JP2002050351A - Manufacturing method of battery hydrogen storing alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of securing safety when the furnace is opened to the atmosphere after vacuum melting or atmospheric melting by suppressing the evaporation of melted magnesium while containing a prescribed amount of magnesium in the alloy. SOLUTION: As a material for adding Mg, a Mg metal or a Mg alloy having a melting point of 650 deg.C or more is used, and further Mg is added after a high melting point metal such as Ni and Co or the like are melted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a hydrogen storage alloy, and more particularly to a method for producing a hydrogen storage alloy for a negative electrode used in a nickel-metal hydride secondary battery.

[0002]

2. Description of the Related Art In a nickel-hydrogen secondary battery, a high-frequency melting method, an arc melting method, and the like have been conventionally used as a method of melting a hydrogen storage alloy used for a negative electrode. The raw material is a rare earth metal such as La, Ce, Pr, Nd, or Sm or a misch metal (hereinafter, a mixture thereof).
It is called “Mm”. ) And nickel, cobalt, manganese,
Aluminum metal has been used. Recently, it has been found that by adding about 0.5% by weight of magnesium in the alloy in addition to these metals, pulverization is suppressed and the amount of hydrogen occlusion is increased. Conventional Mm and the like also contain Mg as an impurity, but evaporate during melting and hardly remain in the completed alloy. The reason is that the saturation vapor pressure of magnesium is higher than that of other metals, and the alloy of rare earth and Mg has a lower melting point, so that melting is faster, and as a result, the time in the molten metal is longer, and Is known to evaporate.
Evaporated magnesium adheres to the melting furnace wall, melts, casts, and then releases the atmosphere replacement chamber to the atmosphere,
Very flammable with possible burning or explosion.

[0003]

SUMMARY OF THE INVENTION The present invention solves these problems of the prior art, in which evaporation of magnesium during melting is suppressed, a predetermined amount of magnesium is contained in the alloy, and vacuum melting or atmosphere melting is performed. An object of the present invention is to provide a method for ensuring safety when the inside of a furnace is released to the atmosphere after melting.

[0004]

The present invention is characterized in that a Mg metal or a Mg alloy having a melting point of 650 ° C. or more is used as a raw material for adding Mg.
It is characterized in that it is added after dissolving a high melting point metal such as i or Co. Therefore, the added material of Mg has a melting point of 650.
° C or more, or when adding magnesium metal, by adding after melting a high melting point metal such as Ni or Co, the time during which the magnesium-containing metal is present as a molten metal is shortened, M evaporating from
The effect of suppressing the amount of g is expected. As a result, the amount of Mg adhering to the furnace walls and the like is reduced, and the furnace can be operated more safely when the furnace is opened to the atmosphere.
The magnesium content in the finished alloy can be increased.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen storage alloy to which the present invention is applied is a LaNi ₅ , MmNi ₅ , LmNi ₅ (Lm represents a La-rich misch metal) series alloy, and is characterized by being composed of Ni. Some may be replaced with Co, Al, Mn.

The method for producing a hydrogen storage alloy according to the present invention is performed as follows. A predetermined amount of each element is weighed, and an inert gas such as Ar gas (0.02 to
Dissolve in a). As the melting raw material, Mg metal or melting point 6
Use an alloy at 50 ° C. or higher. For example, MgNi _{2 and the} like can be mentioned. The amount of addition is 0.05-2.0% by weight, preferably 0.1-1.
The content is preferably 0% by weight. In the method of the present invention, when the rare earth-based hydrogen storage alloy contains Ni and / or Co, and the additive material of Mg is added at the time of melting, at least Ni and / or C
After melting the high melting point metal of o, it is added to the molten metal. For example, at the time of melting, a predetermined amount of weighed Ni, Co, Mn, and Al is put into the initial crucible and melting is started. After they dissolve, La, Ce, Pr, N
At the same time as d or Mm, the Mg metal or Mg alloy is added to the molten metal. At this time, once the molten metal temperature drops, wait for the temperature to rise again to the predetermined temperature,
Alternatively, pour onto a table and cool.

The alloy obtained by the production method of the present invention is heat-treated and pulverized by a known method to obtain a hydrogen storage alloy for an electrode.
For example, under an inert atmosphere such as Ar gas (0.08-0.
2 MPa) at 800 to 1200 ° C. for 5 to 20 hours, and thereafter, under an inert atmosphere such as Ar or the like, to an average particle size of 4 to 70 μm by a pulverizer such as an impact or pulverizer or a jet mill. Thus, the hydrogen storage alloy of the present invention can be obtained.

[0008]

Hereinafter, the present invention will be described in detail with reference to Examples.
The present invention is not limited to this. Example 1, Comparative Example 1 An alloy represented by the following composition formula (1)
In order to produce an alloy containing 0.28% by weight of g, a method of manufacturing a hydrogen storage alloy in which Ni, Co, Mn, and Al are first dissolved when the alloy is melted, and then Mg metal is added simultaneously with Mm. In Example 1, Mg was Mm, Ni, Co,
When added simultaneously with Mn and Al and dissolved from the beginning,
Comparative Example 1 was used. Table 1 shows the amount of Mg in the alloy relative to the amount of Mg added during melting as a residual ratio. The melting was performed using a high-frequency melting furnace and argon gas (0.034 MPa), and the temperature was 1340 to 1420 ° C. MmNi _4.17 Co _0.4 Mn _0.38 Al _0.30 (1) As Mm, La 80% by weight, Ce 12% by weight, Pr
A composition of 4% by weight and 4% by weight of Nd was used.

[0009]

[Table 1]

Example 2 and Comparative Example 2 In the manufacturing method shown in Example 1, a method of alloying Mg to be added with Ni and adding an alloy having a higher melting point (1100 ° C.) is referred to as Example 2, Comparative Example 2 was a method of adding an alloy of which the melting point was low (550 ° C.) with an alloy of Al and Al, and the residual ratio of Mg is shown in Table 2 in the same manner as in Example 1.

[0011]

[Table 2]

As can be seen from Tables 1 and 2, Ni, Co
Mg is added after dissolution, and the melting point is Mg metal (6
It can be seen that a temperature of 59 ° C. or higher remains more in the alloy, the radiation to the outside of the alloy is suppressed, and it is possible to work more safely even if the furnace is opened to the atmosphere during the melting operation.

[0013]

According to the method for producing a hydrogen storage alloy of the present invention, a safer hydrogen storage alloy can be produced by setting the Mg content in the alloy to a predetermined value and suppressing evaporation during melting.

Claims (2)

[Claims] 1. A method for producing a rare earth-based hydrogen storage alloy to which Mg is added, wherein a melting point of the Mg-added material is 65
A method for producing a hydrogen storage alloy, comprising using an Mg alloy or Mg metal at 0 ° C. or higher. 2. The method according to claim 1, wherein the rare earth hydrogen storage alloy is Ni and / or Ni.
2. The method for producing a hydrogen storage alloy according to claim 1, wherein when the additive material of Mg is added at the time of melting, at least the high melting point metal of Ni and / or Co is added to the molten metal. .