1. Stretching of wire
The stretching of the wire refers to a pressure processing method in which the wire blank is plastically deformed by the die hole under a certain tensile force to reduce the section and increase the length.
2. Characteristics of stretching
(1) The stretched wire has a relatively precise size, the surface is smooth, and the cross-sectional shape can be varied.
(2) It can stretch wires of large length and various diameters.
(3) Mainly in cold processing, the drawing process, mold and equipment are simple, and the production efficiency is high.
(4) The tensile energy consumption is large and the deformation is limited.
3. The principle of stretching
Stretching is a range of pressure processing. In addition to producing very little dust, the volume changes little during the stretching process, so the volume of the metal before and after stretching is substantially equal.
4. Factors affecting stretching
(1) Copper and aluminum rod (wire) materials. When the other conditions are the same, the tensile strength of the drawn copper wire is larger than that of the drawn aluminum wire, and the drawn aluminum wire is easily broken, so a larger safety factor should be taken when pulling the aluminum wire.
(2) The tensile strength of the material. There are many factors for the tensile strength of materials, such as the chemical composition of the material, the calendering process, etc., and the tensile strength is high when the tensile strength is high.
(3) Degree of deformation. The greater the degree of deformation, the longer the length of the deformation section of the die hole, thus increasing the positive pressure of the die hole against the wire, the frictional force also increases, and the tensile force also increases.
(4) The coefficient of friction between the wire and the die hole. The greater the coefficient of friction, the greater the tensile force. The coefficient of friction is determined by the finish of the wire and mold material, the composition and quantity of the lubricant.
(5) The size and shape of the working area and sizing area of the wire die hole. The larger the sizing zone, the greater the tensile force.
(6) The position of the wire mold. Improper placement of the wire mold or skewing of the mold base also increases the tensile force. Also the wire diameter and surface quality are not up to standard.
(7) External factors. The wire is not straight, the jitter of the wire in the process of pulling the wire, and the resistance of the wire release will increase the tensile force.