1. The characteristics of the casing round thread: The casing round thread is a V-shaped thread with an eye thread axis taper of 1:16. Its two side angles are equal, and each tooth angle is half of 60°, that is, 30°. The crest and the bottom of the tooth are flattened and rounded at a certain radius;
2. The sealing mechanism of the circular thread of the casing, after the circular threads of the casing are connected to each other, a press fit is caused between the external thread and the internal thread. This radial contact creates a large coupling circumferential stress, forming a pressure seal at the point of contact. In addition, there is a gap of 0.78 mm between the crest of the round thread of the casing and the bottom of the tooth. The metal particles contained in the thread sealant create a bridge between the gaps to form a grease seal, which is the main seal of the thread.
3. The tensile performance of the circular thread of the casing, and the casing string is formed by the screw connection between the single casings. The casing string transmits the lower load to the upper casing through the side of the thread under the action of the weight of the lower casing, and compressive stress is generated on the side of each thread. The direction of the compressive stress is perpendicular to the side of the thread, which can be decomposed into the shaft. The component force and the radial component force, wherein the axial component force is always equal to the casing self-weight load.
4, casing round thread has the following advantages: easy to manufacture and low cost; design accuracy allows operation under normal conditions without causing serious damage to the thread; with the cooperation of high-quality sealing grease, can meet 60mpa, 140 °C or more Fluid seal; adapt to repeated shackles, under normal circumstances, the shackle can be repeated three times without failure.