1. Effect of Effective Crystallizer Height on Mechanical Properties of Cast Ingots

Reducing the effective height of the crystallizer advances the timing of direct secondary water cooling for the cast ingot, increasing the cooling intensity. This results in two outcomes: firstly, a finer intragranular structure, and secondly, a flatter sump with improved structural compactness, thereby enhancing the average mechanical properties (strength and plasticity) of the ingot. Increasing the effective crystallizer height first causes performance degradation in the surface layer of the ingot, which is clearly related to changes in the shape of the crystallization front and the size of the transition zone.

2. Effect of Effective Crystallizer Height on Crack Susceptibility of Cast Ingots

This is a highly complex issue. Reducing the effective crystallizer height generally advances the point at which the ingot is exposed to water cooling. Under otherwise identical conditions, for round ingots, the increased cooling intensity causes the bottom of the sump to tend to contract inward toward the crystallizer; conversely, the reduction in the absolute value of the effective crystallizer height causes the sump bottom to tend to extend outward from the crystallizer. If the combined effect of the two tendencies favors the former, the propensity for tensile stress to form on the ingot surface at the start of casting increases, raising the risk of surface cracking. If the latter tendency prevails, it helps eliminate surface cracks in round ingots but simultaneously increases their susceptibility to center cracks and other types of cracks. Practical experience indicates that reducing the effective crystallizer height increases the hot cracking susceptibility of flat ingots.

3. Effect of Effective Crystallizer Height on Surface Quality of Cast Ingots

Reducing the effective crystallizer height weakens the primary cooling intensity of the ingot, shortening the solidified shell formed solely by cooling from the crystallizer wall, thus reducing the tendency of the ingot to develop scratches and tears. Additionally, a flatter sump decreases the propensity for segregation floaters to form on the ingot surface. However, the reduced effective crystallizer height increases the overall cooling intensity of the ingot, which, under equivalent conditions, raises the tendency for cold shuts (laminations) to form. This issue is addressed using heating caps on the crystallizer in hot-top casting and air-cushion casting. In conventional casting, it can be resolved by increasing the casting speed or temperature, as well as through precise liquid level control.

Under actual production conditions, casting tools are mostly fixed. On-site adjustment of the effective crystallizer height is limited to vertical casting using standard crystallizers, via liquid level controllers. In other processes such as horizontal casting and hot-top casting, the effective height is non-adjustable unless the crystallizer is replaced. Therefore, the crystallizer height can be regarded as a parameter determined concurrently with the casting method. Although the water cooling height can be adjusted by modifying the water line position of the ingot, this does not conform to the definition of effective crystallizer height.