts Yu.Yu., Legeta Ya.P., Petrov O.P.

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

GREY THERMITE CAST IRON FOR NEEDLE STRUCTURE

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. 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] (for Al₂O₃ 2400 K).

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.

3. The directions of studies

Grey thermite cast iron is being manufactured very well by cutting, much more better than chilled and white cast irons. The burden composition for synthesis, chemical composition and components of the burden for getting wear resistant thermite cast iron and its mechanical properties are shown in table 1 and 2

The composition of burden and chemical composition of thermite wear resistant cast irons with needle structure is shown in tables 1 and 2.

Table 1

Chemical structures of burden for synthesis of thermite wear resistant cast irons with needle structure

№	Electrode powder, %	Ferrosi-licium (ФС 75)	Ferroman-ganese (ФМн 75)	Powder Ni	Ferrocromium, (ФХ100А) Ferromolibdeni-um (ФМО55А)	Alloying composition «ЖКМК» (nominator) WO3 (denominator)	Ferroalumi-nium thermite
1	3,6–4,2	2,8–3,5	0,4–0,7	1,2–2,1	0,3 FeСr; 0,5–1,0 FeMo	0,3 –	the rest
2	3,5–4,2	2,7–3,4	0,7–1,2	1,5–2,7	0,3 FeCr; 0,5–0,9 FeMo	0,3 –	the rest
3	4,0–4,5	3,0–3,6	0,8–1,8	2,5–3,6	0,3 FeCr; 0,4–0,8 FeMo	0,3 –	the rest
4	4,4–4,7	3,2–3,5	1,2–1,8	2,8–3,9	0,3 FeMo; 0,5–0,7 FeCr	0,3 ̣ 3,0–5,1	the rest
5	3,9–4,5	3,0–3,4	0,4	2,5–3,1	0,3 FeCr; 0,6–0,9 FeMo	0,3 ̣ 2,5–2,8	the rest

Table 2

Chemical composition of thermite wear resistance cast iron with needle structure

№	Element content, %
	С	Si	Mn	P	S	Cr	Mo	No	Mg and W
1	2,9–3,4	2,1–2,6	0,3–0,5	<0,03	<0,01	0,2	0,5–1,0	1,0–2,0	0,1 Mg
2	2,8–3,3	2,0–2,5	0,5–0,9	<0,03	<0,01	0,2	0,5–0,9	1,5–2,5	0,1 Mg
3	3,2–3,6	2,2–2,7	0,6–1,3	<0,03	<0,01	0,2	0,4–0,8	2,5–3,5	0,15 Mg
4	3,3–3,7	2,4–2,6	0,9–1,3	<0,03	<0,01	0,2	0,5–0,7	2,8–3,8	3,0–5,1 W
5	3,1–3,6	2,3–2,5	0,3	<0,03	<0,01	0,2	0,6–0,9	2,5–3,0	2,5–2,8 W

For these types of cast irons the content of carbon, silicon, Mn and Mo is increased with the aim to get needle structure [3]. Under the synthesis of cast iron by aluminothermic method the oxides of Mo and W may be added to increase greatly the temperature of reaction and form better conditions for controlling the process of synthesis and melting. Synthesized cast irons have the hardness HB 280–340 and are rather well manufactured by cutting.

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

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

1. Жигуц Ю.Ю. Термитные нихарды, синтезированные металлотермией// Вісник СумДУ. − Суми. − 2005. − №1(73). − С. 157−161.

2. Жуков А.А., Семенов А.Н., Жигуц Ю.Ю. Полосчатое строение литого металла и инверсия микроструктуры карбидной эвтектики в сплавах Fe-С// Изв. ВУЗов. − Черная металлургия. − 1987. − № 9. − С. 139−140.

3. Патент України №50954 А МПК: 6С22С1/05. Екзотермічна суміш для термітних ливарних додатків// Ю.Ю. Жигуц, Ю.Ю. Скиба Опубл. 15.11.2002; − Бюл. №11.