HIGH-HARDNESS CONSTANT-MODULUS ALLOY INSENSITIVE TO MAGNETISM, PROCESS FOR PRODUCING SAME, BALANCE SPRING, MECHANICAL DRIVING DEVICE, AND WATCH

摘要

[Task] A constant-modulus alloy, which has a low saturation magnetic flux density to provide weakly magnetic properties, a high Young's modulus, a low temperature coefficient of Young's modulus, and high hardness, is provided. A hairspring, a mechanical driving apparatus and a watch and clock, in which the alloy is used, are provided. [Means for Solution] The alloy consists essentially of, by atomic weight ratio, 20 to 40% Co and 7 to 22% Ni, with the total of Co and Ni being 42.0 to 49.5%, 5 to 13% Cr and 1 to 6% Mo, with the total of Cr and Mo being 13.5 to 16.0%, and with the balance being essentially Fe (with the proviso that Fe is present in an amount of 37% or more) and inevitable impurities. The alloy is heated to a temperature of 1100 degrees C or higher and lower than the melting point, followed by cooling. The alloy is subsequently subjected to repeated wiredrawing and intermediate annealing at 800 to 950 degrees C, thereby forming a wire at a working ratio of 90% or more. The resultant wire has a fiber structure having a <111> fiber axis. The wire is subsequently cold rolled .at a rolling reduction of 20% or more, thereby obtaining a sheet, followed by heating the sheet at a temperature of 580 to 700 degrees C. The obtained magnetically insensitive, highly hard, constant modulus alloy has a {110}<111> texture. 2500 to 3500G of saturation flux density, (-5ˆ¼+5)×10 -5 degrees C -1 of temperature coefficient of Young's modulus as measured at 0 to 40 degrees C, and 350 to 550 of Vickers hardness