JPH0341535B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing boride-based particle dispersion-strengthened copper mainly used as an electrical material.

[Conventional technology]

Particle-dispersion-strengthened copper, in which fine particles of oxides such as Al ₂ O ₃ are mixed into copper, has conventionally been used as an electrical material used in places where high-temperature strength is required.

However, this oxide-based particle dispersion-strengthened copper uses materials such as Al ₂ O ₃ that have poor electrical conductivity, so even if high-temperature strength can be effectively increased by adding reinforcing particles, it is difficult to increase the amount of addition. When the amount of reinforcing material increases, the electrical conductivity decreases significantly. Especially in the case of Al ₂ O ₃ based reinforcing materials, the electrical resistance of the reinforcing material itself is very high, so there is a problem that even a small amount of the reinforcing material significantly reduces the electrical conductivity.

Therefore, the present inventors focused on carbide-based fine particles with good electrical conductivity, produced carbide-based particle dispersion-strengthened copper, and found that its properties were superior to oxide-based particle-dispersion-strengthened copper. We confirmed this and proposed its technical content in Japanese Patent Application No. 79427/1983.

However, it goes without saying that particle dispersion-strengthened copper with even better properties is generally required.

In addition, powder metallurgy has conventionally been used as a method for producing the above-mentioned particle dispersion strengthened copper, but there are problems in that it requires a complicated production process and large-scale equipment. On the other hand, the CompoCast method is also known, in which the alloy is rotated and stirred while adding reinforcing materials in a solid-liquid coexisting state. Since we use a method of stirring while adding large reinforcement particles at room temperature, the reinforcement at room temperature immediately after addition becomes a quenching plate, creating a gap at the interface between the reinforcing material and the highly viscous metal alloy in a semi-solid state. The reinforcement surface cannot be completely wetted by the metal alloy. This phenomenon occurs in each reinforcing material particle by rotary agitation, forming a large number of micropolicies, which has the disadvantage of deteriorating the mechanical and electrical properties of the material. .

Moreover, if there is a difference in specific gravity between the molten metal and the reinforcing material particles, even if the reinforcing material particles are uniformly dispersed during stirring, when the stirring is stopped, the difference in specific gravity results in a non-uniform mixing state. As the copper solidifies while changing to

[Problem to be solved by the invention]

In order to obtain particle dispersion-strengthened copper having better properties than the carbide-based particle dispersion-strengthened copper mentioned above, the present inventors conducted intensive research focusing on boride-based fine particles with good conductivity. We have confirmed that composite materials with specific properties can be manufactured using a simple casting method.

The present invention is based on this knowledge, and its technical problem is to solve the following problems by using the boride-based fine particles described above.
The object of this invention is to enable the production of particle-dispersion-strengthened copper with electrical and mechanical properties comparable to those of powder metallurgy materials using a simple casting method.

[Means and actions for solving problems]

The method of the present invention for solving the above-mentioned problems involves adding high conductivity boride particles to copper in advance, heating and dissolving it, and adding mechanical rotational stirring using a stirring bar while cooling it. By continuing rotary stirring until the initial stage of solidification, boride-based fine particles are uniformly dispersed between the copper crystals, and the copper crystals are grown after the rotary stirring is stopped.

To explain the method of the present invention in more detail, the particle dispersion strengthened copper produced by the present invention is
Generally, it is constructed by uniformly dispersing boride-based fine particles with high conductivity not exceeding 20 wt% between copper crystals. Boride reinforcements with high conductivity include AgB ₂ , AlB ₁₀ , AlB ₁₂ ,
AsB, AuB ₂ , BaB ₆ , Be ₂ B, Be ₅ B, BeB ₂ ,
_BeB4 , _CaB6 , _CeB6 , _Co2B , θ- _CrB2 , _Cr2B ,
_Cr4B , _Cr5B3 , CrB, _Cr3B4 , _{DyB6 , ErB6 ,
Fe2B} , FeB, _GdB6 , _HfB2 , _LaB4 , _LaB6 ,
LuB ₂ , LuB ₆ , MgB ₂ , MnB ₂ , Mn ₂ B, MoB ₂ ,
_Mo2B , _Mo2B5 , _NbB2 , _{Nb3B2 ,} NbB, _{NdB6 ,
Ni2B} , _Ni3B , NiB, _OsB2 , _{Os2B5 ,} PB, _PrB6 ,
PtB, PuB, PuB ₂ , RuB ₂ , Ru ₂ B ₅ , ScB ₂ ,
SiB ₆ , SmB ₆ , SrB ₆ , TaB ₂ , TaB, Ta ₃ B ₂ ,
_Ta3B4 , β _{- Ta2B} , _TbB6 , _ThB4 , _ThB6 ,
TiB ₂ , Ti ₂ B ₅ , TmB ₆ , UB ₂ , UB ₁₂ , VB ₂ ,
V ₃ B ₂ , V ₃ B ₄ , α−WB, WB ₂ , WB ₄ , W ₂ B,
W ₂ B ₅ , YB ₂ , YB ₄ , YB ₆ , YbB ₆ , ZrB, ZrB ₂ ,
Examples include ZrB ₁₂ . These generally have a resistivity on the order of 10 ^-5 ohm cm, which is close to that of metal, and even if they are added to copper, the electrical conductivity will not decrease significantly.

In addition, generally the conductivity reduction above is 70% IACS
Therefore, as mentioned above, it is desirable that the amount of boride-based fine particles added does not exceed 20 wt%, but if the conductivity decreases by 70%,
It can be increased or decreased as appropriate without exceeding IACS.

In order to obtain particle dispersion-strengthened copper reinforced with the boride-based fine particles, first, pure copper and boride-based fine particles with high conductivity are placed in a crucible and heated and melted in an electric furnace or the like.

In this way, by heating copper and boride-based fine particles at the same time from room temperature, the boride-based fine particles are also brought to a high temperature state with almost no temperature difference when the copper is melted, so that they are semi-solidified during solidification by rotary stirring, which will be described later. The boride-based fine particles can be completely wetted by the copper in the state, and no micropolicy is formed at the interface between the copper and the boride-based fine particles.

The heated and melted composite material is slowly cooled by, for example, taking the crucible out of the furnace, and then a stirring rod is inserted into the center of the molten metal, which is immediately rotated to perform mechanical rotational stirring using the stirring rod. Add.

When performing such rotary stirring, if there is a difference in specific gravity between the molten metal and the boride-based fine particles, even if the fine particles are uniformly dispersed during stirring, when stirring is stopped, due to the difference in specific gravity. It rapidly changes to a non-uniform mixed state and solidifies in that state, making it impossible to obtain uniform particle-dispersed reinforced copper.

However, in the present invention, it was confirmed that the boride-based fine particles could be uniformly dispersed by continuing rotary stirring until the initial stage of copper solidification, and based on this knowledge, efforts were made to obtain uniform particle-dispersed strengthened copper. I have to. In other words, as mentioned above, if the molten metal is stirred even during the solidification of copper, even if there is a difference in specific gravity between the molten metal and the boride particles, the boride particles will be forced between the formed copper crystals. Since the boride is confined and uniformly dispersed, solidification is completed while the boride remains trapped between the crystals, thereby making it possible to obtain extremely homogeneous particle-dispersed reinforced copper. Then, the stirring rod is taken out after the initial stage of copper solidification has been completed and the solid phase ratio has further increased, and in this state natural solidification is performed to grow copper crystals.

As a result, a homogeneous electrical material with electrical properties comparable to pure copper, significantly higher mechanical properties than pure copper, and temperature-independent electrical and mechanical properties can be easily created using a casting method. can.

〔Effect of the invention〕

According to the present invention described above, the electrical and mechanical properties are superior to that of particle dispersion strengthened copper made of oxide fine particles such as Al ₂ O ₃ , which has been conventionally produced by powder metallurgy, in the following points. Alternatively, a material that is easier to manufacture can be obtained.

Conventionally, in the case of oxide-based reinforcing materials such as Al ₂ C ₃ that were made using powder metallurgy, the electrical conductivity decreases significantly due to the addition of such reinforcing materials, so 1wt%
It has been difficult to obtain particle-dispersed reinforced copper with excellent electrical and mechanical properties because only the following trace amounts can be added, but the reinforcing material used in the present invention has excellent conductivity, so 20wt%
It is possible to significantly improve the mechanical properties without significantly impairing the electrical properties.

According to the boride-based particle dispersion-strengthened copper according to the present invention, it is possible to obtain a material having properties equivalent to or better than those of the carbide-based particle dispersion-strengthened copper previously proposed by the present inventor.

When using a powder metallurgy method, a complicated manufacturing process and large-scale equipment are essential, but since the present invention uses a casting method, particle dispersion is possible at an extremely low cost compared to the powder metallurgy method described above. Reinforced copper can be produced.

Moreover, by heating copper and boride-based fine particles at the same time from room temperature, it is possible to improve wetting of the boride-based fine particles by copper and reliably prevent the formation of micropolicies at the interface between them. Material properties can be obtained.

〔Example〕

Fine particles of pure copper and tantalum boride as test materials were placed in a crucible, heated and melted in an electric furnace, then taken out of the furnace together with the crucible, and a stirring rod was inserted into the center of the molten metal to rotate and stir. This rotary stirring was continued until the initial stage of solidification to uniformly disperse the tantalum boride fine particles between the copper crystal grains, and after the rotary stirring was stopped, the stirring rod was pulled out to allow natural solidification to grow copper crystals. .

As a result of experiments with varying amounts of tantalum boride,
As shown in Figure 1, with the increase of tantalum boride, the mechanical properties are significantly improved, whereas the electrical properties (conductivity) are almost the same as pure copper.
It was confirmed that the decrease was very small.

According to the experimental results, even if tantalum boride is added in a very small amount to about 20wt%, the mechanical properties are improved without significantly impairing the electrical properties, and compared to conventional oxide-based materials such as Al ₂ O ₃ . In the case of particles
Although only less than 1 wt% of reinforcing material can be added, it can be seen that mechanical properties can be effectively improved by adding reinforcing material.

[Brief explanation of the drawing]

FIG. 1 is a graph showing experimental results regarding the electrical and mechanical properties of the particle dispersion strengthened copper of the present invention.

Claims (1)

[Claims] 1. Boride-based fine particles with high conductivity are added to copper in advance, heated and dissolved, and then mechanically stirred with a stirring rod while being cooled, and the rotational stirring is continued until the initial stage of solidification of the copper. A method for producing particle dispersion-strengthened copper for electrical materials, which comprises uniformly dispersing boride-based fine particles between copper crystals and growing the copper crystals after rotational stirring is stopped.