JPS6160835A - Electroslag remelting furnace - Google Patents

Abstract

PURPOSE:To average components of the top part and the bottom part of a steel ingot, and to obtain a uniform steel ingot of high purity by constituting a consumable electrode of the steel ingot used for an electroslag remelting furnace, by dividing the steel ingot into plural parts and reversing alternately its top part and bottom part. CONSTITUTION:A steel ingot to be remelted is set as a consumable electrode 1, an AC power source 3 is connected between said electrode and a water cooling crucible 2, electric conduction is applied through a molten slag 4, the electrode 1 is melted successively and a non-metallic inclusion is removed by a refining effect of the slag 4, and said ingot is cooled and coagulated by a water flow 6, and a steel ingot 7 of high purity is obtained. In this case, the steel ingot used for the consumable electrode 1 is divided into plural parts extending from the top part direction to the bottom part direction, and bound so that its top part 1a and bottom part 1b are reversed alternately, and the consumable electrode 1 is constituted thereby. In this way, the top part 1a and the bottom part 1b are melted simultaneously, also stirred by an electromagnetic force, and the steel ingot 7 of high purity consisting of a uniform component is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical field to which the invention pertains The present invention relates to an electroslag remelting furnace for refining steel ingots.

[Prior art and its problems]

One way to remove impurities by remelting and scouring a steel ingot once manufactured is to use an electroslag remelting furnace (ESR).
(abbreviated as “furnace”) is used.

An example of this conventional ESR furnace is shown in FIG. Here, the steel ingot to be remelted is used as a consumable electrode l, its top part 1a is used as one power supply end, the water-cooled crucible 2 is used as the other power supply end, an AC power supply 3 is connected between these, and the bottom part 1b of the electrode l is melted. Contact slug 4 and turn on electricity. The electrode 1 melts sequentially from the bottom 1b due to the resistance heat of the slag 4, passes through the molten slag 4 in the form of drops, forms a molten steel boule 5 in the crucible 2, and is melted by the water flow 6 surrounding the crucible 2. It is cooled, solidified, and gradually deposited to form the steel ingot 7 again. Non-gold inclusions such as desulfurization and deoxidation are removed from the consumable electrode melted in the slag due to the refining effect of the slag, resulting in a steel ingot with high purity σ). Furthermore, since the molten steel in the crucible is rapidly cooled, there are advantages such as less segregation of components within the same cross section. Especially large ES
In the R furnace, in order to reduce the electrode glue actance and improve the circuit blade, two electrodes are arranged symmetrically, and multiple
Although they may be connected in parallel as @, the refining effect is exactly the same.

[, Kaji: The steel ingots used as consumable electrodes in BSR furnaces are usually melted in arc furnaces or induction furnaces, and sometimes degassed steel ingots are used, but all of these steel ingots are vertically long. and is poured into the vm from the ladle during melting,
It gradually solidifies from the bottom and surrounding areas, and finally solidifies at the top.

When molten steel gradually solidifies in this way, the parts that precipitate first and the parts that solidify later have different compositions, causing so-called segregation. In particular, the top 1ζ of the steel ingot contains many impurities with a low melting point. [7] Since diffusion within a solid is very slow, the composition remains non-uniform.

When the above-mentioned steel ingot is remelted in an ESR furnace, the steel ingot can obtain the effects already mentioned, but the steel ingot is melted sequentially from the bottom in contact with the slag to the top, and is deposited and solidified in the same order. Therefore, for components other than the impurities to be removed, it is considered that the same steel ingot was subdivided in the direction perpendicular to its length and moved one after another. Therefore, it is not possible to make the components in the length direction uniform. For example, Figure 5 shows the conventional E
When a turbine rotor is manufactured from 12% Cr steel melted in an SR furnace with the axis extending from the top 1a to the bottom 1b of the steel ingot, this is a graph showing the carbon content % in the longitudinal direction. % is higher on the top la side and decreases in proportion to the length of the bow.

In this way, even if a steel ingot is remelted in an ESR furnace, its composition will still differ depending on the part, and structures manufactured by processing and shaping this ingot have the disadvantage that properties such as strength and toughness will differ depending on the part. be.

[Purpose of the invention]

An object of the present invention is to provide an ESR furnace capable of producing a steel ingot with fewer differences in composition at each location.

[Key points of the invention]

The gist of the present invention is to provide an electroslag remelting furnace in which a steel ingot is connected to a consumable electrode, an alternating current is passed through a molten slag between the electrode and a water-cooled crucible, and the steel ingot is remelted by the resistance heat of the slag. , simultaneously melting the tops and bottoms of the steel ingots containing different components in an electric furnace in which a plurality of the steel ingots are connected to the same power supply terminal with the tops and bottoms alternately reversed during melting, The aim is to quickly re-solidify this molten steel to average out the contained components, thereby reducing differences in components depending on the location of the steel ingot, and thereby reducing differences in properties. Note that the plurality of steel ingots are preferably formed by cutting and dividing one steel ingot from the top to the bottom during melting, and these plurality of steel ingots are tied together to form one electrode. It may be something that you have.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 3. In FIG. 1, the ESR furnace has an AC power source 3 connected between the electrode 1 and a water-cooled crucible 2 as a consumable electrode 1, which is a steel ingot to be remelted, as in the conventional ESR furnace. As shown in Fig. 2, the electrode is divided into four parts from the top 1a to the bottom 1b (solidification direction during previous melting), and the top 1a and bottom 1b are alternately tied together in opposite directions, which is different from the conventional electrode. Very different. In addition, when the tip of the electrode 1 is brought into contact with the molten slag 4 and electricity is applied, the electrode 1 is sequentially melted starting from the tip, and a molten steel pool 5 is formed in the water-cooled crucible 2.
The steps of forming a steel ingot, cooling it with a water stream 6 to solidify it, and forming a steel ingot 7 again are the same as those of the conventional method. However, in this case, half of the top 1a and half of the bottom 1b of the steel ingot are simultaneously melted, and this molten steel is further stirred by the electromagnetic force characteristic of the electric furnace, and the components of the molten steel pool 5 are transferred to the top 1a.
The mixed molten steel is successively rapidly cooled and solidified and deposited to form the steel ingot 7 again. Therefore, the composition of this steel ingot 7 is uniform with little difference between parts. Of course, since the molten steel is rapidly cooled, the stirring effect is not very great, so it is preferable to increase the number of bound steel ingots as much as possible to make the alloy components uniform within the cross section in the direction perpendicular to the solidification direction. In this way, the electrode 1 gradually advances to the center in the current direction, but the molten steel of the molten steel pool 5 formed at this time and the solidifying part always have the same composition.
A steel ingot with uniform composition in the direction of solidification of molten steel can be obtained.

Moreover, the advantages such as removal of non-metallic inclusions other than carbon due to the scouring effect of the slag 4 and less segregation of components within the same cross section due to the quenching effect remain.

Next, in a large furnace, as already mentioned, multiple electrodes are connected in parallel with -1 at the source end 'M! ! Continued. In this case, a plurality of divided and recombined electrodes may be connected in parallel as described above.
Also, as shown in Figure 2, one steel ingot is divided into the required number of pieces,
As shown in FIG. 3, the same number of alternate top portions 1a or bottom portions 1b may be connected to the same power terminal. Further, the top portion 1a or bottom portion 1b of each steel ingot produced in the same manner may be alternately connected to the same power source terminal several times. If the ESI-LFl constructed in this way is energized and melted, the same effect as in the case of a single electrode can be obtained.

〔Effect of the invention〕

As described above, the ESR furnace according to the present invention is produced by melting in an arc furnace, a trout induction furnace, etc., and the tops or bottoms of a plurality of steel ingots having a large difference in composition between the tops and bottoms are alternately reversed and the same power source is used. It is connected to the end to serve as a consumable electrode, and the tip is sequentially melted and rapidly cooled to average the top and bottom components of the steel ingot, making it possible to obtain a uniform steel ingot. Moreover, the steel ingot produced in this manner is subjected to the scouring effect and quenching effect of molten slag in the same way as in the conventional method, so that an excellent steel ingot can be obtained in a remelting furnace.

[Brief explanation of drawings]

W, Figure 1 is a vertical cross-sectional view showing an embodiment of the electroslag remelting furnace according to the present invention, Figure 2 is a perspective view of a consumable electrode used in the remelting furnace shown in Figure 1, and Figure 3 is a multi-electrode electrolyte. A vertical cross-sectional view showing an example of electrode connection in a slag remelting furnace, Figure 4 is a vertical cross-sectional view showing an example of a conventional electroslag remelting furnace, and Figure 5 is a vertical cross-sectional view showing an example of a conventional electroslag remelting furnace. 2 is a graph showing the carbon content in the longitudinal direction of a turbine rotor made of 12% Cr steel. l... Steel ingot used as an electrode, 1a... Top of steel ingot, 11
)... Bottom of the steel ingot, 2... Water-cooled crucible, 3... AC power supply, 4... Molten slag. Iwa Yamaguchi, Patent Attorney Figure 1

Claims (1)

[Claims] 1) Electroslag remelting, in which a steel ingot is used as a consumable electrode, and an alternating current is passed through the molten slag between the electrode and a water-cooled crucible, and the steel ingot is remelted by the resistance heat of the slag. An electroslag remelting furnace characterized in that a plurality of the steel ingots are connected to the same power source terminal with their tops and bottoms alternately reversed during melting. 2) In the electroslag remelting furnace according to claim 1, the plurality of steel ingots are formed by cutting and dividing one steel ingot from the top to the bottom during melting. An electroslag remelting furnace featuring: 3) In the electroslag remelting furnace according to claim 1 or 2, the electroslag remelting furnace is characterized in that a plurality of steel ingots are bound together to form one electrode. Furnace.