The Influence of Peritectic Reaction/Transformation on Crack Susceptibility in the Continuous Casting of Steels

Abstract

The work presented here examines the surface cracks that can form during the continuous casting of near peritectic steels due to the volume changes during the peritectic reaction/transformation. The investigated samples were collected during plant trials from two different steel grades. The role and mode of the peritectic reaction/transformation are found to depend on the composition of the alloy, resulting in different types of surface cracks. The effect of the local variation in the cooling rate on the formation of the different types of cracks present in each steel grade, which can be due, for example, to the formation of oscillation marks, is demonstrated. The enhanced severity of the surface and internal oxidation, both of which depend on the alloy composition and consequent peritectic reaction, is highlighted. Experimental and theoretical studies show that different types of surface cracks can occur in peritectic steels depending upon the alloy composition and cooling rate, both of which define the fraction of the remaining liquid upon completion of the peritectic reaction/transformation.

Identification of Cracking Issues and Process Improvements through Plant Monitoring and Numerical Modelling of Secondary Cooling during Continuous Casting of HSLA Steels

“…peritectic transformation) promote higher volume changes than the one from liquid to austenite. [13][14][15][16][17] This new modified distance (gap) between mould and shell affects significantly the heat transfer coefficient (HTC). [18][19][20] Thus, an inadequate combination of these factors increases the risk to form deep oscillation marks, which act as preferential sites for solid-state crack formation during bending and straightening in the secondary cooling zone.…”

Study on Surface Longitudinal Crack Formation of Typical Hypoeutectoid Steel Produced on a Caster with Billet and Slab

“…Hence, control of cracks formation is currently a crucial issue, as industry engineering develops rapidly [3]. The causes of cracks in various steel grades are different, and there are corresponding control methods for different types of cracks [4][5][6][7][8][9][10][11][12][13]. Wang et al [14] analyzed the effect of inclusions on the initiation of cracks.…”

Influence of Alloy Elements on Cracking in the Steel Ingot during Its Solidification

“…Some alloys are susceptible to cracking during solidification, which has attracted the interest of many researchers. One of the most important examples in industrial practice is the production of peritectic steels in continuous casting, in which frequently occurring cracks are called hot tears, including surface longitudinal cracks and internal cracks [1][2][3][4][5][6][7][8]. Surface longitudinal crack formation is caused by the brittleness of the dendritic front, and all cracks observed originate and propagate along the interdendrites in the mushy zone [6,8].…”

“…The mushy zone contains liquid and dendritic grains, where dendritic grains are separated from one another by liquid, and this semisolid substance has little strength and ductility. When the tension deformation caused by shrinkage is directed perpendicularly to the dendrite axis to separate them in the deformation dendrite roots, cracks can form if the interdendritic liquid is isolated and cannot be fed from the surrounding liquid [3].…”