JPH1029042A - Chill mold and metal remelting method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-cooled chill mold for producing an improved ingot or continuous casting, and an apparatus and an electroslag remelting method for such a chill mold for continuous casting. SOLUTION: A short water-cooled lower surface for manufacturing an ingot or a continuous cast body using an ESR (electroslag remelting) method or a continuous casting method in which a meniscus of a casting surface is covered with a conductive slag. A chill mold (10) open to the surface of the conductive element (24) which is not directly water-cooled in the area of the slag bath (20) on the casting surface
And a connection to a power supply (42) can be made through the conductive element. As a material of the conductive element (24), graphite or a high melting point metal such as W, Mo, Nb, or the like is used. In certain embodiments, the conductive elements (24) are electrically insulated from the water-cooled portions and from each other by non-water-cooled, non-conductive, eg, ceramic, elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a block, an ingot or a continuous casting, in which a casting upper surface is covered with a conductive slag, and an ingot,
Alternatively, a continuous cast body is formed, and the ingot or continuous cast body can be pulled out of the mold by lifting the mold or pulling down the formed body itself. This relates to a chill mold that is open toward the user. The present invention also relates to an apparatus for continuously casting metal, a method for remelting electroslag, and a method for using a chill mold.

[0002]

BACKGROUND OF THE INVENTION Continuous casting and electroslag remelting of metals, particularly steel, can be effected by using a short, water-cooled downwardly open chill mold, and the insert of the chill mold is , Generally made of copper or a copper alloy. These inserts have a tubular configuration, in which cooling water is flowed around the inserts in a water box, or, especially in the case of large flat shapes (slabs or blooms), the inserts are held together by a support. It has a number of thick copper plates held. In the case of such a plate-type chill mold, the cooling water passes through the distribution ring, is sent to individual cooling holes provided in the plate, exits from the other end of the cooling hole, and is sent again to the collecting manifold. Cycles thereafter by repeating this method. In addition, monoblock chill molds in the form of thick, generally forged rings are also known,
The cooling water in this case passes through individual cooling holes as in the case of the plate type chill mold.

A so-called vertical chill mold, which is used in the electroslag remelting process of another method and can accommodate the entire ingot to be remelted,
In this case, no consideration is given.

In the chill mold to be used in this case,
Unlike the above, continuous casting makes it possible to produce a continuous casting or ingot that is considerably longer than a water-cooled mold that is drawn vertically or in an arc shape downward. In the case of the electroslag remelting method, the ingot formed in the chill mold can be pulled down by lowering the bottom plate, but the remelt ingot is formed on the fixed bottom plate by lifting the mold. Is also possible.

[0005] Regardless of the casting method, it is of paramount importance to prevent the castable material from being re-oxidized by the atmosphere. It is believed that this problem is largely solved in the electroslag remelting process because the molten metal sump is covered by the slag bath, thus preventing direct contact with air. Direct contact between the dissolved metal and the atmosphere is avoided because the tip of the electrode is also consumed in the slag bath.

[0006] Since continuous casting was initially performed in air, it was essential to keep the oxidation within certain limits by adding oil to the casting surface or to the top of the casting. Casting powder for coating the casting surface (casting po
With the introduction of wder) and the use of a dip tube to supply the molten metal into the mold, this problem in continuous casting has been further improved.

However, the casting powder has a high acidic composition, that is, Ca
SiO ₂ and Al ₂ O rather than O and MgO components
There are many compositions like ₃ . In addition, large amounts of carbon additives often have to be added to ensure the properties required for continuous casting.

In the production of extremely pure steel, a meniscus formed by contact with the casting surface, in particular the wall of the chill mold, simultaneously with the casting process using basic slag.
It is required today to completely coat us). This requirement cannot be met today or fully or at all because the melting point of basic slag is relatively high,
This is because the heat provided by only the molten metal cannot maintain a liquid state, and furthermore, this slag is
Partly due to the loss of more energy due to radiation to the environment than to acidic slag or powder mixtures.

In an electroslag process in which a basic slag applied to a metal surface is generally heated by an electric current flowing from an electrode to an ingot and maintained in a liquid state,
The condition of the meniscus is not always ideal. In particular, when manufacturing a large-diameter ingot, it is often necessary to suppress power supply in order to reduce the wear effect to a sufficiently low level and improve the configuration of the ingot. In this case, the supply of heat at the meniscus of the metal reservoir may not be sufficient to produce a good ingot surface without grooves or tears.

However, a parallel mold, similar to continuous casting, or one of the known molds, the T extending upwards
The mold has a cross-section similar to that of small continuous castings, but even in the case of the electroslag process modified to continuously melt them, the current strength for the desired casting speed, Or, a case where the necessary power cannot be transmitted may occur. In the opposite case, overheating of the metal pool and an inappropriate solidification structure cannot be avoided.

In order to overcome this difficulty, Japan has attempted to allow a part of the current to flow from the slag bath to the chill mold wall. However, in this case, it is inevitable that a small arc flies between the meniscus of the slag bath and the chill mold wall. For this reason, the copper of the mold is invaded on the upper surface of the slag bath, and the life of the chill mold is greatly shortened.

[0012]

SUMMARY OF THE INVENTION In order to solve the above problems, the supply of energy to a liquid, electrically conductive slag bath applied on the meniscus of the melt pool affects the casting speed or melting temperature. Being able to control without it is desirable. This can in principle be achieved by using one or more non-consumable electrodes which are immersed in a slag bath as already disclosed elsewhere.

However, this method is generally not possible for small cross-sectional areas for space reasons. When making large-diameter products with long remelting times, this type of non-consumable electrode is heated significantly, so that not only graphite but also tungsten or molybdenum is oxidized very quickly by oxygen in the air, so it is used. It is impossible.

With this in mind, it is an object of the invention to overcome the difficulties and problems discussed above.

[0015]

This object is fulfilled by the teachings of the independent claims, while the dependent claims define preferred structures.

According to the invention, at least one conductive element which is not directly water-cooled is mounted on a wall of a mold formed from a water-cooled copper element in contact with a slag bath, wherein the conductive element in this case is a slag. It is mounted completely below the surface of the bath, but without reaching the upper surface of the dissolution. The connection with the power supply can be made by the above-described element.

It is desirable to use graphite as the material of the above-mentioned conductive element, but other refractory metals such as tungsten and molybdenum are also suitable.

In a specific embodiment, a slag bath is contained,
Furthermore, the top of the chill mold, in which one or more conductive elements are mounted, may extend into a funnel structure. This may be particularly suitable for the production of continuous casts with a diameter or side length of less than 300 mm or a small cross-sectional area.

In another embodiment of the chill mold according to the invention, one or more of the mounted conductive elements are electrically insulated from the copper part of the mold by using non-conductive elements. It is conceivable to use a refractory ceramic material, for example, refractory clay, Al ₂ O ₃ , MgO or the like for the non-conductive element.

When installing at least two conductive elements, they can also be insulated from each other by inserting additional non-conductive elements between each other.

The individual embodiments of the chill mold according to the invention enable the construction of a series of different devices and alternative methods for electroslag remelting or continuous casting, the main features of which are described below.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages, features and details of the invention will be apparent from the following description of preferred embodiments and from the drawings.

FIG. 1 shows a schematic structure of a chill mold 10 having a tubular structure for so-called electroslag remelting (ESR). The remelted ingot, or block 16, is shaped at the water cooled lower portion 12 of the mold, and when pulled out of the chill mold 10, the meniscus of the melt pool 18 is located at the water cooled lower portion 12. Above the meniscus of the dissolution pool 18 is a liquid slag bath 20 in which the consumable electrode 22 is immersed.

In the area of the slag bath 20, there are conductive elements 24. The conductive element 24 is not directly cooled by water, but is entirely annular or consists of a number of sections or sections, and, as shown here, also without water cooling. The non-conductive external element 26 can be electrically insulated from the chill mold lower part 12 and the optional water-cooled chill mold upper part 14.

For the sake of clarity of the drawing, the supply of cooling water to the chill mold parts 12, 14 is indicated by 28, and the discharge from the parts is indicated by 30.

In a simplified embodiment, the water-cooled chill mold top 14 and / or the non-water-cooled non-conductive element 26 are not required in a series of possible use cases.

In principle, the chill mold 10 described above is
It is also suitable for continuous casting as shown in (1). Also in this case, the continuous cast body 32 drawn from the chill mold 10
The meniscus of the dissolution pool 18 is covered by the liquid slag bath 20. The slag bath is retained in the area of conductive elements 24 that are not directly water cooled and non-conductive elements 26 that are also not directly water cooled. The liquid metal 36 in the intermediate container 34, which expands upward, flows through the take-out tube 38 in the form of a casting jet 40 in the X direction, and flows into the melting pool 18.

There are several possible ways to heat the slag bath 20, the most important of which can be seen in FIGS.

FIG. 3 shows the chill mold 10 shown in FIG.
1 schematically shows the structure of an ESR device using a sliding chill mold using the ESR. The installation of the conductive element 24 in the area of the slag bath 20 allows for the selection of various connection configurations in which the switches 44, 46, 48 and 50 are properly combined with respect to the connection of the device to an AC or DC power supply 42. Becomes possible.

Switch 44 in line 45 between power supply 42 and electrode 22 and switch 48 in line 49 between power supply 42 and bottom plate 52 are closed, as is commonly found in conventional electroslag remelting. Switch 46
When is open, current flows. The switch 46
Is a switch connected to the conductive element.

Conversely, if switches 44 and 48 are closed and switch 46 in line 47 is also closed and switch 50, also incorporated in line 47, is applied to switching contact 54, Total dissolution current is electrode 2
2 to the slag bath 20. Bottom plate 52 on which conductive element 24 of chill mold 10 and ingot 16 are mounted
Can be used as a current return line. Each part of the current is adjusted according to the respective resistance. In the case of the above operation mode, the outer element 26 which is a non-conductive element in the chill mold 10 can be omitted.

Next, when switch 48 is opened, all current returns to power supply 42 through conductive element 24 mounted in mold 10 and switch 50 through switch 46 and switching contact 54. The switching contact 54 is connected to the line 49.

In another method of energizing, when the switches 44, 46 and 48 are closed, the switch 50 can be applied to a switching contact 56 connected to the line 45.
In this case, the supply of current to the slag bath 20 is performed by the electrode 2
2 and through the conductive element 24 attached to the chill mold 10, depending on the respective resistance, whereas the return of the total melting current to the power supply 42 utilizes the ingot 16 and the bottom plate 52. In the case of this operation mode, it is essential to mount the non-conductive element 26 which is not water-cooled.

Next, when the switch 44 is opened, the slag bath 2
The power supply to the electrode 22 immersed in 0 is cut off, and all power is supplied through the conductive element 24 incorporated in the chill mold 10.

In the case of electrode slag remelting, there are several options for switch placement, but the water-cooled chill mold lower part 1 by a non-conductive, non-water-cooled element 26.
In the case of continuous casting as shown in FIG. 2 with a conductive element 24 electrically insulated from that of FIG.
2 is continuously and conductively connected by a casting jet 40 to a distribution device or metal bath 36 of an intermediate vessel 34.
In this case, the melting current for heating the slag bath 20 is supplied from a power supply (not shown) through the conductive elements, and the current is supplied to the continuous casting 32, or to a distribution device or metal in the intermediate vessel 34. Return through bath 36.

FIGS. 4 and 5 show another embodiment. In FIG. 4, 2 in the chill mold 10 according to the present invention.
The two conductive elements 24a and 24b are electrically insulated from the water-cooled chill mold lower part 12 and the water-cooled chill mold upper part 14, respectively, by the non-conductive element 26, and also in the horizontal direction, similarly as shown in FIG. Intermediate element 58 of
Are electrically insulated from each other. In this case, the first conductive ring portion 24a is connected to a power source (not shown).
, And the second conductive ring portion 25b can be connected to the other pole. In this way, current flows through the slag bath 20 between the two conductive parts 24a, 24b. Also, by providing three conductive elements that are insulated from each other and connecting each to each pole of the three-phase AC power supply, it is possible to generate a rotational motion in the slag bath 20 and make the temperature uniform. By increasing the current level, it is also possible to generate a rotational movement in the melt pool 18 in the same way.

[0037]

As described above, according to the present invention,
At least one conductive element that is not directly water-cooled of the chill mold is provided on a mold wall formed from a water-cooled copper element,
The dissolution rate or the dissolution temperature is affected since the conductive element is mounted so as to be in contact with the slag bath and is mounted completely below the surface of the slag bath so as not to reach the upper surface of the dissolution. Without giving, an ingot or a continuous casting with a good surface is obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a tubular chill mold used for electroslag remelting.

FIG. 2 is a longitudinal sectional view of a tubular chill mold for continuous casting.

FIG. 3 is a schematic longitudinal sectional view of an electroslag remelting apparatus provided with a sliding or floating chill mold using the tubular mold of FIG. 1;

FIG. 4 is a longitudinal sectional view of another embodiment of the chill mold.

FIG. 5 is a sectional view taken along the line VV of FIG. 4;

[Explanation of symbols]

10 ... chill mold, 12 ... chill mold lower part, 16 ...
Ingot, 20: slag bath, 24: conductive element, 32:
Continuous casting, 36: liquid metal, 42: power supply.

Claims (14)

[Claims] 1. A chill mold in which an upper surface of a casting is covered with a conductive slag and an ingot or a continuous casting is formed at a lower portion, and the ingot or the continuous casting is pulled out of the mold by lifting the mold or pulling down the ingot or the continuous casting. At least one directly non-water-cooled conductive element is mounted on a mold wall formed from the water-cooled element such that it contacts the slag bath on the one hand and does not reach the upper surface of the molten metal on the other hand, and A short water-cooled downwardly open chill mold for producing an ingot or a continuous casting, characterized in that the connection to the chill mold is made through said conductive element. 2. The chill mold according to claim 1, wherein the conductive element is located completely below the surface of the slag bath. 3. The chill mold according to claim 1, wherein one or more of the non-water-cooled conductive elements is made of graphite. 4. The chill mold according to claim 1, wherein at least one of the non-water-cooled conductive elements is made of a refractory metal such as W, Mo, Nb or the like. 5. The method according to claim 1, wherein
A chill mold containing a slag bath therein and having a funnel-shaped upper portion provided with the conductive element that is not water-cooled. 6. The method according to claim 1, wherein
A chill mold, characterized in that one or more non-water-cooled conductive elements mounted on the chill mold wall are electrically insulated by a non-conductive element from a water-cooled portion of the mold. 7. The method according to claim 1, wherein
Two, three or more of the conductive elements that are not directly water-cooled are mounted on the chill mold wall with the water-cooled elements, and the conductive elements are electrically insulated from each other by the non-conductive, non-water-cooled elements; A chill mold, wherein the element is connected to a corresponding pole of a power supply. 8. The chill mold according to claim 6, wherein the non-conductive element is made of a refractory ceramic material. 9. The chill mold according to claim 1, wherein molten metal is sent from the dispenser to the chill mold through a supply pipe extending to the metal reservoir, and the upper surface of the steel of the chill mold is liquid. For the continuous casting of metal, characterized in that an electric current for heating the slag flows between the casting and the conductive element mounted on the chill mold wall in a slag bath which is not water-cooled. apparatus. 10. The chill mold according to claim 1, wherein the molten metal is sent from the dispensing device to the chill mold through a supply pipe extending to a metal reservoir, and the upper surface of the steel of the chill mold is liquid. Two, three or more of said conductive slags are insulated from each other by non-conductive elements mounted on a chill mold wall in a slag bath in which the current for heating the slag is not water-cooled. An apparatus for continuous casting of metal, characterized by flowing between elements. 11. The chill mold according to claim 1, wherein a melting current supplied to a slag bath through a melting electrode is passed through said water-cooled conductive element mounted on a chill mold wall and a part thereof. Alternatively, a method for remelting a metal electroslag, wherein the whole is flowed to a return circuit. 12. The chill mold according to claim 6, wherein a part or all of the melting current is supplied through the water-cooled conductive element mounted on the chill mold wall and returned through the ingot and the bottom plate. A method for remelting electroslag of a metal, wherein the metal is passed through a circuit. 13. The chill mold according to claim 1, wherein a part or all of the melting current is passed through the non-water-cooled conductive element mounted on the chill mold wall on both the sending side and the returning side. A method for remelting a metal electroslag, characterized by flowing. 14. A method for using the chill mold according to any one of claims 1 to 8 in an apparatus for performing the method according to any one of claims 11 to 13.