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CGL - Continuous Galvanizing Line

CGL - Continuous Galvanizing Line
The purpose of the continuous galvanizing line (CGL) is to apply a coating of zinc or zinc/aluminium onto the surface of steel strip to improve corrosion resistance. 

Galvannealing is optionally performed to alloy the coating into the steel substrate. This requires accurate temperature monitoring at the exit of the galvanneal section. 

AMETEK Land has supplied the steel industry with high-quality, reliable temperature measurement solutions for more than 70 years. Our range of specialist instruments includes the SPOT GS which is designed specifically for automated furnace management and provides close control of the reaction and position of the reaction zone, which delivers tighter control of product quality in the galvanneal process.



 
APPLICATION NOTE
Infrared Process Imaging Systems For Vertical Continuous Annealing Lines - Application Note ENINFRARED PROCESS IMAGING SYSTEMS FOR VERTICAL CONTINUOUS ANNEALING LINES
The continuous annealing line is used to modify the grain structure of steel through heat treatment, changing properties including hardness and strength. To ensure the accurate, edge-to-edge temperature monitoring required, a solution has been devised that overcomes the challenges caused by surface reflections and strip emissivity. Read More > Watch the video >


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  • Frequently Asked Questions +


    Question Answer 
    What is a CGL? A CGL (Continuous Galvanizing Line) is a high-speed production line that applies a protective zinc coating to steel strip by continuously running it through cleaning, heat treatment, a molten zinc bath and finishing operations. CGLs can process strip at speeds exceeding 180 meters per minute and produce millions of tonnes of galvanized steel annually for automotive body panels, appliances, construction materials and other corrosion-critical applications.
    What does CGL stand for? CGL stands for Continuous Galvanizing Line, distinguishing it from batch hot-dip galvanizing processes. The 'continuous' aspect is fundamental—strip is welded end-to-end and processed as an uninterrupted ribbon through all stages, maximizing throughput and coating consistency. This contrasts with batch processes where individual pieces are dipped separately. Major steel producers operate dozens of CGLs globally to meet automotive and construction demand for corrosion-protected steel.
    What are the main CGL steps? A CGL follows a precise sequence: Entry (uncoiler, welder), Cleaning (alkaline cleaning, brushing, rinsing to remove oils), Annealing (heating to ~700-850°C in controlled atmosphere to prepare metallurgy), Zinc Pot (immersion in molten zinc at ~460°C), Gas Wiping (air knives control coating thickness), Cooling, Skin Pass Mill (improves surface finish and mechanical properties), Inspection (surface quality verification) and Exit (coiler). Each stage requires tight process control for quality output.
    Why is temperature control critical? Temperature is the critical control variable throughout a CGL. In the annealing section, precise heating determines steel recrystallization and formability. At the zinc pot, strip temperature affects how zinc wets and bonds to the steel surface—too cold causes poor adhesion, too hot leads to excess intermetallic growth. Deviations of even ±10°C can cause coating defects, surface quality issues and customer rejections. This is why accurate non-contact temperature measurement is essential for CGL yield and quality.
    How do pyrometers help? LAND pyrometers provide accurate strip temperature measurement at critical CGL zones. The SPOT+ GS is optimized for galvanized strip measurement after coating, while the SPOT+ measures bare strip in annealing sections. The SPOT+ MM (Meltmaster) can monitor zinc pot temperature. These instruments deliver the real-time temperature data that process engineers need to maintain coating consistency, optimize line speed and reduce scrap—helping CGL operators achieve first-time quality rates that meet demanding automotive specifications.

  • Applications +

    • CGL - Galvanneal Exit
      Galvanneal Exit

      Once the strip leaves the zinc bath, it is subjected to in-line heat treatment to alloy the coating into the steel substrate. AMETEK Land’s SPOT+ GS is designed for measurement of this process.

      Keep Reading

    • CGL - Top Roll
      Top Roll

      The LSP-HD 61 monitors temperature across the entire width of the strip at this location.

      Keep Reading

  • Videos +

    • SPOT GS - Temperature Measurement of Galvannealed and Galvanized Strip
      AMETEK Land SPOT GS - Temperature Measurement of Galvannealed and Galvanized Strip

      SPOT GS enables automated furnace management to provide close control of the reaction and position of the reaction zone, delivering tighter control of product quality. By maintaining control of the reaction zone, SPOT GS accommodates rapid changes of line speed and furnace power with changes of substrate or coating weight. This allows furnace optimisation; reducing heating costs, maximising throughput and avoiding excessive over-reaction and powdering or flaking of the coating during subsequent forming operations.

    • Advances in Non-Contact Temperature Measurement for Continuous Annealing and Galvanizing Lines
      Advances in Non-Contact Temperature Measurement for Continuous Annealing and Galvanizing Lines

      We introduce how advances in accurate non-contact temperature measurements for continuous annealing (CAL) and galvanizing (CGL) lines ensure required metal characteristics and surface conditions are achieved in steel production. We will then focus on the SPOT GS, an advanced non-contact infrared spot pyrometer specifically designed for continuous, highly accurate measurements of coated steel strip temperature during the galvanneal reaction.

    • Improving Process Efficiency, Monitoring, and Control with Continuous High-resolution Thermal Imaging in Furnaces and Boilers
      Improving Process Efficiency, Monitoring, and Control with Continuous High-resolution Thermal Imaging in Furnaces and Boilers

      We introduces how ground-breaking advances in high-resolution thermal imaging in large furnaces and boilers dramatically improve process efficiency, monitoring and control. It will consider a wide range of continuous process monitoring and controlling applications, used in metal reheat, glass melt and reformer tube furnaces, cement kilns, and coal-fired power and biomass boilers, requiring highly accurate temperature measurement.

  • Documentation +