Method of manufacturing steel ingot

Abstract

To provide a method of manufacturing a steel ingot which can be joined at a desirable position on an electrode, as the result, can equalize side-gaps between an electrode and molds and, therefore, can provide the steel ingot more excellent in quality.SOLUTION: A method of manufacturing a steel ingot in which a stub is attached on an edge surface of an electrode, the stub is gripped, and is lifted up by a clamp, an electrode is charged into a mold of a remelting furnace and operations of melting the electrode and solidifying it are included, includes a process of preparing a jig which causes a center C on a specific cross-section of the electrode on a previously specified straight line L and causing a lateral surface to closely adhere onto the jig, a process of measuring a position of a lateral surface of the electrode and, thereby, specifying the position of the center C of the cross-section of the electrode, and a process of attaching the stub onto the edge surface of the electrode so that a center shaft ω1 of the electrode specified from the position of the center C and a center shaft ω2 of the clamp coincide with each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a steel ingot. [Background technology]

[0002] In the past, several proposals have been made regarding the method of joining a stub to an electrode used for remelting steel.

[0003] For example, Patent Document 1 describes a process in which, prior to loading an electrode into a mold in a remelting furnace, a stub is welded to the upper end surface of the electrode, and a distance measuring sensor is used to measure the distance between the outer circumferential surface of the electrode and the distance measuring sensor at a plurality of measurement points in the longitudinal direction of the electrode, the distance being measured using the distance measuring sensor that revolves around the outside of the electrode around the center line of the mold and stub clamp section as its axis; image processing is performed at each measurement point based on the measurement information, an electrode cross-sectional view is drawn with the position of the center line as the origin coordinate, a virtual mold circle of the same diameter as the mold is drawn with a certain point present in the drawn electrode cross-sectional view as its center point, and the center point (GP') is determined so that the difference between the virtual side gaps drawn between the electrode cross-sectional view and the virtual mold circle is minimized over the entire circumference of the electrode cross-sectional view. the step 2 of calculating coordinates; the step 3 of drawing a virtual axis (Z) in the longitudinal direction of the electrode by approximately connecting the coordinates of the center points in all of the electrode cross-sectional views, and adjusting the inclination of the electrode so that the inclination of the virtual axis (Z) at the upper end surface of the electrode with respect to the center line is 1.5 mm / m or less; the step 4 of vertically moving the coordinate of the center point (GP'') of the virtual axis (Z) along the origin coordinate of the center line to the upper end surface of the electrode, and setting the coordinate at the upper end surface as the position coordinate of the welding point; and the step 5 of transporting the stub to the welding point by a stub transport means having a coordinate system with the center line as the origin coordinate, and then welding the stub to the upper end surface of the electrode at that position.

[0004] For example, Patent Document 2 describes an auxiliary jig for welding a stub and a square consumable electrode, which is characterized in that an electrode attachment having a square opening in the center for mounting the square consumable electrode is placed on a turning table, the square consumable electrode is mounted in the opening of the electrode attachment, and the square consumable electrode can be rotated by the turning table around its longitudinal axis.

[0005] For example, Patent Document 3 describes a method for joining an electrode and a stub, which comprises calculating the weight of the electrode and the moment acting on the joint surface of the stub from the outer diameter and length of the electrode, determining the diameter and number of bolts from these values, providing an integrated flange for attaching the bolts to the lower end surface of the stub, drilling screw holes in the upper end surface of the electrode, and then joining the stub and electrode by fastening them with bolts. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-69263 A [Patent Document 2] JP 2012-143764 A [Patent Document 3] JP 2012-144753 A Summary of the Invention [Problem to be solved by the invention]

[0007] When joining the stub to the electrode used for remelting steel, it is preferable to join the stub to the electrode at a desired position, because in that case, the side gap between the electrode and the mold can be made more uniform, and as a result, a steel ingot of better quality can be obtained.

[0008] The present invention provides a method for producing steel ingots that can join a stub to a desired position on the electrode, thereby making the side gap between the electrode and the mold more uniform, and as a result, producing a steel ingot of better quality. [Means for solving the problem]

[0009] The present invention relates to the following (1) to (6). (1) A method for producing a steel ingot, comprising the steps of attaching a stub to an end face of an electrode, gripping and lifting the stub with a clamp, inserting the electrode into a mold of a remelting furnace, and then melting and solidifying the electrode, a step of preparing a jig that can position a center C of a specific cross section of the electrode on a predefined straight line L when the side surface of the electrode is brought into close contact with the jig, and bringing the side surface of the electrode into close contact with the jig; a center position determining step of measuring the position of a side surface of the electrode, thereby determining the position of a center C of a cross section of the electrode; a stub attachment process of attaching the stub to the end surface of the electrode using the clamp so that a central axis ω1 of the electrode identified from the identified position of the center C coincides with a central axis ω2 of the clamp; A method for producing a steel ingot comprising the steps of: (2) In the center position specifying step, A method for producing a steel ingot as described above in (1), in which the position of the side surface of the electrode is measured at different positions in a direction parallel to the central axis ω1 of the electrode. (3) In the adhesion step, 3. The method for producing a steel ingot according to claim 1, wherein the jig is a V-shaped roller. (4) In the adhesion step, The method for producing a steel ingot according to any one of (1) to (3) above, wherein a side surface of the electrode, which is arranged so that a central axis ω1 is in the vertical direction, is brought into close contact with the jig using a supporting means. (5) In the center position specifying step, The method for producing a steel ingot according to any one of (1) to (4) above, wherein the position of the side surface of the electrode is identified using a laser distance meter. (6) In the center position specifying step, The method for producing a steel ingot as set forth above in any one of (1) to (5), wherein two positions of the side surface of the electrode are specified on the straight line L. Effect of the Invention

[0010] According to the present invention, since the stub can be joined at a desired position on the electrode, the side gap between the electrode and the mold can be made more uniform, thereby providing a method for manufacturing steel ingots that can produce steel ingots of better quality. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows a state in which an electrode is placed on a V-shaped roller in a jig, where FIG. 1(a) is a schematic top view, FIG. 1(b) is a schematic side view, and FIG. 1(c) is a cross-sectional view taken along line AA in FIG. 1(a). [Diagram 2] 1 is a schematic side view showing a state in which the electrodes are arranged so that their central axes ω1 are in the vertical direction. [Diagram 3] FIG. 3(a) is a schematic cross-sectional view similar to the cross-sectional view taken along line AA in FIG. 1(a), showing an example in which the V-shaped roller 13 has been deformed due to wear or the like, and FIG. 3(b) is a schematic cross-sectional view similar to the cross-sectional view taken along line AA in FIG. 1(a), showing an example in which a foreign substance is attached to the surface of the electrode and part of it has been scraped off to form a dent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The manufacturing method of the present invention will now be described. The manufacturing method of the present invention is a method for manufacturing a steel ingot, comprising the steps of attaching a stub to an end surface of an electrode, gripping and lifting the stub with a clamp, loading the electrode into a mold of a remelting furnace, and then melting and solidifying the electrode, and comprising the steps of: preparing a jig that can position the center C of a specific cross section of the electrode on a pre-specified straight line L when the side of the electrode is pressed against the jig; a center position identifying step of measuring the position of the side of the electrode and thereby identifying the position of the center C of the cross section of the electrode; and a stub attaching step of attaching the stub to the end surface of the electrode using the clamp so that the central axis ω1 of the electrode identified from the identified position of center C coincides with the central axis ω2 of the clamp.

[0013] The manufacturing method of the present invention relates to a method for manufacturing a steel ingot by a remelting method (secondary melting method) such as the ESR method (electroslag remelting method) or the VAR method (vacuum arc remelting method).

[0014] In secondary melting methods such as the ESR method and the VAR method, the electrodes obtained from primary melting using an AF furnace (electric arc furnace) or VIM furnace (vacuum induction melting furnace) are loaded into a mold in the secondary melting method, melted, and solidified to produce steel ingots.

[0015] The electrodes are typically cylindrical, but may be other shapes. The type of the electrode is not particularly limited, but may be, for example, maraging steel, stainless steel, Ni-based superalloy, or the like.

[0016] Before the electrode is inserted into the mold, a stub is attached to the end of the electrode by welding or other methods. The stub is then grasped and lifted with a clamp, and the electrode is inserted into a mold to be used in the secondary melting process. The stub may be, for example, a cylindrical member thinner than the electrode, and may be made of stainless steel (SUS) or the like.

[0017] When attaching a stub to the end face of the electrode, it is preferable that the central axis ω1 of the electrode and the central axis ω3 of the stub coincide with each other. Here, it is considered that the two central axes coincide when the central axis ω1 and the central axis ω3 exist on a straight line. In reality, it is not easy to make the two central axes completely coincident, but it is preferable to make them as close to coincident as possible. In that case, the gap between the electrode and the mold in the circumferential direction (side gap) can be made more uniform over the entire circumferential direction. If the side gap is uniform over the entire circumferential direction, the amount of heat inside the mold can be maintained, and the cleanliness of the surface of the molten steel in the mold tends to be kept high. As a result, a steel ingot of better quality can be obtained. Furthermore, if the side gap is uniform over the entire circumferential direction, the solidification rate of the molten steel can be made uniform.

[0018] <Adhesion process> The adhesion step in the manufacturing method of the present invention will be described. In the adhesion process, first, a jig is prepared. The jig is of a type that, when the side surface of the electrode is brought into close contact with the jig, the center C of a specific cross section of the electrode can be positioned on a straight line L that has been specified in advance. An example of such a jig is one that includes a V-shaped roller. It may be a jig that does not function as a roller and simply has a part with a V-shaped cross section. In addition to a V-shaped cross section, it may also be a U-shaped cross section. The surface of the V-shaped roller is flat, but the flat surface may be a gently curved surface. If the portion of the jig that comes into contact with the electrode functions as a roller, the electrode can be moved on the jig.

[0019] The jig may be, for example, as shown in Fig. 1, a plurality of V-shaped rollers 13 fixed on a substrate 11. Fig. 1 shows a state in which an electrode 3 is placed on the V-shaped rollers 13 in such a jig 1, with Fig. 1(a) being a schematic top view, Fig. 1(b) being a schematic side view, and Fig. 1(c) being a cross-sectional view taken along line AA in Fig. 1(a).

[0020] As shown in FIG. 1(c), when the side of the electrode 3 is pressed against the V-shaped roller 13, the center C of a specific cross section of the electrode 3 can be made to lie on a predefined straight line L that passes through the center of the V-shaped roller 13.

[0021] 2, it is preferable to bring the side surface of the electrode 3 into close contact with the jig 1 (V-shaped roller 13 in the jig 1) using a support means 5 in a state in which the central axis ω1 of the electrode 3 is oriented vertically. This is because, in the subsequent stub attachment step, it is preferable to attach the stub in a state in which the central axis ω1 of the electrode 3 is oriented vertically.

[0022] The support means 5 may include, for example, a steel pipe obtained by cutting the end face of the steel pipe in the longitudinal direction at two circumferential points. The support means 5 preferably has a function of further bringing it into close contact with the side surface of the cylindrical electrode 3 and pressing the electrode 3 against the V-shaped roller 13 to bring the electrode 3 into close contact with the V-shaped roller 13.

[0023] The adhesion step is a step of preparing a jig as described above and adhering the side surface of the electrode to the jig.

[0024] <Center position identification process> The center position specifying step in the manufacturing method of the present invention will be described. In the center position specifying step, the position of the side surface of the electrode is measured. For example, as shown in Fig. 1(c), by using a laser rangefinder 7 to determine the distance between the laser rangefinder 7 and the side surface of the electrode 3, it is possible to determine the position of the center C of the cross section of the electrode 3. For example, as shown in Fig. 1(c), by arranging two laser rangefinders 7 on a line L and positioning the electrode 3 between the two laser rangefinders 7, it is possible to determine two positions of the side surface of the electrode 3 on the line L, and therefore the position of the center C of the cross section of the electrode 3 can be easily determined. It is possible to determine the position of center C even if the laser rangefinder 7 is not located on line L, and it is also possible to determine the position of center C with only one laser rangefinder 7. However, the more laser rangefinders 7 there are, the more accurately the position of center C can be determined.

[0025] 2, it is preferable to measure the position of the side surface of the electrode 3 at different positions in a direction parallel to the central axis ω1 of the electrode 3, i.e., at multiple positions in the height direction. In FIG. 2, laser range finders 7 are placed at two positions in the height direction. In this way, the positions of a plurality of centers C in the height direction can be identified, so that the position of the central axis ω1, which is a set of centers C, can be identified with higher accuracy.

[0026] Here, for example, if the V-shaped roller 13 is deformed due to wear or the like, if there is foreign matter on the surface of the electrode 3, or if the surface of the electrode 3 is scraped off, the position of the center C cannot be accurately determined even if the sides of the electrodes are brought into close contact. For example, Figures 3(a) and (b) are schematic cross-sectional views similar to the cross-sectional view along line AA in Figure 1(a) as in Figure 1(c), but Figure 3(a) is an example in which the V-shaped roller 13 has been deformed due to wear or the like, and Figure 3(b) is an example in which a foreign matter 31 is attached to the surface of the electrode 3 and part of it has been scraped off to form a dent 33. 3(a), the center C of the electrode 3 in a specific cross section cannot be located on the predefined straight line L. As a result, the position of the center C cannot be accurately specified. In the case of FIG. 3(b), the position of the center C cannot be identified accurately. Therefore, it is preferable to set a tolerance range in advance for the result of measuring the position of the side surface of the electrode in the center position specifying step, and if the measurement result exceeds the tolerance range, it is preferable to determine that some kind of abnormality has occurred, as shown in Figures 3(a) and (b).

[0027] <Stub installation process> The stub attachment step in the manufacturing method of the present invention will now be described. The central axis ω1 of the electrode 3 is identified from the position of the center C of the specific cross section of the electrode 3 identified in the central position identifying process, and the stub is attached to the end face of the electrode 3 so that this central axis ω1 coincides with the central axis ω3 of the stub. However, since it is difficult to specify the shape of the stub, it is also very difficult to specify the position of the central axis ω3 of the stub. Therefore, instead of the central axis ω3 of the stub, the central axis ω2 of the clamp holding the stub is arranged to coincide with the central axis ω1 of the electrode 3, and the stub is attached to the end face of the electrode by welding or the like. In this way, the stub is attached to the end face of the electrode 3 so that the central axis ω1 of the electrode and the central axis ω3 of the stub coincide with each other.

[0028] In the stub attachment process, the stub is attached to the end face of the electrode 3 using a clamp so that the central axis ω1 of the electrode 3 specified from the position of the specified center C coincides with the central axis ω2 of the clamp, but it is not intended that the central axis ω1 of the electrode 3 specified from the position of the specified center C coincides completely with the central axis ω2 of the clamp. It is intended that the central axis ω1 and the central axis ω2 of the clamp coincide as closely as possible. Even if the central axis ω1 of the electrode 3 and the central axis ω2 of the clamp do not coincide completely, it is within the scope of the present invention. [Explanation of symbols]

[0029] 1 Jig 3 electrodes 5 Support means 7 Laser rangefinder 11 Substrate 13 V-shaped roller 31 Foreign object 33 Dent

Claims

1. 1. A method for producing a steel ingot, comprising the steps of attaching a stub to an end face of an electrode, gripping and lifting the stub with a clamp, inserting the electrode into a mould of a remelting furnace, and then melting and solidifying the electrode, a step of preparing a jig that can position a center C of a specific cross section of the electrode on a predefined straight line L when the side surface of the electrode is brought into close contact with the jig, and bringing the side surface of the electrode into close contact with the jig; a center position determining step of measuring the position of a side surface of the electrode, thereby determining the position of a center C of a cross section of the electrode; The central axis ω of the electrode identified from the position of the identified center C 1 and the central axis ω of the clamp 2 a stub attachment step of attaching the stub to the end surface of the electrode using the clamp so that the ends of the stub and the end surface of the electrode coincide with each other; A method for producing a steel ingot comprising the steps of:

2. In the center position specifying step, The central axis ω of the electrode 1 2. The method of claim 1, further comprising measuring the position of the side of the electrode at different positions in a direction parallel to the electrode.

3. In the adhesion step, 3. The method for producing a steel ingot according to claim 1 or 2, wherein the jig is a V-shaped roller.

4. In the adhesion step, central axis ω 1 3. The method for producing a steel ingot according to claim 1, wherein a side surface of the electrode is brought into close contact with the jig using a support means.

5. In the center position specifying step, The method for producing a steel ingot according to claim 1 or 2, wherein the position of the side surface of the electrode is identified using a laser distance meter.

6. In the center position specifying step, 3. The method for producing a steel ingot according to claim 1 or 2, wherein two positions of the side surface of the electrode are specified on the straight line L.

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