SU1654365A1 - Cast iron - Google Patents

Abstract

The invention relates to metallurgy, in particular to the search for corrosion-resistant cast irons. The aim of the invention is to increase the corrosion resistance of cast iron in an molten aluminum environment. The proposed cast iron contains, wt%: carbon 2.5 - 3.2; silicon 1.5-3.5; manganese 0.5 - 0.8; aluminum 1.5-3.5; chromium 0.5-0.8; niobium 0.3-0.5; iron and impurities else. The use of the proposed cast iron will make it possible to increase the service life of crucibles, which are of interest in the process of aluminum casting, by 202. 3 tab. SS

Description

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The invention relates to metallurgy, in particular, to the search for cruss-resistant cast irons.

The purpose of the invention is to increase the corrosion resistance of cast iron in the environment of molten aluminum.

Cast iron, carbon, silicon, manganese, chromium, aluminum and iron with impurities are additionally introduced with niobium in the following ratio of components, wt,

Carbon Silicon Manganese Aluminum Chromium, Niobium

Iron and impurities (sulfur up to 0.12 wt.%,

2.5-3.2 1.5-3.5 0.5-0.8 1.5-3.5 0.5-0.8 0.3-0.5

phosphorus to

0.20 wt.%) The rest

Carbon limits are limited by the need to prevent chill, reduce shrinkage and improve the processability of the iron. When the carbon content is below 2.5 wt.%, Cementite appears in the cast iron structure, which causes a decrease in strength properties. An increase in the carbon content of more than 3.2 wt.% Leads to the appearance in the steel structure of a large amount of graphite phase in the form of large lamellar precipitates and, as a result, to a significant decrease in mechanical properties.

Manganese at a content within the specified limits (0.5–0.8 wt.%) Contributes to the structure perlitization,.

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preventing the appearance of ferrite. The obtained castings are characterized by a uniform structure over the cross section and high height-resistance. In the structure of cast iron with a manganese content of more than 0.8 wt.%, Chill is observed, which leads to a decrease in strength properties. A decrease in the manganese content below 0.5% by weight leads to a decrease in the stability. This causes an increased distortion of cast iron castings during operation at elevated temperatures.

When the aluminum content is above 3.5 wt.% And silicon is above 3.5 wt.%, The mechanical properties of the alloys are drastically reduced. This is due to an increase in the proportion of free ferrite and graphite in the iron structure. With a decrease in the aluminum and silicon content below 1.5 wt.% And of chromium below 0.5 wt.%, The heat resistance deteriorates sharply. The introduction of chromium cast iron in an amount greater than 0.8 wt.% Causes chill, which leads. to reduce the strength characteristics. The introduction of niobium in the composition of iron in an amount of 0.3-0.5 wt.% Increases to a large extent corrosion resistance, mechanical properties,

promotes uniform distribution of the carbide phase in the alloy structure. In quantities smaller than 0.3 wt.% ,. its effect is negligible. The addition of niobium to more than 0.5% by weight is not advisable, since the corrosion resistance remains almost unchanged.

Example. To confirm the substantiation of the selected limits of the content of the components, the iron is smelted, the chemical compositions of which are presented in Table. 1, and mechanical and corrosion testing of the samples was carried out. The test results are presented in Table. 2. Along with experienced cast iron, smelting and testing of famous cast iron is carried out. Experimental melting is carried out in an acid lined induction furnace. The raw materials used are cast iron LK4, steel scrap, pig aluminum A99, ferrosilicon FS75, ferrosilicochromium PECH3 and ferroniobium FN4. Ferro-Iiobium, ferrosilicochrome, ferrosilicon are fed into molten iron. Solid aluminum is introduced into the crucible at the end

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melting The superheat temperature is 1723 K, the pouring temperature. 1623-V653 K.

Test specimens are cast in dry sandy clay forms. The tensile strength (GB) is determined on standard specimens by standard methods. Corrosion resistance is determined by a gravimetric method when testing samples with a diameter of 10 mm and a height of 20 mm in molten aluminum at 1073 K for 200 hours. Aluminum sticking to the samples during the test process is removed by poisoning with a 10% aqueous solution of NaOH. Heat resistance is determined by a gravimetric method according to a known method at 1073 K for 200 h.

From the analysis of the test results given in table. 2, it follows that the optimal set of mechanical and corrosion properties are samples of the proposed iron.

The results of comparative tests of crucibles made from the proposed and famous cast iron | are given in table. 3

The results show that the proposed cast iron compared with the known has a higher corrosion resistance in the environment of molten aluminum. This makes it possible to use it as a material for distributing crucibles for melting aluminum and its alloys. Aluminum castings, obtained in the process of production using crucibles from the proposed pig iron, have higher strength and plastic properties due to a decrease in the contamination of aluminum by corrosion products entering the melt as a result of dissolving the walls of the crucibles.

Claims (1)

Invention Formula Cast iron containing carbon, silicon, manganese, aluminum, chromium and iron, characterized in that, in order to increase the corrosion resistance in the environment of molten aluminum, it additionally contains niobium in the following ratio of components, wt.%: Carbon2.5-3.2 1.5-3.5 0.5-0.8 1.5-3.5 2.5 1.5 Chrome 0.5-0.8 Niobium 0.3-0.5 IronErest Table 1 1.9 0.5 0.5 0.4 Rest table 2 Table 3