Reaction Mechanism between Alumina Graphite Immersion Nozzle and Low Carbon Steel.

Abstract

Reaction between refractory and molten steel causes clogging in the immersion nozzle in continuous casting process. Reaction mechanismbetweenthe silica-containing alumina graphite nozzle and the molten steel was studied on the observation of the used immersion nozzle and the basic experiments. The results are summarized as follows.( 1) The used immersion nozzle refractory reveals a reacted zone where the SiO. and C contents are reduced and there are many pores.( 2) The overall reaction in the refractory can be arranged as Si02(s) +C(s) =SiO(g) +CO(g) With the Si02-C refractory containing no Al20.. 50"/. of Si02 is reduced by the C to the SiO gas, and the remaining 500/0 is reduced by the C to SiC. On the other hand, with the AI.O.-Si02-C refractory.all of SiO. is reduced to the SiO gas.

Studies of the decarburisation phenomena during preheating of submerged entry nozzles (SEN) in continuous casting processes

“…In addition, Poirier et al [6] observed three area zones in the RBM to the hot face; a decarburised area, a first layer of deposited material and a final layer of the deposit. The decarburisation of the RBM resulted in changes in the density and the apparent porosity in the decarburised area, due to the graphite and oxide losses [2,13]. Another study of the interface between an Al 2 O 3 -C RBM and molten steel showed an increased carbon pick-up by the molten steel with increased carbon levels in the RBM.…”

“…This steel flow through the SEN can be disturbed by nonmetallic inclusions which accumulate on the SEN's internal surface and lead to clogging of the SEN. This in turn can result in halted production, production losses, impaired quality and therefore increased costs [1][2][3][4]. During steelmaking the molten steel has a temperature of around 1600°C and if the SEN is at room temperature before being put in contact with the steel there is a high risk for thermal shock and resulting damage of the refractory base material (RBM).…”

Material Evaluation to Prevent Nozzle Clogging during Continuous Casting of Al Killed Steels.

“…This causes the oxidation of Al Fe , while Si and C will dissolve in the liquid steel. 6) Once this first alumina layer has been formed, deposition and accumulation of inclusions from the molten steel onto the inner wall of the SEN will occur.…”

Cold Isostatic Pressing of Alumina-Graphite Castables, a New Technology to Manufacture Special Refractories

“…The most critical components of the flow control system are LS and SEN, LS is used between the ladle and the tundish and the function of SEN is to protect the molten steel stream whilst teeming the tundish into the mould. The required properties for LS and SEN are extensive, they include excellent resistance to thermal shock, [1][2][3] mechanical strength to withstand the molten steel stream and high temperature, 4) vibration and handling, 5) high corrosion and erosion resistance to molten steel, mould flux and slag, 6,7) clogging resistance, [8][9][10][11] particularly for aluminum killed steel and suitable cost of production. 12) For the time being, alumina-graphite materials have been of wide use to cope with these requirements and satisfy these demands.…”

“…Calcium aluminate (CA) is the most important hydraulically setting cement phase. 16) Hydration starts by forming the hexagonal crystals of CAH 10 and C 2 AH 8 (H stand for H 2 O) which depending on time and temperature of hydration convert to the cubic crystals of C 3 AH 6 and AH 3 . During firing these hydrates break down, leaving very reactive products, which in turn recrystallize to anhydrous calcium aluminates.…”