JP3170658B2 - Degassing method and apparatus 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 and an apparatus for degassing a holding furnace, which are used for low pressure casting.

[0002]

2. Description of the Related Art In a low-pressure casting method, a degassing gas is blown into a molten metal to prevent the oxidation of the molten metal in a holding furnace. In this case, if the internal pressure in the holding furnace is higher than the supply pressure of the degassing gas, the molten metal may flow backward in the degassing gas supply path. If a backflow occurs), the internal pressure in the holding furnace is made equal to the atmospheric pressure by opening the exhaust valve of the holding furnace by appropriate means to prevent the occurrence of an accident based on the backflow.

[0003]

[Problems to be solved by the invention]

However, in such a conventional method for preventing accidents based on backflow, since the exhaust valve of the holding furnace is opened, the casting operation has to be stopped, and as a result, the operation efficiency has to be reduced. There was a disadvantage that it could not be obtained.

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

[0006]

According to a first aspect of the present invention, there is provided a method for degassing a holding furnace for low pressure casting, wherein a mold is provided above the holding furnace, and the molten metal in the holding furnace is removed. In a low-pressure casting device to fill the mold at low pressure,
In a degassing method for a low-pressure casting holding furnace for performing degassing by blowing a degassing gas through a gas supply path for degassing into the molten metal in the holding furnace,

[0007] When there is a sign of a backflow of the molten metal in the degassing gas supply path, the inside of the holding furnace is communicated with an appropriate position of the degassing gas supply path.

In the degassing apparatus for a holding furnace for low pressure casting according to the second invention, a mold is installed above the holding furnace,
In a low-pressure casting apparatus for filling the mold with the molten metal in the holding furnace at a low pressure, a degassing gas is blown into the molten metal in the holding furnace through a degassing gas supply path to degas the molten metal. In the degassing device of the holding furnace for low pressure casting,

A backflow sensor is installed in the gas supply path for degassing, and an upstream side of the sensor in the supply path and the inside of the holding furnace are communicated by a gas degassing bypass path. An exhaust valve is installed in the bypass, and the exhaust valve is operated based on information from the backflow sensor.

[0010]

The degassing method of the holding furnace for low pressure casting according to the first invention is configured as described above, so that when there is a sign of the backflow of the molten metal (when the molten metal flows back to a predetermined position),
The internal pressure in the holding furnace and the degassing gas pressure at an appropriate position in the degassing gas supply path can be balanced.

Further, the degassing apparatus for the holding furnace for low pressure casting according to the second invention is configured as described above, so that the first invention can be easily implemented.

The operation is further simplified if the exhaust valve is an electromagnetic valve.

[0013]

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. An upper space 231 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. Also, as shown in FIG.
Are formed with a pair of through holes 232 and 233 to allow the molten metal M to be recirculated as the impeller 73 rotates. Reference numeral 24 denotes a guide wall (see FIG. 4), and the holding furnace main body 21 is provided.
And is integrally formed with the partition wall 23 in a state of being erected on the bottom surface. The guide wall 24 extends to the molten metal holding chamber F, and the molten metal M
The range of reflux is extended.

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. In addition, 31 is an exhaust valve installed in the holding furnace main body 21, and 4, 4, ... are the same heaters. 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, reference numeral 7 denotes 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.

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 performing the arithmetic processing on the information, the control unit C controls the supply pressure control means 754 so that the difference between the degassing gas supply pressure and the holding furnace internal pressure becomes substantially constant. 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. Also,
Reference numeral 756 denotes a backflow sensor, which is installed at the top of the shaft hole of the rotary shaft 71. The backflow sensor 756 is
Is detected (a 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.

[0019]

According to the first aspect of the present invention, in the method for degassing a holding furnace for low-pressure casting, a mold is installed above the holding furnace, and the molten metal in the holding furnace is filled into the mold at a low pressure. A degassing method for a low-pressure casting holding furnace in which a gas for degassing is blown into the molten metal in the holding furnace through a gas supply path for degassing to degas the molten metal,

When there is a sign of the backflow of the molten metal in the gas supply path for degassing, the inside of the holding furnace is communicated with an appropriate position of the gas supply path for degassing, so that there is a sign of the backflow of the molten metal. In this case (when the molten metal flows backward to a predetermined position), the internal pressure in the holding furnace and the degassing gas pressure at an appropriate position in the degassing gas supply path can be balanced.

Therefore, if this degassing method is used, the backflow of the molten metal in the degassing gas supply furnace can be prevented without opening the door of the holding furnace.

Further, in the degassing apparatus for a holding furnace for low pressure casting according to the second invention, a mold is installed above the holding furnace,
In a low-pressure casting apparatus for filling the mold with the molten metal in the holding furnace at a low pressure, a degassing gas is blown into the molten metal in the holding furnace through a degassing gas supply path to degas the molten metal. In the degassing device of the holding furnace for low pressure casting,

A backflow sensor is installed in the gas supply path for degassing, and an upstream side of the sensor in the supply path and the inside of the holding furnace are communicated by a gas bypass path for gas removal. Since the exhaust valve is installed on the road and the exhaust valve is operated based on the information of the backflow sensor, the first invention can be easily implemented.

If the exhaust valve is an electromagnetic valve, the operation is further simplified.

[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.

FIG. 6 is a partially enlarged view taken along the arrow VI in FIG. 2;

[Explanation of symbols]

 2 ... Holding furnace 751 ... Degassing gas supply path 756 ... Backflow detection sensor 752 ... Inert gas bypass path 753 ... Solenoid valve (exhaust valve) 8 ... Mold M ... Molten metal

Claims (3)

(57) [Claims] 1. A low-pressure casting apparatus in which a mold is placed above a holding furnace and the molten metal in the holding furnace is filled into the mold at a low pressure, and a gas supply path for degassing the molten metal in the holding furnace. A degassing method for a low-pressure casting holding furnace for performing degassing of the molten metal by blowing a degassing gas through the degassing method, wherein when a sign of a backflow of the molten metal occurs in the gas supply path for degassing, the inside of the holding furnace is A degassing method for a low-pressure casting holding furnace, wherein the degassing gas supply path is communicated with an appropriate position. 2. A low-pressure casting apparatus in which a mold is installed above a holding furnace and the molten metal in the holding furnace is filled into the mold at a low pressure, and a gas supply path for degassing the molten metal in the holding furnace. A degassing device for a low-pressure casting holding furnace for degassing the molten metal by injecting a degassing gas through a degassing gas supply path, and installing a backflow sensor in the gas supply path for degassing, The upstream side and the inside of the holding furnace are communicated with each other by a degassing gas bypass passage, and an exhaust valve is installed in the degassing gas bypass passage, and the exhaust valve is operated based on information of the backflow sensor. Degassing equipment for holding furnace for low pressure casting. 3. The degassing apparatus for a low pressure casting holding furnace according to claim 2, wherein said exhaust valve is an electromagnetic valve.