| 摘要 |
A making method comprises of (1) heating steel material composed of 0.17-0.65 wt.% C, 1.0-2.0 wt.% Si, 0.60-0.90 wt.% Mn at most 0.030 wt.% P, at most 0.035 wt.% S, at most 0.20 wt.% Cu, 5-35 ppm B and 0.010-0.050 wt.% Ti 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 such as compressive and tensile strengh, high yield point and low relaxation ratio and it can apply to reinforce concrete pile, electric pole and railroad tie.
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