RU2360007C2 - Method of magnesium-bearing nanomodifying agent receiving - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy field and can be used for manufacturing of high-duty cast iron with globular graphite. For receiving of magnesium-bearing nano- modifying agent is blended with water solution of polyvinyl alcohol, chloride of magnesium and iron in molar correlation (10-5):1:1, agreeably, it is evaporated specified mixture before gel formation after what it is implemented carbonation at temperature 350-500°C in atmosphere of inert gas with formation of carbon nanotube, filled by chloride of magnesium and iron.

EFFECT: invention decrease magnesium losses 1,5-2 times with introduction of nano- modifying agents into the cast iron.

6 ex, 1 tbl, 6 dwg

Description

The invention relates to the field of metallurgy and can be used in the production of ductile iron with spherical graphite.

A known method of producing a magnesium-containing ligature, comprising introducing granular magnesium into the molten stream of a silicon-containing ferroalloy simultaneously with a salt additive in a ratio of 10: (0.2-1). As a salt additive, a mixture of halogens of alkali and alkaline earth metals is used, the melting point of which is lower by 50-200 ° C of the melting point of magnesium (RF Patent No. 2058416, M. cl. C22C 35/00, C21C 1/10, 04/20/1996).

The disadvantage of this method is that when granular magnesium is introduced into the ferrosilicon melt, significant losses of magnesium occur due to its evaporation, since the evaporation temperature of metallic magnesium (1120 ° C) is lower than the melting point of ferrosilicon 1220-1400 ° C. Magnesium losses are not ruled out when a modifier is introduced into cast iron, since the salt additive evaporates at the melting point of cast iron. The quality of the modification of nodular cast iron is also reduced.

Another disadvantage of the above method is the need for its implementation of expensive specialized metallurgical equipment: induction furnace, metering bucket, a powerful source of electrical energy. An appropriate energy consumption will be required for the melting and technological overheating of ferrosilicon in the range of 1400-1500 ° C. Therefore, to use this method requires significant depreciation and energy costs.

A known method for producing metal-containing carbon nanostructures from an organic compound with the addition of inorganic salts, which includes heating to 300 ° C a mixture of polyvinyl alcohol and metal chlorides, in particular copper chloride (1) or (2), taken in molar ratios of polyvinyl alcohol: copper chloride ( 20-1): 1. The initial mixture of polyvinyl alcohol and copper chloride (2) is prepared by mixing solutions of these compounds and then drying it to obtain a gel (RF Patent No. 2221744, M. Cl. C01B 31/02, B82B 3/00, publ. 20.01.2004).

The disadvantage of this method is that it is used to obtain carbon copper-containing nanostructures and cannot be used to obtain a modifier for spheroidizing carbon in cast iron, since copper is not a spheroidizing element.

The problem solved by the invention is to obtain a modifier having a set of properties for producing high-strength nodular cast iron.

A method of producing a magnesium-containing nanomodifier is characterized by mixing aqueous solutions of polyvinyl alcohol, magnesium chloride and iron, taken in a molar ratio (5-10): 1: 1, respectively, evaporating this mixture with the formation of a gel, after which carbonization is carried out at a temperature of 350-500 ° C in an inert gas atmosphere with the formation of carbon nanotubes filled with magnesium chloride and iron.

In the process of obtaining a nanomodifier, aqueous solutions of polyvinyl alcohol, magnesium chloride and iron are mixed, then they are evaporated to form a gel, which is a preliminary step before carbonization. In the process of carbonization, carbon nanotubes are formed, partially filled with magnesium chloride and iron chloride, i.e. magnesium chloride and iron chloride are trapped in carbon nanotubes. Carbonization in an inert gas atmosphere additionally protects magnesium, iron, carbon from oxidation. When introduced into molten iron, nanotubes are freed from magnesium chloride and iron chloride. Magnesium provides spheroidization of cast iron, iron chloride helps immersion of the modifier in the melt. Carbon nanotubes contribute to the grinding of grain in cast iron. When a nanomodifier is introduced into cast iron, magnesium losses are not significant, since it is enclosed in nanotubes. When the ratio of polyvinyl alcohol to magnesium chloride and iron chloride in the heated mixture is more than (10): 1: 1, nanotubes are formed that are not filled with magnesium chloride and iron chloride; therefore, the modifier does not sink in the molten metal, which increases magnesium fumes. The effect of modification is reduced.

When the ratio of polyvinyl alcohol to magnesium chloride and iron chloride in the heated mixture is less than (5): 1: 1, magnesium chloride and iron chloride partially appear outside the carbon nanotubes and, when a nanomodifier is introduced into cast iron, magnesium losses increase. Modification is not effective enough.

At a temperature of heating the mixture less than 350 ° C, carbonization does not occur; at a temperature of heating above 500 ° C, the destruction of nanotubes begins.

Thus, the technical result of the method is to reduce the loss of magnesium upon receipt of the modifier and the reduction of its fumes during modification by enclosing it in nanotubes. In addition, significantly reduced energy costs to obtain a modifier.

The invention is illustrated by drawings, where Figs. 1, 2, 3, 4, 5, 6 show fragments of the structure of a magnesium-containing nanomodifier. The proposed method for producing a magnesium-containing nanomodifier is implemented as follows.

Example 1

Mixed aqueous solutions of polyvinyl alcohol (PVA), magnesium chloride and iron in a molar ratio of PVA: MgCl ₂ : FeCl ₂ = 10: 1: 1. A mixture of solutions was poured with a layer thickness of 5 mm into ceramic dishes. The mixture of solutions was evaporated at a temperature of 100 ° C with the formation of a gel, and then carbonization was carried out by heating to a temperature of 350 ° C in an argon atmosphere. Figure 1 shows a fragment of the structure of nanotubes filled with magnesium and iron chlorides.

Example 2

Mixed aqueous solutions of polyvinyl alcohol (PVA), magnesium chloride and iron in a molar ratio of PVA: MgCl ₂ : FeCl ₂ = 10: 1: 1. A mixture of solutions was poured with a layer thickness of 5 mm into ceramic dishes. The mixture of solutions was evaporated at a temperature of 100 ° C with the formation of a gel, and then carbonization was carried out by heating to a temperature of 500 ° C in an argon atmosphere. The structure of the obtained nanomodifier is shown in figure 2, similar to that shown in figure 1.

Example 3

Mixed aqueous solutions of polyvinyl alcohol (PVA), magnesium chloride and iron in a molar ratio of PVA: MgCl ₂ : FeCl ₂ = 5: 1: 1. A mixture of solutions was poured with a layer thickness of 5 mm into ceramic dishes. The mixture of solutions was evaporated at a temperature of 100 ° C with the formation of a gel, and then carbonization was carried out by heating in an argon atmosphere to a temperature of 350 ° C. Figure 3 shows a fragment of the structure of nanotubes filled with magnesium and iron chlorides.

Example 4

Mixed aqueous solutions of polyvinyl alcohol (PVA), magnesium chloride and iron in a molar ratio of PVA: MgCl ₂ : FeCl ₂ = 5: 1: 1. A mixture of solutions was poured with a layer thickness of 5 mm into ceramic dishes. The mixture of solutions was evaporated at a temperature of 100 ° C with the formation of a gel, and then carbonization was carried out by heating in an argon atmosphere to a temperature of 500 ° C. The structure of the obtained nanomodifier is shown in figure 4, similar to that shown in figures 1, 2, 3.

Example 5

Mixed aqueous solutions of polyvinyl alcohol (PVA), magnesium chloride and iron in a molar ratio of PVA: MgCl ₂ : FeCl ₂ = 11: 1: 1. A mixture of solutions was poured with a layer thickness of 5 mm into ceramic dishes. The mixture of solutions was evaporated at a temperature of 100 ° C with the formation of a gel, and then carbonization was carried out by heating in an argon atmosphere to a temperature of 500 ° C. Figure 5 shows a fragment of the structure of nanotubes, it can be seen that the obtained nanotubes, poorly filled with magnesium and iron chlorides. As a result, magnesium fumes increase when a modifier is introduced into cast iron.

Example 6

Mixed aqueous solutions of polyvinyl alcohol (PVA), magnesium chloride and iron in a molar ratio of PVA: MgCl ₂ : FeCl ₃ = 4: 1: 1. A mixture of solutions was poured with a layer thickness of 5 mm into ceramic dishes. The mixture of solutions was evaporated at a temperature of 100 ° C to form a gel, and then carbonization was carried out when heated to a temperature of 500 ° C. Figure 6 shows a fragment of the structure of nanotubes, it is seen that an excess of the crystalline phase of magnesium and iron chlorides is obtained. As a result, magnesium fumes increase when a nanomodifier is introduced into cast iron.

At mixture heating temperatures of less than 350 ° C and above 500 ° C, single nanotubes are encountered, which does not allow the product to be used as a modifier.

The structure and composition of the obtained carbonization products were studied by transmission electron microscopy using a JEM-200CX transmission electron microscope.

The obtained modifier was tested to obtain cast iron with spheroidal graphite grade ВЧ60, the experimental results are shown in Table 1, which showed that when modifier is introduced into the molten iron, spherical graphite is formed, examples 1, 2, 3, 4 are optimal. The amount of cast iron nanomodifier was determined by calculation. Upon receipt of the nanomodifier, magnesium losses are almost completely eliminated; magnesium losses are reduced when the nanomodifier is introduced into cast iron.

The proposed method for producing a magnesium-containing nanomodifier makes it possible to obtain a modifier for producing spheroidal graphite cast iron, magnesium losses are almost eliminated when receiving the modifier, magnesium fume during cast iron modification is reduced by 1.5-2 times. The method is energetically low cost.

Claims (1)

A method of producing a magnesium-containing nanomodifier, characterized in that aqueous solutions of polyvinyl alcohol, magnesium chloride and iron are mixed in a molar ratio (10-5): 1: 1, respectively, the mixture is evaporated to form a gel, after which carbonization is carried out at a temperature of 350-500 ° C in an inert gas atmosphere with the formation of carbon nanotubes filled with magnesium chloride and iron.

Images