JP2004001013A - Method and device for flameproofing molten magnesium alloy and its melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely flameproof a molten magnesium alloy without loads on the environment. <P>SOLUTION: An inert gas with a high specific gravity is used as a cooling medium in order to flameproof the molten magnesium alloy 12 reserved in a furnace 10. The inert gas is introduced to a space 30 above the face of the molten metal inside the furnace. The surface of the molten metal of the molten magnesium alloy 12 is coated with a film-like solid magnesium alloy 30. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for making a molten magnesium alloy flame-retardant used in die casting and a melting furnace for the method.
[0002]
[Prior art]
Magnesium alloys are lightweight, highly rigid, and excellent as lightweight materials among metal materials.Die-casting enables the production of precise and thin-walled magnesium alloy products in large quantities. Attention has been paid.
[0003]
Magnesium alloys have the property of easily igniting magnesium when exposed to oxygen when melted in a melting furnace or holding furnace. , The furnace is filled with sulfur hexafluoride (SF6) gas or argon (Ar) gas.
[0004]
When the molten magnesium alloy comes into contact with sulfur hexafluoride gas, a fluorine protective film is formed on the surface of the molten metal, so that direct contact between oxygen and magnesium can be prevented. Argon gas is a high specific gravity gas having a deoxidizing effect, and prevents oxidation of magnesium.
[0005]
[Problems to be solved by the invention]
However, sulfur hexafluoride gas, which is often used as a protective gas, is a substance with excellent insulating properties between oxygen and magnesium, but has a greenhouse effect that causes global warming. Restrictions are being added and are no longer available as protective gas.
[0006]
On the other hand, argon gas uses the deoxidizing effect of a high-density gas, instead of the mechanism of making the molten magnesium alloy flame-retardant, as in the case of sulfur hexafluoride, which insulates magnesium from oxygen through a protective film. Therefore, there is a problem that reliability in terms of fireproof is low.
[0007]
Therefore, an object of the present invention is to solve the problems of the prior art, to eliminate the burden on the environment, and to make the molten magnesium alloy flame-retardant, and to provide a method and apparatus for making the molten magnesium alloy flame-retardant. It is to provide a melting furnace.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a method for flame retarding a molten magnesium alloy according to the present invention is a method for flame retarding a molten magnesium alloy stored in a furnace, wherein an inert high specific gravity gas is used as a cooling medium. The inert high specific gravity gas is introduced into the space above the molten metal surface in the furnace, and the surface of the molten magnesium alloy is coated with a film-shaped solid magnesium alloy.
[0009]
Further, the flame-retarding device for molten magnesium alloy according to the present invention is a device for flame-retarding the molten magnesium alloy stored in the furnace, and a pressure vessel for storing an inert high specific gravity gas used as a cooling medium, A cooling device for cooling the inert gas having a high specific gravity supplied from the pressure vessel; and a supply pipe for introducing the inert gas having a high specific gravity cooled by the cooling device into a space above the surface of the molten metal in the furnace. When,
It is characterized by having.
[0010]
Further, a melting furnace for a molten magnesium alloy according to the present invention is characterized by having the above-described flame retardant device and a furnace body for storing the molten magnesium alloy.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a method and an apparatus for making a molten magnesium alloy flame-retardant according to the present invention and a melting furnace thereof will be described with reference to the accompanying drawings.
[0012]
First Embodiment FIG. 1 is a view showing an embodiment in which a molten magnesium alloy flame retardant apparatus of the present invention is applied to a molten metal holding furnace for storing a molten magnesium alloy to be supplied to a die casting machine.
[0013]
In FIG. 1, reference numeral 10 indicates the entire molten metal holding furnace. A molten magnesium alloy 12 is stored in a furnace body 11 of the molten metal holding furnace 10, and a space 13 is formed above the molten metal surface of the molten magnesium alloy 12. In the upper part of the furnace main body 11, a hole 14 for inserting a supply pipe 25 for supplying an inert high specific gravity gas used as a cooling medium to be described later into the space 13 to the space 13 and a hole 16 for inserting a return pipe 26 are formed. Have been.
[0014]
In FIG. 1, reference numeral 20 denotes a pressure vessel storing an inert high specific gravity gas. As the inert high specific gravity gas, for example, Kr gas or Xe gas is used. Further, Ar gas may be used. The pressure vessel 20 is connected to a suction port of a cooling device 22 via a pipe 21.
[0015]
The cooling device 22 has a cooling unit 23 that cools the inert high specific gravity gas, and a pump unit 24. One end of a supply pipe 25 is connected to the discharge port of the pump section 24, and the other end is inserted into the hole 14 of the furnace body 11. Similarly, one end of a return pipe 26 is connected to the cooling unit 23, and the other end is inserted into the hole 15 of the furnace main body 11.
[0016]
Next, the operation and effect of the present embodiment will be described in relation to the method of making the molten magnesium alloy flame-retardant.
[0017]
First, a molten magnesium alloy 12 is supplied into the furnace body 11 from a melting furnace (not shown). Then, the inert high specific gravity gas is introduced from the pressure vessel 20 to the molten metal holding furnace 10 from the supply pipe 25 via the cooling device 22, and the inert high specific gravity gas is filled in the space 13 inside the furnace main body 11.
[0018]
In addition, while the inert high specific gravity gas is cooled in the cooling unit 23, the pump unit 24 is operated to send the inert high specific gravity gas to the space 13 through the supply pipe 25, and the inert high specific gravity of the space 13 is also controlled. The gas is returned to the cooling unit 23 from the return pipe 26.
[0019]
When the inert gas having a high specific gravity is circulated in this way, heat exchange occurs between the surface of the molten magnesium alloy in the furnace and the inert high specific gas, and the heat specific gravity of the magnesium alloy 12 is small. The surface is quickly covered with a cooled solidified solid magnesium alloy layer 30. In addition, by circulating, the amount of gas required is small and the efficiency is high.
[0020]
When the surface of the molten magnesium alloy 12 is covered with the solid magnesium alloy layer 30, the solid magnesium alloy itself is a stable compound and is nonflammable, so that the molten magnesium alloy 12 is insulated from oxygen and its ignition is prevented. be able to.
[0021]
In addition, inert high specific gravity gas such as Kr or Xe has deoxidizing property like Ar gas which has been conventionally used as a protective gas for molten magnesium alloy. In addition, it becomes possible to make the molten magnesium alloy 12 flame-retardant without fail.
[0022]
Second Embodiment Next, a second embodiment of the method for making a molten magnesium alloy flame-retardant according to the present invention will be described with reference to FIG. The molten metal holding furnace and the flame retarding apparatus used to carry out the flame retarding method according to the present embodiment are the same as those in FIG. 1, and the same components are denoted by the same reference numerals and detailed description thereof will be omitted. Description is omitted.
[0023]
In the second embodiment, a lump of foamed aluminum alloy 32 is spread over the surface of the molten magnesium alloy 12 stored in the molten metal holding furnace 10 in advance so as to float on the entire surface of the molten metal.
[0024]
Then, the inert high specific gravity gas is circulated as in the first embodiment. Since the foamed aluminum alloy 32 is made porous by foaming, the contact area with the inert high specific gravity gas is remarkably increased. Therefore, heat is generated between the molten magnesium alloy surface and the inert high specific gravity gas. It promotes exchange and contributes to efficient formation of the film-like solid magnesium alloy layer 30.
[0025]
Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is an embodiment in which a device for controlling the operation of the cooling device 22 is provided.
[0026]
In FIG. 3, reference numeral 40 is a temperature detector for detecting the temperature of the inert high specific gravity gas. The position of the temperature detector 40 is a position where it is possible to avoid the influence of the vertical fluctuation of the molten metal level accompanying the supply of the molten metal to the die casting machine and the replenishment from the melting furnace, and a position as close as possible to the inlet of the return pipe 26. It is preferable that
[0027]
In FIG. 3, reference numeral 41 denotes a control unit. The control unit 41 includes a comparator 42, a setting device 43, and a relay 44. The temperature detector 40 is connected to a comparator 42, and the comparator 42 is connected to a setter 43 for setting a set value of the in-furnace temperature of the inert high-specific-gravity gas. The set values are the following lower limit temperature T1 and lower limit temperature T2.
[0028]
In order to make the molten magnesium alloy flame-retardant, if the thickness of the solid magnesium alloy layer 30 is too small, the flame-retarded state cannot be stabilized, so that a certain degree of thickness is always maintained. There is a need. In order to stably maintain the thickness of the solid magnesium alloy layer 30 necessary for making the molten magnesium alloy flame-retardant, what temperature range of the temperature of the inert high specific gravity gas should be, The above-mentioned lower limit temperature T1 and lower limit temperature T2 are determined by experimentally obtaining in advance.
[0029]
45 is a contact of the relay 44. The contact 45 is a contact that opens and closes a power supply circuit between the power supply 46 that supplies power to the cooling device 22 and the cooling device 22.
[0030]
When the temperature T detected for the inert high-specific-gravity gas in the comparator 42 is lower than the lower limit temperature T1, the relay 44 is energized, the contact 45 is turned on, the cooling device 22 is operated, and the detected temperature T is increased to the upper limit. When the temperature is higher than the temperature T2, the relay 44 is demagnetized, the contact 44 is turned off, and the operation of the cooling device 22 is stopped.
[0031]
According to the third embodiment described above, when the formation of the solid magnesium alloy layer 30 for making the molten magnesium alloy 12 flame-retardant is in progress, the heat between the molten magnesium alloy 12 and the inert high specific gravity gas is increased. As the replacement proceeds, the gas temperature of the inert high-specific-gravity gas increases. However, when the temperature exceeds the upper limit temperature T2, the cooling device 22 automatically stops, so that the thickness of the solid magnesium alloy layer 30 does not increase any more. Thus, the thickness of the solid magnesium alloy layer 30 can be maintained at a stable thickness.
[0032]
On the other hand, when the casting cycle in the die casting machine is performed many times and the molten magnesium alloy 12 stored in the molten metal holding furnace 10 is reduced and it becomes necessary to supply hot water, the gas temperature in the furnace gradually decreases. Eventually, the temperature falls below the temperature T1. Then, the cooling device 22 starts operating by itself and the circulation of the inert high-specific-gravity gas starts. Then, when the molten magnesium alloy is supplied into the furnace, the solid magnesium alloy layer 30 is formed on the surface of the molten metal, so that the supplied molten magnesium alloy is made flame-retardant. In this way, the operation of the cooling device 22 can be released from human management, and can be operated when necessary to perform more efficient operation.
[0033]
In the above embodiment, the cooling device 22 is ON / OFF controlled by using the relay 44. However, the control is performed such that the temperature of the inert high specific gravity gas is directly controlled as a control target within a certain range. You may.
[0034]
As described above, the present invention has been described with the embodiment applied to the molten metal holding furnace. However, the present invention is not limited to the molten metal holding furnace, but the molten metal melting furnace, and the molten metal holding furnace having the integrated structure of the holding furnace and the melting furnace. The same can be applied to the above.
[0035]
【The invention's effect】
As is clear from the above description, according to the present invention, a greenhouse effect gas such as sulfur hexafluoride gas is not used, so that there is no burden on the environment, and the molten magnesium alloy can be reliably used for advanced purposes. Flame retardancy can be maintained.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a molten metal holding furnace to which a method for making a molten magnesium alloy flame-retardant according to one embodiment of the present invention is applied.
FIG. 2 is an explanatory view of a molten metal holding furnace to which a method for making a molten magnesium alloy flame-retardant according to another embodiment of the present invention is applied.
FIG. 3 is an explanatory view of a molten metal holding furnace to which a molten magnesium alloy flame retarding apparatus according to another embodiment of the present invention is applied.
[Explanation of symbols]
Reference Signs List 10 molten metal holding furnace 11 furnace body 12 molten magnesium alloy 13 space 20 pressure vessel 22 cooling device 23 cooling unit 24 pump unit 25 supply pipe 26 return pipe 30 solid magnesium alloy layer 32 foamed aluminum alloy 40 temperature detector 41 control unit 42 comparison Device 43 setting device 44 relay 45 contact

Claims (8)

A method of making a molten magnesium alloy stored in a furnace flame-retardant, using an inert high-specific-gravity gas as a cooling medium, introducing the inert high-specific-gravity gas into the space above the molten metal surface in the furnace, A method for making a molten magnesium alloy flame-retardant, comprising coating the surface of the molten alloy with a film-like solid magnesium alloy. The method for flame retarding a molten magnesium alloy according to claim 1, wherein the inert high specific gravity gas is circulated between inside and outside the furnace while being cooled outside the furnace. The method of claim 1, wherein the inert high specific gravity gas is Kr gas, Xe or Ar. The method for flame-retarding a molten magnesium alloy according to any one of claims 1 to 3, wherein a foamed aluminum alloy is previously floated on a molten metal surface of the molten magnesium alloy in the furnace. A device for making the molten magnesium alloy stored in the furnace flame-retardant,
A pressure vessel for storing an inert high specific gravity gas used as a cooling medium,
A cooling device for cooling the inert high specific gravity gas supplied from the pressure vessel,
A supply pipe for introducing the inert high-specific-gravity gas cooled by the cooling device into a space above the surface of the molten metal in the furnace,
A flame retardant device for a molten magnesium alloy, comprising: The molten magnesium alloy according to claim 5, wherein the furnace and the cooling device are connected by a return pipe, and the inert high-specific-gravity gas is circulated between the cooling device and the furnace. Flame retarding device. Gas temperature detecting means for detecting the temperature of the inert high specific gravity gas in the furnace,
Temperature comparison means for comparing the detected gas temperature with a preset set temperature range for the temperature of the inert gas,
Control means for controlling the operation of the cooling device so that the detected temperature of the inert high specific gravity gas falls within the set range;
The flame retardant apparatus for a molten magnesium alloy according to claim 5 or 6, further comprising: A melting furnace for a molten magnesium alloy, comprising: a furnace main body for storing a molten magnesium alloy; and the flame-retarding device for a molten magnesium alloy according to any one of claims 5 to 7.

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