RU2761062C1 - Method for obtaining electrodes of anode earthing devices - Google Patents

Abstract

FIELD: physical chemistry.

SUBSTANCE: invention relates to the production of electrodes for anode earthing devices made of high-silicon cast iron. Cast iron containing 9-12% silicon is used, a modifier is added to the melt in an amount of 0.01% of the total mass of the components, a complex modifier based on multicomponent ligatures is used as a modifier with the following component content, wt. %: Si 60-65, Fe 2-3, Mn 1-2, Ti 1-1.5, Fe-Zr alloy 0.001-0.01, P 0.05, S 0.05, C 0.5 melt, it is superheated to a temperature of 1530-1560°C, released into a coquille, kept for 2-2.5 minutes, opened, the casting is transferred to a thermostat with the possibility of cooling it to room temperature at a speed of no more than 115-120°C/h, treatment is performed, including cleaning the surface of the cooled casting with an abrasive material, application of hydrated phosphoric anhydride containing P₂O₅ and H₂O, wt.%: P₂O₅ 90.1, H₂O 9.9, holding for 22-26 hours, rinsing with running water and drying at a temperature of 110±5°С, while the operations of application, holding, washing and drying are repeated.

EFFECT: invention makes it possible to obtain an electrode with increased resistance to anodic dissolution with reduced brittleness due to the formation of a highly silicon-doped layer on its surface.

1 cl, 2 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of technology for producing materials with increased resistance to anodic dissolution and can be used in the production of electrodes for anode grounding conductors.

There is a method of steam-thermal oxidation of steel products Patent RU No. 2456370, published on July 20, 2012, IPC С23С 8/18, С21В 9/00, including preliminary heating of products in a furnace retort to a temperature of 250-300 ° С, then heating them in an environment of superheated steam to a temperature of 550-600 ° C, holding at a given temperature for a time that ensures the production of a film of a given thickness, followed by cooling the products in this environment to a temperature of 250-300 ° C, at which forced controlled cooling is carried out by means of a cooling medium circulating in the pipeline, wound from the outside of the retort body.

The disadvantage of this technical solution is the absence in the composition of the processed material of components that provide a sufficiently reliable passivation of the surface in conditions of corrosive solutions.

Known technology for producing corrosion-resistant high-silicon cast iron grades ChS15M4 and ChS17M3 (Foundry Library, No. 6/2010, pp. 2-6), additionally alloyed with molybdenum (antichlora). Smelting of high-silicon cast irons is carried out from a charge consisting of pre-calcined ferrosilicon, steel scrap, return, pig iron L1 or L2. The slag is liquefied with limestone and discharged at 1500-1550 ° C. After that, the alloy is refined with hexachloroethane in an amount of 0.25-0.4% for 2-3 hours and ferromolybdenum is added. Next, the melt is kept in a ladle at a temperature of 1600 ° C for 4-6 hours, after which castings are constructed from it.

The disadvantage of this smelting technology is the changing phase composition of cast iron, in which austenite can be present, characterized by a low dissolution rate, and hypoeutectic cast iron can be formed, for which the dissolution rate increases significantly.

Closest to the claimed method is the technology of smelting ferrosilide and the manufacture of castings of anodes-grounding (Development and development of technology for smelting ferrosilide and the manufacture of castings of anodes-grounding // Foundry. - No. 1, 2015. - P. 21-24), according to which smelting is made from charge materials, limiting cast iron PL1, ferrosilicon, FS75, ferrochrome, ferromanganese FMn78, steel with 0.2% carbon and silicon content and 0.3% manganese, in quantities providing the composition of ferrosilide: silicon 13.8-18, 4% manganese 0.79% chromium 3.52% after the melt has cooled down to 1450 ° C, the cast iron is modified with ferrocerium when discharged into a dried ladle.

To date, there are no ways to obtain electrodes from high-silicon cast iron, which simultaneously have a low rate of anodic dissolution and reduced brittleness.

The technical result of the invention is to obtain electrodes with increased resistance to anodic dissolution, due to the formation of a highly silicon-doped surface layer of the alloy.

The specified technical result is achieved thanks to the proposed method for producing electrodes of anode ground electrodes, which consists in the preparation of a charge of cast iron, a silicon-containing component, ferromanganese and steel in an amount sufficient to obtain high-silica cast iron with a silicon content of 9-12%, loading a small part of the charge materials - cast iron, silicon-containing component and steel in the form of a billet on the bottom of the furnace, the rest of the space is filled with large parts of the charge - a silicon-containing component and cast iron, subjected to melting, after complete melting of the charge at a temperature of 1400-1420 ° C, ferromanganese is introduced into the bath, a modifier is added to the melt before tapping into the ladle and released into a chill mold, and the cast iron contains 9-12% silicon, the modifier is added in an amount of 0.01% of the total charge weight, a complex modifier based on multicomponent ligatures is used as a modifier, which includes Si, Fe, Mn, Ti, Fe-Zr alloy, P, S and C at and x content in the modifier (wt%): Si - 60-65, Fe - 2-3, Mn - 1-2, Ti - 1-1.5, Fe-Zr alloy - 0.001-0.01, P - 0 , 05, S - 0.05, C - 0.5, the melt is overheated to a temperature of 1530-1560 ° C, released into a chill mold, kept for 2-2.5 minutes, opened, transferred the casting to a thermostat, ensuring its cooling to room temperature at a rate of no more than 115-120 ° C / h, a treatment is performed, including cleaning the surface of the cooled casting with an abrasive material, applying over its entire surface hydrated phosphoric anhydride containing P ₂ O ₅ and H ₂ O (wt%): P ₂ O ₅ - 90.1%, H ₂ O - 9.9%, holding for 22-26 hours, rinsing with running water and drying at a temperature of 105-115 ° C, the operations of application, holding, rinsing and drying are repeated.

With a silicon content in high-silicon cast iron of 9-12%, brittleness completely disappears and, in terms of mechanical properties, it becomes similar to low-alloy cast irons. The modifier based on multicomponent master alloys improves the grain structure of high-silicon cast iron, increases the degree of graphitization, contributing to the separate distribution of graphite inclusions in the main metal mass and, thereby, helps to reduce the dissolution rate. Silicon content 60-65% increases the corrosion resistance of the electrode. The content of 1-2% manganese thickens the structure of high-silicon cast iron and increases its corrosion resistance. The 0.5% carbon content contributes to a coarse-grained structure. A phosphorus content of 0.05% improves corrosion resistance. The content of 0.05% sulfur is a harmful impurity that contributes to a decrease in corrosion resistance, but due to the increased content of manganese, it neutralizes its properties. The content of 1-1.5% titanium increases the corrosion resistance and densifies the structure of ferrosilide, at the same time increases its dispersion. The content of 2-3% iron affects the structure of high-silicon cast iron, and when interacting with carbon, affects its dispersion. 0.001-0.01% ferrocerium increases corrosion resistance and seals the structure of high-silicon cast iron. At the same time, the modifier increases the strength of high-silicon cast iron, improves its machinability and wear resistance, ensures uniformity of properties in parts of the casting of various cross-sections, and makes it possible to neutralize surfactant impurities such as sulfur, hydrogen and oxygen during the melting process. That is, the use of a modifier makes it possible to reduce the brittleness and, at the same time, the rate of anodic dissolution.

Overheating of the melt to a temperature above 1560 ° C promotes the formation of a crushed structure, which leads to an increase in ultimate strength, deteriorates its static mechanical properties, an increase in the volume of the melt occurs, which leads to external defects in the workpiece, to the formation of cavities and pores. At temperatures below 1530 ° C, the components are unevenly distributed over the volume of the melt, which leads to uneven mechanical properties and increased dissolution rates.

The use of a chill mold as a form provides a low porosity of the metal, which reduces the dissolution rate by eliminating intercrystalline dissolution. Holding in a chill mold for a time interval of 2-2.5 minutes and subsequent cooling in a bath provides a coarse-crystalline low-porosity structure of high-silica cast iron. With a holding time less than 2 minutes, the structure will not be sufficiently formed, which will lead to defects that affect the rate of anodic dissolution and a decrease in mechanical properties. With a longer exposure time, the formation of macrodefects (shells, pores) and structure refinement begin.

At a cooling rate of more than 115-120 ° C / h, the degree of dispersion increases, therefore, high-silicon cast iron has a lower corrosion resistance, mechanical properties deteriorate, external defects appear, namely, cracks, chips, internal stresses, cavities and pores are formed.

Surface treatment of high-silicon cast iron with hydrated phosphoric anhydride, which is a mixture of meta - and orthophosphoric acids, leads to partial passivation of the surface with iron phosphates and subsequent selective anodic dissolution of iron from the surface layers of high-silicon iron, as a result of which the alloy is enriched in silicon up to the formation of increased iron silicides resistance to anodic dissolution. The composition of the hydration product, P ₂ O ₅ - 90.1%, H ₂ O - 9.9%, is necessary to ensure phosphate passivation of areas containing iron-silicon phases. The holding time of the hydration product on the alloy surface is due to the completeness of the reaction, with a holding time of less than 22 hours, the surface is processed unevenly, a holding time of more than 26 hours is excessive and reduces production productivity.

Rinsing with running water is necessary to remove a mixture of acids from the treated surface, since otherwise the interaction of these acids with water will subsequently contribute to the development of corrosion of the alloy. Drying at 105-115 ° C removes moisture, which can also lead to high corrosive losses.

An example of the implementation of the method

Smelting of electrodes was carried out according to the proposed method. For this, a charge was compiled from cast iron, a silicon-containing component, ferromanganese and steel in an amount sufficient to obtain high-silicon cast iron with a silicon content of 6-13.5%. The charge was melted, the melt was superheated to the temperature indicated in Table 1, released into a chill mold, held for 2-2.5 minutes, opened it, transferred the casting to a thermostat with the possibility of cooling it to room temperature at a rate indicated in Table 1, performed processing, including cleaning the surface of the cooled casting with an abrasive material, applying over its entire surface hydrated phosphoric anhydride containing P ₂ O ₅ and H ₂ O (wt.%): P ₂ O ₅ - 90.1%, H ₂ O - 9, 9%, holding for 22-26 hours, rinsing with running water and drying at a temperature of 105-115 ° C, the operations of application, holding, rinsing and drying were repeated.

Conducted measurements of the rate of anodic dissolution of samples of electrodes made of high-silica cast iron, manufactured under the conditions of the present invention. The measurement results are shown in Table 1.

As can be seen from the data in Table 1, with a silicon content in high-silicon cast iron of 9-12 wt%, holding the melt at 1530-1560 ° C and a cooling rate of 115-120 ° C / h, the samples had a dissolution rate of no more than 0.2 kg / A year. X-ray phase analysis of the samples showed that the intermetallic compound Fe ₁₁ S _{15 was} formed on their surface (Fig. 1), metallographic analysis (Fig. 2) confirmed the coarse-grained structure of high-silicon cast iron. The alloys obtained did not possess the brittleness characteristic of high-silicon cast irons with a silicon content of more than 14 wt%.

Claims (1)

A method for producing electrodes of anode grounding electrodes, which consists in compiling a charge of cast iron, a silicon-containing component, ferromanganese and steel in an amount sufficient to obtain high-silicon cast iron with a silicon content of 9-12%, loading a small part of the charge materials - cast iron, a silicon-containing component and steel in the form of a billet to the bottom of the furnace, the rest of the furnace space is filled with large parts of the charge - a silicon-containing component and cast iron, melted, after complete melting of the charge at a temperature of 1400-1420 ° C, ferromanganese is introduced into the bath, a modifier is added to the melt into the ladle and released into a chill mold, characterized by that the composition of cast iron contains 9-12% silicon, the modifier is added in an amount of 0.01% of the total mass of the charge, as a modifier, a complex modifier based on multicomponent ligatures is used, which includes Si, Fe, Mn, Ti, Fe- Zr, P, S and C, with their content in the modifier, wt%: Si - 60-65, Fe - 2-3, Mn - 1-2, Ti - 1-1.5, Fe-Zr - 0.001-0.01, P - 0.05, S - 0.05, C-0.5, the melt is overheated to a temperature of 1530-1560 ° C, released into a chill mold, hold for 2-2.5 minutes, open it, transfer the casting to a thermostat to ensure its cooling to room temperature at a rate of no more than 115-120 ° C / h, perform a treatment, including cleaning the surface of the cooled casting with an abrasive material, applying it over the entire its surface of hydrated phosphoric anhydride containing P ₂ O ₅ and H ₂ O, wt%: P ₂ O ₅ - 90.1, H ₂ O - 9.9, holding for 22-26 hours, rinsing with running water and drying at a temperature 105-115 ° C, while the operations of application, curing, rinsing and drying are repeated.

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