JPH0585258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is applicable to, for example, electronic devices such as magnetic disks, photosensitive drums, bonding wires, and rotating polygon mirrors of laser beam printers, particle acceleration pipes of synchrotrons, thin film manufacturing devices, The present invention relates to a method for manufacturing extremely low hydrogen concentration aluminum ingots used for manufacturing vacuum equipment such as surface analysis devices and nuclear fusion devices.

In this specification, the term "aluminum" includes both pure aluminum and aluminum alloys. Furthermore, in this specification, the term "inert gas" includes gases that are inert to aluminum, such as nitrogen gas, in addition to inert gases in the periodic table such as argon gas and helium gas.

Prior art and its problems The aluminum ingot used to manufacture the above equipment has a hydrogen content of 0.08
cc/100g or less is required.

To produce such aluminum ingots,
Conventionally, hydrogen removal treatment gas such as chlorine gas or a mixed gas of chlorine gas and inert gas was injected into the molten aluminum in the form of bubbles, or a flux treatment using hexachloroethane or the like was performed, and then this was processed. It was coagulating.

However, the problem with aluminum ingots produced by this method is that it is difficult to reduce the hydrogen content to 0.08 cc/100 g or less.

An object of the present invention is to solve the above problems and provide a method for producing an extremely low hydrogen content aluminum ingot having a hydrogen content of 0.08 cc/100 g or less.

Means for Solving the Problems In the method for producing an extremely low hydrogen concentration aluminum ingot according to the present invention, after melting aluminum, the molten aluminum is solidified by cooling to obtain an aluminum ingot. While stirring, a hydrogen removal processing gas is blown into the vicinity of the solid-liquid interface in the molten aluminum in the form of bubbles to remove hydrogen released from the solid-liquid interface into the liquid phase while cooling the molten aluminum from one direction to solidify it. It is characterized by this.

In the above, all gases effective for removing hydrogen from molten aluminum, such as chlorine gas, inert gas, mixed gas of chlorine gas and inert gas, and freon, can be used as the hydrogen removal processing gas. can.

Further, in the above, the solidification rate is preferably 10 mm/min or less, and desirably 5 mm/min or less.

Furthermore, the upper opening of the crucible or treatment tank in which the molten aluminum is placed is sealed, and the area above the surface of the molten aluminum is placed in a vacuum state, or the area is maintained in a low moisture retaining atmosphere to perform the above treatment. If this is done, the hydrogen removal efficiency will be further improved. In the latter case, it is preferable to fill the area with an inert gas, dry air, or pure oxygen to create a low moisture retention atmosphere in the area.

The ultra-low hydrogen concentration aluminum ingot obtained in this way is either subjected to appropriate mechanical processing and used, or placed in a low moisture retaining atmosphere such as a dry air atmosphere to prevent the hydrogen concentration from increasing. It is remelted and used as ingots in the required shape.

Effect When an aluminum ingot is obtained by cooling molten aluminum and solidifying it at a relatively slow rate, the hydrogen concentration in the initially obtained solid phase is extremely low, and is lower than the hydrogen concentration in the original molten aluminum. It gets lower. This is because, in aluminum, hydrogen solubility in the solid phase is extremely small compared to hydrogen solubility in the liquid phase, so hydrogen is released into the liquid phase at the solid-liquid interface. However, as the solidification progresses, the hydrogen concentration in the liquid phase increases, so when the solid phase ratio exceeds a predetermined value, for example 50%, the hydrogen concentration in the solid phase obtained thereafter begins to increase rapidly.

Since the hydrogen concentration in the liquid phase of aluminum is high near the solid-liquid interface, hydrogen removal treatment gas is injected in bubbles near the solid-liquid interface to remove the hydrogen released from the solid-liquid interface into the liquid phase. By solidifying the molten aluminum while removing hydrogen, hydrogen can be efficiently removed. Furthermore, if the molten aluminum is stirred at this time, the hydrogen removal efficiency is further improved. As a result, even if solidification progresses, the hydrogen concentration in the liquid phase does not increase, but rather decreases. Therefore, even if the solid phase ratio exceeds a predetermined value, the hydrogen concentration in the solid phase is extremely low, and even if the solid phase ratio becomes high, the hydrogen concentration in the obtained ingot is extremely low. Further, when the molten aluminum is solidified by cooling from one direction, the growth direction of the solid phase becomes constant, so that the hydrogen removal processing gas can be easily blown into the vicinity of the solid-liquid interface.

Examples Examples of the present invention will be described below with reference to the drawings together with comparative examples. Throughout the drawings, the same parts or parts are denoted by the same reference numerals and their explanations will be omitted.

Example 1 This example was carried out using the apparatus shown in FIGS. 1 and 2. In FIG. 1, a cooler 2 is disposed slightly below a vertical cylindrical electric furnace 1 with both ends open and at a position overlooking the lower end opening of the electric furnace 1. A cooling water inlet pipe 3 and a cooling water discharge pipe 4 are connected to one side wall of the cooler 2, and the cooling water introduced into the cooler 2 from the cooling water inlet pipe 3 circulates inside the cooler 2 and is turned into a cooling water. It is configured to be discharged from a discharge pipe 4. The cooler 2 is then water-cooled from inside. A cylindrical graphite crucible 5 is placed on the cooler 2, and a molten aluminum 6 is placed in the crucible 5. Almost the entire graphite crucible 5 is placed inside the electric furnace 1.
Further, in the center of the graphite crucible 5, a hydrogen removal treatment gas supply pipe 7 is arranged which can be moved up and down. The lower end of the supply pipe 7 is located near the bottom inside the crucible 5, and a disk-shaped bubble release member 12 is attached thereto. A hydrogen removal processing gas discharge port 13 connected to the supply pipe 7 is provided at the center of the lower surface of the discharge member 12 . Further, an air outlet 13 is provided on the lower surface of the discharge member 12.
A plurality of grooves 14 are provided radially from to the peripheral edge. A rotating magnetic field generating coil 10 is arranged around the electric furnace 1 so as to surround it.
A three-phase AC transformer 11 for generating a rotating magnetic field is connected to this coil 10 by Δ-Δ.

Using such a device, the purity inside the crucible 5 is
99.95wt% molten aluminum 6 was placed in the tank.
Before solidifying the molten aluminum 6, first, a three-phase alternating current is supplied from the transformer 11 to the rotating magnetic field generating coil 10, and a processing gas is blown into the molten aluminum 6 from the outlet 13 on the bottom surface. is. Then, an overcurrent was generated in the molten aluminum 6, Lorentz force was applied to the molten aluminum 6, and the molten aluminum 6 flowed and was stirred as a whole. On the other hand, the processing gas blown out from the outlet 13 is
4 towards the periphery of the discharge member 2 and is discharged from its ends. At this time, the molten aluminum 6
was flowing, so the processing gas was released from the tip of the groove 14 in the form of fine bubbles. After maintaining this state for 10 minutes, supply of cooling water to the cooler 2 is started while stirring the molten aluminum 6 and discharging the hydrogen removal treatment gas, and the molten aluminum 6 is poured into the bottom of the crucible 5. Solidification rate 3 from the direction of
The molten metal 6 was solidified at a rate of mm/min to form an ingot. At this time, as solidification progressed, the supply pipe 7 was gradually raised to constantly blow gas into the vicinity of the solid-liquid interface.

When the hydrogen concentration in the obtained ingot was measured,
The hydrogen concentration in the ingot from the lower end to 70% of the total length is 0.03cc/100g, and the hydrogen concentration in the remaining part gradually increases toward the upper end, reaching 0.08 at the upper end.
It was cc/100g.

Example 2 This example was carried out using the apparatus shown in FIG. In FIG. 3, the upper opening of the crucible 5 is sealed with a lid 15. And lid 15
A hydrogen removal processing gas supply pipe 7 is passed through the center of the pipe. The lower end of the supply tube 7 is located near the bottom of the crucible 5, and a porous ceramic bubble release member 8 is attached thereto. The hydrogen removal processing gas flowing through the processing gas supply pipe 7 is made into fine bubbles while passing through the release member 8 and is released into the molten metal 6. On the left side of the penetration portion of the supply pipe 7, an inert gas supply pipe 16 for supplying inert gas into the crucible 5 is arranged so as to pass through the lid 15. Further, on the right side of the penetration portion of the supply pipe 7, an exhaust pipe 17 is disposed to pass through the lid 15. The exhaust pipe 17 is used to remove the atmosphere originally present in the crucible 5, which is expelled from the crucible 5 by the inert gas supplied into the crucible 5 through the supply pipe 16 in advance, and to process the method of the present invention. This is for discharging an excess of the inert gas fed into the crucible 5 during the operation and an excess of the hydrogen removal processing gas from the crucible 5 to the outside. Further, a rotating magnetic field generating coil 10 is arranged around the electric furnace 1, and a rotating magnetic field generating three-phase AC transformer 11 is Δ-Δ connected to the coil 10.

Using such a device, the purity inside the crucible 5 is
A 99.95wt% aluminum molten metal 6 is placed in the crucible 5 through an inert gas supply pipe 16.
Ni gas is supplied into the crucible 5 to reduce the amount of moisture in the atmosphere above the molten metal 6 to 0.1mg/
The following was made. Prior to solidifying the molten aluminum 6, hydrogen removal treatment gas was released into the molten aluminum 6 in the form of bubbles for 20 minutes. Next, while continuing this discharge, supply of cooling water to the cooler 2 is started, and the molten aluminum 6 is
from the bottom of crucible 5 at a solidification rate of 2 mm/min.
The entire molten metal 6 was solidified to form an ingot. At this time, as solidification progressed, the supply pipe 7 was gradually raised to constantly blow gas into the vicinity of the solid-liquid interface.

When the hydrogen concentration in the obtained ingot was measured,
The hydrogen concentration in the ingot from the lower end to 90% of the total length was 0.01 cc/100 g, and the hydrogen concentration in the remaining portion was 0.05 cc/00 g.

Example 3 This example was carried out using the apparatus shown in FIG. In FIG. 4, the inner diameters of the electric furnace 1 and crucible 5 are larger than those of the electric furnace and crucible of the apparatus shown in FIG. Further, the crucible 5 is not placed on the cooler 2. A plurality of baffles 20 for reducing the flow rate of molten aluminum are provided on the inner peripheral surface of the crucible 5 at predetermined intervals in the circumferential direction. Also, crucible 5
A cylindrical rotary cooling body 22 attached to the lower end of the hollow rotary shaft 21 is disposed therein. A disc-shaped bubble release member 23 is provided on the lower surface of the rotary cooling body 22 and projects downward. Air bubble release member 23
A processing gas outlet 24 is formed in the center of the lower surface of the rotary cooling body 22 , and the processing gas outlet 24 is connected to the inside of the rotary cooling body 22 at the upper end. A plurality of vertical grooves 25 are provided on the circumferential surface of the discharge member 23 at predetermined intervals in the circumferential direction.
The upper end of the vertical groove 25 opens on the upper surface of the discharge member 23,
The lower end is open to the bottom surface. Cooling fluid is fed into the rotary cooling body 22 through the hollow rotary shaft 21, and hydrogen removal processing gas is supplied to the outlet 24 of the discharge member 23. The cooling fluid and the hydrogen removal processing gas may be used together, or they may be used separately. In addition, a portion of the lower surface of the rotary cooling body 22 around the portion connected to the discharge member 23 and a predetermined width portion including the contact portion with the molten aluminum 6 on the outer peripheral surface of the rotary cooling body 22 are each covered with a heat insulating material 26. covered.

Using such a device, the purity inside the crucible 5 is
99.95wt% molten aluminum 6 was placed in the tank.
Then, while rotating the rotary cooling body 22 and the discharge member 23 at a rotation speed of 500 rpm, the rotary cooling body 22
supplying cooling fluid into the discharge member 2;
Hydrogen removal processing gas was supplied to the outlet 24 of No. 3.
The hydrogen removal processing gas is supplied to the outlet 24 at the bottom of the discharge member 23 through the rotary cooling body 22 . Then, due to the centrifugal force generated by the rotation of the discharge member 23 and the action of the vertical grooves 25, the processing gas in the form of fine bubbles rises from the periphery of the discharge member 23 and is generated on the circumferential surface of the rotary cooling body 22. It is supplied near the interface between the solidified lump and the molten metal, and is discharged so as to spread throughout the molten aluminum 6. By maintaining such a state, solidification was performed on the circumferential surface of the cooling body 22 at a solidification rate of 4 mm/min, and a cylindrical ingot with a wall thickness of 50 mm was manufactured.
When the hydrogen concentration in the obtained ingot was measured,
It was 0.02cc/100g.

Comparative Example An ingot was produced in the same manner using the same equipment as in Example 1 above, except that the hydrogen removal treatment gas supply pipe 7 with the bubble release member 12 attached to the lower end was not placed in the crucible 5. Manufactured.

When the hydrogen concentration in the obtained ingot was measured,
The hydrogen concentration in the ingot from the lower end to 40% of the total length is 0.11cc/100g, and the hydrogen concentration in the remaining part gradually increases upward, reaching 1.5 at the upper end.
It was cc/100g.

Effects of the Invention According to the method of the present invention, an aluminum ingot with an extremely low hydrogen concentration can be easily produced as described in the section of the above-mentioned function.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of the device used in Embodiment 1 of the present invention, FIG. 2 is a plan view of the same, FIG. 3 is a vertical sectional view of the device used in Embodiment 2 of the present invention, and FIG. FIG. 7 is a vertical longitudinal cross-sectional view of the device used in Example 3 of the invention. 6... Molten aluminum.

Claims (1)

[Claims] 1 After melting aluminum, the molten aluminum is solidified by cooling to obtain an aluminum ingot, and at the same time the molten aluminum is stirred, hydrogen removal treatment gas is blown into the vicinity of the solid-liquid interface in the molten aluminum in the form of bubbles. A method for producing an ultra-low hydrogen concentration aluminum ingot, characterized in that molten aluminum is cooled from one direction and solidified while removing hydrogen released into a liquid phase from a solid-liquid interface.