JP3170652B2 - Degassing method for holding furnace for low pressure casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for degassing a holding furnace, and is used for low pressure casting.

[0002]

2. Description of the Related Art Heretofore, there has been no method for positively degassing a molten metal in a holding furnace in a low pressure casting method.

[0003]

However, even in the low-pressure casting method, it is difficult to obtain a good cast product unless the molten metal in the holding furnace is degassed.

An object of the present invention is to eliminate such inconvenience.

[0005]

In order to achieve the above object, in a method for degassing a holding furnace for low-pressure casting according to the present invention, a holding furnace and a molten metal placed above the holding furnace are provided. A mold filled at a low pressure, while blowing the degassing gas into the holding furnace through the degassing supply path while stirring the molten metal in the holding furnace, for degassing the molten metal. In the degassing method for a holding furnace, a backflow sensor is provided at an end of the holding furnace of the degassing supply furnace, and a degasser connected to the inside of the holding furnace is provided upstream of the backflow sensor in the degassing supply path. A gas bypass circuit is provided, and a valve is provided in the middle of the degassing bypass circuit, and the valve is opened via a control unit when the backflow sensor detects the backflow of the molten metal. , When serial backflow detecting sensor senses a back flow of the molten metal, the holding furnace pressure is in equilibrium with degassing gas supply pressure, this result, backflow of the molten metal is intended to be prevented.

[0006]

1 and 2, reference numeral 1 denotes a truck, and reference numeral 2 denotes a low-pressure casting holding furnace mounted on the truck 1. The holding furnace 2 includes a main body 21 and a lid 22. In addition,
Reference numerals 11 and 11 denote wheels of a bogie, and reference numeral 12 denotes a motor with a speed reducer for driving the wheels 11.

First, in the holding furnace main body 21, reference numeral 23 denotes a partition wall, which stands on the bottom surface of the main body 21. This partition
Reference numeral 23 partitions the inside of the holding furnace 2 into a molten metal holding chamber F and a degassing processing chamber G. As shown in FIG. 3, the degassing processing chamber G has a gradually decreasing depth on the side of the molten metal supply port 6 described later. In FIG. 3, reference numeral 231 denotes an upper space, which is formed between the leading edge of the partition wall 23 and the ceiling surface of the holding furnace body 21. For this reason, the amount of heat in the molten metal holding chamber F is easily transmitted to the degassing processing chamber G via the gas. As shown in FIG. 3, a pair of through holes 232 and 233 are formed in the partition wall 23,
The molten metal M can be recirculated as the impeller 73 rotates. 24 is a guide wall (see FIG. 4),
The partition wall is erected on the bottom surface of the holding furnace body 21.
It is integrally formed with 23. This guide wall 24 extends to the molten metal holding chamber F, and extends the range of reflux of the molten metal M.

In the molten metal holding chamber F, a cleaning window 25 is formed on the left side wall of the holding furnace body 21. The cleaning window 25 has a door 251. Reference numeral 3 denotes an air supply pipe, which is installed in the holding furnace body 21. The air supply pipe 3 is for supplying air to increase the internal pressure in the holding furnace 2. Reference numeral 31 denotes an open / close valve installed in the holding furnace main body 21, and 4, 4,... Also, 5,5
Reference numeral denotes a Stokes installed on the holding furnace lid 22, and reference numeral 8 denotes a mold installed at the tip of the Stokes 5,5. The molten metal M in the holding furnace 2 is supplied to the mold 8 via the Stokes 5 and 5.

Next, in the degassing chamber G, reference numeral 6 denotes a molten metal supply port, which is provided on the right side wall of the holding furnace body 21. The molten metal M is introduced into the holding furnace 2 through the molten metal supply port 6.
Is supplied. Reference numeral 61 denotes a slide lid, which covers the opening of the molten metal supply port 6. The slide lid 61 is opened and closed by a piston cylinder mechanism 611 (see FIG. 2). In FIG. 2, reference numeral 26 denotes a management window, which is installed on the right side wall of the holding furnace body 21. Through this management window 26, the worker manages the state of the molten metal M. 261
Is a door, which opens and closes the management window 26. A small window 262 is formed on the door 261. A heat-resistant transparent member 263 is fitted to the small window 262 (see FIG. 6), so that the inside of the holding furnace 2 can be managed even when the door 261 is closed.

In the degassing chamber G, 7 is a degassing gas (argon, chlorine, nitrogen, etc.) supply device,
It is installed on the ceiling of the holding furnace body 21. Reference numeral 71 denotes a rotating shaft of the degassing gas supply device 7, which is rotated by a motor 72 (see FIG. 5). The rotating shaft 71 has a shaft hole, and supplies a degassing gas into the molten metal M from the shaft hole. Reference numeral 73 denotes an impeller, which is installed at the tip of the rotating shaft 71. By the rotation of the impeller 73, the degassing gas is uniformly supplied into the molten metal M. This impeller 73
The optimal condition is when a degassing gas of 3 to 6 liters / min is supplied at 300 revolutions / min. If the rotation of the impeller 73 is too fast, the surface of the molten metal causes a turbulent flow and is easily oxidized, while if too slow, it takes time to degas.

In FIG. 5, reference numeral 751 denotes a degassing gas supply passage which communicates with the shaft hole of the rotary shaft 71. 75
Reference numeral 2 denotes a degassing gas bypass passage which connects the degassing gas supply passage 751 to the inside of the holding passage 2. Numeral 753 is an electromagnetic valve for opening and closing the gas degassing passage 752. Note that the solenoid valve 753 is normally closed. Reference numeral 754 denotes supply pressure control means, which is provided in the degassing gas supply passage 751. This supply pressure control means
By the operation of 754, the supply pressure of the degassing gas supplied to the holding furnace 2 is increased or decreased. An internal pressure sensor 755 is installed in the holding furnace 2. Information obtained by the internal pressure sensor 755 is transmitted to the control unit C. Reference numeral 765 denotes a supply pressure sensor, which is installed in the gas supply path 751 for degassing. The information obtained by the supply pressure sensor 765 is transmitted to the control unit C. Then, after the control unit C performs the arithmetic processing on the information, the control unit C controls the supply pressure control unit 754 so that the difference between the degassing gas supply pressure and the holding furnace internal pressure becomes substantially constant. In the optimal state, supply the degassing gas for 10 minutes or more after replenishing the molten metal. The molten metal pressure applied to the lower end of the rotating shaft 71 is calculated from the casting weight (for one time) and the surface area of the holding furnace, and the difference between the sum of the molten metal pressure and the holding furnace internal pressure and the degassing gas supply pressure is calculated. If the supply pressure control means 754 is controlled so that the pressure is substantially constant, the amount of the supplied degassing gas can be maintained more accurately and uniformly. Reference numeral 756 denotes a backflow sensor, which is installed at the top of the shaft hole of the rotating shaft 71. When the backflow sensor 756 detects a sign of backflow of the molten metal M (backflow to a predetermined position), the information is transmitted to the control unit C. Then, after the control section C performs arithmetic processing on this information, it opens the solenoid valve 753 and stops driving the motor 72. When the solenoid valve 753 is opened, the internal pressure of the holding path is balanced with the gas supply pressure for degassing, so that the backflow of the molten metal M is prevented.

[0012]

The method for degassing a holding furnace for low-pressure casting according to the present invention comprises a holding furnace, and a mold installed above the holding furnace and filled with the molten metal of the holding furnace at a low pressure. In the degassing method for a low-pressure casting holding furnace in which a degassing gas is blown into the holding furnace through a degassing supply path while stirring the molten metal in the furnace to degas the molten metal, Providing a backflow sensor at the holding furnace end of the furnace,
A degassing bypass circuit connected to the inside of the holding furnace in an upstream portion of the degassing supply path from the backflow sensor, and a valve provided in the degassing bypass circuit, When the sensor detects the backflow of the molten metal, the valve is opened via the control unit. Therefore, when the backflow sensor detects the backflow of the molten metal, the internal pressure of the holding furnace increases the gas supply pressure for degassing. And as a result, the backflow of the molten metal is prevented.

Therefore, if this degassing method is used, a good cast product can be obtained in the low pressure casting method.

[Brief description of the drawings]

FIG. 1 is a sectional view of a degassing apparatus of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is an enlarged sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a sectional view taken along line V-V in FIG.

[Explanation of symbols]

 2 ... holding furnace 8 ... mold M ... molten metal

Claims (1)

(57) [Claims] 1. A holding furnace, and installed above the holding furnace.
With soluble hot water of the holding furnace and the mold to be filled at a low pressure,
Agitating the molten metal in the holding furnace through the degassing supply path
Then, gas for degassing is blown into the holding furnace,
In the degassing method of the holding furnace for low pressure casting that performs degassing,
A backflow sensor at the holding furnace end of the degassing supply furnace
The provided, and, Contact Keru this backflow feeling to the supply path for degassing
Degasification connected to the holding furnace upstream of the sensor
A bypass circuit for exhaust gas and a bypass circuit for degassing
A valve is provided in the middle of the circuit, and the backflow sensor detects
When a backflow is detected , the valve
Degassing of low pressure casting holding furnace characterized by opening
How .