SU1062293A1 - Modifier for cast iron - Google Patents

Abstract

A MODULATOR FOR CAST IRON, containing aluminum, bismuth, boron and iron, or for example, in order to improve the mechanical properties of ductile iron, it additionally contains rare earth metals, calcium and silicon at the following ratio of components, wt%: 8-15 1-4 Bismuth 1-4 Boron Rare-earth 10-20 Metals Calcium 20-40 Silicon Rest Iron

Description

The invention relates to ferrous metallurgy, more specifically to modifiers, and can be used in the manufacture of ductile iron castings. Modifiers are known that affect the primary crystallization and prevent the formation of primary graphite in cast iron, which affect the freezing and increase in the number of graphite centers and contribute to accelerating the annealing process of ductile iron. Known modifier l for cast iron of the following composition.Av, wt,%: Cerium15-20 Titanium. 10-20 Copper60-70 The disadvantage of the modifier is that it requires deficit and expensive copper. In addition, by providing fairly good durable properties of cast iron, the impact strength at its application remains low; The closest to the proposed technical essence and the achieved result is the complex modifier 2j, containing aluminum, bismuth, boron and iron with the following ratio of components, wt.% Of the weight of liquid iron .: 0.01-0.05 Aluminum 0.001-0.020 Bismuth 0.001-0.006 Boron Iron Else The disadvantage of the known modifier is that when it is used to produce ductile iron, both furnaces do not have the necessary level of mechanical properties, which is explained by the form of graphite inclusions — crab, and when aluminum is introduced, more than 0 , 02% n eobladaet plate shape. With the introduction of bismuth more than 0.005%, annealing is prolonged and the mechanical properties of cast iron are reduced, especially impact strength. The aim of the invention is to increase the mechanical properties: ductile iron. This goal is achieved by the fact that the modifier for cast iron containing aluminum, bismuth, boron and iron additionally contains rare earth metals, calcium and silicon with the following ratio of components, wt,% Aluminum 8-15 Bismuth. 1-4 OBOR1-4 Rare Earth Metals. RZM, 10-20 15-25 Calcium 20-40 Silicon Iron Else Modifier is prepared as follows. All components of the mixture are crushed to granules of 2-5 mm in size except for aluminum, which is introduced into tablets. Bismuth and aluminum are introduced in the form of technically pure materials, boron in the form of ferroboron or other boron-containing materials (boric acid, ferrosilicoboral, etc., REM - in the form of mischmetall or other materials containing REM, calcium, - in the form of silicocalcium and fluorspar in the ratio of 3: 1, respectively, silicon and iron in the composition of the modifying mixture is provided by silicocalcium, materials containing rare-earth metals and boron-containing materials. The modifying mixture, in amounts of 0.1-0.12% by weight of the liquid metal, is introduced into the carpet in paper during the filling with metal. The introduction of a modifying mixture into the metal in an amount of more than 0.12% by weight of liquid iron is not economically feasible, since it does not lead to a further increase in mechanical properties, moreover, an increase in the amount of modifying mixture can lead to the appearance of of graphite of the sammer, which sharply deteriorates the mechanical properties of ductile iron, .The introduction of a modifying mixture in. amount of 0.1% by weight of the liquid metal does not lead to a noticeable change in the mechanical properties of ductile iron. on. Fluorspar in the composition of the modifying mixture causes sparging of the metal, which provides better removal of non-metallic inclusions and more complete assimilation of the mixture components by the alloy. Calcium and rare-earth metals, which are introduced into the cast iron, refines the metal in terms of sulfur and gases, cleans the grain boundaries from low-melting compounds, thereby increasing intercrystalline bonds, provide a part of nonmetallic inclusions of a more compact and rounded shape, crush the structural components of the iron, which improves The mechanical properties of ductile iron, Oxisulfide REM and calcium contribute to an increase in the number of graphite centers and, therefore, reduce the diffusion path of carbon atoms, which, in combination with cleaner grays1 1 and grains accelerates the rate of diffusion of carbon and reduces the heat treatment cycle of white iron to malleable.

Silicon, being a graphitizing element, also contributes to the acceleration of graphitization.

The proposed modifier can be used in the production of white iron castings of the following composition, wt.%: C 2.2-2.8; P To 0.15; Si 1.01, 7; MP 0.4-0.7; S Up to 0.25, Cr 0.050, 2, which, after modification, is subjected to graphitizing annealing for ductile.

Example. In order to evaluate the effectiveness of the proposed mixture in comparison with the known one, special experimental melting of white cast iron was carried out in an induction 300 kilogram of an acidic lining furnace.

The modifying mixture is introduced in paper bags onto the metal jet when dispensed into the pouring ladles. Samples for mechanical testing and metallographic studies are poured into sandy-clay molds at the temperature of liquid iron.

The modifying mixture is introduced in an amount of 0.1-0.12% by weight of the molten iron. Modifying iron of the following composition, wt.%: C 2.45; Cr 0.07 Si 1.5, P 0.07; S 0.16, Mp 0.6, Re Else

Annealing of the samples is carried out on a ferritic structure.

Samples were tested for tensile strength, toughness and metallographic studies.

In tab. 1 shows the compositions used modifying mixtures, in table. 2 - physicomechanical properties of modified ductile iron, depending on the composition, enter Nbix modifying mixtures.

From tab. 1 and 2, it follows that ductile cast iron, modified in a known manner, with an increase in the content, 02 and B 0.005, has low strength / shock and ductility.

The malleable cast iron modified by the proposed modifying mixture has, with the same hardness with the cast iron, modified by a known method, enhanced mechanical properties: tensile strength 380 MPa, impact strength 850 kJ / m elongation of 12%.

Investigations of the rate of annealing of Chuguns modified by known and proposed modifiers were also carried out.

Studies have been conducted on cast irons of the following chemical composition. {; gab. H).

Studies are carried out in laboratory muffle furnaces. The cast iron of composition 1-3, modified with the known and proposed modifier, is annealed onto the ferrite structure. The first stage of annealing is carried out at 950-s and the second - with smooth cooling in the range of 76 ° -720 ° C. Special low-temperature treatment in the case of modifying in a known manner is carried out at 400 ° C for 2 hours, for the cast irons modified with the proposed modifying mixture, Special low temperature treatment is not carried out. 4 shows the results of research.

Thus, when using the proposed modifier, the duration of the heat treatment cycle was reduced by 15-20% compared with the use of the known composition of the modifier.

The economic effect of 120 thousand rubles per year per ton of metal

1811 10 15 20 Remaining 0.12

210 3 3 15 20 30 0.11

315 4 4 20 25 40 0.1

6

5 4

Table

Table 4

Claims (1)

(54) (57) MODIFIER FOR PIG IRON, containing aluminum, bismuth, boron and iron, characterized in that, in order to increase the mechanical properties of ductile iron, it additionally contains rare-earth metals, calcium and silicon, with the following ratio of components by weight. %: Aluminum 8-15 Bismuth 1-4 Boron Rare earth 1-4 metals 10-20 Calcium 15-25 Silicon 20-40 Iron Rest E2 SS ω from Λ hh