Technical Handbook
A practical guide to mould flux functions, slag film heat transfer, and selection levers for continuous casting.
Last updated: March 15, 2026
Overview
In continuous casting, mould flux (casting powder) creates a liquid slag film that lubricates the mould-shell interface and regulates horizontal heat transfer. Literature highlights viscosity, break temperature, and crystalline fraction as the primary levers that control performance.[1]
Functions
Mould flux performs two primary roles: it lubricates the mould-shell gap and it regulates heat transfer across the mould. These roles depend on slag film properties and are sensitive to viscosity, break temperature, and crystalline fraction.[1]
Well-controlled lubrication minimizes friction-related defects and supports steady shell growth at target casting speeds.
Slag Film
Research on slag film formation shows a liquid layer adjacent to the solidifying shell and a solid/crystalline layer toward the mould. Heat transfer depends on film thickness, crystallization, and interfacial resistance, which are assessed using experimental approaches such as hot thermocouple and copper-finger tests.[2]
Property Levers
Controls lubrication and slag flow. Literature positions viscosity as a key property for mould flux performance.[1]
Defines the transition from fluid to solid slag film, influencing heat transfer stability.[1]
Crystallization degree alters thermal resistance and surface quality outcomes.[1]
Performance Properties
Reviews of mould flux performance show that physical properties such as viscosity, melting rate, and crystallization behavior are tightly linked to lubrication stability and heat transfer control in the mould.[4]
These properties are typically balanced to avoid both excessive heat extraction (risking cracks) and insufficient heat removal (risking shell weakness).
Fluorine-Free
Fluorine-free mould flux development is driven by concerns about fluoride evaporation, equipment corrosion, and environmental impact. Studies review alternative systems (for example, TiO2- and B2O3-based designs) that aim to preserve viscosity and crystallization targets without fluorides.[3]
Peritectic Steels
Recent design work on fluorine-free mould fluxes for peritectic steels highlights the need to tune melting and viscosity behavior to maintain a stable slag film in sensitive solidification conditions.[5]
Selection Checklist
Use trial feedback to iterate viscosity and crystallization behavior for your casting window.
Troubleshooting
FAQ
Steel grade, casting speed, mould dimensions, superheat, and defect history are the core inputs used to tune viscosity and crystallization behavior.
Yes, when designed for the required viscosity and crystallization window. Trial feedback is used to validate performance.
Imbalanced lubrication and heat transfer. Adjusting viscosity and crystalline fraction usually resolves these signals.
References