JP2007069263A - Method for welding stub to electrode used for remelting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for welding a stub to an electrode with high precision at the outside of a mold. <P>SOLUTION: The distance between the outer circumference of an electrode 1 and a distance measuring sensor is measured by the distance measuring sensor. Based on the measurement information, the cross-section of the electrode and a virtual mold circle B are drawn, and points G<SB>P1</SB>', G<SB>P2</SB>' and G<SB>P3</SB>' in the electrode at which the variation of virtual side gaps Ln, L'n between the outer circumference of the cross-section in the electrode and the virtual mold circle is made the minimum are calculated. Based on the central point, calculation is performed in such a manner that the inclination θ of a virtual axis Z to the passing core of a mold/stub clamp reaches ≤1.5 mm/m. Further, calculation is performed in such a manner that the central point of the virtual axis Z vertically moves along the passing core to the upper end face 1a of the electrode, thus its intersection G<SB>P</SB>'' with the upper end face of the electrode is obtained, and a stub is arranged at the intersection, so as to be welded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for attaching a stub to a consumable electrode (hereinafter simply referred to as an electrode) used in a remelting furnace, and more particularly, to load and arrange an electrode in a water-cooled mold (hereinafter referred to as a mold) of a remelting furnace. Prior to the method, a stub is attached to the upper end surface of the electrode, and the stub is attached to the electrode so that the gap between the electrode and the mold is small over the entire length of the electrode and the gap is as uniform as possible. It is related with the method of attaching to (welding).

In the vacuum arc remelting method (VAR) and the electroslag remelting method (ESR), the operation is performed in a state where the electrode to be purified is suspended from the water-cooled mold disposed in each remelting furnace.
Specifically, the electrode is suspended in the mold in a state where a stub attached by welding to the upper end surface of the electrode is held by the stub clamp portion.

In each re-melting furnace, the machine center of the stub clamp part and the machine center of the mold are coincident with each other, so that a vertical core is formed between the two.
Therefore, if the electrode to be used is a perfect circle and is not curved in the longitudinal direction, the center (axial center) of the upper end surface of the electrode is aligned with the axial center of the stub, and the two are welded together. When the electrode is suspended, the gap between the outer periphery of the electrode and the inner wall of the mold (hereinafter referred to as a side gap) is the same over the entire length of the electrode, and there is almost no variation in the side gap even during the operation process.

  However, the electrodes actually used have a cross section that is not a perfect circle and is curved in the full length direction. For this reason, when such an electrode is suspended in the mold, the side gap between the electrode and the mold varies greatly both at the start of operation and during operation. And when the dispersion | variation in a side gap becomes large, the quality fall of the steel ingot obtained after an operation will be brought about.

For this reason, in order to reduce the variation in the side gap between the electrode and the mold, the following adjustment work is performed when the electrode is placed in the mold.
One is the following adjustment work.
The electrode is inserted into the mold using, for example, a crane and then settled. Then, the gap between the mold and the electrode was visually observed, and if a variation in the side gap was observed, the electrode was slightly lifted with a crane, and the side gap was equalized by moving the electrode manually using, for example, a bar. After that, it settles in the mold again.

Thereafter, the center of the stub is arranged at the center of the upper end portion of the electrode, and both are welded.
However, in this adjustment operation, since the electrode is usually 2 to 3 m in total length, the side gap in the vicinity of the opening of the mold can be visually observed, but the visual observation in the lower part of the mold is practically impossible. The accuracy of the results is very low.
In addition, the electrode is generally curved or partially deformed, but the above adjustment work cannot be applied to such an electrode.

Furthermore, during adjustment work or during welding of the stub, foreign matter, welding splash, or the like may fall and mix in the mold, which may contaminate the target steel ingot.
Other methods include the following methods.
In this method, the stub is not attached after the electrode is placed and placed in the mold, but the stub is attached to the upper end of the electrode in advance so that the core can be visually observed outside the mold. It is set as an integrated object, and this integrated object is set in a furnace after that. At this time, the upper end part of a stub clamp part protrudes from the upper part of a furnace body.

Then, an XY alignment mechanism is attached to the upper end of the stub clamp portion, and the XY alignment mechanism is operated to adjust the side gap between the electrode located in the mold and the mold.
In this method, since the stub is attached outside the mold, there is an advantage that contamination inside the mold does not occur. However, since the electrodes and the stub cores are visually determined in the same manner as in the method described above, the accuracy is still insufficient.

  When the XY alignment mechanism is operated, the integrated object moves with the upper portion of the furnace body as a fulcrum, and the integrated object does not translate in the XY plane over the entire length. That is, since the moving distance of the upper part of the integrated product and the moving distance of the lower part are different, the side gap cannot be adjusted uniformly over the entire length of the electrode.

  The present invention solves the above-mentioned problems in the prior art, and there is no fear of contaminating the inside of the mold when setting the electrode, and the stub to the electrode that can equalize the side gap between the electrode and the mold with high accuracy is provided. The purpose is to provide a mounting method.

In order to achieve the above object, in the present invention, prior to inserting the electrode into the mold of the remelting furnace, when welding the stub to the upper end surface of the electrode,
A distance measuring sensor that pivots outside the electrode around the core of the mold and the stub clamp at a plurality of measurement points in the longitudinal direction of the electrode, and the distance between the outer peripheral surface of the electrode and the distance measuring sensor Measuring step 1;
At each measurement point, image processing based on the measurement information is performed, and an electrode cross-sectional view with the position of the core as the origin coordinate is drawn, and the mold is centered on a certain point existing in the drawn electrode cross-sectional view. A virtual mold circle having the same diameter as the center point such that a difference between a virtual side gap drawn between the electrode cross-sectional view and the virtual mold circle is minimized on the entire circumference of the electrode cross-sectional view ( Step 2 of calculating the coordinates of _GP ′);
The virtual axis (Z) is drawn in the longitudinal direction of the electrode by approximately connecting the coordinates of the center point in all the electrode cross-sectional views, and the inclination of the virtual axis (Z) with respect to the core of the upper end surface of the electrode is Step 3 of adjusting the inclination of the electrode so as to be 1.5 mm / m or less;
The coordinate of the center point ( _GP ″) of the virtual axis (Z) is vertically moved to the upper end surface of the electrode along the origin coordinate of the core, and the coordinate on the upper end surface is set as the position coordinate of the welding point. Performing step 4; and
A step 5 of welding the stub to the upper end surface of the electrode at the position after the stub is conveyed to the welding point by the stub conveying means having a coordinate system having the core as the origin coordinate;
A method for attaching a stub to an electrode used in a remelting furnace is provided.

According to the present invention, since the stub is attached to the electrode outside the mold, the quality of the steel ingot obtained by preventing foreign matter from entering the mold does not deteriorate. Therefore, when attaching the stub to the electrode, it is not necessary to stop the furnace operation, and it is possible to increase the efficiency of the furnace rotation and improve the productivity.
In determining the stub welding point on the upper end surface of the electrode, measurement information on the electrode cross section at each measurement point is image-processed by a computer, and the virtual side gap drawn between the image of the electrode cross section and the virtual mold circle is drawn. The center point in the electrode cross-section is calculated such that the difference between the electrode cross-section is the minimum in the entire circumference of the electrode cross-section, and the inclination of the electrode with respect to the core of the mold / stub clamp portion is adjusted based on the calculated center point, Further, since the stub welding point on the upper end surface of the electrode is automatically determined, the accuracy of the alignment between the stub and the electrode is improved as compared with the conventional visual operation by the operator.

  In the present invention, when a stub is welded to the upper end surface of an electrode whose cross section is not a perfect circle and is also curved in the longitudinal direction, the stub is gripped by the stub clamp portion, and the electrode is suspended in the mold. Further, the upper end surface of the electrode is such that the variation in the side gap formed between the outer peripheral surface of the electrode and the inner wall of the mold is small in each cross section of the electrode and also in all positions in the longitudinal direction of the electrode. The final goal is to determine the welding point of the stub at.

And in order to achieve this target, the process mentioned later is implemented in conjunction with computer operation.
In that case, the preconditions for the calculation operation by the computer are as follows.
First, the machine center of the mold cross section in the melting furnace is coincident with the machine center of the stub clamp part, and a coordinate system in which the machine center is the origin (0, 0) in the XY coordinates is adopted. . Therefore, the position coordinates of the street which is both machine center core (hereinafter, referred to as _{G M)} has a _G M (0,0).

In addition, all the various mechanical devices that operate the electrodes and stubs in the process until the stub is actually welded, such as distance measuring sensors and stub conveying means described later, all operate based on the coordinate system described above. It is.
Hereinafter, each step will be described in detail.
Step 1: In this step, the cross-sectional shape of the electrode to be used is measured, and the measurement information is introduced into a computer.

First, as shown in FIG. 1, using a predetermined electrode gripping device (not shown) to substantially center and as the core G _M coordinates of one of the cross-section of the electrode 1 (0,0) is matched After the electrode is vertically inverted in this state, a distance measuring sensor 2 such as a laser displacement meter is disposed outside the electrode 1.
Distance measuring sensor 2, as shown in FIG. 2, it is arranged outside the electrodes 1 and the base line G _M in the axial as can be pivoted 360 °, and without changing the pivot axis in the longitudinal direction of the electrode It is arranged so that it can move up and down.

The distance measuring sensor 2, in certain measuring point, by performing a turning operation at the base line G an angle of _M with respect to example 1 ° to 2 ° theta, per total outer peripheral surface of the electrode 1, the electrode peripheral surface ranging The distance a between the sensors 2 is measured. The measurement information is introduced into the computer as information as shown in FIG.
The distance a is measured by the distance measuring sensor at a plurality of positions in the longitudinal direction of the electrode, so that information on the electrode cross-sectional shape at each measurement point in the longitudinal direction of the electrode is obtained and introduced into the computer.

The selection of the measurement point is arbitrary, but at least three locations of the upper end portion, the central portion, and the lower end portion of the electrode 1 are necessary.
Step 2: In Step 2, an electrode cross-sectional view and a virtual mold circle at each measurement point are drawn based on the measurement information obtained in Step 1, and an interval drawn between the electrode cross-sectional view and the virtual mold circle (this) The position coordinates G _P ′ (x, y) of the center point of the virtual malt circle are calculated so that the difference in the virtual side gap becomes the minimum at all points on the entire circumference of the electrode sectional view.

Specifically, as shown in FIG. 4, the measurement information is subjected to image processing by a computer, thereby drawing an electrode cross-sectional view A with the core G _M (0, 0) as the origin coordinate.
By the way, since the surface of the electrode whose surface is not machined has large and small unevenness, the surface of the electrode faithfully drawn according to the measurement information of the distance measuring sensor has large and small unevenness. . Therefore, the electrode cross section computer faithfully rendered based on measurement information of the distance measuring sensor as curve A ₁ in FIG. 4, is drawn as a curve diagram with a recess large a number of fine irregularities and for example two Should be.

In such a case, the computer recognizes these two large dents as an exception, ignores them, and draws the outer circumference of the electrode cross section with a smooth curve as a whole by connecting small convex portions existing on the outer circumference other than the large dent. To do. That is, the electrode cross section A has its outer periphery is drawn as a curve A ₂ in FIG.
When the electrode surface is machined into a perfect circle, the actual axial center of the electrode and G _M (0, 0) in the drawn electrode sectional view automatically match.

Then the computer is to arbitrary point G _P '(x, y) with the electrode cross-sectional view of the center, to render a virtual mold circle B of the mold and the same diameter. In that case, the virtual mold circle B is drawn as circumscribed circle which contacts at any point P already a drawn and are curved A _2.
In this way, the computer displays the virtual side formed between the outer periphery of the electrode cross-sectional view and the virtual mold circle B at that time when the virtual mold circle B is drawn as a circumscribed circle of the curve A ₂ drawn as the electrode cross-sectional view. Recognize the size of gap variation.

Next, as shown in FIG. 5, for example, the computer intersects at this point _GP ′ (x, y) and crosses the electrode cross section to reach the virtual mold circle B (four in the figure). Draw a straight line.
In FIG. 5, four straight lines are drawn. For example, a straight line passing through the point P and the point G _P ′ (x, y) and a point passing through the point G _P ′ (x, y) are orthogonal to the above-described straight line. A total of two straight lines may be drawn.

Each straight line has two virtual side gaps (L ₁ , L ′ ₁ ), (L ₂ , L ′ ₂ ), between the curve A ₂ indicating the outer periphery of the electrode cross section and the virtual mold circle B at both ends. .. (L _n , L ′ _n ) are formed. These virtual side gap values are recognized by the computer. In FIG. 5, the point P is _L 1 = 0 Since contacts of a virtual mold circle B and the curve _{A 2.}

Next, as shown in FIG. 6, the position of the center point G _P ′ (x, y) is changed in the XY plane, and the virtual mold circle B is translated in the XY plane, so that all virtual The side gaps L ₁ , L ₁ ′, L ₂ , L ₂ ′... L _n , L _n ′ have the same value, that is, the center point _GP ′ (x , Y). Then, the point G _P ′ (x, y) of this position coordinate is determined as the point at which the variation in the virtual side gap is minimized over the entire circumference of the electrode sectional view.

This calculation is performed for all of the electrode cross-sectional views obtained at each measurement point in the longitudinal direction of the electrode. Then, for each measured electrode cross section, the position coordinates of the center point G _P ′ (x, y) at which the variation in the virtual side gap formed by the outer periphery and the virtual mold circle is minimized are grasped.
The above description is a case where the virtual mold circle B is drawn as a circumscribed circle of the curve A ₂ , but the step 3 is not limited to this, and for example, any point _GP in the electrode cross section from the beginning. '(x, y) After drawing a virtual mold circle B of the mold and the same diameter around the, G _P the difference between virtual side gap drawn between the electrode periphery at that time is minimized' ( The position coordinates of x, y) may be calculated.

Step 3: In Step 3, when the stub welding point is determined based on the center point ( _GP ′) calculated in Step 2, and the electrode is suspended in the mold, the core G _M (0,0) The inclination of the electrode is adjusted.
As shown in FIG. 7, even if the coordinates of the center points G _P ′ (three points of G _P1 ′, G _P2 ′, G _P3 ′ in the figure) of each electrode cross section calculated in step 2 are simply connected. One straight line is not formed.

Therefore, in step 3, the computer approximates the coordinates of the center points G _P1 ′, G _P2 ′, G _P3 ′, calculates one virtual axis Z, and draws it.
At this time, the upper end face 1a of the electrode 1, when the inclination with respect to the base line _G M of the virtual axis Z (0,0) (θ) is greater than 1.5 mm / m, for example horizontal movement of the stub clamp portion In addition, mechanical correction such as adjustment of the inclination of the electrode gripping device is performed so that the inclination (θ) of the virtual axis Z is 1.5 mm / m or less.

When the relationship of G _P1 ′, G _P2 ′, G _P3 ′ is such that the inclination θ becomes a virtual axis Z greater than 1.5 mm / m, the coordinate position of the virtual axis Z on the upper end surface 1 a of the electrode 1 is set. This is because, when the stub is welded and suspended in the mold in a state where the stub is held by the stub clamp portion, the variation in the side gap increases.
By such calculation, the position coordinates of the temporary welding point on the upper end surface 1a of the electrode 1 are calculated.

Step 4: In this step 4, the position coordinates of the welding point of the stub on the upper end surface of the electrode are determined.
Specifically, as shown in FIG. 8, the coordinates of the center point G _P ′ (m, n) of the virtual axis (Z) determined in step 2 are the coordinates of the core G _M (0, 0). Along the vertical direction to the upper end 1a of the electrode, and the intersection ( _GP '') with the upper end surface 1a is the point at which the welding point of the stub, more precisely, the cross-sectional center of the stub is arranged.

In step 3 until determining the coordinates of the point G _{P '',} the slope as against the core G _{M (0,0)} of the virtual axis Z of the electrode is adjusted to be equal to or less than 1.5 mm / m, In step 2, the point G _P ′ (x, y) is calculated as a point that minimizes the variation of the virtual side gap Ln over the entire length of the electrode, and the point G _P with reference to this point G _P ′ (x, y) _{Since P} ″ has been determined, when a stub is welded to this point G _P ″, the stub is gripped by the stub clamp part, and the electrode is suspended in the mold, the electrode will be mold / stub clamp. The inclination with respect to the core G _M (0, 0) of the part is 1.5 mm / m or less, and the variation in the side gap with the mold is minimized.

Step 5: In this step, after placing the stub determined in step 4 the welding point G _{P '',} welding the stub on the upper end face of the electrode.
Specifically, in response to a command from the computer, the stub is transported to the upper end surface of the electrode by the stub transporting means that operates based on the coordinate system having the core G _M (0, 0) as the origin coordinate, and the cross-sectional center of the stub The coordinates of the welding point and the position coordinates of the welding point determined in step 4 are made to coincide with each other, and the stub is arranged there, and then both are welded.

According to the present invention, since the stub is attached to the electrode outside the mold, the quality of the steel ingot obtained by preventing foreign matter from entering the mold does not deteriorate. Therefore, when attaching the stub to the electrode, it is not necessary to stop the furnace operation, and it is possible to increase the efficiency of the furnace rotation and improve the productivity.
Also, when determining the stub welding point on the upper end surface of the electrode, the computer adjusts the inclination of the electrode with respect to the core of the mold / stub clamp part, and calculates the point that minimizes the variation in the side gap between the electrode and the mold. Since the stub welding point is automatically determined based on the calculated value, the accuracy of aligning the stub with the electrode is improved compared to the visual work by a conventional worker, and the steel ingot without quality deterioration is obtained. Manufacture is possible.

It is a schematic diagram which shows the state which has arrange | positioned the ranging sensor on the outer side of the inverted electrode. It is electrode sectional drawing in a certain measurement point. It is a graph which shows the relationship between the distance of the outer peripheral surface of a ranging sensor and an electrode, and the turning angle of a ranging sensor. It is a schematic diagram which shows the virtual mold circle drawn as an electrode processed sectional drawing and its circumscribed circle. It is explanatory drawing for calculating the virtual side gap which an electrode cross section and the virtual mold circle which image-processed form. It is explanatory drawing for determining point _GP '(x, y) which minimizes the dispersion | variation in the virtual side gap between the outer periphery of an electrode and a virtual mold circle. It is a schematic diagram which shows the inclination of the electrode with respect to a through-core. It is explanatory drawing explaining determination of the welding point _GP '' of a stub.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode 1a Upper end surface of the electrode 1 2 Ranging sensor A Electrode sectional drawing A ₁ The outer periphery of the measured electrode cross section A ₂ The outer periphery of the electrode cross section subjected to image processing B Virtual mold circle Ln, Ln ′ Virtual side gap G _M (0 , 0) origin coordinates of the base line of the mold / stub clamp unit G _P '(x, y) virtual side gap Ln, Ln' G _P 'point to minimize the variation of' welding point of the stub G _P '(m, n) Welding point on virtual axis (Z)

Claims (2)

Prior to inserting the electrode into the mold of the remelting furnace, when welding the stub to the upper end surface of the electrode,
A distance measuring sensor that pivots outside the electrode around the core of the mold and the stub clamp at a plurality of measurement points in the longitudinal direction of the electrode, and the distance between the outer peripheral surface of the electrode and the distance measuring sensor Measuring step 1;
At each measurement point, image processing based on the measurement information is performed, and an electrode cross-sectional view with the position of the core as the origin coordinate is drawn, and the mold is centered on a certain point existing in the drawn electrode cross-sectional view. A virtual mold circle having the same diameter as the center point such that a difference between a virtual side gap drawn between the electrode cross-sectional view and the virtual mold circle is minimized on the entire circumference of the electrode cross-sectional view ( Step 2 of calculating the coordinates of _GP ′);
The virtual axis (Z) is drawn in the longitudinal direction of the electrode by approximately connecting the coordinates of the center point in all the electrode cross-sectional views, and the inclination of the virtual axis (Z) with respect to the core of the upper end surface of the electrode is Step 3 of adjusting the inclination of the electrode so as to be 1.5 mm / m or less;
The coordinate of the center point ( _GP ″) of the virtual axis (Z) is vertically moved to the upper end surface of the electrode along the origin coordinate of the core, and the coordinate on the upper end surface is set as the position coordinate of the welding point. Performing step 4; and
A step 5 of welding the stub to the upper end surface of the electrode at the position after the stub is conveyed to the welding point by the stub conveying means having a coordinate system having the core as the origin coordinate;
A method for attaching a stub to an electrode used in a remelting furnace, comprising:   The method of attaching a stub to an electrode used in a remelting furnace according to claim 1, wherein in the step 2, the virtual mold circle is drawn as a circumscribed circle of the electrode sectional view.

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