JP2003231913A - Apparatus and method for degassing molten metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a degassing apparatus which does not use a complicated apparatus, such as for flow rate control, necessary for a continuous treatment, dose not need maintenance, etc., and is excellent in operability and low in cost. <P>SOLUTION: This degassing apparatus (1) comprises an upstream tank (5) containing a molten metal supplied from a furnace, a downstream tank (6) for receiving a degassed molten metal, immersed pipes (3) of which the lower ends are immersed in the molten metal in the upstream tank (5) and the downstream tank (6) and are used for causing a molten metal to flow from the upstream tank (5) and for causing the molten metal to flow into the downstream tank (6), and a vacuum tank (2) having a pore or porous plug (4) set at the bottom for bubbling an inert gas or a reducing gas. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a molten metal degassing apparatus and method.

[0002]

2. Description of the Related Art Degassing of molten metal is DH mainly in steel.
Method, RH method, etc., which is applied to the molten metal treatment in a vacuum system. However, since these are generally batch processes using ladle, etc., “thermal issues such as heat retention”, “introduction of large vacuum exhaust device for large-scale processing in a short time” "Unsteady work such as pan replacement" occurs, resulting in high processing costs.

In order to prevent these and further reduce the processing cost, a vacuum chamber as in Japanese Patent Publication No. 53-4483, No. 52-80204, No. 7-236950, and No. 2141540. A degassing device using is developed. In the continuous vacuum degassing device shown in Japanese Patent Publication No. 53-4483, the molten copper is transferred using the siphon principle, and the flow control function of molten metal is installed under the vacuum chamber by installing a flow control function such as a slide gate. Is going. Therefore, a device for measuring the level of the molten metal on the discharge side and a control device for the slide gate are required, which causes problems such as high cost and indispensable maintenance.

Further, in the degassing apparatus of Japanese Patent Laid-Open No. 52-80204, in addition to the siphon principle, molten copper is transferred by a gas pump by injecting gas from the tip of the inflow pipe. However, in this apparatus, the flow level of the molten metal flowing to the downstream side largely changes due to the change in the molten metal level of the upstream molten metal. For this reason, strict flow rate control cannot be performed unless the molten metal level on the upstream side and the downstream side is constantly observed and extremely minute gas injection amount control is performed according to the variation. Also, if the gas injection hole wears, the flow rate will change and the flow rate control will not be stable, so it is necessary to grasp the blockage of the hole frequently and control the flow rate, which is an important management point during maintenance. Therefore, maintenance costs are high.

Next, there is a siphon type vacuum degassing apparatus which does not have a flow rate control function as disclosed in Japanese Patent Laid-Open No. 7-236950, but degassing is performed because the molten metal stirring by gas injection is not actively performed. It has a problem of low efficiency. Lastly, there is a method of blowing a reducing gas or the like from the bottom of the tank as shown in JP-A-2-14540, but there is a problem that the degassing efficiency is extremely low because the upper part of the molten metal is not depressurized or vacuumed. is doing.

[0006]

DISCLOSURE OF THE INVENTION The present invention does not use a complicated device such as a flow rate control which is required for performing continuous processing, requires no maintenance, has excellent operability, and is a low-cost degassing device. The purpose is to provide. Also,
It is an object of the present invention to provide a highly efficient vacuum degassing method that can be carried out by a simple method for controlling the flow rate of continuously flowing molten metal.

[0007]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention have made the molten metal flow spontaneously by using the siphon principle, and decompress or vacuum the inside of the tank to obtain the bottom of the tank. By bubbling an inert gas or a reducing gas from the above, it was found that maintenance such as a slide gate and gas flow rate adjustment is not required and the operability is excellent, and furthermore, stirring of molten metal can be promoted and degassing efficiency can be improved, The present invention has been completed based on this finding. That is, the above problems can be solved by the present invention described below. (1) An upstream tank to which molten metal is supplied from the furnace side,
The downstream tank for receiving the degassed molten metal, the lower part is immersed in the molten metal stored in the upstream tank and the downstream tank, for the inflow of the molten metal from the upstream tank and the outflow of the molten metal to the downstream tank. A degassing apparatus comprising: a dip tube for use with a vacuum tank having a hole or a porous plug provided at the bottom for bubbling an inert gas or a reducing gas. (2) The degassing apparatus according to item (1), wherein a plate for controlling the flow of the molten metal is arranged in the vacuum chamber. (3) The degassing apparatus according to item (1) or (2), wherein an induction coil for inducing and stirring the molten metal in the vacuum tank is arranged on the outer circumference of the vacuum tank. (4) A step of flowing molten metal from the furnace side to the upstream tank, degassing while vacuumizing the vacuum tank and transferring the molten metal from the upstream tank into the vacuum tank and bubbling an inert gas or a reducing gas in the vacuum tank. And a step of flowing the degassed molten metal into a downstream tank.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION First, a preferred embodiment of a vacuum degassing apparatus for molten metal according to the present invention will be described with reference to the drawings. In addition, in each of the following drawings, the same reference numerals indicate the same parts. FIG. 1 is a sectional view of a vacuum degassing apparatus for molten metal according to the present invention. The vacuum degassing apparatus 1 of the present invention comprises an upstream tank 5 to which molten metal is supplied from the furnace side, a downstream tank 6 for receiving degassed molten metal, and storage in the upstream tank 5 and the downstream tank 6. The lower part is dipped in the molten metal to be melted, and a dipping pipe 3 for inflow of the molten metal from the upstream tank 5 and for outflow of the molten metal to the downstream tank 6 and an inert gas or reducing gas provided at the bottom are bubbled. And a vacuum chamber 2 having a hole or a porous plug 4.

In the vacuum chamber 2, the molten metal is degassed. The vacuum chamber 2 is connected to a vacuum pump from the chamber upper part 7 in order to reduce the pressure or make the inside of the chamber vacuum. Two or more dip pipes 3 are connected to the bottom of the tank, which allows the upstream tank 5
The molten metal is supplied into the vacuum tank 2 and the degassed molten metal is discharged to the downstream tank 6. The vacuum tank 2 is an upstream tank 5
The liquid level difference L (pressure difference) between the downstream tank 6 and the downstream tank 6 causes the molten metal in the vacuum tank 2 to naturally flow in the downstream tank 6 by the siphon principle.
Flow to. As a result, a slide gate, gas flow rate adjustment, etc. are not required, and a molten metal flow rate control mechanism can be eliminated for continuous degassing.

A hole or a porous plug 4 for bubbling an inert gas or a reducing gas is provided at the bottom of the vacuum chamber 2. By depressurizing or vacuuming the inside of the tank and bubbling an inert gas or a reducing gas from the bottom of the tank, stirring is promoted and degassing efficiency is improved. In addition, unlike the RH degassing device that is implemented with steel or the like, since there is no correlation between the recirculation flow rate control and the gas injection amount, it is possible to freely change the injection gas amount. It is possible to control the amount of gas blown in to lower the gas level.

FIG. 2 (a) is a partial cross-sectional plan view of TT 'of FIG. 2 (b), and FIG. 2 (b) is an enlarged view of the vacuum chamber 2 in the degassing apparatus 1 shown in FIG. It is explanatory drawing shown by the side sectional view. In this figure, the number of blowing holes or porous plugs 4 provided at the bottom of the vacuum chamber 2 is one, and it is provided at the center of the vacuum chamber 2.

By changing the number and arrangement of the blowing holes or the porous plugs 4 at the bottom of the vacuum chamber 2 and the flow pattern of the molten metal in the vacuum chamber 2, the stirring state in the chamber can be changed. The degassing efficiency can be improved. 3 to 8 are explanatory views of another embodiment of the vacuum chamber 2 in the degassing apparatus 1 of the present invention, and FIG. 3A is a partial cross-sectional plan view of TT ′ in FIG. (B) is a sectional view taken along the line SS ′ of FIG. The holes or porous plugs 4 may be arranged in a line as shown in FIGS. 3 and 4, or may be arranged around the immersion pipe 3 on the upstream tank side as shown in FIG. 5, and as shown in FIG. You may distribute and arrange in the whole bottom part of the vacuum chamber 2. In addition, as shown in FIGS.
It is also possible to arrange a plate 8 for controlling the flow of the molten metal therein. Further, as shown in FIG. 8, the induction coil 9 may be arranged on the outer circumference 10 of the vacuum chamber in order to induce and agitate the molten metal in the vacuum chamber 2 by using electromagnetic force.

Although not shown in FIG. 1, the upstream tank 5 and the downstream tank 6 are continuous with each other, and if the vacuum tank 2 is clogged due to solidification of the molten metal or the like, it flows from the furnace side. The molten metal coming out overflows from the upstream tank 5 to the downstream tank 6. Therefore, it is possible to prevent a disaster such as a leak of hot water.

Next, a method of using the vacuum degassing apparatus of the present invention will be described. FIG. 9 is an explanatory view of a method of using the apparatus of the present invention, FIG. 9 (a) is an explanatory sectional view of the apparatus of the present invention in an initial state of molten metal inflow, and FIG. 9 (b) is a degassing execution state. 3 is an explanatory cross-sectional view of the device of the present invention in FIG.
First, molten metal is flowed from the furnace side to the upstream tank. At this time, FIG.
As shown in (a), the initial low temperature molten metal is allowed to flow downstream. This is because when the temperature of the molten metal at the beginning of the inflow is low, the trouble of solidification in the vacuum chamber 2 occurs. When the temperature of the molten metal reaches a predetermined temperature or higher, the dip pipe 3 provided in the vacuum tank 2 is lowered and immersed in the upstream tank 5 and the downstream tank 6.

Next, when the pressure inside the vacuum chamber 2 is reduced, the molten metal rises from the upstream chamber 5 and flows into the vacuum chamber 2 due to the difference from the atmospheric pressure. At this time, gas is blown through a gas blowing hole or a porous plug 4 provided at the bottom of the vacuum chamber 2. The surface of the molten metal is extremely depressurized and the vacuum chamber 2
By degassing the gas from the bottom of, the degassing process can be performed in an extremely short time.

Further, since the molten metal flows into the upstream tank 5 from the furnace side, the liquid level of the molten metal in the upstream tank 5 becomes higher than that in the downstream tank 6. Therefore, the upstream tank 5 and the downstream tank 6
The difference in the liquid surface level between and causes a pressure difference, and the molten metal in the vacuum tank 2 naturally flows out to the downstream tank 6.

When the inflow amount of the molten metal increases, the residence time in the vacuum chamber 2 decreases and the degassing effect decreases.
The relationship between the blown gas amount, the degree of vacuum, and the degassing amount is grasped in advance, and stable degassing is performed by controlling the gas blowing amount and the vacuum degree according to this relational expression. In this case, since the amount of blown gas does not directly affect the flow rate of the molten metal, R
It is possible to take a wide range of condition setting range, such as blowing gas at 10 times or more the amount used in the H 2 degasser.

FIG. 10 is an explanatory view of an installation example of the apparatus of the present invention. This apparatus can industrially process the metal continuously melted and produced in the shaft furnace 11 and the electric furnace as shown in FIG. Although the present apparatus is installed downstream of the holding furnace 12 in FIG. 10, there is no problem even if it is installed upstream of the holding furnace 12. The molten metal continuously treated here is then supplied to the semi-continuous / total continuous casting machine 13.
As a result, there are no defects caused by hydrogen gas or oxygen gas, and good ingots and rough drawn lines can be obtained.

As described above, the degassing apparatus of the present invention is an inexpensive apparatus which can continuously perform degassing with high efficiency and is excellent in operability. In addition, since the flow rate control function is not used, maintenance of the slide gate etc. is unnecessary,
It is a structurally extremely simple and safe degassing device.

Next, the degassing method of the present invention will be described. Specific examples of the degassing method of the present invention include (1) a step of flowing molten metal from the furnace side to an upstream tank (2) vacuumizing the vacuum tank to transfer the molten metal from the upstream tank into the vacuum tank, and And (3) degassing while bubbling the inert gas or reducing gas, and (3) flowing the degassed molten metal into the downstream tank. These steps can be performed continuously.

As already described in the description of the degassing apparatus, first, molten metal is flowed from the furnace side to the upstream tank (step (1)). Next, the inside of the vacuum tank is decompressed, and the molten metal is moved upward from the upstream tank into the vacuum tank due to the difference from the atmospheric pressure.
Gas is blown from a hole for blowing gas or a porous plug 4 provided at the bottom of the. By depressurizing the surface of the molten metal extremely and bubbling gas from the bottom of the vacuum chamber 2, degassing treatment is carried out in an extremely short time (step (2)).

Further, since the molten metal flows from the furnace side into the upstream tank 5, the liquid level of the molten metal in the upstream tank 5 becomes higher than that in the downstream tank 6. Therefore, the upstream tank 5 and the downstream tank 6
The difference in the liquid level between and causes a pressure difference, and the molten metal in the vacuum tank 2 naturally flows out to the downstream tank 6 (step (3)).

As described above, the degassing method of the present invention can be carried out by a method in which the flow rate of the continuously flowing molten metal can be easily controlled, and the degassing process can be continuously performed with high efficiency.

The molten metal to which the present invention is applied means a molten material of ferrous and non-ferrous metals (for example, steel, copper and copper alloys, aluminum and aluminum alloys, etc.).

[0025]

The present invention will be described in more detail based on the following examples. Continuous degassing treatment was performed in a shaft furnace using molten copper obtained by melting only electrolytic copper as a raw material. This experiment was performed using molten copper whose gas composition was stable after about 1 hour by controlling and changing combustion conditions and the like, and the molten metal temperature was liquidus temperature + 50 ° C. Then, the molten copper was sucked and coagulated by a vacuum pin sampler from the molten copper in the upstream tank and the downstream tank located under the vacuum tank, and the oxygen / hydrogen concentration of this sample was analyzed.

The experiments were conducted with the degassing apparatus shown in Tables 1 to 3 at the molten copper inflow rate (melting amount), vacuum degree, gas type and blowing gas flow rate shown in Tables 1 to 3. . As a comparative example, gas blowing was stopped in the apparatus of FIG. 2 and the degassing ability was evaluated. In addition, Example 1
For Nos. 6 to 6, gas was blown into the molten copper from the through hole of φ1 mm, and for Examples 7 to 10, gas was blown using a porous plug (porous body), and Example 11 was used.
About 20, gas injection was performed using a slit type plug. As the porous plug, a high porosity refractory material having a diameter of about 40 mm to 200 mm at a portion in contact with the molten metal was used. Further, in Examples 11 to 20, carbon monoxide was used as the blowing gas, and the degassing ability (effective difference of the blowing gas) per unit blowing gas was calculated using the following calculation formula. K = (C _in −C _out ) × W / V (wherein C _in : inflow gas concentration (ppm), C _out : outflow gas concentration (ppm), W: passing molten metal weight (ton / hr), V: Blow gas amount (liter / min)) The results are shown in Tables 1 to 3. In Table 2, K (hydrogen) and K (oxygen) indicate the dehydrogenation / deoxygenation efficiency calculated by the above formula.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

Observing the state inside the vacuum chamber, in the examples, the molten metal inside the vacuum chamber was significantly stirred by the blowing gas, and the degassing process proceeded efficiently. on the other hand,
In the comparative example, the surface of the molten metal was extremely gentle, and the molten metal was estimated to flow out in a short circuit from the dipping pipe on the upstream tank side to the dipping pipe on the downstream tank side, and the residence time in the tank was estimated to be very short. It was confirmed that when carbon monoxide gas was used as the blowing gas, the deoxidizing effect was large. As a result, oxygen-free copper could be easily produced from the produced molten metal.

[0031]

EFFECTS OF THE INVENTION According to the degassing apparatus of the present invention, a complicated apparatus such as a flow rate control which is necessary for performing continuous processing is not used, maintenance such as a slide gate is unnecessary, and operability is excellent, The cost can be reduced. That is, the degassing apparatus of the present invention can continuously perform degassing stably for a long time with high efficiency, and is structurally extremely simple and safe. By degassing the non-ferrous metal melted in a shaft furnace or a melting furnace using this device, it is possible to obtain good ingots and rough drawn lines without defects due to hydrogen or oxygen. . Also, high-quality oxygen-free copper (oxygen-free copper for lightning tubes and oxygen-free copper for accelerators) can be obtained at low cost. Further, according to the continuous degassing method of the present invention, the flow rate of the molten metal flowing in continuously can be controlled by a simple method, and the degassing treatment can be continuously performed with high efficiency.

[Brief description of drawings]

FIG. 1 is a sectional view of a vacuum degassing apparatus for molten metal according to the present invention.

2A is a partial cross-sectional plan view of TT ′ of FIG. 2B, and FIG. 2B is an explanatory view showing an enlarged side view of the vacuum chamber in the apparatus shown in FIG. is there.

FIG. 3 is an illustration of another embodiment of the device of the present invention,
(A) is a TT 'partial cross section top view of (b), (b) is a SS' side sectional view of (a).

FIG. 4 is an illustration of another embodiment of the device of the present invention,
(A) is a TT 'partial cross section top view of (b), (b) is a SS' side sectional view of (a).

FIG. 5 is an illustration of another embodiment of the device of the invention,
(A) is a TT 'partial cross section top view of (b), (b) is a SS' side sectional view of (a).

FIG. 6 is an illustration of another embodiment of the device of the present invention,
(A) is a TT 'partial cross section top view of (b), (b) is a SS' side sectional view of (a).

FIG. 7 is an illustration of another embodiment of the device of the invention,
(A) is a TT 'partial cross section top view of (b), (b) is a SS' side sectional view of (a).

FIG. 8 is an illustration of another embodiment of the device of the present invention,
(A) is a TT 'partial cross section top view of (b), (b) is a SS' side sectional view of (a).

FIG. 9 is an explanatory diagram of a method of using the device of the present invention,
(A) is explanatory sectional drawing of the apparatus of this invention in a molten metal inflow initial state, (b) is explanatory sectional drawing of the apparatus of this invention in a degassing implementation state.

FIG. 10 is an explanatory diagram of an installation example of the device of the present invention.

[Explanation of symbols]

1 Vacuum degasser 2 vacuum chamber 3 immersion pipe 4 holes or porous plug 5 upstream tank 6 downstream tanks 7 Upper part of vacuum tank 8 Plates that control the flow of molten metal 9 induction coil 10 Vacuum tank outer circumference 11 shaft furnace 12 holding furnace 13 Semi-continuous / Full-continuous casting machine

Continued front page    (72) Inventor Chitsuna Kamata             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Satoshi Teshigawara             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Akiyuki Ota             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Kenjiro Sato             Daido Special, 9 Takiharu-cho, Minami-ku, Nagoya-shi, Aichi             Special Steel Co., Ltd. Takiharu Techno Center (72) Inventor Takashi Miyajima             Daido Special, 9 Takiharu-cho, Minami-ku, Nagoya-shi, Aichi             Special Steel Co., Ltd. Takiharu Techno Center F-term (reference) 4K001 AA02 AA09 AA10 BA23 EA02                       EA03 GA18 GB01 GB02 GB06                 4K013 BA07 CA01 CA05 CA23 CC06                       CE03 CE05 CE09 CF13 DA05                       DA12 DA13

Claims (4)

[Claims] 1. An upstream tank to which molten metal is supplied from the furnace side, and a downstream tank to receive degassed molten metal,
The lower part is immersed in the molten metal stored in the upstream tank and the downstream tank, and an inert gas is provided in the immersion pipe and the bottom for inflow of the molten metal from the upstream tank and outflow of the molten metal to the downstream tank. A degassing device comprising a vacuum chamber having a hole or a porous plug for bubbling gas or reducing gas. 2. The degassing apparatus according to claim 1, wherein a plate for controlling the flow of the molten metal is arranged in the vacuum chamber. 3. The degassing apparatus according to claim 1, wherein an induction coil for inducing and stirring the molten metal in the vacuum chamber is arranged on the outer periphery of the vacuum chamber. 4. A step of flowing molten metal from the furnace side to the upstream tank, and vacuuming the vacuum tank to transfer the molten metal from the upstream tank into the vacuum tank while bubbling an inert gas or a reducing gas in the vacuum tank. A degassing method comprising a step of degassing and a step of flowing the degassed molten metal into a downstream tank.