SU1211325A1 - Method of inoculating iron-carbon alloy - Google Patents

Description

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The invention relates to foundry and can be used to process a liquid melt using modifying mixtures.

The purpose of the invention is to increase the absorption of magnesium, the elimination of chill in the iron structure and the improvement of its mechanical properties.

Fine magnesium-containing modifying mixture is loaded at the bottom of a hot dipper. Before filling the ladle with an alloy, a layer of powdered fluorspar with a thickness of 1-10 mm is applied to the surface of the modifying mixture. At the same time, the residence time of the modifying mixture in hot air before filling it with an alloy should not exceed 5 minutes.

The technical implementation of the proposed method lies in the fact that a finely dispersed magnesium-containing modifying mixture is placed at the bottom of a heated bucket up to 800 ° C and above. The surface of the latter is then coated with powdered fluorspar, which is not wetted by cast iron. The ladle is filled with melt. Due to the fact that the liquid metal does not wet the powdered fluorspar, the flotation force arising at the metal-material interface keeps the mixture on the surface of this section and prevents it from flowing into the iron.

When the evaporation temperature of magnesium in the mixture reaches, it diffuses into the volume of the metal, and the filler, together with the deposited fluorspar, slags and floats up, passing through the entire volume of the metal, refining it. The protective layer of fluorspar creates a certain delay in the beginning of the interaction of the modifying mixture with the mixture, thereby increasing the layer of pig iron over the magnesium-containing modifying mixture, which in turn leads to an increase in the absorption of magnesium by the iron. The elimination of the supply of bell-shaped devices or a carrier gas to the melt during the injection of the modifier into the melt contributes to an increase in the temperature of the casting of iron into the mold. This ensures the production of castings without chill in thin sections.

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The change in the rate of modification is influenced by the thickness of the coating layer of fluorspar, with an increase in which the delay time of the beginning of the process of interaction of the cast iron with the mixture increases. When the coating layer is less than 1 mm thick, there is no delay in the start of the interaction process. In contrast, with a thickness of

 A strong pyroelectric effect occurs with a cast iron spike due to an increase in the residence time of the mixture in the heated ladle. When the modifying mixture is in the heated ladle for more than 5 minutes, the magnesium in the mixture interacts with the oxygen of the air, as a result of which the modifying mixture smolders and pours the cast iron into

20 bucket during smoldering of the mixture is not recommended, as intense metal emissions from the bucket may occur during pouring.

The proposed method is checked in

 manufacturing conditions. Cast iron is melted in a 6 ton cupola with two rows of tuyeres. The temperature of the cast iron at the release is in the range of 1380-1420 C. The initial chemical

30 composition of cast iron is as follows, rtac.%: C 3.16, Si 2.34; Mp 0.60. P 0.08; S 0.10. The prepared magnesium-containing modifying mixture is placed on the bottom of a heated ladle.

35 The composition of the modifying mixture,%: Magnesium 6 Silicocalcium 15 Silikomyelmetal 20 Fluorspar 8

40 cast iron

shavings Else The modifying mixture is coated with fluorspar powder. Mixture consumption 2% by weight otrabaty-

45 of the cast iron. The time the mixture is in the heated ladle before it is filled with metal is different. The thickness of the coating layer of fluorspar is 1-11 mm. Modification of cast iron is carried out

5Q in a 1.5 ton bucket. After loading the modifying mixture and applying a coating layer of fluorspar, open the vane of the cupola and the bucket is filled with iron. Visually and with

The stopwatch start time and end time are measured using the stopwatch. The beginning of the modification corresponds to the beginning of the visible bubbling of the metal with magnesium vapor, the termination of the process corresponds to the termination of the bubbling of the metal.

The temperature of the cast iron, its structure after modification, the degree of absorption of magnesium by the cast iron, and the modification time according to the proposed method are given in Table 1.

A comparative test of two methods of modifying the pig iron of the proposed and known in identical conditions to reveal the positive effect of the proposed method was carried out.

According to a known method, 1% of a mixture consisting of 60% magnesium-containing additive and 40% of a low-melting flux is introduced into the heated ladle. Cryolite is used as a flux. Magnesium-containing additive consists of 6% magnesium brand MPF1 15% silicalc CK15; 20% silica gel of metal FSZORMZOB and 51% of cast iron chips. Fraction of a mixture of 0.01-2 mm. A well-mixed modifying mixture is compacted by tamping to form

calling a dense crust on its surface. Compaction time is 30 s. Magnesium smoldering (oxidation) was noted during compaction,

J crust formation on its surface is local. After the mixture is compacted, cast iron is poured into the ladle. In the processing of cast iron observed. It has a strong pyro effect. Modified according to a known method, cast iron is poured technological samples for chemical, microstructural analyzes, as well as for determining mechanical properties.

f5 The test results of the known and proposed methods for modifying the cast iron are given in Table 2.

The magnesium absorption rate of cast iron 20 according to the proposed method for modifying iron-carbon alloys is more than three times higher and the structure of cast iron is obtained without chill, since it is free from cementite. Plastic properties are improved while simultaneously increasing the strength properties of the iron.

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Claims (2)

1. METHOD OF MODIFICATION OF IRON-CARBON ALLOYS, including loading finely dispersed magnesium-containing modifying mixture onto the bottom of the heated ladle, pouring alloy into the ladle, downloading slag and casting the alloy, characterized in that, in order to increase the absorption of magnesium, the iron is removed and its structure improved properties, a layer of powdered fluorspar 1-10 mm thick is applied to the surface of the magnesium-containing modifying mixture. 2. The method of claim 1, characterized by the fact that the residence time of the modifying mixture in the heated Bucket before filling it with the alloy is no more than 5 minutes.