High strength, low thermal expansion alloy wire and method of making the

Abstract

In a high strength, low thermal expansion alloy wire, particularly used as the material for central section wire of low relaxation, overhead power transmission line, the number of rupture twisting is improved with retaining desired tensile strength (100 kgf/mm.sup.2), elongation (1.5% or more) and linear thermal expansion coefficient (average in the range of room temperature to 300.degree. C., .alpha.<5.times.10.sup.-6 /.degree. C.). The wire is made of an Fe-Ni-based alloy of specifically selected alloy composition. Process for preparing the wire comprises, hot rolling the alloy material, peeling the rolled wire, cold drawing, annealing and surface coating the drawn wire. The above improvement can be achieved by carrying the hot wire rolling under such conditions that the quantity of intergranular precipitations is up to 2% and/or that the averaged crystal grain size in the rolling direction is in the range of 5-70 .mu.m, at finishing the hot wire rolling.