The core equipment of Galvanized steel plate starts from the pickling section, which requires a continuous pickling line with a hydrochloric acid concentration of 12%-18%, with the acid temperature controlled within the range of 70-85℃, and the steel plate traveling speed up to 200m/min. Data from Baosteel’s fifth cold rolling show that the design of its turbulent pickling tank reduces acid consumption to 3.8kg per ton of steel plate, compresses the loss rate of metallic iron to 0.05%, and saves 40% energy compared to traditional processes. The modern acid recovery system adopts the Ruthner method, which can recover 98% of free acid and produce iron oxide powder with a purity of 99.9%, saving $28 per ton of production cost.
The core equipment for hot-dip galvanizing is a ceramic zinc pot with a capacity of up to 300 tons, and the temperature of the zinc bath is precisely controlled at 450±5℃ (as required by ASTM A385 standard). The aluminum content in the zinc bath needs to be maintained at 0.18% -0.22%, and is monitored in real time by the electromagnetic skimming system, with a slag removal efficiency of 98.5%. The induction heating zinc pot at Nippon Steel’s Muroran plant in Japan achieves precise temperature control at 0.3℃/min, with the adhesion of the zinc coating increased by 50% and the zinc consumption per ton of steel reduced to 32.5kg (the industry average is 40kg). The air knife system is the key to controlling the thickness of the coating. Its high-pressure nozzle (with a pressure of 15-80 kpa) can adjust the thickness of the zinc coating to a tolerance of ±1.5μm, corresponding to a zinc coating quality range of 80-275 5g/m².
The post-processing equipment directly affects the final performance. The polishing machine is equipped with a 7000kN rolling force unit. Zinc flowers are eliminated at a reduction rate of 0.3%-3%, and the surface roughness is reduced to Ra 0.4-0.8μm. The chromium-free passivation tank forms a passivation film of 1.5-2.0g/m² by roller coating or spray coating, and the detection limit of hexavalent chromium is less than 0.01μg/cm². In 2023, ArcelorMittal introduced a laser etching system, which enabled the engraving of anti-counterfeiting codes with an accuracy of ±0.05mm at a production line speed of 180m/min, reducing annual counterfeiting losses by 2.6 million euros.
Expand the functional applications of coating equipment. The coating accuracy of the roller coater can reach ±1.5μm. When the polyester (PE) coating is 15-25μm, the curing temperature requirement is 230℃±5℃, and the weather resistance life can reach 10 years. The fluorocarbon (PVDF) production line requires an independent 30-meter-long drying tunnel to maintain the plate temperature at 232℃ to ensure that the cross-linking degree of the coating is over 90%. Nippon Paint Industrial Coatings’ measured data: The coating utilization rate of its fully automatic electrostatic spraying system reaches 95%, saving 37% of material costs compared to manual spraying. The VOC emissions comply with the EU standard of ≤35g/m².
The intelligent control system integration ensures stable quality. The real-time monitoring accuracy of the X-ray coating thickness gauge is ±0.5g/m². Combined with the PID regulation of the air knife pressure, the thickness dispersion is ≤4%. The Siemens Simatic S7 system can collect 1,250 process parameters every 10 milliseconds, ensuring that the temperature fluctuation of the zinc pot is less than 0.5℃. In the intelligent factory of China Baosteel’s Zhanjiang base, the online surface defect detection system (CCD resolution 12μm) has reduced the product defect rate to 0.18%, and the annual quality loss has been reduced by 120 million yuan.
The environmental protection equipment system meets the requirements of sustainable development. The efficiency of the acid mist recovery tower is ≥99%, and the emission concentration is ≤5mg/m³ (the limit value stipulated in the national standard GB16297). The vacuum distillation equipment for zinc slag has a processing capacity of 15 tons per day, and the zinc recovery rate reaches 99.2%. The Best Available Technology (BAT) certification requirements of the European Union: For the production of each ton of Galvanized steel plate, a heat recovery device must be equipped to reduce natural gas consumption to 1.05GJ and the utilization rate of waste heat from exhaust gas to over 80%. In 2025, ThyssenKrupp’s Duisburg plant will adopt a hydrogen-powered zinc pot heating system, which is expected to reduce CO₂ emissions by 470,000 tons annually.
Innovate auxiliary equipment to optimize comprehensive benefits. The induction heating alloying system can complete the heat diffusion at 550℃ within 15 seconds, forming an Fe-Zn alloy layer and enhancing the corrosion resistance of the steel plate by 300%. The electromagnetic stabilization device effectively suppresses the amplitude of zinc bath fluctuations to ±0.3mm (±3mm for traditional zinc POTS), and optimizes the standard deviation of coating thickness by 40%. The high-speed production line (250m/min) of POSCO in South Korea is equipped with a laser deburring machine. The burr height of the steel plate cut is controlled at ≤3μm, and the service life of the subsequent processing molds is extended by 70%.