| 摘要 |
<p>A process for producing a spiral steel pipe having ribs formed on the inner surface thereof, comprising: a preparation step of preparing an untempered spiral steel pipe using a hot-rolled coil that has ribs formed on the inner surface thereof, comprises C, Si, Mn, P, S, Nb, Ti, Al, N and O and has a CE value ranging from 0.35 to 0.45; an arrangement step of arranging the untempered spiral steel pipe so that the direction of the length of the steel pipe is in line with the substantially vertical direction; a heating step of heating the untempered spiral steel pipe to a temperature of 900 to 1150°C; a water-cooling step of cooling the untempered spiral steel pipe with water at a cooling rate of 10°C/sec. or more starting at a time point at which the surface temperature of the steel pile reaches 860°C or higher and terminating at a time point at which the surface temperature of the steel pile reaches 300°C or lower; and a temper treatment of tempering the untempered spiral steel pipe at a temperature of 650°C or lower.</p> |
