The ball of the surfacing welding connection fixed cast steel ball valve produced and sold by Huadian Group Company is fixed and does not move after being pressed. Fixed ball valves are equipped with floating valve seats, after the pressure of the medium, the valve seat moves, so that the sealing ring is tightly pressed on the ball to ensure the seal. It is usually equipped with bearings on the upper and lower shafts with the ball, and the operating torque is small, which is suitable for high pressure and large diameter valves. In order to reduce the operating torque of the ball valve and increase the reliability of the seal, in recent years, the oil seal ball valve has appeared, which not only presses special lubricating oil between the sealing surfaces to form a layer of oil film, that is, enhances the sealing, but also reduces the operating torque, and is more suitable for high-pressure large-diameter ball valves.