Method for cleaning an electron beam melting furnace and method for manufacturing titanium ingots

Abstract

The present invention provides a cleaning method that can efficiently clean an electron beam type melting furnace and a method for manufacturing titanium ingots. [Solution] The cleaning method for an electron beam melting furnace includes a step of spraying water at a pressure of 20 MPa or more from a nozzle with a spray angle of 10° or more and 30° or less onto the inner wall of the electron beam melting furnace to which titanium-containing deposits are attached.

Description

Technical Field

[0001] Embodiments of the present invention relate to a method for cleaning an electron beam melting furnace and a method for manufacturing a titanium-based ingot.

Background Art

[0002] As a method for manufacturing a titanium ingot, there is a method using an electron beam melting furnace. In this method, the melting raw material is melted by irradiating the melting raw material with an electron beam in a vacuum furnace, and the molten metal is poured into a mold and solidified to cast an ingot having a predetermined shape. Examples of the melting raw material include sponge titanium and rod-shaped titanium.

[0003] In this case, since titanium evaporated mainly from the molten metal adheres to and grows on the inner wall of the furnace, it is necessary to periodically clean the inner wall of the furnace. For example, titanium adhering to and growing on the inner wall, which is the ceiling, may fall from the ceiling. Further, when the furnace is opened to the atmosphere for cleaning, the titanium adhering to the inner wall of the furnace is mainly oxidized or nitrided, and cleaning is performed to prevent the oxidized or nitrided titanium from being mixed into the ingot manufactured thereafter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An embodiment of the present invention aims to provide a cleaning method capable of efficiently cleaning an electron beam melting furnace and a method for manufacturing a titanium-based ingot. [[ID=4^]]

Means for Solving the Problems

[0006] A cleaning method for an electron beam melting furnace according to an embodiment of the present invention comprises the step of spraying water at a pressure of 20 MPa or more from a nozzle with a spray angle of 10° or more and 30° or less onto the inner wall of an electron beam melting furnace to which titanium-containing deposits are attached.

[0007] A method for manufacturing a titanium ingot according to an embodiment of the present invention comprises the steps of casting a titanium ingot in an electron beam melting furnace and cleaning the inner wall of the electron beam melting furnace. The cleaning step is carried out by the cleaning method described above. [Effects of the Invention]

[0008] According to embodiments of the present invention, it is possible to realize a cleaning method that can efficiently clean an electron beam melting furnace and a method for manufacturing titanium ingots. [Brief explanation of the drawing]

[0009] [Figure 1] Figures 1(a) and 1(b) illustrate a method for manufacturing a titanium-based ingot according to an embodiment. Figure 1(a) shows the casting process for the titanium-based ingot, and Figure 1(b) shows the cleaning process for the electron beam melting furnace. [Figure 2] Figure 2(a) is a side view showing a robot used in the cleaning method of an electron beam melting furnace according to an embodiment, and Figure 2(b) is a top view thereof. [Figure 3] Figure 3 is an end view showing a cleaning method for an electron beam melting furnace according to an embodiment. [Figure 4] Figure 4 is an end view showing the operation of the robot in the embodiment. [Figure 5] Figure 5 is an end view showing the operation of the robot in the embodiment. [Figure 6] Figure 6 is an end view showing the operation of the robot in the embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below. Figures 1(a) and 1(b) illustrate the manufacturing method of the titanium ingot according to this embodiment, where Figure 1(a) shows the casting process of the titanium ingot and Figure 1(b) shows the cleaning process of the electron beam melting furnace. Note that Figures 1(a) and (b) are schematic representations and have been exaggerated and simplified as appropriate. The same applies to the other figures described later.

[0011] In this specification, ingots made of so-called industrial-grade pure titanium and ingots made of titanium alloys are collectively referred to as "titanium-based ingots." Titanium-based ingots are made of materials with metallic properties, and their titanium content may be 50% by mass or more, 75% by mass or more, 85% by mass or more, or 95% by mass or more. Examples of industrial-grade pure titanium include those of types 1 to 4 as defined in JIS H 4600.

[0012] First, in this embodiment, we will describe the electron beam melting furnace (hereinafter also referred to as the "EB furnace") used in the production of titanium ingots and which is subject to cleaning.

[0013] As shown in Figure 1(a), the EB furnace 100 used in this embodiment includes a housing 101, a feeder 102 for supplying the molten material 201 into the housing 101, a hearth 103 located at the bottom of the housing 101 and holding the molten material 201, one or more electron guns 104 mounted on or near the ceiling of the housing 101, and a mold 105 located at the bottom of the housing 101 and connected to the hearth 103. In addition to the molten material 201, the hearth 103 may also hold molten metal from the molten material 201.

[0014] The melting raw material 201 is, for example, sponge titanium, titanium bars, titanium scraps, briquettes, or the like. In addition, titanium oxide may be included in order to adjust the oxygen content of the titanium-based ingot. When using a titanium bar as the melting raw material 201, the titanium bar stock may be placed above the hearth 103, and an electron beam may be irradiated onto the titanium bar from the electron gun 104 to melt it, and the molten metal may be supplied to the hearth 103. Alternatively, the titanium bar may be directly placed on the hearth 103 and melted on the hearth 103 by irradiating it with an electron beam.

[0015] The housing 101 is, for example, entirely formed of stainless steel. The housing 101 is provided with a gun port 101a for attaching the electron gun 104, a raw material inlet 101b through which the feeder 102 passes, and a viewport 101c for an operator to observe the inside of the housing 101. The housing 101 may be provided with other openings. For example, when it may be necessary to collect the molten metal and confirm its composition, a sampler port for inserting a sampler may be further provided.

[0016] A member for trapping deposits derived from vapor generated from the molten metal, such as a punching metal or a mesh member, may be attached to the inner surface of the housing 101. Note that the member for trapping has a large number of through holes from the perspective of the form of attachment of the deposits. Therefore, even when this member for trapping is used, titanium vapor generated from the molten metal reaches the inner wall of the housing 101, and titanium solidified in contact with the inner wall adheres as a deposit. The configuration of the housing 101 is not particularly limited, but for example, the following two types are conceivable.

[0017] In the first type, the housing 101 is formed in a box shape with one end on the side being openable, and the feeder 102 is attached to the housing 101. In addition, a structure including the hearth 103 and the mold 105 is loaded into the housing 101. The shape of the housing 101 is, for example, a substantially rectangular parallelepiped.

[0018] In the second type, the ceiling portion of the housing 101 is separable from the main body portion. An electron gun 104 is attached to the ceiling portion, and a feeder 102, a hearth 103, and a mold 105 are attached to the main body portion. The shape of the main body portion is, for example, a substantially rectangular parallelepiped, and the shape of the ceiling portion is, for example, a part of a substantially elliptical cylinder.

[0019] In both the first type and the second type, parts such as the gun port 101a, the raw material inlet 101b, and the viewport 101c are often joined by some members and often have uneven portions formed. On the other hand, the portions constituting simple walls are often flat or curved surfaces.

[0020] The feeder 102 supplies the molten raw material 201 containing titanium onto the hearth 103 while maintaining a high-vacuum atmosphere inside the housing 101. The hearth 103 holds the supplied molten raw material 201 such as sponge titanium. Only one hearth 103 may be provided, or a plurality of hearths 103 may be combined. When the number of hearths 103 increases, the moving distance of the molten metal becomes longer and the purification ability of impurities improves. The hearth 103 may be, for example, a combination of a melting hearth for melting the molten raw material 201, a purification hearth for flowing and purifying the molten metal, and a pouring hearth having a pouring port for pouring the molten metal into the mold 105.

[0021] The electron gun 104 irradiates the molten material 201 placed on the hearth 103 with an electron beam. This heats and melts the molten material 201, producing molten titanium. The electron gun 104 also irradiates the molten metal in the hearth 103 or the mold 105 with an electron beam. Often, different electron guns 104 are used to irradiate the molten metal in the hearth 103 and electron guns 104 to irradiate the molten metal in the mold 105. In this case, the angle of each electron gun 104 relative to the inner surface of the housing 101 may differ. The mold 105 is made of, for example, copper and is equipped with a water cooling mechanism. Molten titanium is poured into the mold 105 from the hearth 103, cooled and solidified to cast a titanium ingot 202. The mold 105 may be configured to be removable from its bottom, which makes it easier to manufacture long titanium ingots.

[0022] If the raw material 201 is sponge titanium, it can be manufactured, for example, by the Chroll process. The Chroll process generally utilizes the reaction shown in the following chemical equation (1). In the Chroll process, sponge titanium is formed into large lumps, which are then crushed to produce sponge titanium that can be used as a raw material. Magnesium chloride (MgCl2) is produced as a by-product in the Chroll process, and sponge titanium may contain MgCl2 as an unavoidable impurity.

[0023] TiCl4 + 2Mg → Ti + 2MgCl2 (1)

[0024] As shown in Figure 1(a), in the process of casting titanium ingots, the inside of the housing 101 is evacuated and the pressure is 10 -4 Pa~10 -2 A vacuum atmosphere of approximately Pa is maintained. In this state, the molten material 201 is supplied using the feeder 102. The feeder 102 can supply the molten material 201 onto the hearth 103 while maintaining the vacuum atmosphere inside the housing 101. The electron gun 104 irradiates the molten material 201 on the hearth 103 with an electron beam. As a result, the molten material 201 is heated and melted, becoming molten metal.

[0025] The molten metal flows into the mold 105 from the pouring port of the hearth 103. The mold 105 cools and solidifies the molten titanium that flows in from above, while simultaneously being withdrawn downwards. As a result, a titanium ingot 202 is formed inside the mold 105.

[0026] At this time, vapor is generated from the surface of the molten metal held in the hearth 103 and mold 105, and this vapor is deposited on the inner wall of the housing 101. In particular, titanium adheres in large quantities to the ceiling of the housing 101, and the amount of adhesion increases as the production of titanium-based ingots 202 continues. As described above, the inside of the EB furnace 100 is a vacuum atmosphere, and the nitrogen and oxygen concentrations are sufficiently low, so the titanium adhering to the inner wall of the housing 101, although containing impurities, is not covered by an oxide film and is in the state of metallic titanium.

[0027] After the production of the titanium ingot 202, when the casing 101 is opened to the atmosphere for maintenance or other purposes, the titanium adhering to the inner wall of the EB furnace 100, including the casing 101, reacts with oxygen and nitrogen in the atmosphere to form a titanium-containing deposit 203. In addition to titanium, the titanium-containing deposit 203 contains titanium compounds such as titanium oxides, titanium nitrides, and titan oxynitrides.

[0028] If the titanium-containing deposits 203 remain attached to the inner wall of the housing 101, they may eventually fall into the hearth 103 or mold 105. If the fallen titanium-containing deposits 203 remain unmelted and the molten titanium solidifies in the mold 105, the titanium-containing deposits 203 will become mixed into the titanium-based ingot 202. Even if titanium-containing deposits 203 become mixed into the titanium-based ingot 202, if they are not exposed on the surface, they will not be detected during inspection, and the titanium-based ingot 202 will be shipped out.

[0029] These defects then appear when the titanium ingot 202 is rolled at the destination. Even when the titanium ingot 202 is forged or otherwise processed without rolling, titanium oxides, nitrides, and oxynitrides have different hardness and ductility compared to metallic titanium, which can cause cracks. Thus, if titanium-containing deposits 203 are mixed into the titanium ingot 202, defects may occur when the titanium ingot is processed. For this reason, it is necessary to periodically clean the inner wall of the housing 101 to remove the titanium-containing deposits 203 and then resume the production of titanium ingots.

[0030] In this context, while the EB furnace 100 may also be cleaned in addition to the housing 101, the hearth 103 and mold 105 may also be cleaned. However, if at least one of these, for example the housing 101, is cleaned, it will be treated as if the EB furnace 100 has been cleaned.

[0031] As shown in Figure 1(b), in the process of cleaning the inner wall of the electron beam melting furnace, for example, the entire or a part of the inner wall of the housing 101 is cleaned. In the case of the first type described above, as an example, the entire inner wall of the housing 101 is cleaned. In the case of the second type described above, as an example, the inner wall of the ceiling of the housing 101 is cleaned. If perforated metal or mesh members for trapping molten metal vapor were installed inside the housing 101, these are removed before cleaning. In Figure 1(b), an example of cleaning the inner wall of the ceiling of the housing 101 is shown. This removes the titanium-containing deposits 203 from the inner wall of the housing 101.

[0032] Figure 2(a) is a side view showing a robot used in the cleaning method of the electron beam melting furnace according to this embodiment, and Figure 2(b) is a top view thereof. As shown in Figures 2(a) and (b), rails 390 extending in one direction are laid on the housing 101 of the EB furnace 100. If the housing 101 is of the first type described above, the rails 390 are provided on the floor surface of the housing 101. The rails 390 may be shared with the rails for the cart on which the hearth 103 and mold 105 etc. are mounted. If the housing 101 is of the second type described above, the rails 390 are provided on the floor surface of the washing area, and the ceiling of the housing 101 is positioned above them.

[0033] Hereafter, for the sake of explanation, the XYZ Cartesian coordinate system will be used in this specification. The direction in which rail 390 extends will be referred to as the "X direction". The X direction is one of the horizontal directions. The horizontal direction perpendicular to the X direction will be referred to as the "Y direction". The vertical direction perpendicular to both the X and Y directions will be referred to as the "Z direction".

[0034] In this embodiment, the robot 300 is provided with a trolley 310, a motor for the trolley 315, a turntable 320, a servo motor for the turntable 325, a first arm 330, a servo motor for the first arm 335, a second arm 340, a servo motor for the second arm 345, a nozzle 350, a water supply unit 360, a water supply pipe 365, and a control unit 370.

[0035] The trolley 310 is movable on the rail 390 by the trolley motor 315 and is therefore capable of reciprocating motion in the X direction. The trolley motor 315, turntable 320, turntable servo motor 325, first arm 330, first arm servo motor 335, second arm 340, second arm servo motor 345, and nozzle 350 are mounted on the trolley 310. The trolley motor 315, turntable 320, and turntable servo motor 325 are fixed to the trolley 310.

[0036] The turntable 320 includes a disc-shaped member and is capable of rotating within an angular range of 180° or more along the XY plane, including the X and Y directions, by a servo motor 325 for the turntable. The first arm 330 is substantially rod-shaped, and its first end 331 is rotatably connected to the turntable 320. As a result, the first arm 330 is capable of rotating in a plane including the Z direction by a servo motor 335 for the first arm, which is fixed to the turntable 320. When the turntable 320 is facing any direction parallel to the XY plane (hereinafter referred to as the "W direction"), the first arm 330 is capable of rotating in the WZ plane.

[0037] The shape of the second arm 340 is also roughly rod-shaped. The second arm 340 is rotatably connected to the second end 332 of the first arm 330. As a result, the second arm 340 is rotatable in the WZ plane by a servo motor 345 for the second arm, which is fixed to the second end 332 of the first arm 330. The nozzle 350 is fixed to the second arm 340 and extends in roughly the same direction as the second arm 340. Therefore, the direction in which the nozzle 350 faces, that is, the central axis of the direction of water 400 injection, is any direction in the WZ plane.

[0038] The water supply unit 360 and the control unit 370 are not mounted on the trolley 310. The water supply unit 360 is connected to the nozzle 350 by a water supply pipe 365. The water supply pipe 365 is a flexible pipe, such as a rubber hose. However, the water supply pipe 365 is not limited to a rubber hose; for example, it may be a corrugated hose made of stainless steel. The water supply unit 360 includes, for example, a pump that pressurizes water 400 and supplies it to the nozzle 350 via the water supply pipe 365. The water 400 is, for example, tap water. The water supply unit 360 may have pressure regulating means such as a pressure regulating valve.

[0039] The control unit 370 controls the position of the trolley 310 in the X direction by controlling the trolley motor 315, determines the orientation of the turntable 320, i.e., the W direction, by controlling the turntable servo motor 325, controls the rotation angle of the first arm 330, i.e., the elevation angle of the first arm 330 with respect to the XY plane, by controlling the first arm servo motor 335, controls the rotation angle of the second arm 340, i.e., the bending angle of the second arm 340 with respect to the first arm 330, by controlling the second arm servo motor 345, and controls the pressure and spray volume of water 400 by controlling the water supply unit 360. The control unit 370 may be programmable. By pre-programming the operation of each part of the robot 300 in the control unit 370, the robot 300 can perform the cleaning work fully automatically. Alternatively, the water supply unit 360 may control the pressure of the water 400, and the control unit 370 may control the spray volume. The division of control over water pressure and injection volume can be determined as appropriate. Furthermore, the number of control units 370 is not limited; one robot 300 may be controlled by one control unit 370, or two or more control units 370 may be used for one robot 300, with each control unit 370 sharing the control responsibilities.

[0040] As shown in Figures 2(a) and (b), when cleaning the EB furnace 100, the control unit 370 of the robot 300 performs the following series of controls. Specifically, the control unit 370 drives the trolley motor 315 to move the trolley 310 along the rail 390 to determine its position in the X direction. The control unit 370 drives the turntable servo motor 325 to determine the direction (W direction) of the turntable 320. The control unit 370 drives the first arm servo motor 335 to determine the elevation angle of the first arm 330. The control unit 370 drives the second arm servo motor 345 to determine the bending angle of the second arm 340 relative to the first arm 330. Through this series of operations, the position and angle of the nozzle 351 of the nozzle 350 are arbitrarily selected.

[0041] In this state, the control unit 370 drives the water supply unit 360 and supplies water 400 to the nozzle 350 via the water supply pipe 365. As a result, water 400 is ejected from the nozzle opening 351 of the nozzle 350. The water 400 collides with the titanium-containing deposit 203 and removes the titanium-containing deposit 203 from the inner wall of the housing 101. For example, the titanium-containing deposit 203 is scraped off or detached from the housing 101.

[0042] The control unit 370 drives the robot 300 to scan the spray position of the water 400 so that the water 400 is sequentially sprayed onto the areas of the inner wall of the housing 101 that are to be cleaned. As a result, the titanium-containing deposits 203 are removed from the inner wall of the housing 101, and the EB furnace 100 is cleaned.

[0043] Figure 3 is an end view showing a cleaning method for an electron beam melting furnace according to this embodiment. As shown in Figure 3, in this cleaning process, the spray angle θ of the water 400 is set to be 10° or more and 30° or less. Preferably, the spray angle θ is 10° or more and 20° or less. Also, the pressure P of the water 400 at the nozzle 351 of the nozzle 350 is set to be 20 MPa or more. Preferably, the pressure P is 30 MPa or more. Here, the spray angle θ is the angle of the water 400 sprayed from the nozzle 351 of the nozzle 350. If the spray angle of the water 400 is anisotropic, such as when the shape of the nozzle 351 is not circular, the maximum and minimum spray angles should be determined and their average value should be adopted as the spray angle θ. The spray angle θ can be adjusted by appropriate means such as replacing or adjusting the nozzle 350 or parts of the nozzle 350.

[0044] Furthermore, it is preferable that the nozzle 350's injection port 351 be positioned within 1 m of the titanium-containing deposit 203. More precisely, it is preferable that the distance d between the injection port 351 and the intersection point 353 of the extension of the nozzle 350's centerline 352 and the surface of the titanium-containing deposit 203 is 1 m or less.

[0045] When the spray angle θ is 10° or more and 30° or less, the cleaning efficiency is higher compared to when the spray angle θ is less than 10° or greater than 30°. "Cleaning efficiency" refers to the area that can be cleaned by removing titanium-containing deposits 203 per unit time. Generally, the smaller the spray angle θ, the stronger the force of the water 400, and the more effective it is at removing titanium-containing deposits 203 from the inner wall of the housing 101, but the area to which water 400 is sprayed at one time becomes smaller.

[0046] Even if the spray angle θ is less than 10°, the effect of removing titanium-containing deposits 203 does not increase significantly, and on the other hand, the area over which water 400 is sprayed at once becomes smaller, so it takes time to scan the entire area to be cleaned, and the cleaning efficiency decreases. Conversely, if the spray angle θ is greater than 30°, the force of the water 400 weakens, reducing the effect of removing titanium-containing deposits 203, and the probability that titanium-containing deposits 203 will not be removed with a single spray increases. In this case, it becomes necessary to spray water 400 at the same location for a long time or multiple times, which again reduces the cleaning efficiency.

[0047] Furthermore, when the spray angle θ is 10° or greater and 20° or less, the cleaning efficiency is higher than when the spray angle θ is greater than 20° and 30° or less. This is because the probability of removing the titanium-containing deposits 203 with a single spray of water 400 is higher.

[0048] In one test example, when the inner diameter of the nozzle 351 of the nozzle 350 was set to 30 mm, the distance d to 0.5 m, and the spray angle θ to 0°, the titanium-containing deposits 203 remained in a striped pattern between the parts where the water 400 collided with the titanium-containing deposits 203. In other words, titanium-containing deposits 203 remained in the area to be cleaned. In this case, if an attempt was made to remove the striped titanium-containing deposits 203 in a second cleaning operation, precise control of the robot 300 would be required, resulting in a heavy workload. In contrast, when the inner diameter of the nozzle 351 was set to 130 mm, the distance d to 0.5 m, and the spray angle θ to 15°, the area was cleaned without leaving any striped trajectories. That is, no residue of titanium-containing deposits 203 was observed in the area to be cleaned.

[0049] When the pressure P of the water 400 at the nozzle 351 of the nozzle 350 is 20 MPa or higher, the cleaning efficiency is higher compared to when the pressure P is less than 20 MPa. Generally, the higher the pressure P, the more effective it is at removing the titanium-containing deposits 203 from the inner wall of the housing 101. When the spray angle θ is within the range of 10° to 30° and the pressure P is 20 MPa or higher, the probability of removing the titanium-containing deposits 203 from the inner wall of the housing 101 with a single spray of water 400 increases, improving the cleaning efficiency.

[0050] Furthermore, it is more preferable that the pressure P be 30 MPa or higher. This shortens the time from when the water 400 comes into contact with the titanium-containing deposit 203 until the titanium-containing deposit 203 is removed, allowing the scanning speed of the nozzle 350 to be set higher. As a result, cleaning efficiency is further improved.

[0051] According to other test examples, when the pressure P was 20 MPa, it took two people three hours to clean the housing 101, but when the pressure P was 35 MPa, it took one person three hours to clean the same housing 101. A high-pressure washer was used for this work, and the pressure was controlled by the settings of the high-pressure washer.

[0052] When the distance d between the nozzle 350's injection port 351 and the titanium-containing deposit 203 is 1 m or less, the cleaning efficiency is higher compared to when the distance d is greater than 1 m. Generally, the shorter the distance d, the higher the flow velocity at which the water 400 contacts the titanium-containing deposit 203, thus increasing the effectiveness of removing the titanium-containing deposit 203 from the inner wall of the EB furnace 100, such as the housing 101. However, because the water 400 does not spread sufficiently, the area of ​​the region where the water 400 is sprayed at one time becomes smaller. When the spray angle θ is set to 10° or more and 30° or less, and the pressure P of the water 400 is set to 20 MPa or more, and the distance d is set to 1 m or less, the time from when the water 400 contacts the titanium-containing deposit 203 until the titanium-containing deposit 203 is detached is shortened, thus further improving the cleaning efficiency.

[0053] Figures 4 to 6 are end views illustrating the operation of the robot in this embodiment. Figures 4 to 6 show an example of cleaning the ceiling portion of the housing 101. The shape of the ceiling portion is part of an elliptical cylinder with its axial direction extending in the X direction. However, the shape of the housing 101 is not limited to this.

[0054] As shown in Figure 4, the trolley 310 of the robot 300 is guided by the rail 390 and can reciprocate in the X direction by driving the trolley motor 315. This allows the position of the nozzle 351 of the nozzle 350 to be arbitrarily selected in the X direction.

[0055] As shown in Figure 2(b), by driving the servo motor 325 for the turntable, the turntable 320 can arbitrarily select the direction (W direction) in which the first arm 330, the second arm 340, and the nozzle 350 face in the XY plane.

[0056] Furthermore, as shown in Figure 5, the elevation angle of the first arm 330 in the WZ plane can be arbitrarily selected by driving the servo motor 335 for the first arm. In addition, the bending angle of the second arm 340 relative to the first arm 330 in the WZ plane can be arbitrarily selected by driving the servo motor 345 for the second arm.

[0057] In this way, the position and angle of the nozzle 351 can be arbitrarily selected. As a result, the distance d between the nozzle 351 and the titanium-containing deposit 203 can be adjusted to any range, for example, a range of 1 m or less. Although Figure 5 shows a YZ cross-section, the same applies to a WZ cross-section.

[0058] There are various types of shapes for the EB furnace 100, and the inner wall of the casing 101 of the EB furnace 100 has openings such as a gun port 101a for attaching the electron gun 104 and a viewport 101c for observing the inside of the furnace from the outside, so there are quite a few uneven areas on the inner wall. When cleaning the inner wall of the casing 101, not only the smooth surfaces but also these uneven areas, the work is complicated and burdensome.

[0059] In contrast, according to this embodiment, as shown in Figure 6, even when titanium-containing deposits 203 adhere to parts with complex shapes, such as the gunport 101a and the viewport 101c, the direction of water 400 injection can be controlled in various ways by selecting the position and angle of the injection nozzle 351. Therefore, water 400 can be injected from the most effective direction and distance to each part of the titanium-containing deposits 203. This allows for efficient cleaning of the housing 101 of the EB furnace 100. As a result, titanium-based ingots 202 can be manufactured efficiently.

[0060] Furthermore, a hearth 103 and mold 105 are arranged inside the housing 101 of the EB furnace 100, and titanium-containing deposits may adhere to these as well. Since the hearth 103 and mold 105 also constitute the inner wall of the EB furnace 100, removing the titanium-containing deposits adhering to the hearth 103 and mold 105 is also included in the cleaning of the EB furnace 100 according to this embodiment.

[0061] Next, the effects of this embodiment will be described. In this embodiment, water 400 is injected at a pressure of 20 MPa or more from a nozzle 350 with an injection angle θ of 10° or more and 30° or less onto the inner wall of the EB furnace 100, for example, the inner wall of the housing 101, to which titanium-containing deposits 203 are attached. This allows for efficient removal of the titanium-containing deposits 203 from the inner wall of the EB furnace 100, and efficient cleaning of the EB furnace 100. As a result, titanium-based ingots 202 can be manufactured efficiently.

[0062] Furthermore, according to this embodiment, the nozzle 350's injection port 351 is positioned within 1 m of the titanium-containing deposit 203, and water 400 is injected. This allows for more efficient removal of the titanium-containing deposit 203, thereby improving the cleaning efficiency of the EB furnace 100.

[0063] The EB furnace 100 can be cleaned particularly efficiently if the injection angle θ is set to 10° or more and 20° or less, the water pressure P is set to 30MPa or more, and the distance d from the injection nozzle 351 to the titanium-containing deposit 203 is set to 1m or less.

[0064] Furthermore, according to this embodiment, the inner wall of the housing 101 is cleaned using a robot 300. In the robot 300, the trolley 310 is capable of reciprocating motion in the X direction, the turntable 320 mounted on the trolley 310 is capable of rotating along the XY plane within an angular range of 180° or more, the first arm 330 is capable of rotating in the WZ plane relative to the turntable 320, the second arm 340 is capable of rotating in the WZ plane relative to the first arm 330, and the nozzle 350 is fixed to the second arm 340. This allows the position and angle of the nozzle 351 to be arbitrarily selected, and the cleaning of the housing 101 can be performed unmanned. The effects of this will be explained below.

[0065] Traditionally, EB furnaces were cleaned manually by workers using water. However, manual cleaning had problems such as variations in the quality of the results depending on the worker's skill, and it was also burdensome for the workers. These burdens included risks such as chemical burns, burns, and gas poisoning.

[0066] Regarding chemical burns, the water used to wash away the titanium-containing deposit 203 is acidic, with a pH of approximately 5. This water can splash back under high pressure and potentially come into contact with workers. If workers' protective measures are insufficient, they may suffer chemical burns.

[0067] Regarding burns, the surface of the titanium-containing deposit 203 is covered with a coating consisting of titanium oxide, titanium nitride, and titanium oxynitride. However, if this coating is removed by washing with water, metallic titanium is exposed. Metallic titanium reacts violently with nitrogen and oxygen in the atmosphere and burns. As a result, burning titanium may fall from the ceiling of the enclosure 101 and come into contact with workers. If workers are not adequately protected, they may suffer burns.

[0068] Regarding gas poisoning, sponge titanium is produced by the Chlor process according to the above chemical reaction equation (1), and therefore contains MgCl2 as an impurity. When this MgCl2 is mixed with titanium-containing deposit 203, it reacts with water during washing to generate hydrochloric acid gas. Therefore, if workers' protective measures are insufficient, they may suffer from gas poisoning.

[0069] According to this embodiment, since the cleaning work is performed unmanned using the robot 300, these dangers can be avoided. As a result, the burden on workers can be reduced.

[0070] However, this embodiment is not limited to the use of the robot 300. Even when workers perform the cleaning work manually, the EB furnace 100 can be efficiently cleaned by setting the spray angle θ to 10° or more and 30° or less, and the water pressure P to 20MPa or more. Cleaning efficiency can be further improved by setting the distance d from the spray nozzle 351 to the titanium-containing deposit 203 to 1m or less. When workers perform the cleaning work manually, the hearth 103 and mold 105 can also be cleaned in addition to the housing 101.

[0071] The embodiments described above are examples that embody the present invention, and the present invention is not limited to these embodiments. For example, the present invention also includes the addition, deletion, or modification of some components or processes in the embodiments described above. [Explanation of Symbols]

[0072] 100 EB furnace 101 cabinets 101a Gunport 101b Raw material input port 101c Viewport 102 Feeder 103 Haas 104 Electron Gun 105 Mold 201 Melting raw materials 202 Titanium Ingot 203 Titanium-containing deposits 300 robots 310 bogies 315 Motor for trolley 320 Turntable 325 Servo motor for turntable 350 nozzles 351 Nozzle 352 Extension of the center line of nozzle 350 353 Intersection of extension line 352 and the surface of titanium-containing deposit 203 360 Water supply section 365 Water supply pipe 370 Control Unit 390 rails 400 water P Water pressure 400 d Distance between intersection 353 and nozzle 351 θ Nozzle 350 spray angle

Claims

1. A cleaning method for an electron beam melting furnace, comprising the step of spraying water at a pressure of 20 MPa or more from a nozzle with a spray angle of 10° or more and 30° or less onto the inner wall of the electron beam melting furnace to which titanium-containing deposits are attached.

2. The cleaning method according to claim 1, wherein the nozzle is positioned within 1 m of the titanium-containing deposit and the water is sprayed.

3. The cleaning method according to claim 1, which uses a robot comprising: a trolley capable of reciprocating in a first direction; a turntable mounted on the trolley and capable of rotating within an angular range of 180° or more along a plane including the first direction and a second direction perpendicular to the first direction; a first arm whose first end is connected to the turntable and capable of rotating in a plane including a third direction perpendicular to the first direction and the second direction; a second arm connected to the second end of the first arm and capable of rotating in a plane including the third direction; a water supply unit for supplying the water to the nozzle; and a control unit capable of controlling the trolley, the turntable, the first arm, the second arm, and the water supply unit, wherein the nozzle is fixed to the second arm.

4. The cleaning method according to claim 3, wherein the first and second directions are horizontal and the third direction is vertical.

5. The process of casting a titanium ingot in the aforementioned electron beam melting furnace, A step of cleaning the inner wall of the electron beam melting furnace, Equipped with, The method for manufacturing a titanium ingot, wherein the cleaning step is carried out by the cleaning method described in any one of claims 1 to 4.

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