RU2314355C1 - Consumable electrode production method - Google Patents

Abstract

FIELD: electric metallurgy, namely production of consumable electrode for electroslag refining.

SUBSTANCE: method comprises steps of simultaneously feeding liquid metal and solid metallic component in the form of metallized pellets into ingot mold; simultaneously feeding liquid metal and metallized pellets heated up to 100-200°C at relation (3.4 - 4.2) : 1 by batches forming layer with height 100 - 150 mm; using as ingot mold siphon tubes made with use of waste flux of electroslag refining process of metallized pellets.

EFFECT: possibility for producing consumable electrodes with high chemical uniformity and with sufficient mechanical strength, possibility for making ingots with flawless structure and good surface at small cost price.

2 cl, 2 tbl, 2 dwg, 1 ex

Description

The invention relates to the field of electrometallurgy, in particular to the production of consumable electrodes for electroslag remelting.

There is a method of producing consumable electrodes, which consists in compacting a lump charge, which, with the aim of hardening the electrode and stabilizing the composition of the slag bath during remelting, is poured into the mold and filled with a melt of the working flux of the ESR [Chekotilo L.V., Medovar B.I., Martan V. M. Auth. St. USSR, class C21C 5/56, claimed 01/24/73 (21) 1875572 / 22-02, publ. 06/05.80, bulletin No. 21].

The disadvantage of this method of producing consumable electrodes is that the use of ESR flux as a binder leads to the fact that during further electroslag remelting, the mass of liquid flux increases along the fusion of the consumable electrode. To maintain an unchanged amount of working flux during remelting, it is necessary to download it, which is very difficult on ESR installations with a stationary mold. This method involves the use of a non-consumable electrode for the implementation of electroslag process, because passing an electric current through the consumable electrode obtained by this method is very difficult, due to the redistribution of the zones of Joule heat, since the consumable electrode is inhomogeneous and most fluxes in the solid state are non-conductive. This circumstance greatly complicates the process and worsens the technical and economic indicators. The use of a non-consumable graphite electrode leads to carburization of the metal obtained during ESR, and makes it difficult to obtain low-carbon steel grades.

A known method of producing consumable electrodes, including filling the charge materials in portions into the matrix and pressing, while the first portion of the charge materials make ligature additives in the amount of 30 ... 70% [Bakumenko SP, Yakushev OS, Shatov V. M. Auth. St. USSR, class B22d 7/00, C 21 s 5/56, No. 427778, claimed 04/18/72, publ. 01/29/75].

The disadvantage of this method is that there is an uneven distribution of the ligature additives along the height of the resulting consumable electrode, the content in the lower layer of the consumable electrode is higher than in the subsequent higher layers. In the process of pressing, an unequal degree of compression is observed, as well as insufficient mechanical strength, which makes it difficult to obtain consumable electrodes of large diameter.

A known method of producing consumable electrodes using pre-heated to a temperature of 650 ... 850 ° C metallized pellets fed initially to the mold, in which the liquid metal is supplied to the mold from below under a pressure of 2 ... 3 atm in relation to the pellets 1 :( 1 ... 2.5) [Chumanov V.I., Potapov V.I., Chumanov I.V., Votinov V.V. The method of obtaining consumable electrodes. Patent for invention №2260065, IPC 7 С22В 9/18, Н 057/07. Application No. 2004129609. Priority of the invention on October 8, 2004. Registered on September 10, 2005].

The disadvantage of using this method of pouring liquid metal under pressure from below the preheated and filled metallized pellets into the mold is that additional devices are required to implement this method to create an excess pressure of the liquid metal supplied from below, which is very difficult under industrial conditions and requires additional costs. Preheating of metallized pellets to temperatures of 650 ... 850 ° C leads to their secondary oxidation, which greatly worsens further electroslag remelting. The supply of liquid metal from below to the mold under pressure leads to extrusion of the upper layers of metallized pellets and requires the presence of special devices on top that prevent this phenomenon and do not impede the free exit of gases.

As a prototype, a method for producing consumable electrodes was adopted, including pouring a solid metal component with liquid metal simultaneously supplied to the mold of a special form in the ratio (2.7 ... 3.3): 1, with a feed speed of metallized pellets 3-5 kg / s and liquid metal 1-2 kg / s. Metallized pellets are used as a solid metal component [Chumanov V.I., Chumanov I.V., Pyatygin D.A., Votinov V.V. The method of obtaining consumable electrodes. Patent for invention №2233895, IPC 7 С22В 9/18, Н 057/07. Application No. 2003108193. Priority of the invention March 24, 2003. Registered August 10, 2004].

The disadvantage of this method of obtaining a consumable electrode is that it is necessary to sufficiently adhere to the technological parameters, namely, compliance with constant ratios and speeds of their joint supply. As the mold is filled in a special form, the metallized pellets float up. With minor violations of the set technological parameters, an uneven distribution of metallized pellets occurs in the volume of the resulting consumable electrode, which leads to further chemical melting of the resulting metal inhomogeneity. With the simultaneous supply of liquid metal and metallized pellets, a sufficiently high preliminary heating of the latter is required, which leads to the development of secondary oxidation processes, and also reduces the attractiveness of this technology in terms of technical and economic indicators.

The objective of the invention is to reduce the cost of manufacturing electrodes for electroslag remelting.

The problem is solved in that in the method for producing consumable electrodes, including the simultaneous pouring of liquid metal with a solid metal component mainly in the form of metallized pellets into the mold, according to the invention, the simultaneous supply of liquid metal and metallized pellets heated to 100 ... 200 ° C, in the ratio (3.4 ... 4.2): 1 is carried out in portions, the height of each layer being 100-150 mm.

Another difference is that siphon tubes made using spent flux from the process of electroslag remelting of metallized pellets (ESMPO) are used as molds.

Using in the process of filling a consumable electrode the simultaneous supply of metallized pellets together with liquid metal in the ratio (3.4 ... 4.2): 1, depending on the bulk density of metallized pellets, allows for more uniform distribution of pellets in the volume of the consumable electrode and to reduce temperature of their preheating. Lowering the temperature of the preheating of metallized pellets to 100 ... 200 ° C prevents the intensification of the processes of their secondary oxidation, and also increases the attractiveness of this technology from the point of view of technical and economic indicators. The total specific energy consumption per tonne of metal thus smelted is reduced, and the “fumes” of alloying additives are reduced.

Using the simultaneous supply of metallized pellets and liquid metal in portions of 100-150 mm high allows for optimal crystallization and distribution of liquid metal throughout the volume.

The use of a mold for shaping the sacrificial electrode, which during the further remelting process is the shell of the consumable electrode made of siphon tubes made using the spent flux of the ESHMO process, as well as various deoxidizers and alloying additives. This mold allows you to refuse the introduction of a large number of deoxidizing agents and alloying fluxes on the surface of the working flux, and also contributes to the constant conditioning (updating) of the working flux during ESHME.

The use of metallized pellets as a solid metal component makes it possible to obtain a close-packed consumable electrode with a uniform distribution of the iron component throughout the volume, achieved as a result of the fact that the metallized pellets have a spherical shape and a high bulk density. The metal obtained as a result of further electroslag remelting has a low content of harmful gases, non-ferrous metal impurities, as well as other harmful impurities that are not removed during the ESR.

The method is illustrated by photographs, where photo 1 shows the average section of the resulting consumable electrode; in photo 2 - its side surface.

The method is as follows. When the height of the serving portion is 100 ... 150 mm from metallized pellets and liquid metal in the ratio (3.4 ... 4.2): 1, depending on the bulk density of the pellets used and the temperature of their preheating to 100 ... 200 ° C, an insignificant time of crystallization processes was observed, with obtaining a uniform distribution of pellets throughout the entire volume of the thus consumed electrode.

When the height of the serving portion is less than 100 ... 150 mm from metallized pellets and liquid metal in the ratio (3.4 ... 4.2): 1, depending on the bulk density of the pellets used, and the temperature of their preheating to 100 .. .200 ° C, an insignificant time of crystallization processes was observed with obtaining a uniform distribution of pellets throughout the entire volume of the thus consumed electrode. However, the use of a small height of the supplied portion led to a significant increase in the time taken to obtain the finished consumable electrode, which negatively affected the technical and economic indicators.

When the thickness of the feed portion is more than 100 ... 150 mm from metallized pellets and liquid metal in the ratio (3.4 ... 4.2): 1, depending on the bulk density of the pellets used and the temperature of their preheating to 100 ... 200 ° C, incomplete penetration of the metal along the height of the elementary layer was observed, which led to an uneven distribution of liquid metal over the entire volume of the consumable electrode obtained in this way and led to a decrease in the mechanical strength required for further ESME. To carry out the impregnation of the portion height chosen in this way, it was necessary to significantly increase the temperature of the preheating of metallized pellets, which led to the intensive development of their secondary oxidation processes and worsened technical and economic indicators.

An example of a specific implementation of the method.

Industrial studies were carried out at OJSC “Zlatoust Metallurgical Plant” in ESPC No. 3.

Obtaining a consumable electrode includes the following technological operations: pre-heated to a temperature of 100 ... 200 ° С metallized pellets with a diameter of 12 ... 15 mm, poured in portions (portion size was about 100 ... 150 mm) simultaneously with the liquid metal of the specified chemical composition at a temperature of 1600 ... 1620 ° C in the mold. The mold was assembled from siphon tubes of a predetermined chemical composition previously obtained in the refractory workshop. Waste flux grade ANF-6, as well as powder deoxidizers and finely ground (fractions less than 5 mm) ferroalloys were used as the main components for siphon tubes. After pouring each portion, a small technological exposure was made for 1-2 minutes and the next portion was poured.

The following steel grades were used as liquid metal for impregnation of metallized pellets: 07Х17Н6, ЭП56, 20Х23Н18, 40Х13.

The resulting consumable electrodes were subjected to electroslag remelting at the A-550 installation in a mold with a diameter of 120 mm and a height of 500 mm under an ANF-6 flux in the amount of 2.5 kg for melting. In order to increase the fused part, inventory heads were welded to the remelted consumable electrodes. The process was wired at a current of 1.5 kA, at a voltage of 48 V. The main melting period was held at a current of 2.5 kA and a voltage of 48 V. Shrinkage was not performed. The remelting process proceeded fairly steadily; slag foaming took place. Significant current surges were absent. Dust during the process was negligible. The study of the quality of the metal after electroslag remelting made it possible to ascertain the presence of a dense defect-free structure characteristic of electroslag metal with a fairly good surface of the ingot.

At present, metallurgical plants use three methods for the production of electrodes for ESRs: rolling in large sections, casting in molds and forging on hammers.

Comparison of the cost of existing methods for the production of consumable electrodes, conducted on the most representative steel grades in the ESR range: ШХ15, 38ХМЮФА, 40ХНМА, was carried out in the conditions of the plant that has the largest capacities for the production of rolled and cast electrodes.

The specific metal consumption in the manufacture of electrodes, shown in table 1, shows that the lowest metal consumption is observed in the production of cast electrodes.

Table 1.
Consumption ratios of metal in the manufacture of consumable electrodes Type of electrodes steel grade SHX15 38HMYuA 40XNMA Rolled 1,260 1,250 1,252 Forged 1,239 1,229 1,231 Mold casting (proposed method) 1,096 1,087 1,089

All calculations were carried out per ton of the fused part of the electrode as applied to remelting in molds with a cross section of 390x425 mm (2.4 t ingot). Since in the ESPC a single calculation of the ingots is made regardless of the method of their breakdown, according to the chosen method, the prime cost of the molten steel and ingots from the molds was calculated separately. Next, the cost of the finished electrodes was already determined. At the same time, the amount of metal waste during rolling and forging of the electrodes was taken according to established standards.

If casting into molds makes it possible to obtain an almost finished electrode (it is only necessary to remove the defective part), then the other two methods require additional labor-intensive redistribution in the rolling or forging shops.

Table 2 presents the average cost of consumable electrodes for ESR, taken as a percentage. For the base cost, the cost of rolled electrodes was selected.

Table 2.
Cost of consumable electrodes of some steel grades,% Type of electrodes steel grade SHX15 38HMYuA 40XNMA Rolled 100.00 100.00 100.00 Forged 114.60 109.60 108.18 Mold casting (proposed method) 82.39 84.18 84.94

As follows from table 2 cast electrodes have the lowest cost. Moreover, for relatively cheap grades, the lowest current costs, despite the relatively higher metal consumption, are provided by casting the electrodes into special molds. This is due to lower redistribution costs.

Forged electrodes have the highest cost, which is explained by the highest costs for redistribution in blacksmith shops compared to other methods.

As a result, the task set above is achieved. Using the proposed method of casting electrodes, their cost is significantly reduced, while satisfying the quality of the electrode surface according to GOST.

Industrial applicability.

The proposed method can be used in a single and mass production, in the manufacture of consumable electrodes for electroslag remelting.

Claims (2)

1. A method of producing consumable electrodes, including the simultaneous supply of liquid metal and a solid metal component in the form of metallized pellets in a mold, characterized in that the simultaneous supply of liquid metal and metallized pellets heated to 100 ... 200 ° C in the ratio (3 , 4 ... 4,2): 1, in portions with the height of each layer 100-150 mm. 2. The method according to claim 1, characterized in that the siphon tubes made using the spent flux of the process of electroslag remelting of metallized pellets (ESPMO) are used as molds.

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