| 摘要 |
A making method comprises of (1) heating steel material composed of 0.17-0.65 C, 1.0-2.0 Si, 0.60-0.90 Mn, at most 0.030 P, at most 0.035 S and at most 0.20 Cu, in wt.%, at 900-1200 deg.C for 5-40 sec. by the heating method (e.g., high frequency induction heating and direct electric heating), (2) quenching and heating it at 300-600 deg.C for 4-30 sec., and (3) cooling and tempering it. In this method, mechanical properties cannot promote when content of C is lower than 0.17 wt.%. When content of C is higher than 0.65 wt.%, it becomes brittle and its welding-ability becomes worse. It has good mechnical properties as well as corrosion- and stress corrosion-resistance and it can apply to reinforce pre-stressed concrete because it has high temperature relaxation-resistance.
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