Reducing surface cracking in hot charged HSLA cast slabs by surface quenching prior to hot charging – experimental study on heat transfer behaviour

Abstract

Surface quenching of cast slabs between casting and hot charging to prevent the occurrence of surface cracks in high strength low-alloy steel slabs has been investigated. In order to accurately control the quenching process and obtain the desired cooling rate, an experimental study on the heat transfer behaviour of a high temperature slab cooled by a water nozzle was performed. The surface temperature and heat transfer flux were calculated using a two-dimensional transient inverse heat conduction model, based on the finite element method. The effect of the water flowrate and inclination of the spray on the heat transfer is discussed. Based on a regression analysis of the experimental data, the heat transfer coefficient is provided as a function of slab temperature and water flow density. A surface quenching trial with a water flowrate of 46 m³ h⁻¹ was conducted in a steel mill. Good correlation was found between the temperature predicted using the proposed heat transfer coefficient and the temperature measured during the surface quenching process.

Keywords:

• Heat flux
• Heat transfer coefficient
• Hot charge
• Surface quenching