| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a drilling hollow steel rod having an improved life by effectively inhibiting hardness degradation near a joint due to friction pressure welding between a stem part and a screw part. <P>SOLUTION: A used steel for the drilling hollow steel rod 10 having the stem part 12 and a female screw part 16 located at the axial end of the stem part 12 is of a steel type having a composition of C: 0.20-0.80 mass%, Si: 0.10-0.50 mass%, Mn: 0.10-1.00 mass%, P: ≤0.015 mass%, S: ≤0.050 mass%, Cu: ≤0.50 mass%, Ni: less than 0.50 mass%, Cr: 2.00-5.00 mass%, Mo: 0.20-0.80 mass%, B: 0.0002-0.0050 mass%, Ti: 0.005-0.050 mass%, Al: 0.005-0.050 mass%, N: ≤0.050 mass%, and Fe and inevitable impurities for the rest. To a male screw 18 and a female screw 20 of a male screw part 14 and the female screw part 16, respectively, high-frequency hardening is previously applied for joining the female screw part 16 and the stem part 12 separate from each other with friction pressure welding. <P>COPYRIGHT: (C)2012,JPO&INPIT |
