JPH0465134B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molten metal heating device in a molten aluminum processing apparatus for removing hydrogen gas and nonmetallic inclusions contained in molten aluminum.

Molten aluminum before casting contains harmful gases such as hydrogen gas and nonmetallic inclusions such as oxides of aluminum and magnesium. The hydrogen gas and nonmetallic inclusions cause defects in the obtained ingot and products made from this ingot. Conventionally, as a method for removing these, a molten metal treatment method has been adopted in which an inert gas such as nitrogen gas or argon gas or chlorine gas is blown into the molten aluminum in the form of bubbles. When performing the above-described treatment on molten aluminum, it is necessary to heat the molten aluminum in the tank to a predetermined temperature. Therefore, it is conceivable to heat the molten aluminum to a predetermined temperature using a heating device equipped with an electric heater and a temperature control circuit, but there is a risk that the thyristor in the temperature control circuit will be damaged if it is grounded or short-circuited.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heating device in which a temperature control circuit, especially a thyristor, is not damaged even if it is grounded or short-circuited.

The molten metal heating device in the molten aluminum processing apparatus according to the present invention includes an electric heater for heating the molten metal disposed in a bottomed cylindrical ceramic heater cover that hangs from the lid of the molten metal processing tank; It is equipped with a temperature control circuit and a zero-sequence current detection and cutoff device that is provided between the electric heater and the temperature control circuit and detects the zero-sequence current and cuts off the connection between the electric heater and the temperature control circuit. be.

In the above, the heater cover is made of silicon carbide ceramics, for example. As the electric heater, a heater equipped with a non-metallic heating element is used. The temperature control circuit includes a temperature detector such as a thermistor, and uses a thyristor to control the temperature. The zero-sequence current detection and disconnection device is equipped with a detector that detects the zero-sequence current that occurs in the event of a grounding or short circuit, and an electromagnetic switch. When activated, the contacts open and have the function of cutting off the connection between the electric heater and the temperature control circuit.

According to the molten metal heating device of the present invention, in the event of a grounding or short circuit, it is possible to detect a zero-sequence current and thereby cut off the connection between the electric heater and the temperature control circuit. Therefore, damage to the thyristor of the temperature control circuit can be prevented, and there is no need to spend a lot of time repairing the temperature control circuit, such as replacing the thyristor. What's more, it also works to prevent electric shock when you touch the wiring to the electric heater.

This invention will be explained below with reference to the drawings.
In the following description, left and right refer to those toward FIG. 1.

The molten aluminum processing equipment includes a processing tank 1 for molten aluminum, two vertically long rails 2 disposed above the processing tank 1, a running body 3 running left and right along the rails 2, and a running body 3. 3 and a vertically movable elevating body 5 having two rotating shafts 4 for blowing processing gas, and a processing tank 1 provided with a heating device for molten aluminum.

The processing tank 1 consists of a tank body 7 lined with silicon nitride-bonded silicon carbide ceramics and a lid 8. The lid 8 has two rotating shaft insertion openings 9 and a plurality of heater cover insertion openings 10. ing.
The rotating shaft insertion port 9 has a flange 1 facing outward at the upper end.
1a is attached with a seat 11 for a seal member made of silicon carbide, each having an inwardly directed flange 11b integrally provided at its lower end. Inward flange 11
A heat-resistant paper 12 is attached to the upper surface of b. The heater cover insertion opening 10 has a tapered shape with a diameter decreasing toward the bottom. The heating device for molten aluminum includes a bottomed cylindrical heater cover 13 made of silicon carbide ceramics which is inserted into a heater cover insertion opening 10 and is removably attached to the lid 8 in a hanging shape, and the heater cover 13 an electric heater 14 having a nonmetallic heating element disposed therein; a temperature control circuit 15 for the heater 14 provided between the electric heater 14 and its power source (not shown);
4 and the temperature control circuit 15, and detects the zero-phase current to connect the electric heater 14 and the temperature control circuit 1.
Zero-phase current detection and cutoff device 16 that cuts off the connection with 5
It becomes more. The temperature control circuit 15 includes a temperature detector (not shown) such as a thermistor, and is configured to control the temperature using a thyristor. The zero-sequence current detection and cutoff device 16 is caused by the heater cover 13 being damaged and the molten aluminum falling into the cover 1.
A detector 17 detects a minute zero-sequence current of about 100 mA caused by a grounding or short circuit that occurs when the zero-sequence current enters the device. It is equipped with an electromagnetic switch (not shown) that opens. Further, a no-fuse circuit breaker 19 is provided between the temperature control circuit 15 and the power source to prevent excessive current from flowing.

The traveling body 3 includes a frame 21 , wheels 22 that are attached to the frame 21 and run on the upper rail 2 , and the frame 2
a motor 2 attached to 1 and driving a wheel 22;
3 and more. The traveling body 3 also includes a downward power cylinder 24 that moves the elevating body 5 up and down, and a pair of left and right vertical guide bars 25 that guide the elevating body 5.
It is equipped with

The elevating body 5 is a piston of the power cylinder 24.
It is attached to a rod 24a, and wheels 26 provided on the left and right sides of the rod 24a roll along a vertical guide bar 25. Further, a rotational drive shaft 27 is arranged within the elevating body 5. The rotary drive shaft 27 is driven by a motor 28 disposed within the elevating body 5, and a belt pulley 29 attached to the driving shaft of the motor 28, a belt pulley 30 attached to the upper end of the rotary drive shaft 27, and both belt pulleys. It is designed to be rotated via a belt 31 hung between 29 and 30. Furthermore, a processing gas passage 32 is provided inside the rotary drive shaft 27 . Although not shown, a processing gas supply pipe extending from a processing gas supply source is connected to the upper end of this passage 32 via a rotary joint.

The rotation shaft 4 for blowing processing gas is a rotation drive shaft 27.
The connecting member 33 is connected to the lower end of the connecting member 33. Further, the rotating shaft 4 is made of carbon, and is provided with a processing gas passage 34 communicating with the passage of the rotational drive shaft 27 inside, and a smooth bubble-shaped processing gas discharge member 35 is provided at the lower end. There is. The processing gas discharge member 35 is provided with a processing gas outlet 35a that communicates with the processing gas passage 34 and is open on the lower surface. Furthermore, radial grooves 35b are formed on the lower surface of the processing gas release member 35. An annular seal member 36 made of silicon oxide, which has an inner diameter larger than the outer diameter of the rotary shaft 4 and moves up and down together with the rotary shaft 4, is disposed around the upper end of the rotary shaft 4. The annular seal member 36 is attached to a mounting frame 37 provided between the lower edges of both the front and rear walls 5a of the elevating body 5 via four bars 38. bar 38
is movable up and down relative to the frame 37, and its lowering position can be determined by a stopper 39 attached to its upper end. The annular seal member 36 is attached to the lower end of the bar 38 so as to be able to move up and down slightly relative to the bar 38. Moreover, the bar 3 is located between the annular seal member 36 and the mounting frame 37.
A coil spring 40 is attached to 8 to constantly urge the annular seal member 36 downward. An upper end portion of a cylindrical body 41 made of silicon dioxide, which is fitted over the rotating shaft 4 and is shorter than the rotating shaft 4, is attached to the annular seal member 36. A male thread is formed on the outer peripheral surface of the upper end of the cylinder 41, and by screwing this part into a female thread formed on the inner peripheral surface of the annular seal member 36, the cylinder 41 is connected to the seal member 36.
It is removably attached to the

In such a processing apparatus for molten aluminum, the electric heater 14 is energized and the temperature control circuit 15 heats the molten metal in the processing tank 1 and the atmosphere above the molten metal to a predetermined temperature. First, the traveling body 3 is moved above the processing tank 1, and then the power cylinder 24 is operated to lower the elevating body 5. Then, the rotating shaft 4 is lowered, and the annular seal member 36 and the cylinder 41 are also lowered, and the rotating shaft 4 and the cylinder 41 enter the processing tank 1 through the rotating shaft insertion port 9. When the rotating shaft 4, that is, the elevating body 5 descends to the lower limit position, the annular seal member 36 is received by the inward flange 11b of the seal member seat 11, and the lower end of the cylindrical body 41 is inserted into the molten aluminum in the tank 1. immersed in. At the lower limit position of the elevating body 5, the mounting frame 3
Since the coil spring 40 is slightly compressed by 7,
The annular seal member 36 is urged downward and brought into close contact with the inward flange 11b. Therefore, entry of the atmosphere from between the annular seal member 36 and the seat 11 is completely prevented. Further, since the lower end of the cylinder 41 is immersed in the molten metal, the atmosphere entering through the opening at the upper end of the cylinder 41 contacts only the portion surrounded by the cylinder 41 of the entire surface of the molten metal. Therefore, it is less susceptible to atmospheric influences and processing efficiency is improved. In this state, from the processing gas supply source (not shown) to the processing gas passage 3 of the rotary drive shaft 27 and the rotation shaft 4.
When the processing gas is supplied to the discharge member 35 through the air outlet 2 and 34 and the rotary drive shaft 27 and the rotary shaft 4 are rotated by the motor 28, the processing gas discharged from the outlet 35a of the discharge member 35 is supplied to the discharge member 35. Due to the centrifugal force generated by the rotation of the bubbles and the action of the grooves 35b, the bubbles are dispersed and released into fine bubbles throughout the tank 1. Hydrogen gas and nonmetallic inclusions in the molten aluminum are removed by this processing gas.

In addition, in the molten aluminum processing apparatus as described above, the heater cover 13 naturally wears out.
Alternatively, the heater cover 13 may be damaged for some reason. In this case, when molten aluminum enters the heater cover 13, it is grounded (short circuited) and a zero-sequence current is generated. This zero-sequence current flows to the detector 1
7, and the contact 18 of the electromagnetic switch is opened. In this way, the connection between the temperature control circuit 15 and the electric heater 14 is cut off, and the thyristor in the temperature control circuit 15 is prevented from being damaged. If some of the plurality of heater covers 13 are damaged, the molten aluminum can be heated by the electric heater 14 placed inside the other heater covers 13, so the damaged heater covers 13 and The electric heater 14 disposed therein can be replaced without interrupting the molten aluminum processing operation.

Furthermore, if you accidentally touch the wiring to the electric heater 14, a zero-sequence current is generated, but this zero-sequence current is detected by the detector 17, and the contact 18 of the electromagnetic switch is opened. Become. Therefore, the current that touches the electric heater 14 is cut off, thereby preventing electric shock.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view of an aluminum molten metal processing apparatus equipped with a molten metal heating device of the present invention;
The figure is an enlarged sectional view taken along the - line in a state where the elevating body is lowered, and FIG. 3 is a circuit diagram showing the electrical configuration of the molten metal heating device. DESCRIPTION OF SYMBOLS 1... Molten metal processing tank, 8... Lid, 13... Heater cover, 14... Electric heater, 15... Temperature control circuit, 16... Zero-phase current detection cutoff device.

Claims (1)

[Claims] 1 An electric heater 14 for heating the molten metal disposed inside a bottomed cylindrical ceramic heater cover 13 hanging from the lid 8 of the molten metal processing tank 1, a temperature control circuit 15 for the electric heater 14, Heater 14
is provided between the electric heater 14 and the temperature control circuit 15, and detects the zero-phase current to connect the electric heater 14 and the temperature control circuit 15.
A molten metal heating device in an aluminum molten metal processing apparatus, comprising a zero-phase current detection and cutoff device 16 for cutting off connection with the molten metal.