When smelting shifts from cast iron to stainless steel, alloy steel, or more complex slag systems, acidic systems are often no longer optimal. Al-Mg dry ramming mixes (Al2O3-MgO) become a common route: stronger chemical stability and better resistance to basic slag attack.

The key mechanism in the Al-Mg system is "in-situ spinel formation." At service temperature, MgAl2O4 forms and improves high-temperature structural stability and corrosion resistance, but it also brings significant volume expansion. Studies clearly indicate about 8% volume expansion from in-situ spinel formation; if structure design and particle grading do not match, internal stress is induced and lining life is shortened.

Therefore, the upgrade core is not "the more spinel the better," but turning expansion from a destructive factor into "usable self-densification": with proper particle packing and additive systems, expansion closes pores at the micro scale and reduces slag penetration, instead of cracking the lining at the macro scale. Related research systematically discusses how additives (such as calcium magnesium aluminates) affect slag penetration and structural evolution, aiming to find a more stable balance between slag resistance and thermal shock resistance.

Execution on the engineering side usually comes down to three points:

1. Write the "allowable expansion" into the formulation and structure (thickness, buffer layer, transition layer);

2. Treat dry-out/heating as reaction-process control rather than simple drying;

3. Treat slag system changes as selection inputs, avoiding a single grade to cover all steel grades and furnace conditions.

Xinhui's basic/neutral ramming mix route focuses on "controlled spinel formation": through grading, bonding, and additive strategies, expansion risk is locked into a safe window. The on-site goal is not a one-time maximum life, but "stable furnace life + predictable maintenance."