BT20 Titanium Alloy Oil Drill Pipe

The BT20 titanium alloy oil drill pipe has a low specific strength, with a density of only 57% that of steel. When used in deep and ultra-deep wells, it can significantly reduce the weight of the drill pipe itself, effectively reducing the load on the drilling rig. Additionally, the advantages of applying it to oil drill pipes are also reflected in the fact that as the well depth increases, the well temperature also rises. The temperature in ultra-deep wells is generally between 160°C and 220°C, requiring drill pipe materials to have excellent high-temperature performance. The BT20 titanium alloy has high thermal strength and a low thermal conductivity, maintaining high strength within the working temperature range of 150°C-500°C, and it can also operate for a longer time at 450-500°C without failure.

Currently, domestically produced high-temperature titanium alloys can be used at 600°C and exhibit excellent high-temperature performance, such as Ti-60 and Ti750 titanium alloy, which can be used briefly at 750°C. Tables 1 and 2 show the high-temperature titanium alloys developed at home and abroad over the past few decades.

The conventional heat treatment process for BT20 titanium alloy oil drill pipes includes solution treatment, aging, and annealing. Such processes effectively enhance the high-temperature performance of the material through microstructure regulation. Titanium alloy oil drill pipes generally use dual-phase titanium alloys, and various factors such as the morphology and size of the α phase and β phase affect high-temperature performance.

BT20 titanium alloy oil drill pipes generally use solution treatment and aging. A longer solution treatment time allows the internal alloying elements to diffuse more evenly, but an excessively long solution treatment time can lead to uneven formation and distribution of precipitates, reducing creep resistance.

The high-temperature performance of BT20 titanium alloy oil drill pipes is closely related to thermal processing technology. Its forming techniques are mainly forging and rolling, and the creep resistance can be significantly improved by controlling the combination of temperature and deformation rate parameters. Rolling is divided into cold rolling and hot rolling. Cold rolling generally strengthens the metal through work hardening. After cold rolling, internal defects are likely to occur and annealing is required to eliminate these defects. Combining cold rolling and annealing can achieve more ideal mechanical properties. The conventional preparation of titanium alloy drill pipes relies on the hot rolling process, and key parameters such as temperature and deformation amount play a decisive role in the microstructure and mechanical properties.

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