Passivated lime is primarily used to address desulfurization issues in KR steelmaking. Its main characteristic is excellent moisture resistance. Passivated lime is an efficient desulfurizing flux in steel smelting, with the following composition: w(CaO) 70~80%, CaF₂ 8~12%, w(S) ≤0.05%, and activity ≥300ml. It is produced by calcining high-quality limestone to create active lime, which then undergoes processes such as grinding, proportioning, briquetting, granulation, and passivation. Basic oxygen furnace (BOF) steelmaking has poor desulfurization capability and is prone to sulfur reversion, especially when the molten iron has w(S) ≤0.02%. Under such conditions, the BOF has virtually no desulfurization ability, making it very difficult to produce "dual-high products" like cord steel and pipeline welding steel, which have stringent sulfur content requirements. After deep desulfurization of molten iron, the slag on the surface is removed, but the thin slag between the iron and slag is hard to eliminate, leading to high sulfur levels. To address this, the technology of slag adhesion for molten iron desulfurization was developed. After desulfurization blowing with passivated lime, 0.9~1.2 kg of passivated lime is added per ton of iron, and nitrogen is blown through the desulfurization lance for dynamic stirring. Slag removal is repeated until the process is complete. After using this method, the slag basicity is R:1.520, and w(S) ≤1.740%. The former method yields better results. Additionally, using passivated lime for slag adhesion increases the viscosity of the molten iron slag, making desulfurization slag easier to remove, shortening slag removal time, and reducing iron loss during slag skimming.

Currently, Wuhan Iron and Steel in China has adopted this slag adhesion technology. After implementation, the average tapped steel sulfur content from the converter is w(S) ≤0.006%, sulfur reversion is below 0.0036%, and iron loss during slag removal is reduced by 2.47 kg/t, resulting in significant economic benefits.