| 摘要 |
The engineering problem of the claimed invention is to enhance wear-resistance of drill pipe tool joints. The proposed drill pipe consists of a body with upset ends and tool joints connected by means of friction welding, having tapered thread and a double coating, the first layer being applied by means of thermo-diffusion zincing and the second one, by means phosphate treatment. Enhancement of tool joint life, as compared to the tool joints with phosphate coating only, allows no overdimension to be stipulated for future repair purposes, which saves up to several kilos of metal per tool joint, decreasing the drill string weight by several tons. With a view to increasing the joints' durability and reliability of welding seams the thickness delta of the first coating layer as function of thread conicity K is adjusted according to the following formula: delta=0.09 . . . 0.13 K. The segment at 15 to 25 mm from the welding spot on joints is coated with phosphate only.
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