Phase Stability of Dross Particles in Hot-Dip Zn-55wt%Al-1.6wt%Si Galvanizing Bath

Area of Science:

• Materials Science
• Metallurgy
• Physical Chemistry

Background:

• Dross in Zn-Al-Si metal coating baths comprises bath metal and intermetallic phases, notably τ5c-Al20Fe5Si2(+Zn).
• Understanding dross formation and properties at processing temperatures (~600 °C) is vital for enhancing steel sheet coating quality in hot-dip galvanizing.
• Current dross analysis typically occurs at room temperature, raising questions about the representativeness of findings for high-temperature conditions.

Purpose of the Study:

• To investigate the high-temperature behavior of intermetallic phases within hot-dip Al-Zn galvanizing bath dross.
• To determine the crystal lattice parameters and coefficient of thermal expansion (CTE) of the dross intermetallic phase up to 660 °C.
• To elucidate phase formation and stability at elevated temperatures for optimizing steel coating production.

Main Methods:

• In-situ synchrotron X-ray diffraction (XRD) was employed to analyze dross samples.
• Measurements were conducted across a temperature range from 30 °C to 660 °C.
• Crystal lattice parameters and CTE were determined for the intermetallic phase.

Main Results:

• The crystal lattice and coefficient of thermal expansion (CTE) of the intermetallic phase were successfully determined between 30 °C and 660 °C.
• Phase formation and stability of the intermetallic phase within the dross powder at high temperatures were elucidated.
• This provides fundamental data on the high-temperature behavior of dross components.

Conclusions:

• In-situ XRD analysis provides critical high-temperature data on dross intermetallic phases.
• Understanding these high-temperature properties is essential for improving the production processes and quality of hot-dip Al-Zn coated steel sheets.
• The study offers fundamental knowledge for optimizing galvanizing bath operations and coating quality.