JP4356107B2 - Ingot manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing an ingot using consumable electrode arc melting.

  The consumable electrode type arc furnace is a melting furnace of a system in which an electric arc is generated by supplying power to the consumable electrode itself suspended in a Cu crucible, and the molten metal melted and dropped from the consumable electrode is solidified by the arc heat. As a melting method, a melting method called VAR (vacuum arc remelting) or ESR (electroslag remelting) is generally used. Since all have the feature that they can be melted in a non-polluting atmosphere, they are used for the production of ingots of metals such as high-grade steel, high cleanliness steel, and titanium.

  In general, a VAR is a consumable electrode in which a briquette made by press-molding a raw material is first welded to produce a cylindrical base material, a stub is welded to one end of the base material, and this is used as a consumable electrode. This is done by remelting the consumable electrode from the lower end using arc heating between the melting pool and the melting pool. The ingot obtained by this dissolution is subjected to secondary dissolution by VAR again if necessary. Thereby, impurities can be removed, undissolved can be prevented, and the component composition can be made uniform.

  The consumable electrode is fixed and suspended on the stub, and the consumable electrode is dissolved from the lower end, but the dissolution is terminated immediately before the electrode is completely melted so as not to dissolve the stub, that is, immediately before reaching the stub. If the melting end timing is too early, a large amount of electrode residue is generated, and if it is too late, the stub is melted. In the former case, melting yield is deteriorated, and in the latter case, a stub portion that should not be melted is mixed in the ingot, resulting in quality deterioration.

  Also, when the electrode and stub are fixed by welding, the welded portion is melted first or the welded portion is exposed to high temperature, so that the welding strength is reduced and the electrode residue is peeled off from the stub. It also occurs when it falls in a solid state. In this case, it is necessary to cut and remove the mixed portion, or after reworking, to use again for the consumable electrode type arc melting, resulting in significant process loss and loss.

  FIG. 6 shows a conventional ingot manufacturing method. First, as shown to (a), the metal base material used as a raw material is made into a cylinder by welding etc., and is welded with the stub 1. FIG. Alternatively, the raw material is placed on the stub 1 and the raw material is dissolved to prepare the temporary ingot 2. The wire 5 having the same quality as that of the raw material is welded to the joint with the stub on the side surface of the temporary ingot 2. Then, as shown in (b), the stub 1 and the temporary ingot 2 are integrally inserted into the water-cooled copper mold 43 as a consumable electrode, and vacuum arc remelting is performed. At this time, the welded wire 5 is observed with a camera 6 or the like as a mark, and the arc melting is finished. As shown in (c), the water-cooled copper mold 43 is solidified to produce a primary ingot 26. This is the primary VAR.

  Subsequently, the primary ingot 26 is taken out, turned upside down, and welded again to the stub 11 as shown in FIG. At this time, the wire 5 having the same quality as the ingot is welded to the upper portion of the primary ingot 26. This wire is observed by the camera 6 when the secondary VAR is performed, and the timing of stopping electricity is determined. Then, the secondary VAR is performed as shown in (e). At this time, it is necessary to stop electricity at a position where the welded portion between the stub 11 and the primary ingot 26 is not melted. In this VAR, the wire 5 welded to the primary ingot 26 is monitored by the camera 6. Determine the end time of VAR. However, the power stop mark is unclear and the timing is likely to be incorrect. If the power is stopped early, the remaining material increases and the yield deteriorates. If the power is stopped late, there is a risk that the primary ingot 26 falls from the welded portion.

  Accordingly, an object of the present invention is to produce an ingot by consumable electrode arc melting that prevents deterioration of the quality of the secondary ingot due to dropping of the primary ingot or melting of the stub, and reduces the remaining amount of the consumable electrode to improve the melting yield. Is to provide a method.

Means for Solving the Problems and Effects of the Invention

The manufacturing method of the ingot of the present invention for solving the above problems is as follows.
A stub attached to the upper end surface of the primary ingot, and in a state where the primary ingot is suspended through the stub, the primary ingot is used as a consumable electrode and melted from the lower end surface side, and a mold provided below the primary ingot In the method of obtaining a secondary ingot by solidifying within,
The primary ingot is suspended on the upper end surface of the main body having a cross-sectional area larger than the cross-sectional area of the stub, the cross-sectional area perpendicular to the hanging direction of the primary ingot being melted to produce the secondary ingot Producing a primary ingot having a cross-sectionally reduced portion whose cross section perpendicular to the direction is smaller than the cross section of the main body portion;
By connecting the cross-sectional reduced portion of the primary ingot to the bottom surface of the stub and energizing the stub in this state, the stub is changed based on the outer edge shape change of the cross-sectional reduced portion or the connecting portion between the cross-sectional reduced portion and the main body portion. Dissolving the main body while grasping the power supply stop timing to, and producing the secondary ingot by the mold;
Ru Monodea by consumable electrode arc melting containing.

  In the present invention, the primary ingot is provided with a reduced section. The cross-sectionally reduced portion is a portion in which the cross section perpendicular to the suspending direction of the primary ingot is formed on the upper end surface of the main body portion smaller than the cross section of the main body portion. Moreover, the cross-sectional area orthogonal to the hanging direction of a primary ingot is larger than the cross-sectional area of a stub. Such a reduced section of the primary ingot is connected to the bottom surface of the stub and energized in this state to melt the main body. With the stub, main body, and reduced cross-section having such a cross-sectional area relationship, the power supply stop timing to the stub is grasped based on the change in the outer edge shape of the cross-section reduced portion or the connecting portion between the reduced-size section and the main body. can do. That is, since the cross-sectional area of the cross-sectional reduced portion is smaller than the cross-sectional area of the main body, it can be confirmed that the upper end surface gradually becomes red-hot when observed from the upper end surface side while dissolving the main body portion from the lower end. When melting is further performed while power is supplied, the outer edge of the cross-sectionally reduced portion or the connecting portion between the cross-sectionally reduced portion and the main body portion starts to be chipped, so that the main body portion can be easily grasped. If the power supply is stopped due to the change in the outer edge shape, the thickness of the stub welded portion can be secured and the amount of remaining material can be reduced while preventing the stub from being melted. The amount of remaining material can be reduced to 1/2 to 1/3 as compared with the conventional method.

  And the cross-sectional reduction part can form the upper end surface of the main-body part of a primary ingot flat, and can form a cross-sectional reduction part as a protrusion part which protrudes from an upper end surface. The upper end surface of the main body portion is flattened, the cross-sectional reduction portion is protruded, a stub is connected to the protruding portion, and the main body portion is dissolved. Only the stub connection part of the ingot is convex, and the wall thickness is secured. Observing from the upper end surface side, it is easy to see that the outer edge of the main body becomes red-hot and starts to chip, and it is possible to accurately grasp the power supply stop timing. In other words, in the case of a convex consumable electrode, it can be clearly confirmed that the periphery of the consumable electrode becomes red-heated and the surrounding gradually begins to be missing when the power stop is approaching, so that the power stop timing is hardly mistaken. Thereby, the amount of remaining material of the consumable electrode can be reduced.

  The ingot manufacturing method of the present invention preliminarily melts the raw material of the primary ingot, and casts the molten metal into a mold having a bottom inner surface shape corresponding to the reduced cross-sectional portion, whereby the bottom inner surface shape of the mold is ingot. The primary ingot which is transferred to the bottom and becomes the cross-sectional reduced portion is obtained, and the primary ingot is turned upside down to connect the stub to the cross-sectional reduced portion.

  The cross-sectional reduced portion of the primary ingot can be produced by preliminary melting. The raw material is melted and cast into a mold having a bottom inner surface shape corresponding to the cross-section reduced portion, thereby forming a cross-section reduced portion in the primary ingot. In order to form a cross-sectional reduced portion of the primary ingot according to the shape of the inner surface of the bottom portion of the mold, the upper and lower portions are turned upside down so that the cross-sectional reduced portion is on the upper side, and a stub is connected thereto to melt the primary ingot. By producing a primary ingot by preliminary melting and further producing a secondary ingot by main melting, a metal or a homogeneous alloy with few impurities can be produced.

  In addition, the cross-sectional reduced portion of the primary ingot can be formed by forging. Alternatively, a plurality of ingots can be connected by welding to produce a primary ingot having a reduced cross section.

  Further, preliminary melting for producing a primary ingot can also be performed by arc melting using a consumable electrode composed of the raw materials. Producing a primary ingot by vacuum arc remelting (VAR), and then re-melting the vacuum arc again to produce a secondary ingot, thereby producing a metal or a homogeneous alloy with few impurities by using the double VAR method. Can do. Since it can be melted in a non-polluting atmosphere, ingots such as high-grade steel, high cleanliness steel, and titanium can be manufactured.

  As a method for producing the primary ingot, while forming the raw material for producing the primary ingot on the temporary stub, the raw material molded body is integrated with the temporary stub, and then inverted upside down to form the raw material molded body. Dissolves from the bottom surface.

  The raw material is melted by, for example, plasma on a temporary stub, molded, integrated with the stub, and turned upside down to form a consumable electrode, which is melted from the lower end side to produce a primary ingot with a mold. When the raw material and the stub are connected by welding, the connecting portion is weak, and if the raw material molded body is melted to the vicinity of the connecting portion, there is a risk that these will fall as a lump. However, according to this method, it is possible to connect more firmly, and the main body can be melted to a position close to the connecting portion between the stub and the molded body of the raw material, and the yield of melting can be improved.

In the step of forming the primary ingot, the upper end surface of the main body portion is formed flat, and the cross-sectional reduction portion is formed as a protruding portion protruding from the upper end surface.
The raw material of the primary ingot is preliminarily melted at a first current density, and the molten metal is cast into a concave portion corresponding to the cross-sectional reduced portion of the mold, and after the inside of the concave portion is cast, it is larger than the first current density. Pre-melt the raw material at a second current density.

  When forming the protrusion part which protrudes from the upper end surface of a main-body part in an ingot, the casting_mold | template which has a recessed part corresponding to the protrusion part is used. In this case, the raw material is melted at the first current density which is a low current so that the arc does not become unstable between the concave portion and the raw material until the concave portion is cast with a molten metal in which the raw material is melted. And after a recessed part is cast, it raises from the 1st current density of a low current to a larger 2nd current density, and melt | dissolves a raw material. By suppressing the first current density in this way, it is possible to prevent the arc from becoming unstable and damaging the mold. After the recess is cast, the primary ingot can be efficiently manufactured by increasing the current density.

  Further, when a mold having a recess is used to form a protrusion on the ingot, conductive particles are dispersedly arranged in the recess of the mold to stabilize the preliminary melting due to the first current density. The arc can be stabilized by spreading waste metal powder, such as cutting powder, in the recesses and dissolving the raw material with the first current density.

  By producing an ingot having a reduced cross-section as described above and performing secondary melting, the impurities can be removed or undissolved while reducing the amount of remaining material, and the component composition can be made uniform. Can be planned. Further, by forming a cross-sectionally reduced portion in the ingot produced by secondary melting and performing tertiary melting, it is possible to achieve more uniform and highly purified while improving the yield. If necessary, quaternary dissolution or more may be performed by a similar method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the manufacturing process of the ingot of the present invention. As shown to (a), the base material 2 obtained by compression-molding or melt | dissolving metal materials, such as a granular form and piece shape, is welded to the stub 1 which is a jig | tool for suspension. In this example, titanium was dissolved on the stub 1 by plasma and integrated with the stub 1. According to this method, the adhesion between the stub 1 and the base material 2 can be improved, and the base material 2 can be dissolved up to the vicinity of the joint between the stub 1 and the base material 2. Further, a wire 5 having the same quality as that of the raw material was attached in the vicinity of the connecting portion between the raw material molded body 2 and the stub, and this was used as a mark for stopping electricity during melting. This is used as a consumable electrode, and is inserted into the water-cooled copper mold 3 and melted by arc as shown in FIG. The base material 2 of the consumable electrode is melted from the lower end by the arc. In this case, there is a possibility that the arc becomes unstable in the concave portion 4 which becomes the cross-sectional reduced portion forming portion of the water-cooled copper mold 3, and the consumable electrode is melted at a low current until the concave portion is cast.

  This will be described with reference to FIG. The water-cooled copper mold 3 has a recess 4 having a shape for forming a cross-sectional reduced portion in the ingot. As shown in (a), the base material 2 is suspended from the water-cooled copper mold 3. And as shown in (b), this preform | base_material is melt | dissolved from a lower end with an arc, a molten metal casts the recessed part 4, and the cross-sectional reduction part 21 is formed. There is a possibility that the arc becomes unstable in the vicinity of the recess 4 until the reduced section 21 is formed, and the base material 2 is melted at a low first current density until the recess 4 is cast. . After the recess 4 is cast and the formation of the cross-sectionally reduced portion 21 is completed as shown in (c), the base material 2 is melted at a second current density higher than the first current density. By increasing the current density, the base material 2 can be efficiently dissolved. By the way, as shown in (d), when the cutting powder 50 or the like of the waste metal material is spread on the concave portion 4 before starting the melting, the melting can be performed more stably.

  Returning to FIG. 1, after the concave portion is cast, the current is increased, and then the consumable electrode is dissolved as shown in (c) and (d). The power stop timing is determined by observing the wire 5 with the camera 6. As described above, if the base material 2 and the stub 1 are integrally formed using plasma or the like, it is possible to dissolve up to the vicinity of the joint between the base material 2 and the stub 1. By this primary VAR, a primary ingot 25 having a protruding portion as a cross-sectionally reduced portion 21 at one end of the main body portion 20 is manufactured. In the consumable electrode type arc melting furnace of the present embodiment, the shape of the bottom of the water-cooled copper mold 3 is concave, and this portion forms the cross-sectional reduced portion 21 in the primary ingot. The cross-sectional reduction portion 21 is a portion welded to the stub 21 when performing the secondary VAR, and is formed with substantially the same area as the bottom surface of the stub 21.

  Next, the primary ingot 25 is taken out and turned upside down, and the cross-sectionally reduced portion 21 of the primary ingot 25 is set as the upper part. And as shown to (e), the cross-sectional reduction part 21 is welded with the bottom face of the stub 11. As shown in FIG. In order to pass a large current, welding must be performed so that it is in close contact. Further, as shown in (f), the primary ingot 25 is inserted into the water-cooled copper mold 13 and the secondary VAR is performed by an arc. The primary ingot 25 is melted from the lower end by the arc. As shown in (g), when the melting proceeds to the upper part, the color of the upper part of the ingot 25 becomes red-hot, and the periphery of the main body part 20 starts to be chipped. By determining the end time as the end time and stopping the power supply, the remaining amount can be reduced and the stub can be prevented from dissolving. Thereby, it is possible to manufacture the secondary ingot 30 while improving the dissolution yield while preventing problems due to dissolution of the stub. In addition, in order to achieve further uniform ingot and higher cleaning, also in the case of tertiary melting, a cross-sectional reduced portion is formed in the secondary ingot 30 and the amount of remaining material can be reduced according to the same method. Can do. The same applies when performing quaternary dissolution or higher.

  FIG. 3A shows an embodiment of the primary ingot 25 in the present invention. The primary ingot 25 serves as a consumable electrode for producing the secondary ingot 30 as described above. As described above, the primary ingot 25 has the cross-sectional reduction portion 21 on the upper surface side of the main body portion 20 with the side to which the stub is connected as the upper surface. The area of the upper surface of the cross-sectional reduced portion 21 is the same as or larger than the bottom surface of the stub. The cross-sectional area perpendicular to the direction in which the primary ingot is suspended is smaller than the main body 20. By welding the reduced cross-sectional portion 21 to the bottom surface of the stub 11, a consumable electrode is obtained.

  FIG. 3B shows a plan view of the primary ingot 25. The upper cross-sectional reduction part 21 is substantially circular in accordance with the stub shape as shown in FIG. This circle is formed to be the same diameter or larger than the stub. Further, it is formed at substantially the center of the upper end surface of the main body portion 20. However, as long as it can be connected to the stub, the cross-sectional reduction portion 24 may be a quadrangle or other shape as shown in FIG. The shape must be weldable to the bottom surface of the stub.

  An ingot having a cross-sectional reduced portion that is the same shape as the bottom surface of the stub or larger than the cross-sectional area of the main body is welded to the stub to form a consumable electrode. When arc melting is performed using this consumable electrode, the consumable electrode is melted from the lower end, and as the upper end is approached, the area around the convex portion becomes red, and the end time of arc melting can be known. Thus, it is possible to prevent an error in the timing for stopping arc melting.

  FIG. 4 shows another embodiment of the cross-sectional reduction portion. As shown in (a) and (b), primary ingots 121 and 122 having a shape raised from the main body 2 such as the cross-sectionally reduced portions 125 and 126 may be produced. In addition, a primary ingot 123 whose cross section is reduced in multiple stages, such as a cross-sectional reduction portion 127, can be manufactured.

  Furthermore, the ingot which has a cross-sectional reduction part comprised from a raw material can also be manufactured by welding. FIG. 5 shows a manufacturing process by welding. First, briquettes 61 and 62 having a fixed shape are manufactured by pressing or the like. The briquettes are welded together to form a primary ingot 25. The primary ingot 25 uses a briquette 61 having a convex portion so that the cross-sectional reduced portion 21 is formed at one end. The reduced section 21 and the stub 11 thus formed are welded to form a consumable electrode.

  Furthermore, as another manufacturing method of the primary ingot 25 having the cross-sectional reduced portion 21, the cross-sectional reduced portion 21 can be manufactured by forging. First, a cylindrical ingot is manufactured, and a cross-sectional reduced portion 21 is formed at one end by forging.

  As described above, by providing the cross-sectionally reduced portion at one end of the main body portion of the primary ingot, it is possible to easily grasp the power supply stop timing during melting and increase the yield. In addition, if a cross-sectional reduction part is a form where a cross section becomes smaller than the cross section of the main-body part orthogonal to the suspending direction which suspended the primary ingot, it will not be restricted to the form of an Example.

The figure explaining the manufacturing process of this invention. The figure explaining casting to the recessed part formed in the water-cooled copper mold. The example of the ingot which formed the cross-sectional reduction part in the end. An example of a section reduction section. The figure which shows preparation of the ingot by welding of a briquette. The figure explaining the conventional manufacturing process.

Explanation of symbols

1,11 Stub 2 Base material 3 Water-cooled copper mold (mold)
4 Concave portion 21 Cross section reduced portion 25 Primary ingot

Claims (5)

A stub attached to the upper end surface of the primary ingot, and in a state where the primary ingot is suspended through the stub, the primary ingot is used as a consumable electrode and melted from the lower end surface side, and a mold provided below the primary ingot In the method of obtaining a secondary ingot by solidifying within,
The primary ingot is suspended on the upper end surface of the main body having a cross-sectional area larger than the cross-sectional area of the stub, the cross-sectional area perpendicular to the hanging direction of the primary ingot being melted to produce the secondary ingot The raw material of the primary ingot is preliminarily melted so as to produce a primary ingot having a cross-sectional reduced portion smaller than the cross-section of the main body portion , and the molten metal is shaped into the bottom inner surface corresponding to the cross-sectional reduced portion. A step of transferring the shape of the inner surface of the bottom of the mold to the bottom of the ingot to obtain the primary ingot having the reduced cross-section by casting into a mold having
The primary ingot is turned upside down, the cross-sectional reduced portion is connected to the bottom surface of the stub, and energized in that state, thereby changing the outer edge shape of the cross-sectional reduced portion or the connecting portion between the cross-sectional reduced portion and the main body portion. Based on the above, dissolving the main body part while grasping the power supply stop timing to the stub, and producing the secondary ingot by the mold,
A method for producing an ingot, characterized in that it is based on consumable electrode arc melting. The ingot manufacturing method according to claim 1, wherein the preliminary melting is performed by arc melting using a consumable electrode made of the raw material . While forming the raw material for producing the primary ingot on a temporary stub, the molded body of the raw material is integrated with the temporary stub, and then turned upside down to dissolve from the lower end surface side of the molded body of the raw material, The manufacturing method of the ingot of Claim 1 or 2 which produces the said primary ingot . In the step of forming the primary ingot, the upper end surface of the main body portion is formed flat, and the cross-sectional reduction portion is formed as a protruding portion protruding from the upper end surface.
The raw material of the primary ingot is melted at a first current density, and the molten metal is cast into a recess corresponding to the reduced section of the mold, and after the interior of the recess is cast, the first current density is greater than the first current density. The manufacturing method of the ingot of Claim 2 or 3 which melt | dissolves the said raw material with two current density . The manufacturing method of the ingot of Claim 4 which disperse | distributes the conductive granule which has a main component common to the said raw material of an ingot in the said recessed part of the said mold, and stabilizes melt | dissolution by said 1st current density .

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