Gyro Nozzle - An Innovative Submerged-Entry Nozzle Design for Billet and Bloom Casting

摘要

Fluid flow in the mold is known to have a significant impact on the product quality and process stability of the continuous casting process of steel. In addition to the operating conditions, the design of the submerged entry nozzle (SEN) plays an important role. Depending on the caster type, different strategies for the SEN design are being followed to meet the specific requirements. For long product casting, namely billet and bloom casting, usually straight through design nozzles also known as single port SENs are used, due to their simplicity, However, as demand for steel cleanliness increases, research has indicated that this type of SEN may not be suitable to meet all the requirements. Due to the considerable penetration depth of the jet into the liquid pool, notation of nonmetallic inclusions towards the mold surface where they are absorbed by the slag is prevented. In recent years, there has been a trend to use multi-port SENs in bloom casting for high-grade steel, such as bearing and rail steels. It is considered that the multi-port SEN has a better ability to remove nonmetallic inclusions in the mold than a single-port SEN and provide a better energy transport tow ards the meniscus. Lately, the process is increasingly supported by the use of electromagnetic fields, such as mold electro-magnetic stirrers (M-EMS). This device is positioned in the mold region and produces an almost homogeneous, planar and rotating magnetic field in the strand. It is reported, that electromagnetic stiiring provides a number of benefits such as the homogenization of the liquid steel flow, the reduction of surface and sub-surface defects and an enhanced transition from columnar to equiaxed solidification.