SU1027261A1 - Modifying mixture - Google Patents

Description

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The invention relates to foundry, is intended for the processing of cast iron by means of intra-form modification and can be used in foundries of machine-building plants for the production of nodular cast iron (HF) with spherical graphite.

Various modifiers are used to obtain HF by modifying the cast iron in the mold. They contain magnesium, calcium, rare earth metals (REM) and other components 1.

Modification of cast iron with such my fixators does not give positive results, both in the form of graphite in the structure of cast iron, and in obtaining healthy castings, i.e. without casting effects, due to their relatively low reactivity and low melting point. These ligatures are applicable for a solubility factor of 0.06-0.07.

The closest technical grip and the achieved effect to the invention. is the modifying mixture 21 taken at the next composition of components, wt.%:, Magnesium

Ferrosilicon 90

The solubility factor of the known mixture is 0,, 07, which corresponds to a certain mass rate of casting iron into the mold, for example, for a metal mold of 60 kg, the casting time is 25-30 s, 30 kg - 15-20 s, etc. while casting molds of the same metal capacity with high-strength cast iron from a ladle lasts 15 and c, respectively. Therefore, when machining the cast iron in the mold with the aid of this modifying mixture, the productivity of the modifying process is lost compared with the bucket machining of the cast iron.

The processing of cast iron in such a mold. the modifier does not give positive results on the degree of spheroidization of graphite in the iron structure at elevated rates of pouring it into the casting mold. When the sulfur content in the initial cast iron is more than 0.01, the form of graphite in its structure is vermicular. Therefore, the mechanical properties of the HF obtained in this way are low. Thus, the use of this mixture reduces the productivity of the modification process.

requires increased consumption of the modifier, increased temperature of the iron and its comparative purity for harmful impurities m.

5 The aim of the invention is to increase the productivity of the process of modifying the cast iron in a mold, increasing the mechanical properties of high-strength cast iron and reducing the cost of the modifying mixture.

This goal is achieved by the fact that the modifying mixture containing magnesium and ferrosilicon additionally contains silicocalcium and silico-metal 5 in the following ratio of components, wt. |:

13-20

Magnesium

Silikokaltsy 5-15

Silikomishmetall 5-50

Ferrosilicon

The higher magnesium content is necessary to increase the solubility factor of the mixture, i.e. for modifying cast iron at a faster casting speed. The lower limit of the magnesium content is selected for the solubility factor of 0.11, and the upper limit of the limit is 0.15, all other conditions being equal.

When the content of magnesium is less than 13 0, the solubility factor decreases, which affects the deterioration of the graphite shape, the homogeneity of the RF microstructure, the NTO leads to the deterioration of its mechanical properties, and when the cast iron is treated with a mixture that contains more than 20% magnesium, it is difficult to fill the mold with metal. due to emissions during pouring.

A higher content of magnesium in the mixture helps to reduce its consumption in the processing of iron in the form.

The specified content of silicocalcium in the modifier is sufficient for

black spots prevention

RF structure as well as for obtaining healthy castings. Silicocalcium is a strong graphitizer, and the precipitation of graphite occurs in the liquid state of the melt, thereby increasing the number of nuclei of crystallization of graphite, and contributes, from a thermodynamic point of view, to the globalization of graphite and the solidification of cast iron.

5 The lower limit of the silicocalcium content in the mixture is required at elevated pouring rates (solubility factor is 0.15), and the upper limit is at the solubility factor of 0.11.

With a lower content of silicocalcium in the mixture (less than 5), the degree of spheroidization of graphite in iron decreases, and with a higher content of silicocalcium in the mixture (more than 15) the modifying mixture does not completely dissolve in the reaction chamber, the castings are affected by nonmetallic. inclusions, which reduces the quality of castings.

The content of silica-metal within the specified limits in the mixture does not affect the shape of the graphite and the HF matrix, but allows modification of cast iron with a higher sulfur content (up to 0.12%). The modifier with the bottom element of the content of silico-metal (5) is used in the treatment of relatively pure electric furnace cast iron for sulfur and demodification, and with the upper (50) for the processing of cast iron for cupola melting.

When the content of silica-metal in the mixture is less than 5% and more than 50 is worsening-. The shape of graphite RF structure is

. Ferrosilicon is a filler modifying mixture, with an increase in the brand of which the solubility factor grows.

The proposed modifying mixture was tested on a mold with a solubility factor of 0.11-0.15, the metal and IMKOCTb forms were 60 kg and 30 kg, the filling times were 15-17 and 7 s, respectively.

The consumption of the proposed mixture for cast iron of electric melting was 0.6%, the consumption of a known mixture was 1.2%. For cupola cast iron, these figures were 1 and 1.5%, respectively.

The casting temperature of the cast iron into the mold was 1 50t30 ° C for electric furnace cast iron and 1320t30 ° C for cupola iron.

The chemical composition of cast iron is presented in Table. one.

Table 1, the content of components,%

Cast iron

IfL-bl.

With ISi | MP IP | MD

Modifying mixtures were made by simply mixing the powdered components.

For the preparation of modifying mixtures, magnesium MPF1 (GOST 6001-5.1), silicocalcium grade CK15 (GOST 4762-71), silico-type metal SCTSEMISH1 (TU 1-5-78-76), ferrosilicon of FS75 brand (GOST 1415-70 ). The size of fractions of the modifying mixture did not exceed 2 mm.

The composition of the tested modifying mixtures is given in table 2, table 2

Chemical composition, structure and mechanical properties of the obtained HF

taking into account the solubility factor, the results in Table. 3

Variants 1-7 relate to the treatment of diesel-cast iron, variants 812 to cast iron of the melting furnace, and variants 13 and 14 to cast iron treated with a known modifier. Cast iron 1-7 was treated using modifying mixtures 1-7 (Table 2), and cast iron 8-12 using modifying mixtures 1, 5, 2, and 7, respectively.

As can be seen from the table. 3, when the content of magnesium in the mixture is below 13%, silicon and silica and metal, less than 5%, the degree of spheroidization of graphite is 75 for electric fusible pig iron and 65% for cupola iron for melting (options 1 and 8). HF variants were obtained by treating the melt with modifying mixtures of the composition proposed, and its mechanical properties and structure satisfy the requirements imposed on the brand.

Similar results were obtained when processing the cupola cast iron, although the consumption of the proposed modifying mixtures was 1.5-2.0 times higher.

Castings, cast iron 6, treated with modifying mixture 6, were affected by slag inclusions. This is due to the increased content in the mixture of silicocalcium and silico-metal, which reduce the solubility factor of the mixture. The mechanical properties of cast irons 6 and 12 and their structure are somewhat worse than the HF properties obtained using modifying 2d5 mixtures.

; The treatment of the cast irons with the modifying mixture 7 was accompanied by the release of metal from the funnel of the mold, and the body of the castings was hit by slag inclusions. The mechanical properties of HF 7 and 12 are comparable with those of HF 1 and 8. ChuguNs, treated with a known mixture in the form with a solubility factor of 0.12, did not give positive results both in the structure of the cast iron and in its mechanical properties. Graphite in the cast iron structure is vermicular and mechanical; properties 1, times lower than the RF processed by the proposed modifying mixture.

According to preliminary calculations, the expected technical and economic efficiency from the use of the proposed modifying mixture will be 18 rubles. per 1 ton of usable casting due to an increase in the productivity of the modification process by 1.2–2 times, an increase in the mechanical properties of 1.21, 3 and a decrease in the consumption of the modifier and fixative by 1.5–2 times;

Claims (1)

MODIFICATING MIXTURE containing magnesium and ferrosilicon, characterized in that, in order to increase! productivity 'of the process of modifying cast iron, increasing the mechanical properties of ductile iron and reducing the consumption of the modifying mixture, it additionally contains silicocalcium and silicomishmetal, and the components are taken as follows 13-20 5-15 5-50 The rest of the ratio, wt.%: . Magnesium Silicocalcium Silikomishmetall Ferosilicon (L with 1 1027261