Galvanized steel wire is widely used in construction, hardware, wire mesh, power and telecommunications, agriculture and animal husbandry, highway guardrails, and steel rope manufacturing. Product quality directly affects project safety, service life, and reliability; therefore, strict, unified, and quantifiable quality standards must be implemented throughout the entire production process.
The basic raw material for galvanized steel wire is hot-rolled low-carbon steel wire rod, commonly made of materials such as Q195, Q215, Q235, SAE 1006, SAE 1008, SAE 1010, and SWRCH18A. Raw material quality is the primary factor determining the mechanical properties, surface quality, and zinc plating adhesion of the finished product. Carbon content directly affects the strength, toughness, and drawability of the steel wire and must be strictly controlled: C≤0.15%, Si≤0.07%, Mn0.30%~0.60%, P≤0.035%, S≤0.035%. P and S are harmful impurities; excessive levels can lead to increased brittleness, draw fracture, and poor zinc plating adhesion. Therefore, strict adherence to the upper limits is essential.
Mechanical properties often determine the application areas of Galvanized Steel Wire. We require a tensile strength of 290~420MPa, elongation ≥25%, reduction of area ≥55%, and hardness HRB 60~75. The wire rod must not have obvious segregation, delamination, or shrinkage cavities; otherwise, it is prone to breakage during drawing and cracks in the finished product. Many users have very strict requirements for the surface quality of Galvanized Steel Wire. Professional manufacturers must ensure that the surface is free of cracks, folds, scars, burrs, excessively thick iron oxide scale, rust spots, oil stains, and impurities upon leaving the factory. The diameter tolerance should be ±0.20mm, and the ellipticity ≤60% of the diameter tolerance. Wire rods with severe surface rust are prohibited from production; otherwise, pickling will be incomplete and zinc layer adhesion will be poor.
The core purpose of pretreatment is to remove oxide scale, rust, and oil, ensuring a clean and activated steel wire surface to guarantee a good metallurgical bond between the molten zinc and the steel substrate. Poor pretreatment during the production of Galvanized Steel Wire can directly lead to zinc layer peeling, incomplete plating, and discoloration.
Degreasing and oil removal quality standards: Alkali concentration 5%~10%, temperature 60~80℃, treatment time 3~8min. Inspection standard: No oil stains or saponification residue on the steel wire surface, continuous and uniform water film, no shrinkage cavities.
Acid pickling and rust removal quality standards: Commonly used hydrochloric acid pickling. Concentration, temperature, and time must be strictly controlled. Hydrochloric acid concentration 12%~18%, temperature room temperature~45℃, time 5~15min. After pickling, the surface should have a completely exposed silver-gray metallic luster, no oxide scale residue, and no over-corrosion. Over-corrosion is judged by the appearance of pitting, hydrogen embrittlement, or blackening on the surface; if found, the surface must be scrapped.
Water washing quality standards: After acid pickling, multi-stage countercurrent rinsing is required. The first stage uses running clean water to remove free acid. The second stage uses pH ≥ 4 to prevent acid from being carried into the fluxing tank. Inspection standard: No acid residue or iron salt adhesion on the surface.
Fluenting treatment quality standards: Flux is usually zinc chloride + The ammonium chloride mixed solution serves to prevent secondary oxidation and improve the wettability of the zinc bath. We require a concentration of 150-250 g/L, a temperature of 50-70℃, a pH of 4.0-5.5, a treatment time of 1-3 minutes, a drying temperature of 120-200℃, and a standard drying time of complete surface dryness, free of moisture, salt stains, and uneven crystallization. The flux solution must be filtered regularly to remove slag; otherwise, zinc slag and zinc nodules will form, affecting the surface quality of the Galvanized Steel Wire.
Galvanizing is divided into hot-dip galvanizing and electro-galvanizing, and the quality standards of the two differ significantly, making it a key focus of foreign trade inspections.
Hot-dip galvanized steel wire quality standards: Hot-dip galvanizing results in a thick zinc layer and long corrosion resistance, conforming to ISO 1460, ASTM A641, and GB/T 20492. Raw material zinc ingots are 99.99% pure zinc, conforming to GB/T 470. Zinc bath temperature is 440~465℃, aluminum content is 0.18%~0.22%, zinc bath impurities are ≤0.02% Fe, and the use of recycled zinc is prohibited.
Electro-galvanized steel wire quality standards: Electro-galvanized steel wire has a smooth surface and a thinner zinc layer, suitable for precision products. The zinc layer weight is 10~40g/m², thickness is 1.4~5.6μm, the surface is bright and uniform, without scorching or darkening, and it has low brittleness, making it suitable for bending and forming. Its corrosion resistance is weaker than hot-dip galvanizing, and it is not suitable for highly corrosive environments.