Технические науки/1. Металлургия

Zhiguts Yu., Levdar K.

Uzhhorod National University, Ukraine

THERMITE FOUNDRY PROFIT FOR SUPPLY OF HIGH-ALLOYED STEELS

Introduction. Termite foundry profits are used to feed castings by using different types of exothermic mixtures [1]. But these mixtures cannot be used to supply liquid metal castings from high-alloy steels due to high segregation and a number of other technological reasons. Exactly then, the alloying of steel with an exothermic mixture, for example, ferromanganese in a ladle is used [2]. A disadvantage of these and similar mixtures [3, 4] is the use of alloying elements in them, while metallothermic reactions allow them to be recovered from cheaper and less scarce raw materials. The industry uses special also foundry moulds, the design of which allows for an in-mould process (modification in the internal cavity of the mold), in which the liquid steel is alloyed additionally by additives directly in the mold system [3]. A drawback of this method is the need to provide in the gating system a reaction chamber-pit in which the alloying additive interacts with the melt of the steel. This use of such a pit chamber significantly complicates the moulding process and leads to a "meltdown" of the melt.

The aim was the research to obtain high-manganese steel from a metallothermic charge using manganese from metallurgical waste. The metallothermic mixture was planned to be used to heat up profits in the technology of thermite casting profits of a high temperature gradient. This technology makes it possible to significantly save the liquid melt and eliminate shrinkage defects, in addition to heating the profit-making zone and feeding steel casting of the same chemical composition as steel poured into the mold. The theoretical basis is the development for the solution of the problem of exothermic powder mixtures for heating the metal by initiating the high-temperature metallothermic reaction process and conducting it [5-9].

Experimental research. Several plants were used to blow steel 110G13L for the production of track tractor tracks in the experimental industrial conditions. The necessary amount of aluminum chips was determined (with a purity of 93-95% in metallic aluminum) per 1 kg of manganese dust by calculation from the stoichiometric ratio of the reactions. We get that for 1 kg of manganese dusts, 230 g of metallic manganese and 139 g of metallic iron are recovered. Accordingly, to produce high-manganese steel with 12% Mn, it is necessary to introduce into the system 1917 g of iron (including 139 g of manganese dusts), that is, 1,548 g of iron from the thermite mixture.

It is known that the yield of termite iron from the batch is approximately 50% of the standard iron-aluminum termite (75% Fe₂O₃+25% Al). Then, in order to carry out the carburization of 1917 g of thermite steel, it is necessary to introduce 1,2% C into it, taking into account the carbon monoxide – 7%. This gives 24,5 g of carbon in the form of graphite. In general, the following composition of the metallothermic charge (g) is obtained from the reagent per 1 kg of manganese dusts: iron-aluminum termite – 3100,0; manganese dusts – 1000,0; aluminum powder – 150,0; the carbon powder – 24,5; or in % by weight: iron-aluminum termite – 72,5; manganese dusts – 23,4; aluminum powder – 3,5; the carbon powder is 0,6.

The melting was carried out on the basis of the charge of the above calculated composition in a special open-type metallothermic reactor [10] in the foundry laboratory. The mixture was ignited with a powder of titanium, which, in turn, was lit with an ordinary match. Titanium was then burned to TiO₂ and not reduced by aluminum, so it got into the slag, and not into thermite high-carbon steel. The high manganese steel received ingot weighing 1,5 kg. The steel “110Г13Л” is obtained within the limits of the chemical composition regulated by the standard, as can be seen from the data given. The study of mechanical properties confirmed that the melted thermite steel has strength not lower, and the toughness is higher (by 14%) than in industrial steel of a similar grade (as shown in table 1). The first experiments were not carried out, the calcination of manganese dust, which led to a higher content of sulfur and phosphorus in steels. In batches is taken into account this subsequent.

Table 1

Physical and mechanical properties of the thermite steel “Г13Л”¹

Specific weight, kg/m^3(×10^3)	σb, MPa	δ	Ψ	аn, MJ/m^2	Linear shrinkage, %
		%
7,81	840	27	34	2,7	2,1

¹The thermic treatment of steel was in quenching with 1050ºC followed by cooling in water.

Conclusions. 1. Each ton of manganese dust allows to return to production about 230 kg of manganese. 2. The method proposed for synthesizing high-alloy steels makes it possible to obtain repair casting from steel “110Г13Л” (“110Г12Л”) in workshops and other production facilities that are not suitable for conventional methods of steel melting. 3. This method is suitable also for thermite welding of parts made of high-manganese steel, in the long term. 4. The problem of supplying castings with thermite casting profits of a high-temperature gradient is successfully solved under conditions of mass production and mass production using the developed exothermic mixtures and high-temperature termite manganese steel.

Literature:

1. Zhiguts, Yu.Yu. Technologies of obtaining and features of alloys synthesized by combined processes [Text] / Yu.Yu. Zhiguts, V.F. Lazar. – Uzhhorod: Invasor, 2014. – 388 p. ISBN 978-966-8224-74-4.

2. The patent of Ukraine No. 49264 A IPC 7С22С1 / 00 Exothermic mix for feeding high-alloy steels [Text] / Yu.Yu. Zhiguts. 16.09.2002; - Bul. №9.

3. Patent of Ukraine. No. u 200606530 A IPC: В22С9 / 00 Metalothermic reactor [Text] / Yu.Yu. Zhiguts, Yu.Yu. Skyba, 15.01.2007. - Bul. № 1.

4. Zhiguts, Yu., Lazar V., Skyba Yu. Novel technologies of synthesizing nihard by metallothermic methods / Intercollegiate collection of Lutsk National Technical University "Scientific Notes". – 2016. – № 54. – С. 130 - 134.

5. Patent of Ukraine. No. 50954 А, IPC 6 С22С1/05. Exothermic mixture for thermite casting applications / Yu.Yu. Zhiguts, Yu.Yu. Skyba; 15.11.2002. - Bul. № 11.