| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a high intensity PC steel stranded wire P stranded by seven strands, showing high strength and balanced elongation and having excellent delayed fracture properties.SOLUTION: A PC steel stranded wire P is stranded by seven strands 10 having a diameter L of 15.2-15.7 mm. The components of the strand ( 11a and 11b) is C of 0.97-1.02 mass%, Si of 0.80-1.0 mass%, Mn of 0.30-0.60 mass% and Cr of 0.15-0.30 mass% and includes one or more kinds of elements selected from Al, B, Ti, Cu, Mo and N in a total amount of 0.05 mass% or less. A load to an elongation of 1.2 mass% in the strand 10 is 280-290 kN or more, and the maximum elongation is 8% or less. A drawing value of the strand is 55% or less, and a ferrite phase a of 50 volume% or more exists in a metal structure within a depth of 30μm from the surface of the strand. The average hardness within the depth of 30μm from the surface of the strand is 0.6 or more to the hardness of the strand central part c, and a period of time leading to a fracture in a FIP test is 10 hours or more.</p> |
