Neutral ramming mass is mainly composed of neutral refractory aggregates such as magnesia-alumina spinel and corundum. Featuring stable chemical properties, it barely reacts with acid slags and shows strong resistance to corrosion by basic molten slags. It's widely used in parts prone to complex slag corrosion, including melting furnaces, non-ferrous metal kilns and ladles.
I. Core Principle of Slag Resistance
Neutral raw materials possess strong acid-base inertness. The material will not undergo violent low-melting reactions with acidic SiO2 or basic molten slags containing CaO and MgO, thus preventing large-area corrosion pits. After forming with micro-powders and a composite bonding system, the dense compact matrix with low apparent porosity can physically block capillary penetration of molten slag. Internal spinel phases can capture metal ions in slag to form a stable high-melting-point barrier layer, which stops further inward diffusion of slag.
II. Factors Affecting Slag Resistance
1. Mineral composition of aggregates: Pure corundum performs better against acid slag, while magnesia-alumina spinel delivers balanced resistance to both acid and basic slags. Improper aggregate blending will weaken overall slag resistance.
2. Density and pore structure: Excessive open pores with large pore sizes allow molten slag to seep into the matrix easily. Proper particle grading and sufficient ramming can reduce interconnected pores.
3. Matrix bonding system: The matrix is the weak point against slag erosion. Excess impurities in the matrix tend to form low-melting phases in advance, accelerating slag penetration and spalling.
4.Construction and baking procedures: Insufficient ramming or rapid temperature rise causes cracks, which act as channels for molten slag infiltration.
The outstanding dual resistance to both acid and basic slags is the key advantage that distinguishes neutral refractories from acidic and basic counterparts. Proper raw material selection and standardized construction can greatly reduce slag infiltration, lining heaving and spalling, ensuring long-term stable operation of high-temperature equipment.
