The word "熔炼" is formed by combining the characters "熔" and "炼", each constructed with the fire radical "火" to indicate relation to heat: "熔" uses the phonetic component "容" for sound and means to melt, while "炼" uses the phonetic component "柬" (simplified as "东") for sound and means to refine; together they create a compound meaning smelting or refining through melting, with both components reinforcing the thermal process.