Method for preparing polyphase structure drill rod materials

Abstract

The invention relates to a method for preparing polyphase structure drill rod materials, which comprises the following compositions by mass percentage: 0.25 to 0.30 percent of carbon, less than 0.008 percent of sulfur, less than 0.010 percent of phosphorus, 0.5 to 1.0 percent of chromium, 0.6 to 1.2 percent of molybdenum, 0.10 to 0.15 percent of vanadium, 0.10 to 0.15 percent of niobium, 0.25 to 0.5 percent of lanthanum, and other elements and S135 steel grade drill rod elements. The heat treatment process comprises the following steps: firstly, performing vacuum melting and casting forming on various compositions, and treating the obtained product for 30 to 60 minutes at the temperature of between 925 and 935 DEG C after the obtained product is subjected to the production procedures of rolling and drilling of general drill rods; and secondly, cooling the obtained product to the temperature of between 280 and 420 DEG C, performing salt-bath quenching on the obtained product for 10 to 15 minutes, performing oil cooling on the obtained product to the room temperature, and performing tempering on the obtained product for 30 minutes at a temperature of between 560 and 620 DEG C. Compared with a common S135 drill rod, the fatigue life of the drill rod is improved by 3 to 4 times, and the fatigue limit of the drill rod is improved by 40 to 50 percent.

Description

Technical field [0001] The invention relates to a method for preparing a drill pipe material with a complex structure composed of lower bainite, tempered sorbite and a small amount of retained austenite with high fatigue resistance. Background technique [0002] With the development of the world petroleum industry, oil and gas wells are getting deeper and deeper. There are wells more than 8,000 meters deep. The increase in well depth makes drilling conditions more and more complicated. Therefore, during the drilling process, the working conditions encountered by the drill pipe and the forces on the drill pipe are becoming more and more complex, such as tension, compression, bending, torsion, shearing and their combination, alternating loads, etc., which have significantly increased Probability of drill pipe failure. The failure of the drill pipe sometimes leads to the scrapping of the entire well, resulting in significant economic losses, and even casualties. With the development...

AI Technical Summary

Problems solved by technology

When the external energy input is enough, these short cracks will continue to grow and aggregate, and finally form large cracks, which become the source of fatigue cracks, and then expand, causing failure accidents

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