JPH0639639B2 - Double gas shield arc melting method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an arc melting method for a dental metal, and particularly to a dual gas capable of uniformly melting titanium having a high melting point and suppressing oxidation as much as possible. The present invention relates to a shield arc type melting method.

[Conventional technology]

Heretofore, a titanium product which is lightweight, has a large mechanical strength and is excellent in corrosion resistance has been attracting attention in various fields, and a titanium melting method for casting a minute dental part has been provided. In particular, various arc-type melting devices related to the present invention are provided. For example, as a method for melting dental metal, in Patent Application Publication No. 16254 of 1985, inert gases such as argon at atmospheric pressure and the like are inert. In a gas atmosphere, an arc with a large width is generated between the lower electrode installed inside the crucible into which the metal is charged and the upper electrode with a constant spacing, and the entire metal is uniformly wrapped by the arc to gently heat and melt. However, the method requires a sealed furnace with a crucible and an electrode inside and an evacuation device, and when casting is performed in the furnace after melting, the mold is placed in the furnace. A device for arranging and guiding the molten metal to the mold must also be provided inside the furnace, which complicates the entire apparatus, and when performing casting operation outside the furnace, set the pressure inside the furnace to atmospheric pressure. The molten metal must be guided to the mold outside the furnace. Ya Kana operation is requested, it was further not suitable for high-melting-point metal such as titanium. In addition, in 1982 Utility Model Application Publication No. 16569, between an upper electrode provided on the outer periphery with an argon gas guide nozzle part whose lower end opening is set to a size that covers the crucible opening and a lower electrode provided inside the crucible. It has been disclosed a device capable of stably generating an arc and melting dental metal in an unoxidized state without involving external air, but the generation of the arc is concentrated in a part of the metal, and heating is performed. In some cases, the temperature became abrupt and the temperature became high, and a large amount of metal was evaporated, or the metal was unevenly melted.

[Problems to be solved by the invention]

In view of the above-mentioned situation, the present invention is to solve the problems that prevent partial overheating of a metal, particularly titanium having a high melting point, and uniformly dissolve the metal, and oxidize impurities in an inert gas atmosphere in a non-oxidized state. The point is to provide a method for obtaining a molten titanium having a small amount.

[Means for solving problems]

The present invention, in order to solve the above-mentioned problem, injects an inert gas from an outer nozzle having an area sufficient to cover the melted ingot in the crucible, and in this inert gas main jet flow, the inner nozzle From above, an inert gas is further injected downward, an upper electrode for arc generation is arranged inside the inner nozzle, and the electrode and the inner nozzle are integrally changeable in angle with respect to the outer nozzle. It becomes possible to displace the arc generation direction in the injection flow, and the arc discharge toward the ingot in the crucible with the small injection flow of inert gas in the outer periphery in the main injection flow of the inert gas. A double gas shielded arc type melting method was established.

〔Example〕

Next, the details of the present invention will be described based on the embodiments shown in the accompanying drawings.

FIG. 1 is a typical embodiment for carrying out the double gas shield arc type melting method of the present invention. A is an upper electrode portion, B is an inner nozzle, C is an outer nozzle, D is a rotary mounting portion, and E is E. It is a crucible. The upper electrode portion A has a rod-shaped upper electrode 1 protruding from the lower end, which is processed into a shape in which an arc is easily generated, and the protruding length of the upper electrode 1 can be adjusted appropriately. It has a conductive torch part which forms the part 2 and in which a gas flow path 3 is provided, and a gas supply pipe 4 which is continuous with the gas flow path 3 is attached at an appropriate position above the torch part and at the bottom part. A hole 5 continuous with the gas flow path 3 is formed obliquely outward and downward, a male screw 6 is formed on the outer periphery above the hole, and a handle 7 formed of an insulator is screwed on the upper end. The upper end of the gas flow path 3 is mounted so as to be hermetically sealed by the mounting means. The inner nozzle B is a hollow cylindrical body that can be attached below the upper electrode portion A, has a female screw 8 formed in an appropriate place inside, and has a lower inner space serving as a gas inner ejection hole 9, which is heat resistant and insulated. It is made of a flexible material, and the upper end is in sealing contact with the lower part of the spherical convex portion 2 when screwed onto the upper electrode part A, and the lower end is not located below the lower end of the upper electrode 1. Is set in relation to the length of the upper electrode 1. It should be noted that although this material is preferably ceramics, the first
When making a complicated shape other than the simple cylinder shown in the figure,
It is also possible to use a material other than ceramics that can be easily processed. The outer nozzle C has a sufficient area to cover the ingot in the crucible, and the length thereof is a downwardly opened cylindrical body set to be shorter than the length of the inner nozzle B, and the upper electrode portion A is provided at the center of the upper surface. A circular hole 10 having a size that allows the lower part to be inserted from the spherical convex portion 2 is provided, and a plurality of screw holes 12 for inserting a mounting screw 11 are formed on the peripheral surface thereof, and the upper side surface A gas supply pipe 14 which is continuous with the internal gas outside ejection hole 13 is attached to this. Further, in consideration of the uniformity of the downward gas injection flow, the shape of the outer nozzle C is such that the upper portion of the gas outside ejection hole 13 which is continuous with the gas supply pipe 14 is narrowed down as shown in FIG. Can be provided so that the gas is uniformly ejected to the lower side of the gas outside ejection hole 13. Also,
It is also possible to provide a plurality of gas supply pipes 14 on the outer periphery of the upper portion of the outer nozzle C as shown in FIG. 4, and further to provide a gas reservoir 15 on the outer periphery of the upper portion of the outer nozzle C as shown in FIG. The gas can also be uniformly ejected by providing a proper number of ejection holes 13 'around the ejection hole 13 downward. Although not shown, the rotary mounting portion D extends to an arm portion 16 mounted on a fixed base, and has a ball receiving hole 17 that can be brought into close contact with a lower portion than the maximum diameter of the spherical convex portion 2 of the upper electrode portion A. A mounting portion 19 having a screw hole 18 at the same position with the same diameter as the screw hole 12 of the outer nozzle C, and
It has a ball holding hole 20 that can be in contact with the upper side of the maximum diameter of the spherical convex portion 2, and the mounting screw is at the same position as the screw holes 12 and 18.
It is composed of a ball pressing portion 22 provided with a screw hole 21 for screwing 11 together. When assembling the above members, the upper surface of the outer nozzle C is brought into contact with the lower surface of the ball receiving hole 17 of the mounting portion 19 so that the ball receiving hole 17 and the circular hole 10 of the outer nozzle C are substantially aligned with each other. In this state, the upper electrode portion A is inserted from above into the sphere receiving hole 17 and the circular hole from above, and the spherical surface below the maximum diameter of the spherical convex portion 2 of the upper electrode portion A is received. After the inner nozzle B is brought into close contact with the inner surface of the hole 17, the inner nozzle B is screwed to the lower part of the upper embodiment part A from below, and the ball pressing part 22 is connected to the ball pressing hole 20 from above from the upper electrode part A. Fit on the top,
The inner surface of the ball holding hole 20 is brought into close contact with the spherical surface above the maximum diameter of the spherical convex portion 2 of the upper electrode portion A, and the mounting screw 11 fitted with the coil spring 23 is inserted from the inside of the outer nozzle C into the outer nozzle C and The outer nozzle C is inserted into both the screw holes 12 and 18 of the mounting portion 19 and further screwed into the screw hole 21 of the ball pressing portion 22 to mount the outer nozzle C to the mounting portion 19, and the upper and lower spherical surfaces of the spherical convex portion 2. Mounting part
The upper electrode portion A is sandwiched by the ball holding portion 22 and the ball holding portion 22,
That is, the torch portion of the upper electrode portion A and the mounting portion 19 are electrically coupled while elastically supporting the outer nozzle C so that the angle can be changed. Further, the crucible E has a melting tank 25 having an upper opening for using the ingot 24 therein, and a lower electrode 26 is embedded so as to appear on the bottom surface of the melting tank 25 from the outside and contact the ingot 24. And high temperature (1700 ± 100
(.Degree. C.) has extremely low reactivity with molten titanium and has a high refractory temperature, for example, magnesium oxide or zirconium oxide, or a material obtained by compacting and sintering.

When an arc is generated in the gap between the upper electrode 1 and the ingot 24 electrically connected to the lower electrode 26, the gap must be set in consideration of the supply current value, the stability of the arc, and the like. The distance can be adjusted by adjusting the height of the arm portion 16 with respect to the crucible E fixed downward, but it is more convenient if the protruding length of the upper electrode 1 can be adjusted with respect to the upper electrode portion A as well. As shown in FIGS. 6 (a) and 6 (b) as an example of the structure, there is a through hole 27 into which the upper electrode 1 can be inserted in a normal state, and a hook-shaped projection is provided around one side end. , A fastening tube 30 notched inwardly from the end 29
Is inserted into the gas flow path 3 of the upper electrode A, and the upper electrode 1
In the state of being inserted into the through hole 27, the upper end of the fastening pipe 30 is pressed downward as the handle 7 is screwed, and thereby the inner diameter of the inner and lower ends of the gas flow path 3 is reduced. The hook-shaped protrusions 28 can be pressed inward in the radial direction along the inclined surface to set the protrusion length of the upper electrode 1 and then fixed.

Therefore, in order to dissolve titanium as an example of metal using the above-mentioned apparatus embodied to carry out the method of the present invention, the titanium ingot 24 is placed in the melting tank 25 of the crucible E as described above.
Is arranged so as to be in contact with the lower electrode 26, and the arc portion 16 is height-adjusted and fixed to a fixing base (not shown), that is, the crucible E.
The outer periphery of the upper end of the outer nozzle C and the lower end of the outer nozzle C are set to a height that substantially coincides with each other, and the length of the upper electrode 1 projecting downward is set to a distance between the upper electrode 1 and the upper surface of the titanium ingot 24 so that the arc is stably generated. Set to the optimum interval for. In this state,
An inert gas such as argon is introduced from a gas supply pipe 14 provided on the upper side of the outer nozzle C and jetted downward from the gas outside ejection hole 13, and a gas flow path is provided from a gas supply pipe 4 provided on the upper electrode part A. An inert gas such as argon supplied to 3 is introduced into the inner nozzle B through a hole 5 formed below the upper electrode portion A, and is jetted downward from the gas inside jet hole 9 to dissolve the crucible E in the melting tank 25. In an atmosphere in which the interior is constantly filled with an inert gas, the lead wire connected to the arm 16 electrically connected to the upper electrode 1 and the lead wire connected to the lower electrode 26 are supplied with a current from a power source (not shown). The lower electrode of the upper electrode 1 and the lower electrode 26.
That is, while the arc is generated between the upper surfaces of the titanium ingots 24, the handle 7 of the insulator attached to the upper part of the upper electrode portion A is manually operated to integrate the upper electrode 1 and the inner nozzle B into an outer nozzle as shown in FIG. The angle is changed with respect to C, the arc generation place on the titanium ingot 24 is uniformly changed, and the titanium ingot 24 is melted uniformly. Here, although only the device for manually changing the angle of the upper electrode 1 with respect to the outer nozzle C is described in the drawing, the invention is not limited to this, and the handle 7 of the upper electrode portion A is horizontally rotated. The tip of the upper electrode 1 may draw a simple circular orbit by being pivotally connected to the crank, and it is also easy to make a locus that traverses the center of the titanium ingot 24 to the above circular orbit. It is also one mode to uniformly melt the titanium ingot 24 by controlling the complicated trajectory by the computer. Further, by adjusting the flow rates of the inert gas injected from the inner nozzle B and the outer nozzle C, the oxidation of the surface of the molten titanium can be prevented extremely effectively as compared with the conventional melting method. For example, the inner diameter of the inner nozzle B is 12 mmφ, the inner diameter of the outer nozzle C is 30 mmφ, the inner diameter of the melting tank 25 of the crucible E is 40 mmφ, the inner diameter of the bottom is 32 mmφ, and the diameter of the crucible E is 25 mmφ and the height is 17.5 mm. An arc is generated with a melting current of 180 A using the titanium ingot 24, and the lower end of the upper electrode 1 is moved by moving it on a circle having a radius of 8 to 10 mm with respect to the center of the titanium ingot 24, and after about 1 minute, the arc is generated. Stop,
The results are shown in the table below, in which molten titanium was cooled in an atmosphere of argon gas and the surface oxidation state was compared by changing the argon gas flow rates of the inner nozzle B and the outer nozzle C.

a is the case where the gas is not injected from the outer nozzle C, that is, the state where the outer nozzle C does not substantially exist, and in this case, the unoxidized area of the titanium surface after melting and cooling is only 5%.
In addition, b is the case where gas is not injected from the inner nozzle B, and similarly, the area not oxidized is 10%, and the inner nozzle B exists inside, but substantially one nozzle is not used. It is similar to the conventional method used. On the other hand, the titanium melting method according to the present invention, in which argon gas is injected from both the inner nozzle B and the outer nozzle C, and is melted in an argon atmosphere in which a double gas shield is applied to the atmosphere, is used. In both cases, a surface area of 39% that is not oxidized can be obtained, and surface oxidation can be significantly suppressed as compared with the conventional method. It should be noted that although c and d have some difference in flow rate and a magnitude relationship, in the flow rate range of 5 to 15 (/ min), the argon gas injection amount from the inner nozzle B and the outer nozzle C is set very strictly. It is shown that it is not necessary to do so, and if the flow rate range is set to the above range, the effect of suppressing oxidation can be sufficiently achieved. If the injection gas flow rate is increased, the gas shield against the atmosphere will be more complete, but the cooling action of titanium will also increase and effective melting will not be performed, so the flow rate must be experimentally set optimally. I won't. Then, if the gas injection flow rates from the inner nozzle B and the outer nozzle C are set to optimum values, not only a gas shield effect for the atmosphere but also a cooling effect for preventing local overheating of titanium can be added. Similarly, an inert gas other than argon gas can be used as a shield against the atmosphere, but argon gas is the most practical in terms of cost and stability of arc current. Further, it is possible to install the present apparatus in an openable and closable sealed container, shut off the atmosphere, and operate the handle 7 from outside the container to uniformly dissolve the titanium ingot 24.

〔The invention's effect〕

According to the double gas shield arc type titanium melting method of the present invention as described above, the inert gas is injected from the outer nozzle having an area sufficient to cover the titanium ingot in the crucible, and this inert gas main injection flow Among them, since the inert gas is further injected downward from the inner nozzle, a double gas shield can be applied to the atmosphere, and the atmosphere such as oxygen and nitrogen that easily reacts with titanium at high temperature dissolves titanium into the atmosphere. It can be almost completely eliminated from the surface, molten titanium with extremely less oxidation can be obtained compared to the conventional melting method, and the upper electrode for arc generation is arranged inside the inner nozzle, and the electrode and the above Since the angle with respect to the outer nozzle can be changed integrally with the inner nozzle and the arc generation direction can be displaced in the main jet flow, the titanium ingot electrically connected to the lower electrode can be obtained. The position of the arc between the surface and the upper electrode can be changed uniformly with respect to the titanium ingot, and the titanium can be melted uniformly. Good dissolution can be achieved without change. Then, by appropriately adjusting the flow rate of the gas injected from the inner and outer nozzles, synergistically with the displacement effect of the arc generation position due to the change in the angle of the upper electrode, titanium is heated while being cooled by the injection gas, so overheating is prevented. In addition, since the inner nozzle and the upper electrode change the angle together, the inert gas injected from the inner nozzle can always be supplied to the arc generation position at the tip of the upper electrode, and the angle change of the upper electrode. Even if the upper electrode is located on the side of the main jet flow of the outer nozzle with a large value, it is possible to achieve a sufficient gas shield against the atmosphere.

[Brief description of drawings]

FIG. 1 is a partially omitted cross-sectional view of an apparatus for carrying out the double gas shielded arc type titanium melting method of the present invention, and FIG. 2 is a part in which an upper electrode and an inner nozzle are changed in angle with respect to an outer nozzle. An abbreviated sectional view, FIG. 3 is a sectional view showing another aspect of the outer nozzle, FIG. 4 is a plan view of the outer nozzle having a plurality of gas supply pipes provided on the outer periphery, and FIG. 5 is a gas reservoir provided on the outer periphery. A sectional view of the outer nozzle, FIG. 6 (a) is a side view of a fastening tube for adjusting and fixing the protruding length of the upper electrode with respect to the upper electrode portion, and FIG. 6 (b) is inserted in the upper electrode portion. It is explanatory drawing represented with the partial cross section which shows a state. A: upper electrode part, B: inner nozzle, C: outer nozzle, D: rotary mounting part, E: crucible, 1: upper electrode, 2: spherical convex part, 3: gas flow path, 4: gas supply pipe, 5: Hole, 6: Male screw, 7: Handle, 8: Female screw, 9: Gas inner ejection hole, 10: Circular hole, 11: Mounting screw, 12: Screw hole, 13: Gas outer ejection hole, 14: Gas Supply pipe, 15: Gas reservoir, 16: Arm part, 17: Ball receiving hole, 18: Screw hole, 19: Mounting part, 20: Ball holding hole, 21: Screw hole, 22: Ball holding part, 23: Coil spring, 24: ingot, 25: melting tank, 26: lower electrode, 27: through hole, 28: hook-like projection, 29: notch, 30: fastening tube.

Claims (1)

[Claims] 1. An arc-type metal melting method for melting a metal by generating an arc between a lower electrode provided inside a crucible into which a metal is charged and an upper electrode facing the lower electrode with a certain interval. In the method, injecting an inert gas from an outer nozzle having an area sufficient to cover the ingot in the crucible,
In this inert gas main jet flow, an inert gas is further jetted downward from the inner nozzle, an upper electrode for arc generation is arranged inside the inner nozzle, and the electrode and the inner nozzle are integrally formed as described above. The angle can be changed with respect to the outer nozzle, and the arc generation direction can be displaced in the main jet flow.
A double gas shield arc melting method in which an ingot in a crucible is melted by arc discharge toward an ingot while having a small jet flow of an inert gas on the outer periphery in a main jet flow of an inert gas.