Deoxidation and Desulfurization of Liquid Steel with Calcium Complex Alloys

Abstract

In order to determine the effect of immediately injected calcium alloy on the oxygen and sulfur contents of liquid steel, the deoxidation of steel with different calcium complex deoxidizers was studied at 1 600° by means of the high frequency induction melting in a magnesia lined crucible, covering unslaked lime to a depth of 10mm. The results obtained are as follows:
(1) Although 2% of SiMn addition which was done at once or dividingly decreased the oxygen content to 0.004%, the desulfurization was not significantly influenced. The addition of calcium complex deoxidizer containing aluminium, after lowering the oxygen content, decreased the sulfur content considerably below that obtained with CaSi, CaSiMn and CaSiBa additions.
(2) With a constant oxygen content the amount of sulfur was a minimum in the case of steel deoxidized dividingly with the calcium complex deoxidizer containing aluminium; here the S/O ratio was about from 0.67 to 0.90, while when deoxidizing with CaSi or CaSiMn it was about 2.3.
(3) Electron-probe microanalysis of the non-metallic inclusions in ingots, which were produced with the calcium complex deoxidizer containing aluminium, showed various concentrations of CaO (26 to 46%), Al₂0₃ (40 to 54%), and CaS (to 34%), possibly due to the presence of complex oxysulfide inclusions.
(4) From some difference in the yield of silicon and aluminium in ingots and in the ratio of desulfurization to deoxidation, a favorable calcium complex alloy will have to possess the constituent ratio as Al: Ca: Si: Mn: Fe=1:1:1:1:1.