Research on Hydroforming Micro-Sized Spiral Pipe With Equal Wall Thickness

The positive displacement motor is currently the most widely used downhole power tool. In order to reduce the cost of drilling and exploration, small boreholes have been used to replace conventional boreholes. The working conditions are complex, so a high-performance positive displacement motor for micro-holes is required. In order to solve the problem of the difficulty in processing the inner spiral surface of the small size and large aspect ratio, the tiny size spiral tube stator is proposed in this paper and the normal temperature and hot state hydroforming of the small size spiral tube is proposed in this paper. The material is 42crmo, and the uniaxial tensile test is carried out at different temperatures. According to the material mechanical properties experiment and the forming process, the finite element model of the hydroformed spiral tube at different temperatures is established. The study found that the suitable tube size is 48mm in outer diameter, 5.5mm in wall thickness, and 1405mm in length. When the processing temperature is 700℃, the hydraulic pressure required for full expansion of the spiral tube is only 70MPa, and the rebound of the spiral tube is very small. The minimum wall thickness is the maximum of 4.31mm, and the maximum wall thickness is the minimum of 5.356mm, and the wall thickness distribution is relatively uniform. The maximum plastic strain of the spiral tube is 0.65, so the damage to the material during the forming process is small, and when the processing temperature is 700℃, the quality of the spiral tube is better.