JPS6372839A - Method and device for controlling drawing speed of ingot in electroslag refining - Google Patents

Abstract

PURPOSE:To stably drawn an ingot and to prevent the generation of an abnormal layer on a drawn surface by quantifying the relation between throwing power and the liquid level rising speed of a metal pool at the time of electroslag refining and controlling the drawing speed of the ingot in accordance with the relation. CONSTITUTION:The ingot 3 is formed by melting a consumable electrode 7 by the Joule heat generated in molten slag 6, removing the impurities of electrolytically molten drops by the refining effect of the slag and laminating and solidifying the molten drops successively into the water-cooled crucible 2. The ingot is drawn by clamps 4, 5. Supply current I, supply voltage V, the diameter (d) of the consumable electrode 7, the diameter D of the crucible 2 and the thickness L of the molten slag 6 are preliminarily inputted to an arithmetic unit and the throwing power P is calculated by P=IXVX(d/D)<2>XDXL<-1>. The liquid level rising speed S of the metal pool 8 is calculated by the throwing power P and the association between P and S is quantified. The drawing speed of the ingot 3 is thereby automatically controlled in accordance with the liquid level rising data, by which the operator's burden is decreased and the drawing of the ingot 3 is stably executed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is used to perform electroslag remelting in order to obtain a high-quality ingot in an optimal state. The present invention relates to an ingot drawing speed control method and control device in electroslag remelting.

(Conventional technology) Conventionally, vacuum induction melting (
VIM) method, vacuum arc remelting (VAR) method, electroslag remelting (ESR) method, plasma arc melting (PAM) method.

PIM, PAR, PPC) method, electron beam melting (E B
There are various methods such as R) method, each having advantages and disadvantages.

Among these, electroslag remelting (ESR)
This method involves melting consumable electrodes using the Joule heat of molten slag in the atmosphere or under an inert gas, and then solidifying the droplets that have fallen through the molten slag in layers in a water-cooled copper crucible to obtain high-quality ingots. be.

The ESR equipment used to carry out this ESR method can be roughly divided into: ① crucible fixed type;

■Ingot drawing method, ■Crucible moving method.

■There are multi-electrode methods, etc., which can be selected and adopted as appropriate.

In addition, the operation begins with melting the slag, and in this case, there are two methods: a cold start method in which powdered fusix placed in a crucible is melted by an arc, and a hot start method in which separately melted slag is transferred into the crucible. In order to obtain a high quality ingot by the ESR method, it is important to select a slag suitable for the composition of the consumable electrode to be remelted and to set the conditions for remelting the consumable electrode.

In this type of ESR method, a consumable electrode is immersed in molten slag and energized, the consumable electrode is melted by the Joule heat generated in the molten slag, and when the droplets of the consumable electrode fall through the molten slag, Impurities are removed by the refining action of the slag, and the slag is successively cast into a water-cooled steel crucible and solidified in layers to form a high-quality ingot.

The ingots obtained here are then sequentially pulled out from the bottom of the crucible, but in the conventional case, the ingot drawing speed was manually set by the input power when remelting the electroslag, and the liquid level monitoring device Alternatively, an operator manually adjusts the drive speed of the ingot drawing mechanism while monitoring the liquid level by direct visual inspection.

(Problems to be Solved by the Invention) However, in such conventional electroslag remelting, the drawing speed of the ingot was adjusted manually by the worker, which placed a heavy burden on the worker and caused the drawing speed to change. When the value becomes larger than the appropriate value, there is a problem in that a macro abnormal layer may be formed on the ingot surface due to tearing of the metal shell on the crucible wall.

(Object of the Invention) The present invention has been made by focusing on the above-mentioned conventional problems, and it is possible to automatically pull out the ingot during electroslag remelting, thereby reducing the burden on one worker. At the same time, it is an object of the present invention to prevent the formation of an abnormal surface layer by performing stable drawing of the ingot.

[Structure of the Invention] (Means for Solving the Problems) The ingot drawing speed control method in electroslag remelting according to the present invention melts the consumable electrode by Joule heat of the molten slag, and the liquid falling in the molten slag melts. When carrying out electroslag remelting in which droplets are layered and solidified in a crucible and the aR solidified ingot is pulled out from the bottom of the crucible, the relationship between the input power during the remelting and the rate of rise in the liquid level of the metal pool is quantified, The method is characterized in that the drawing speed of the ingot is controlled based on the relationship between the quantified input power and the liquid level rising speed,
The device for controlling the ingot withdrawal speed in electroslag remelting according to the present invention, which is directly used in carrying out the invention of this method, accommodates the molten slag and solidifies the droplets of the consumable electrode melted by the Joule heat of the molten slag in the a-layer. In an electroslag remelting apparatus equipped with a crucible and an ingot pulling mechanism that pulls out the ingot formed by the layered solidification from the bottom of the crucible, the input power and the rate of rise in the liquid level of the metal pool during remelting of the consumable electrode A calculation means is provided for quantifying the relationship between the above-mentioned ingo based on the output of the calculation means.

The present invention is characterized in that it is configured to operate the drive device of the pull-out mechanism.

(Example) FIG. 1 shows an example of a schematic structure of an electroslag remelting device used to carry out the present invention.

In the electroslag remelting equipment 221 shown in the figure, the ingot 3 coming out from the lower side of the crucible 2 having a water-cooled structure includes:
A first clamper 4 and a second clamper 5, which constitute an ingot pulling mechanism for gripping and pulling out the ingot 3 downward, are installed so as to be able to grip the ingot 3 alternately. Further, a molten slag 6 is placed at a predetermined depth inside the crucible 2 at the upper part of the ingot 3.
A metal pool 8 is formed of the consumable electrode 7 melted by Joule heat.

Further, a mist cooling nozzle 9 is provided on the lower side of the crucible 2, so that the cooling rate of the ingot 3 can be controlled as necessary.

On the other hand, an electrode support mast 11 is installed at the base part, and an electrode support 1 is placed in the middle of this electrode support mast 11.
2 is installed so that it can be raised and lowered. The proximal end of an electrode support arm 15 is rotatably connected to the electrode support 12 via an electrode support member 13 and a pivot shaft 14, and the electrode support arm 15 is rotated by driving a power cylinder 16. The pivot shaft 14
It is designed to rotate vertically around the center. Further, this electrode support arm 15 is capable of rotating in the horizontal direction.

Further, the electrode support arm 15 has a consumable electrode fixing portion 17 on the distal end side for fixing the upper end portion of the consumable electrode 7.

Furthermore, the consumable electrode 7, the crucible 2 and both clampers 4
, 5, an AC power source 21 is connected between the crucible 2 and the crucible 2.
By simultaneously supplying power to the crucible 2 and the ingot 3, generation of arc between the crucible 2 and the ingot 3 is prevented, thereby stabilizing the operation. Further, at the lower end of the ingot 3 there is a dummy bar 22 used in the initial stage of melting, and the ingot 3 is cut into appropriate lengths by a plasma cutter 23.

FIG. 2 is a diagram showing a drive device for the first clamper 4 and the second clamper 5, which are the ingot pulling mechanism, and in the figure, AC-M is an AC that raises the first clamper 4 independently.
It is a motor and is equipped with a brake B. Also, AC*
M2 is an AC motor for raising the second clamper 5 independently, and is equipped with a brake B. The first clamper 4 and the second clamper 5 each have an electromagnetic clutch M
A common DC motor (D
C-M). In addition, this DC motor (DC
@M) is also equipped with a brake B and is connected to a tachogenerator TG and an encoder EN.

In the ingot drawing mechanism shown in FIG.
As shown in the figure, when the first clamper 4 is gripping the ingot 3, the electromagnetic clutch MC on the first clamper 4 side is connected and the first clamper 4 is moved by the common DC motor (DC-M). Lower it and pull out ingot 3,
When the descending stroke by the first clamper 4 is completed, the ingot 3 is gripped by the second clamper 5, the electromagnetic clutch MC is turned off, and the electromagnetic clutch MC2 of the 5 second clampers is connected, and the common DC motor (DC-M) lowers the second clamper 5 and pulls out the ingot 3. During this time, the AC motor (AC@M1) raises the first clamper 4 to its original height, and the lowering process by the second clamper 5 is completed. When the ingot 3 is gripped by the first clamper 4, the electromagnetic clutch MC2 is disconnected, and the electromagnetic clutches MC of the four first clampers are connected, and the common DC motor (DC@M) is used to move the ingot 3 to the first clamper. 4 is lowered and ingot 3 is pulled out, as shown in Figure 1.
→Repeat the operation of ■, and each clamper 4.5
The ingot 3 can be continuously pulled out without taking a very large descending stroke. and,
In this case, the ingot drawing speed is determined by the DC motor (DC@M
), and this rotation speed is detected by a tachogenerator TG.

In the electroslag remelting device 1 having such a configuration, the consumable electrode 7 is immersed in the molten slag 6 and energized,
Consumable electrode 7 due to Joule heat generated in molten slag 6
When the droplets of the consumable electrode 7 fall through the molten slag 6, impurities are removed by the refining action of the molten slag 6, which is successively cast into the water-cooled crucible 2 and solidified in 11 layers. The ingot 3 formed by stacking and solidifying is pulled out from the lower part of the crucible 2 by a first clamper 4 and a second clamper 5. Then, mist is injected from a plurality of mist cooling nozzles 2 toward the surface of the ingot 2 and 3 as necessary to control the cooling rate of the ingot 3.

In the process of electroslag remelting, the calculation device (OP) shown in FIG.
, the diameter (D) of the crucible 2, and the thickness (L) of the molten slag 6 are input, and in this calculation device (OP), it is determined by P-I XVX (d/D)2 ×D × L-1. Calculate the input power (P), and calculate this input power (P)
Calculate the rate of rise in the liquid level (S) of the metal pool 8 from Quantify.

FIG. 3 is a diagram showing an example of the relationship between the input power (P) and the rate of rise in the liquid level (S) of the metal pool 8.
DC based on the liquid level rise speed data calculated by P)
The rotation speed of the motor (DC@M) is adjusted to automatically control the drawing speed of the ingot 3. In other words, the input power (
When the value of P) increases and the liquid level rise speed (S) increases, the rotation speed of the DC motor (DC@M) is increased to increase the drawing speed of the ingot 3, and conversely, the input power (P) is increased. When the value becomes small and the liquid level rise speed (S) decreases, by reducing the rotation speed of the DC motor (DC・M) and reducing the drawing speed of the ingot 3,
The liquid level in the metal pool 8 is controlled to be kept constant.

[Effects of the Invention] As explained above, the ingot drawing speed control method in electroslag remelting according to the present invention melts the consumable electrode by the Joule heat of the molten slag, and transfers the droplets falling in the molten slag to the crucible. am coagulate within a
When performing electroslag remelting in which the layer-solidified ingot is pulled out from the bottom of the crucible, the relationship between the input power during the remelting and the rate of rise of the liquid level in the metal pool is quantified, and the relationship between the quantified input power and the liquid level is quantified. The ingot drawing speed control device, which controls the drawing speed of the ingot based on the relationship with the surface rising speed, and which is used directly in carrying out the invention of this method, accommodates the molten slag and uses the Joule heat of the molten slag to control the drawing speed of the ingot. In an electroslag remelting apparatus, the electroslag remelting apparatus is equipped with a crucible that stacks and solidifies droplets of the melted consumable electrode, and an ingot pulling mechanism that pulls out the ingot formed by the a-layer solidification from the bottom of the crucible. A calculation means for quantifying the relationship between the input power during melting and the rate of rise in the liquid level of the metal pool is provided, and the drive device of the ingot drawing mechanism is operated based on the output of the calculation means. It is now possible to automatically pull out the ingot during slag remelting according to the input power, reducing the burden on the operator more than before.
By performing stable drawing of the ingot, it is possible to prevent the formation of an abnormal layer on the surface of the ingot, which is a very excellent effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the schematic structure of an electroslag remelting device used to carry out the present invention, FIG. ) and the liquid level rising speed (S). 1... Electroslag remelting device. 2... Crucible, 3... Ingot, 4... First clamper (ingot extraction mechanism), 5...
・Second clamper (ingot pulling mechanism), 6... Molten slag, 7... Consumable electrode, 8... Full bending pool, ACΦM,, AC・M2... AC motor, DC・M・
...DC motor (drive device for the ingot drawing mechanism), MCI, MC2...electromagnetic clutch, OP...computation device (computation means). Patent Applicant: Daido Steel Co., Ltd. Representative Patent Attorney Yutaka Shio

Claims (4)

[Claims] (1) When performing electroslag remelting, the consumable electrode is melted by the Joule heat of the molten slag, the droplets that have fallen in the molten slag are layered and solidified in the crucible, and the layered and solidified ingot is pulled out from the bottom of the crucible. Quantifying the relationship between the input power and the rate of rise in the liquid level of the metal pool during the remelting, and controlling the withdrawal rate of the ingot based on the quantified relationship between the input power and the rate of increase in the liquid level. A method for controlling the ingot drawing speed in electroslag remelting, characterized by: (2) The input power (P) when performing electroslag remelting is the supply current (I), supply voltage (V), consumable electrode diameter (d), crucible diameter (D), and molten slag thickness (L).
Ingot drawing speed control in electroslag remelting according to claim (1), characterized in that P=I×V×(d/D)^2×D×L^-^1 Method. (3) A crucible that accommodates molten slag and solidifies the droplets of the consumable electrode melted by the Joule heat of the molten slag in layers, and an ingot extraction mechanism that pulls out the ingot formed by the layered solidification from the bottom of the crucible. In the electroslag remelting apparatus, a calculation means is provided for quantifying the relationship between the input power during remelting of the consumable electrode and the rate of rise in the liquid level of the metal pool, and the ingot is drawn out based on the output of the calculation means. An ingot drawing speed control device for electroslag remelting, characterized in that it is configured to operate a driving device of the mechanism. (4) Input power (P) and metal pool liquid level rise rate (
The calculation means for quantifying the relationship with S) is the supply current (I)
, supply voltage (V), consumable electrode diameter (d), crucible diameter (D)
, from the molten slag thickness (L), calculate the input power (P) by P=I×V×(d/D)^2×D×L^-^1, and calculate the liquid level from this input power (P). The ingot drawing speed control device in electroslag remelting according to claim (3), characterized in that the device calculates the rising speed (S).