An ultra-high-strength and high-toughness drill pipe body and its heat treatment process

Abstract

The invention relates to an ultra-high-strength and high-toughness drill pipe body and its heat treatment process. The drill pipe body includes the following components in weight percentage: C0.20-0.28%, Mn0.50-0.6%, P≤0.010% , S≤0.005%, V0.1~0.30%, Al≤0.03%, 1.5%≤Cr+Mo+Ni≤3%, the balance is Fe and trace elements. The heat treatment process includes two times of quenching and one tempering, wherein, the first time of quenching is to heat the drill pipe body to 880-900°C, keep it warm for 30-60min, then take it out of the furnace, spray it with water at 10-40°C, and quench it. The temperature of the final pipe body is not higher than 100°C; the second quenching is to heat the drill pipe body to 800-870°C, keep it warm for 15-30 minutes, and then spray it with water at 10-40°C. The spraying time is not less than 10s; Tempering is to heat the drill pipe body to 560-650°C, keep it warm for 50-80min and then take it out of the furnace, air-cool to 200-300°C for straightening, and air-cool to room temperature. After heat treatment by the method, the mechanical properties of the pipe body can reach: yield strength 150-180Ksi (1033-1240MPa), elongation ≥ 15%, impact energy (longitudinal, -20°C, 3 / 4 size) ≥ 80J . Ductile-brittle transition temperature -45≤℃.

Description

technical field [0001] The invention relates to an ultra-high-strength and high-toughness drill pipe body used for drilling, especially in deep wells and ultra-deep wells, and its heat treatment process, and is especially suitable for a 165 steel-grade ultra-high-strength oil drill pipe body, which belongs to oil and gas The field of drilling technology. Background technique [0002] With the development of drilling technology and the gradual reduction of shallow easy-to-exploit oil and gas layers, the drilling depth is increasing. In recent years, a large number of 7000-8000m ultra-deep wells have been drilled in my country, and my country's offshore drilling is also gradually moving towards deep-sea development. As the depth of the well increases, materials are required to have higher yield strength and matching high toughness. Currently, the highest steel grade S-135 drill pipe that is commonly used in accordance with the regulations of the American Petroleum Institute (A...

AI Technical Summary

Problems solved by technology

As the depth of the well increases, materials are required to have higher yield strength and matching high toughness. Currently, the highest steel grade S-135 drill pipe that is commonly used in accordance with the regulations of the American Petroleum Institute (API) cannot meet its requirements. V-150 Ultra-high-strength drill pipes such as steel grade and 165 steel grade are one of the effective solutions

[0003] The test results show that there are some problems when the commonly used drill pipe body such as 27CrMo is conventionally heat-treated to become ultra-high strength. First, the impact toughness is low. -20℃, 3 / 4 size) is often only about 30~55J; second, the tempering temperature is low, which is not conducive to the subsequent welding seam heat treatment and inner coating spraying process; It is difficult to ensure the hardenability of the thickened end (about 30mm), which leads to a significant decline in the impact performance of the thickened end