Conductive materials

A material intended to conduct electric current with little power loss (or voltage drop). It is used as a conductor for electric wires and cables. Since power loss is proportional to the electrical resistance of the conductor, it is desirable for a conductive material to have a low resistivity and a high reciprocal, its conductivity. Furthermore, from a practical standpoint, in addition to workability, mechanical properties, and corrosion resistance, economic efficiency is also important, and copper, aluminum, and their alloys are widely used.

Copper has the second highest electrical conductivity after silver, is easy to process, and has good mechanical properties and corrosion resistance, making it the most widely used conductive material. In addition, when improved mechanical properties and heat resistance are required, such as for power supply lines for trains (trolley wires), wiring for equipment, and lead wires for electronic components, alloys containing small amounts of silver, tin, chromium, nickel, zirconium, iron, silicon, etc. are used.

Aluminum has a low electrical conductivity of about 60% and a low tensile strength of about 40% compared to copper, but its density is about one-third and it is light. Therefore, an aluminum electric wire with the same conductor resistance as a copper wire has a diameter about 1.3 times larger, but its mass is nearly half. Taking advantage of this light weight, steel-core aluminum stranded wire, which has a central steel strand to supplement its strength, is used in almost all high-voltage overhead transmission lines. In these cases, heat-resistant alloys with small amounts of zirconium added, and alloys with improved strength added with magnesium, silicon, iron, copper, etc., are also used in the same way as pure aluminum, as long as they do not reduce electrical conductivity too much.

Additionally, composite materials combining copper and steel, aluminum and steel, copper and aluminum, and nickel and copper, as well as materials made by plating precious metals or solder on copper, aluminum, or alloy wires of these, are also used for a variety of purposes, taking advantage of their respective characteristics.

[Yoshihiro Naganuma and Yoshiji Oki]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

電力損失（あるいは電圧降下）の小さい状態で、電流を導くことを目的とした材料。電線やケーブルの導体となる。電力損失は導体の電気抵抗に比例するので、導電材料は抵抗率が小さく、その逆数の導電率が大きいことが望ましい。さらに実用面からは、加工性、機械的性質、耐食性のほか、経済性も重要で、銅とアルミニウムおよびそれらの合金が広く使われている。

　銅は銀に次いで導電率が高く、加工が容易なうえに、機械的性質、耐食性も良好なため、導電材料としてはもっとも多く使われている。また電車への電力供給線（トロリー線）、機器用配線、電子部品のリード線など、機械的性質や耐熱性の改善が必要な場合には、銀、スズ、クロム、ニッケル、ジルコニウム、鉄、ケイ素などを少量加えた合金が用いられる。

　アルミニウムは、銅に対して導電率は約60％、引張り強さは約40％と低いが、密度は約3分の1であり、軽い。したがって銅線と同じ導体抵抗をもつアルミニウム電線では、直径は約1.3倍と増えるが、質量はほぼ半減する。この軽量の利点を生かし、中心部の鋼撚(よ)り線で強さを補った鋼心アルミ撚り線は、ほとんどすべての高圧架空送電線に採用されている。この場合、導電率をあまり低下させない範囲で、少量のジルコニウムを加えた耐熱合金、マグネシウム、ケイ素、鉄、銅などを加えて強さを改善した合金も、純アルミニウムと同様に使われている。

　また銅と鋼、アルミニウムと鋼、銅とアルミニウム、ニッケルと銅を組み合わせた複合材や、銅、アルミニウムまたはそれらの合金線に貴金属やはんだをめっきした材料も、それぞれの特徴を生かして、種々の用途に使われている。

［長沼義裕・大木義路］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例