The tube is a significant machine part in a car.It provides the important contact and fixed functions during the steering of a car. An inaccurate tube size cannot provide steering stability. For example, if the difference in diameter between the front and back of a tube is very large, the car moving at high speeds will be to swing, although steering would still be possible. A car can be made safer at high speeds by controlling the difference between the front and back diameters of the tube. High temperature welding of various parts to the tube, heats the tube almost 2,000°C, so the consequent deformation of the tube must be controlled.