High-strength and high-toughness steel for drill rod joint and preparation method thereof

Abstract

The invention discloses high-strength and high-toughness steel for a drill rod joint and a preparation method thereof. The high-strength and high-toughness steel is prepared from the following chemical components in percentage by mass: 0.35 to 0.38 percent of C, 0.20 to 0.30 percent of Si, 0.90 to 1.10 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.004 percent ofS, 0.90 to 1.20 percent of Cr, 0.25 to 0.35 percent of Mo, 0.05 to 0.15 percent of Ni, 0.01 to 0.04 percent of Nb, 0.010 to 0.030 percent of Ti, and the balance of Fe and inevitable impurities. The preparation method comprises the procedures of electric furnace smelting, LF refining, VD vacuum degassing, continuous casting, rolling, segmented forging and pressing, normalizing, quenching and tempering, wherein in the LF refining process, niobium is added into molten steel to control the niobium content to be 0.01 to 0.04 percent by weight; and after the VD vacuum degassing, a titanium wire is fed for titanium alloying to control the titanium content to be 0.010 to 0.030 percent by weight. According to the preparation method, a reasonable alloy element component design is adopted to obtain the steel for the drill rod joint with the yield strength of larger than or equal to 920 MPa, the longitudinal impact absorption energy of larger than or equal to 100 J at the temperature of 20 DEG C,the longitudinal impact absorption energy of larger than or equal to 90 J at the temperature of 20 DEG C below zero, and the performance requirement of an ultra-deep well on the drill rod joint is met.

Description

technical field [0001] The invention relates to steel for drill pipe joints and a preparation method thereof, in particular to a high-strength and high-toughness steel for drill pipe joints and a preparation method thereof. Background technique [0002] Oil drill pipe joint is an important tool for connecting drill pipe to transmit power and transport mud in the process of oil and gas field exploration and development. With the continuous increase of drilling depth, the requirements for the strength and toughness of drill pipe joints are also increasing, and ordinary steel grade drill pipe products have been difficult to meet the mining requirements. In order to meet the criterion of "leak first and then break" when the drill pipe joint fails downhole, the toughness level of the drill pipe joint should increase synchronously with the increase of the material strength. At present, 37CrMnMo is widely used to manufacture oil drill pipe joints. The yield strength of oil drill p...

AI Technical Summary

Problems solved by technology

At present, 37CrMnMo is widely used to manufacture oil drill pipe joints. The yield strength of oil drill pipe joints made of this grade steel is generally 865-920MPa, the longitudinal impact absorption energy AKV at 20°C is generally 90-100J, and the longitudinal impact absorption energy AKV at -20°C is generally It is 80-90J, the strength and impact toughness are obviously low, and it cannot meet the requirements of ultra-deep wells for drill pipe joints

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