Trenchless drill rod steel

Abstract

The invention discloses a trenchless drill rod steel. The trenchless drill rod steel comprises, by mass, 0.26-0.29% of C, 0.17-0.37% of Si, 1.05-1.30% of Mn, 0.010% or less of S, 0.015% or less of P, 0.80-1.10% of Cr, 0.20-0.25% of Mo, 0.10% or less of Ni, 0.07-0.15% of V, 0.1% or less of Cu, 0.015% or less of As, 0.010% or less of Sn, 0.003% or less of Pb, 0.010% or less of Sb, and the balance Fe and inevitable impurities. The steel is hardened and tempered, so the performances of the hardened and tempered steel accord with S135 steel grade standards; the nitridation temperature does not influence the performances of hardened and tempered steel pipes in a subsequent nitridation process; and added alloy elements have a high cost performance, so the obtained steel can be used as trenchless drill rod steel.

Description

technical field [0001] The invention belongs to the technical field of steel preparation, and in particular relates to a steel for trenchless drill pipes. Background technique [0002] The manufacturing process of trenchless drill pipe is different from that of petroleum drill pipe. The thread of petroleum drill pipe is copper-plated, while the thread of non-excavation drill pipe is treated with QPQ salt bath nitriding-oxidation. The steel bells used in the general market often have factors such as large energy consumption, not environmental protection (such as 42MnMo7), or expensive (27CrMo45), or unstable process (26CrMnMo). [0003] Moreover, since the threaded part of the non-excavation drill pipe must undergo QPQ salt bath nitriding-oxidation treatment after quenching and tempering, and this process requires a certain temperature. Melting, and at the same time, the activity is also low, too high salt bath composition is easy to age, and this process temperature require...

AI Technical Summary

Problems solved by technology

The steel bells used in the general market often have factors such as large energy consumption, not environmental protection (such as 42MnMo7), or expensive (27CrMo45), or unstable process (26CrMnMo)

[0003] Moreover, since the threaded part of the non-excavation drill pipe must undergo QPQ salt bath nitriding-oxidation treatment after quenching and tempering, and this process requires a certain temperature. Melting, and at the same time, the activity is also low, too high salt bath composition is easy to age, and this process temperature requires that the tempering temperature of the non-excavation drill pipe should not be lower than 580 ° C at least after quenching, otherwise the thread of the drill pipe will be nitrided The performance of the part is reduced, so that it cannot meet the standard of S135 steel grade

[0004] The tempering temperature of 42MnMo7 after quenching is just about 550°C, which is equivalent to secondary tempering after nitriding, which still has a certain effect on its performance. At the same time, this material must be quenched (water quenching is easy to crack), which consumes energy and causes pollution. quite serious

The tempering temperature of 27CrMo45 after quenching is about 580°C, so that the subsequent nitriding will not reduce the performance after tempering, but due to the excessive addition of Mo element (while molybdenum element is more expensive), its production cost is high

26CrMnMo is tempered at about 540°C after quenching, and the performance of the thread part is slightly reduced after salt bath nitriding, resulting in a large difference in the performance of the entire pipe body

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