The Role of Aluminum in Steel

Influence of Aluminum on Microstructure and Heat Treatment of Steel

1. Aluminum has a strong affinity with oxygen and nitrogen, acting as a deoxidizing and nitrogen-fixing agent during steelmaking.
2. Aluminum exhibits minimal affinity with carbon, and aluminum carbides rarely form in steel.
3. Aluminum refines the inherent grain structure of steel, raising the temperature threshold for grain coarsening. However, when the solid-solution aluminum content exceeds a critical value, austenite grains may instead become prone to coarsening.

Impact of Aluminum on Mechanical Properties of Steel

1. Aluminum reduces steel’s sensitivity to notches and mitigates or eliminates aging effects, particularly lowering the ductile-to-brittle transition temperature (TDBT) to enhance low-temperature toughness.
2. Aluminum provides significant solid-solution strengthening, with high-aluminum steels offering high specific strength. Ferritic Fe-Al alloys exhibit superior high-temperature strength and creep resistance compared to Cr13 steel, but suffer from low ambient-temperature ductility/toughness and difficulty in cold deformation.
3. Austenitic Fe-Al-Mn steels demonstrate well-balanced comprehensive performance.

Effects of Aluminum on Physicochemical Properties of Steel

1. Iron-chromium alloys with low thermal resistivity coefficients are suitable for electrochemical applications.
2. Aluminum alloying enhances oxidation resistance, thereby improving corrosion resistance.
3. Aluminum intensifies labor requirements during steel processing.