RU2026405C1 - Cast iron - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: cast iron containing carbon, silicon, manganese, nitrogen and iron has additionally one or more components taken from the group containing aluminium, titanium and zirconium nitrides at the following ratio of components, wt.-%: carbon 2.6-4.8; silicon 0.5-3.6; manganese 0.15-2.0; nitrogen 0.008-0.05; nitrides of aluminium, titanium, zirconium 0.005-0.15, and iron - the rest. Addition of aluminium and/or titanium and/or zirconium nitrides ensures to increase dispersity of graphite inclusions and decrease tendency of cast iron to the chill. EFFECT: enhanced quality of cast iron. 1 tbl

Description

 The invention relates to metallurgy and foundry, in particular to the development of cast iron compositions for metallurgical and engineering castings.

 Known cast iron, containing, wt.%: Carbon 2.5-3.75; silicon 0.5-2.5; manganese 0.3-1.0; sulfur up to 0.15; phosphorus up to 0.2; nitrogen 0.0-5 0.1; iron and impurities - the rest [1].

 The disadvantage of this cast iron is its high tendency to bleach.

 Cast iron is also known, containing, wt.%: Carbon 3.4; silicon 2.43-2.62; manganese 0.7-0.8; phosphorus 0.2; sulfur 0.06-0.11; nitrogen 0.0074-0.028; iron - the rest [2].

 This cast iron has the same drawback as the one mentioned.

 The closest in composition to the claimed is cast iron, containing, wt.%: Carbon 2,8-4,0; silicon 1.0-4.0; manganese 0.1-2.0; nitrogen 0.005-0.04; iron and impurities - the rest [3].

 The disadvantages of this cast iron are the low dispersion of graphite inclusions and the high tendency to form bleached due to weak nucleation.

 The aim of the invention is to increase the dispersion of graphite inclusions and reduce the tendency of cast iron to bleach.

 To achieve this goal, in the cast iron containing carbon, silicon, manganese, nitrogen and iron, nitrides of aluminum, titanium, zirconium are additionally introduced in the following ratio of components, wt.%: Carbon 2.6-4.8 Silicon 0.5-3, 6 Manganese 0.15-2.0 Nitrogen 0.008-0.05 Nitrides of aluminum, titanium, zirconium 0.005-0.15 Iron The rest.

 The nitrides of aluminum, titanium, zirconium are refractory and chemically neutral with respect to the elements of cast iron and manifest themselves as heterogeneous nuclei for the crystallization of graphite inclusions. An increase in the amount of the germinal phase in cast iron increases the dispersion of graphite inclusions and reduces the tendency of cast iron to bleach.

 When the nitride content in cast iron is less than 0.005 wt.%, The purpose of the invention is not achieved, since their number is insufficient to effectively influence the crystallization of cast iron (see table, experiment No. 18). When the nitride content is more than 0.15 wt.%, The dispersion of graphite inclusions decreases due to the formation of macrosegregations of nitrides (see table, experiment 21).

 Carbon is a part of cast iron as a graphitizing element. The optimum carbon content of cast iron is 2.6-4.8 wt.%. When the content is less than 2.6 wt.% Carbon, the tendency to bleach cast iron increases due to a decrease in the ability of the alloy to graphitize (see table, experiment 2). An increase in carbon content of more than 4.8 wt.% Is accompanied by a decrease in the dispersion of graphite inclusions due to a violation of the ratio between graphitizing and perlitizing elements in the composition of cast iron (see table, experiment 5).

 Silicon is part of cast iron as a graphitizing element. The optimum silicon content in cast iron is 0.5-3.6 wt.%. When the silicon content is less than 0.5 wt.%, There is no reduction in the tendency of cast iron to bleach due to the reduced ability of the alloy to graphitization (see table, experiment 6). An increase in silicon content in excess of 3.6 wt.% Is accompanied by an enlargement of graphite inclusions, since silicon reduces the solubility of carbon in iron (see table, experiment 9).

 Manganese is part of cast iron as a perlitizing element. When its content is less than 0.15 wt.%, The dispersion of graphite inclusions is not increased due to the high carbon activity in iron (see table, experiment 10). When the manganese content is more than 2.0 wt.%, The tendency of cast iron to bleach increases due to an excessive decrease in the activity of carbon in iron with manganese (see table, experiment 13).

 Nitrogen is part of cast iron as a perlitizing element, its optimal content is 0.008-0.05 wt.%. When the nitrogen content is less than 0.008 wt.% Does not provide an increase in the dispersion of graphite inclusions (see table, experiment 14). When the nitrogen content is more than 0.05 wt.%, The tendency of cast iron to bleach increases due to the stabilizing effect of nitrogen (see table, experiment 17).

 Iron is the basis of cast iron.

 PRI me R. Checking the advantages of the invention was carried out by performing experiments on obtaining in the conditions of the pilot production of the Institute for Casting Problems of the Academy of Sciences of Ukraine the inventive and known cast irons. The experimental conditions were maintained identical in all cases. From cast iron, castings and process samples were obtained, which evaluated the tendency of cast iron to bleach and the dispersion of graphite inclusions.

 The metal melts are made in an induction furnace with an acid lining. The mixture, consisting of pig iron, steel scrap and ferroalloys, was melted, nitrided with carbamide, then when the metal was poured from the furnace into the ladle, briquettes obtained by powder metallurgy from aluminum, titanium, zirconium nitrides were introduced into the bucket. In experiments with cast iron of known composition, nitrides were not introduced into cast iron. The nitride powders used to produce the said briquettes had particle sizes of 50 μm or less. Thus prepared cast iron was poured into molds. After natural cooling of the castings, they were cut and studied the microstructure and measured the depth of bleached.

 The results of the experiments are shown in the table. A comparative analysis of the data shows that cast iron of the claimed composition has a high dispersion of graphite and a low tendency to bleach. So, in comparison with cast iron of known composition, the average length of graphite inclusions decreased by 15-55 microns, the bleached depth decreased by 3-13 mm.

 Experiment 1 was performed with cast iron of known composition, experiments 2-23 with the claimed. In experiments 2, 5, 6, 9, 10, 13, 14, 17, 18, 21, the objective of the invention was not achieved, since the content of cast iron components went beyond the claimed limits. The following notation is used in the table: H - depth of bleached cast iron, mm; L is the average length (dispersion) of graphite inclusions, microns.

Claims (1)

PIG IRON containing carbon, silicon, manganese, nitrogen and iron, characterized in that it additionally contains one or more components from the group consisting of aluminum, titanium, zirconium nitrides, in the following ratio, wt.%:
Carbon - 2.6 - 4.8
Silicon - 0.5 - 3.6
Manganese - 0.15 - 2.0
Nitrogen - 0.008 - 0.05
One or more components from the group comprising aluminum, titanium, zirconium nitrides - 0.005 - 0.15
Iron - Else

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