High-strength bead wire, wire material for bead wire, and production method thereof

摘要

PROBLEM TO BE SOLVED: To obtain high strength bead wire having high strength, excellent in toughness and good in straight workability by specifying the contents of C and Si, imparting high tensile strength and elongation thereto by controlled cooling after hot rolling and optimumly regulating lattice strains by intensive wire drawing and low temp. annealing. SOLUTION: A material contg., by weight, 0.65 to 0.75% C and 0.5 to 1.5% Si is subjected to hot rolling, is thereafter held at =920 deg.C for =1sec and is next subjected to controlled cooling of executing cooling to 800 to 600 deg.C at a rate of 5 to 10 deg.C/sec and furthermore executing cooling to 600 to 550 deg.C at a rate of 1 to 3 deg.C/sec. In this way, a wire rod for bead wire having 0.11 to 0.13m cementite lamellar interval, =2m colony diameter, =10m old particle size, =1% pro-eutectoid particle size and =3% pro-eutectoid ferrite can be obtd. This wire rod is subjected to cold wire drawing at =2.5% true strain and is annealed at 380 to 450 deg.C for 3 to 7sec. Thus, the high strength bead wire having =2,200N/mm2 tensile strength, =4% elongation and 0.02 to 0.1% lattice strain can be obtd.