Inclusion Evolution after Calcium Addition in Low Carbon Al-Killed Steel with Ultra Low Sulfur Content

Abstract

Inclusions in steel samples collected 0.5, 2, 5, 10 and 20 min after calcium addition were investigated in Low Carbon Aluminum Killed steel (LCAK steel) with ultra low sulfur content (0.04-0.065% Al, 9 ppm S). It's found that inclusions change from CaO to CaO-CaS and finally to CaO-Al2O3-CaS with time. Al2O3 in inclusions linearly decreases by increasing T.Ca/T.O of the steel and disappears when T.Ca/T.O exceeds 3. CaS/CaO of the inclusions linearly increases by increasing S/T.O of the steel. Contents of CaO, Al2O3 and CaS can be estimated through T.Ca, S and T.O. CaO-CaS clusters are found at 5 min. The mechanism of inclusion evolution and formation of CaO-CaS clusters are discussed.

Control of Inclusion Composition in Calcium Treated Aluminum Killed Steels

“…5, where the spots with the shape of box and solid triange are reported by M. Numata et al 3,4) and G. W. Yang et al 1,2) respectively and their results is almost in accordance with the ones in present work in the case of T.Ca/T.O less than 1. steel less than 0.5, Al 2 O 3 content in inclusion is very high even close 90%, which indicates the type of inclusion is Al 2 O 3 inclusion or low modified calcium aluminates; In the case of T.Ca/T.O in steel greater than 0.5 and less than 1.5, the type of inclusion is Al 2 O 3 -CaS inclusion.…”

“…Yang et al 1,2) studied the effect of calcium addition on the variation of inclusion composition in low carbon Al-killed steel with induction vacuum furnace and found that the Al 2 O 3 content in inclusions linearly decreased by increasing T.Ca/T.O in steel and it disappeared when T.Ca/T.O exceeded 3 and CaS/CaO of the inclusions linearly increased by increasing S/T.O in steel. Numata et al 3,4) investigated the calcium consumption and calcium addition pattern on the change of inclusion composition.…”

“…It is found that T.Ca/T.O could better replace dissolved Ca to evaluate the extent of modification of alumina inclusions by Ca. Inclusions changed from Al 2 addition. Choudhary et al 5) developed a thermodynamic model for predicting the formation of oxide-sulfide duplex inclusions in Al-killed steel and found that increasing S content in steel made complete modification of alumina inclusions into liquid calcium aluminate become difficult.…”

Improvement of Heat-Affected Zone Toughness of Steel Plates for High Heat Input Welding by Inclusion Control with Ca Deoxidation

“…The ∆G r have been calculated by Equation (2) [16]. The content of C, Si, Mn, Al, Ca are shown in Table 2.…”

“…The α CaO is greater than 0.03 when the content of CaO is greater than 20%, therefore, the reaction of Equation (6) only exists in C11 and C27 samples. The ΔGr have been calculated by Equation (2) [16]. The content of C, Si, Mn, Al, Ca are shown in Table 2.…”