What's wrong with the uneven steel wire?

For the heat treatment method of heat-treated wire rod or semi-finished steel wire, see steel wire heat treatment. Heat treatment includes raw material heat treatment, intermediate heat treatment and finished product heat treatment. (1) wire rod heat treatment is used to produce some medium and high carbon steel wires and alloy steel wires. Its main purpose is to improve the structure and inhomogeneity of wire rod and eliminate internal stress, thus improving the plasticity and cold-drawing properties of wire rod. (2) Intermediate heat treatment is the heat treatment of semi-finished steel wire, that is, intermediate wire blank. Its main purpose is to eliminate work hardening during cold drawing and restore the plasticity of wire blank for further drawing. If there is no finished product heat treatment process in production, the intermediate heat treatment before finished product drawing also requires to ensure the proper structure and properties of finished steel wire. (3) The heat treatment of the finished product is carried out after the finished product is drawn, and the function is to make the product reach the specified structure and performance, and whether it is carried out depends on the delivery requirements. The wire rod or intermediate wire blank is deformed through the die hole of the wire drawing machine under the traction of the winch (see wire drawing machine), so as to reduce the cross section and change the shape, and obtain the steel wire with the required size, shape, performance and surface quality. Steel wire drawing usually needs multiple passes, and the area shrinkage (see area shrinkage) of each pass is about 10% ~ 40%. The dies used for drawing steel wire mainly include fixed dies, roller dies (see roller die diagram) and rotating dies. , give priority to with fixed mould. The fixed die is a wire drawing die made of integral material, which has a round cake shape and a hole in the center. The die is fixed during wire drawing. In the early days, steel plate molds and chilled cast iron molds were used, but later they were eliminated because they were not wear-resistant and had a short service life. At present, cemented carbide dies are widely used. In addition to cemented carbide, natural diamond is also a molding material. However, due to its scarce resources and high price, it is only used to draw alloy steel filaments and ultra-fine filaments. Since the 1970s, wire drawing dies made of polymeric polycrystals, synthetic diamonds and corundum ceramics have appeared. Roller die is a die composed of 2 ~ 4 rotatable rollers. Roller die drawing is usually used to draw some special-shaped steel wires and steel wires that are not easily deformed. However, with the improvement of the rigidity of the roller die device, it is easier to improve and adjust the accuracy, and its application scope is also expanding. The body structure of the rotary die is the same as that of the fixed die during drawing, but it rotates around the steel wire shaft driven by the transmission mechanism during drawing. The advantages are that the friction direction between the steel wire and the die wall changes during drawing, the shear stress acting on the steel wire increases, and the steel wire is easy to deform, thus reducing the drawing force and drawing power; Reduce axial friction and uneven deformation of inner and outer layers of steel wire during drawing; Due to the high-speed rotation of the die, the wear of the die hole becomes uniform, and the roundness and surface roughness of the steel wire are improved. However, when using the rotary die, the steel wire is easy to rotate or even twist with the die, which is currently limited to the drawing of thick wire. In the case of fixed die drawing, if post-tension is applied to the inlet end of steel wire, reverse drawing will be formed; If ultrasonic vibration is applied to the mold, ultrasonic wire drawing is formed; If hydrostatic or hydrodynamic lubrication is used, it is called forced lubrication diagram. The microstructure and mechanical properties of steel wire will change during cold drawing, leading to work hardening. With the increase of cold deformation, the tensile strength, hardness and elastic limit of ordinary steel wire increase, while the elongation and area shrinkage decrease. Due to work hardening, when the drawing deformation reaches a certain value, the cold working performance of steel wire is obviously reduced, so it is not suitable for further drawing, and intermediate heat treatment is needed to restore its processability. Generally speaking, the surface reduction rate in the first drawing process is about 70% ~ 90%. Therefore, the process of steel wire production has the characteristics of reciprocating cycle. The capacity of wire drawing machine is generally expressed by the size of its drum diameter and the number of winding slips. Drawing speed of wire drawing machine is related to steel grade, diameter, heat treatment quality, lubrication and cooling conditions, deformation degree, structure of wire drawing machine and coil weight of wire rod. With the modernization of steel wire production, the drawing speed is getting higher and higher. In order to reduce friction, reduce drawing force and die loss, and obtain products with smooth surface and satisfactory size and shape, lubricants must be used for lubrication during drawing. When using solid lubricant, it is called dry drawing; Wet wire drawing using lubricant aqueous solution and completing the drawing process uses water tank wire drawing machine. In the process of drawing, the temperature of steel wire and die increases due to the heat generated by the transformation of friction and deformation work, especially during high-speed drawing (see drawing heat). The increase of die temperature will affect its service life, and the increase of steel wire temperature will reduce its toughness (torsion and bending performance). In order to reduce the temperature rise, it is necessary to cool the mold and drum, and the direct water cooling of steel wire has also been developed (see wire drawing cooling).