In the process of cold drawing, only the cold-drawing stress control is called single control, and the cold-drawing rate and cold-drawing stress applied simultaneously during cold drawing are called dual control. The advantage of using a single control is that the construction is relatively simple and convenient, but for steel bars with uneven materials, it is impossible to test the quality of the cold drawing one by one. The dual control method can avoid the above problems. The control stress has been reached during cold drawing, but if the cold drawing rate has been reached and the cold tensile stress has not yet reached the control stress, this kind of steel bar needs to be reduced in strength. For the prestressed steel bar, a double control method is required.