October 26, 2021

Foundry Solutions: Neutral Ramming Mass Vs. Silica Linings

Foundry solutions in both ferrous and non-ferrous industries relies on the longevity of critical units (coreless induction furnaces, vacuum furnaces, channel furnaces, pouring ladles, launders, crucibles, spouts, etc.). Manufacturers aim to maintain a high standard of finished quality via innovative and cost-effective foundry solutions; by internally lining these components using refractory materials.

These refractory solutions must be tailored based on a range of key design and operating parameters, including the chemical nature of the molten material, structural design properties, temperature, and more.

To address application-specific use cases, Saint-Gobain offers an exclusive portfolio of customized foundry solutions based on NORVIBE™ product range. Especially the high-performance neutral ramming masses are used for steel production in coreless furnaces where silica linings were currently used with mitigated performances.

Silica Linings

Silica linings are the conventional lining solution widely used in both ferrous and non-ferrous foundries. Mainly made of crystalline silica and commonly known as acidic ramming mass, the typical binding agents that aid in the sintering of silica linings are boron-based.

This refractory lining exhibits mainly low thermal expansion and have excellent thermal shock resistance. However, silica linings are susceptible to corrosion and pose a higher risk of chemical reactivity with molten metals and slags. Especially when in contact with basic molten slags, the silica linings can experience severe chemical erosion.

At Saint-Gobain Refractories, we have developed a novel solution to the performance issues associated with silica linings: Neutral Ramming Masses (NRMs).

Neutral Ramming Mass

Neutral ramming masses are a unique, chemically neutral foundry solution that form joint-less linings. The in-situ spinels synthesise at high temperatures inside the refractory lining, creating a unique 3-layer structure. The outermost layer in contact with the molten metal is a hard, sintered surface, followed by an intermediate fritted layer. The innermost layer stays in a powdery form.

Foundry solutions based on such multilayered structures offers several key advantages. NRMs exhibit a distinctive microstructure characterized by microcracks that impart a toughening mechanism, significantly improving the mechanical properties. The innermost sintered, hard layer provides excellent wear and corrosion resistance (against chemically harsh slags). When the inner layer is exposed or eroded, the intermediate layer sinters in situ via spinel formation when exposed to high temperatures. Thus, the integrity of the linings is preserved even in the case of lining wear.

The optimisation of the 3-layer structures and characteristics enhances high resistance to corrosion and prevents molten metal leakage, adding to the safety of the staff. Neutral ramming masses are also highly chemically stable in both acidic and basic media. All these properties of neutral ramming masses make them an ideal, state-of-the-art foundry solution for high-temperature components such as the induction blast furnace.

Additionally, neutral ramming masses are the greener solution compared with silica-based refractories. We are committed to helping customers to significantly reduce their carbon footprint as net zero initiatives take effect in in various markets. Our foundry solutions have not only helped to reduce CO2 emissions by up to 5%, they are also an EHS-friendly product.

Like to learn more? Contact a member of the Saint Gobain Refractories team today.