Cold-drawn wire: A practical product of metal cold processing

Definition of Cold Drawing Wire
Cold drawing wire is a process where metal raw materials (typically hot-rolled round bars, etc.) are drawn through molds at room temperature to reduce their diameter, thereby obtaining wire with specific dimensions and properties. This processing method is named "cold drawing" because it does not involve a heating process. After cold drawing, the internal structure of the metal wire changes. Compared to the raw materials, the strength and hardness increase, the surface quality improves, the dimensional accuracy is higher, and it can meet the strict requirements of many fields for wire materials.
Production Process
Raw Material Preparation: Commonly used are Q195, Q235, etc. of low-carbon steel round bars. It is necessary to verify the steel's factory inspection report to ensure that the carbon content is within 0.12%-0.20%, manganese content is 0.30%-0.65%, and phosphorus and sulfur content are all no more than 0.045%. The bar surface should be smooth, without folding, cracks, or severe oxide scale, with a diameter tolerance of ±0.1mm, and good straightness to facilitate subsequent cold drawing processing.
Surface Treatment: Successively undergo shell removal, acid washing, water washing, and lubrication. Shell removal is achieved by using a multi-roll straightening machine to remove the adhered iron oxide scale on the bar surface. By adjusting the spacing of the straightening rollers, the bar undergoes appropriate plastic deformation, removing the oxide scale while not damaging the base material. Acid washing uses a 15%-20% concentration of hydrochloric acid solution, with a temperature controlled at 40-60℃, and the time is adjusted according to the rusting degree to 20-40 minutes to thoroughly remove the oxide scale and prevent over-acid washing from corroding the iron base material. After acid washing, the surface is rinsed with flowing clean water for 3-5 minutes to make the residual acid pH value close to 7. Lubrication is usually done using lime water (concentration 80-120g/L, temperature 50-70℃) or borax solution, forming a uniform calcium soap lubricating film about 5-10μm thick on the bar surface to reduce the drawing friction.
Cold Drawing Process: The molds are mostly made of hard alloy or diamond. The sizing band length is determined according to the wire diameter. For diameters ≤5mm, it is 3-5mm, and for diameters >5mm, it is 5-8mm; the inlet cone angle of the mold is 12°-18°, and the outlet cone angle is 3°-5°, which reduces the drawing resistance and mold wear. The reduction rate per single cold drawing is controlled at 10%-30%, and the total reduction rate is usually no more than 80%. The drawing speed is generally 0.5-3m/s, and an inappropriate speed will affect the quality of the wire and production efficiency. At the same time, the tension of the drawing machine should be monitored in real time, controlled at 20%-30% of the material's yield strength to prevent wire breakage or slipping.
Heat Treatment: The wire after cold drawing needs to undergo heat treatment to eliminate work hardening and improve mechanical properties. If a higher strength is desired, low-temperature annealing (150-200℃) for 1-2 hours can be used; if the plasticity and toughness are to be improved, recrystallization annealing is performed, heating to 600-700℃, with the holding time adjusted to 0.5-2 hours depending on the wire diameter, followed by furnace cooling or air cooling. During heat treatment, the atmosphere inside the furnace should be controlled, with protective gases such as nitrogen introduced to keep the oxygen content below 100ppm to prevent oxidation and decarburization on the wire surface.
Quality Inspection: Online use a laser diameter measuring instrument to measure the wire diameter. For diameters ≤4mm, the tolerance is controlled within ±0.05mm, and for diameters >4mm, the tolerance is controlled within ±0.1mm; use an eddy current flaw detector to detect surface cracks, folds, etc. Offline, at least 5 pieces are inspected per hour, testing mechanical properties such as tensile strength, elongation, etc. The tensile strength deviation is controlled within ±5%, and the elongation meets relevant standards. In addition, ensure the wire surface is smooth, free of oil stains, and rust, and for cold-drawn wire with a coating, the adhesion and uniformity of the coating should also be tested.
Specifications
Diameter: Commonly 1-5mm, ranging from 0.5-10mm. Length: Can be customized according to customer requirements, with fixed-length (such as 2 meters, 3 meters, 4 meters) and non-fixed-length options.
Material: Mainly includes low-carbon steel, medium-carbon steel and high-carbon steel. Low-carbon steel has good plasticity but low strength, while high-carbon steel has high strength and high hardness, and is suitable for different scenarios.
Application fields
Building materials industry: As prestressing wire used in concrete prefabricated components and wall tie bars, it enhances the stability, durability and seismic resistance of building structures; manufacturing steel wire mesh in decoration projects to prevent cracking and detachment of the plaster layer on the wall.
Agricultural field: Used to make breeding cages, capable of withstanding the activities and weight of poultry and livestock; constructing the framework of agricultural greenhouses to resist wind loads and snow loads, ensuring the growth environment of crops.
Industrial use: Manufacturing various springs to meet the elastic support requirements of car seat springs, etc.; used as raw materials for cutting processing to make screws, nuts and other standard parts.
Daily life: Widely used in clothes drying racks, anti-theft nets, guardrails and the production of metal wire handicrafts.
Market situation
According to Huazhong Chengsi Research, the global market size of cold-drawn wire will be considerable in 2024, and is expected to continue to grow steadily until 2031, with a stable annual compound growth rate in the next six years. The domestic market size is continuously expanding, with an annual compound growth rate of over 5%. The eastern coastal areas have developed economies and prosperous manufacturing industries, with large market demand and the largest industrial scale in the country; the central region is developing rapidly with resources and industrial foundations, and is expected to become a new growth point; the western region's market potential is gradually being released under the promotion of the Western Development Strategy.
Development trends
High-performance: In high-end manufacturing fields such as aerospace and medical devices, there is an increasing demand for high-strength, high-precision, corrosion-resistant high-performance cold-drawn wire.
Green environmental protection: Enterprises are increasingly emphasizing energy conservation and emission reduction, developing low-energy consumption and low-pollution processes, and practicing green development.
Intelligentization: The introduction of intelligent manufacturing technology improves production efficiency and reduces labor costs.
Customization: With the increasing individualized demands in the market, customized services for cold-drawn wire have become a trend to meet the diverse needs of different customers.