Morphology Control for Al2O3 Inclusion Without Ca Treatment in High-Aluminum Steel

Abstract

Nozzle blockage is a major problem during continuous casting of Al-containing steel. Herein, we analyzed the thermodynamic equilibrium behavior between aluminum and oxygen in steel at 1873 K (1600°C) and demonstrated that, the dissolved [O] initially decreases with increasing the dissolved [Al] until approximately 0.1 wt pct [Al], and after that, the dissolved [O] increases with dissolved [Al]. Thus, for high-aluminum steel with 1.0 wt pct dissolved [Al], the precipitation of Al 2 O 3 inclusion can be avoided during cooling from deoxidation temperature to the liquidus temperature, if the actual dissolved [O] can be kept from increasing when the dissolved [Al] further increases from 0.1 to 1.0 wt pct. Hence, a method of inclusion control for highaluminum steel without traditional Ca treatment technology was proposed based on the thermodynamic analysis. Industrial tests confirmed that low-melting point Ca-aluminate inclusions were observed typically through a slag washing with SiO 2-minimized high-basicity slag during tapping, accompanied by two-step Al-adding process for production of high-aluminum steel. Moreover, there was no nozzle clogging occurred for five heats of continuous casting.

The Effect of a High Al Content on the Variation of the Total Oxygen Content in the Steel Melt during a Secondary Refining Process

“…MgO · Al 2 O 3 and CaO–Al 2 O 3 phases are known to be thermodynamically more stable than the Al 2 O 3 phase in commercial steels with reduction refining . In this study, the MgO · Al 2 O 3 phase was detected in inclusions similarly to those found in the previous work .…”

“…Modifying Al 2 O 3 or MgO · Al 2 O 3 into liquid CaO–Al 2 O 3 inclusions can prevent nozzle cloggings . Therefore, the mechanism of the inclusion evolution from Al 2 O 3 or MgO · Al 2 O 3 phase into the liquid CaO–Al 2 O 3 phase has been deeply studied in both laboratory and plant scale trials …”

Mechanism of Melt Separation in Preparation of Low-Oxygen High Titanium Ferroalloy Prepared by Multistage and Deep Reduction

“…A low melting point of the slag provides a good condition for a fast metal-slag separation. In addition, the dissolution time of Al 2 O 3 inclusion in the high basicity slag is much shorter than the separation time of Al 2 O 3 at the slag-metal interface (< 5 s) [25]. At the same time, the dissolution rate of Al Table 4 shows the chemical composition of alloys.…”

Melt fluxing to elevate the forming ability of Al-based bulk metallic glasses

“…The reaction produces new oxides that have a lower interfacial energy with the melt and also possibly form clathrate compound with the residual aluminum oxide inclusions 51, 52 .…”

“…Thus, a large negative Δ G c v signals an easier reaction. The formation of different products such as MgO or clathrates in the melt could be determined by the equilibrium constant of the actual molten salt system 52 . This is consistent with West’s view 55 .…”