Sinter return fines are iron-rich by-products of iron ore sintering, but conventional re-sintering is energy-intensive and often leads to repeated circulation. This study developed a cold-bonding and hot-hardening briquetting (CBHHB) process to convert these fines directly into blast-furnace burden. Screening of 34 binders, followed by binary and ternary optimization, binder A₂B₃C₁ was identified as the optimal composite binder. Combined with Dinger–Funk particle-packing design and hot hardening at 550 °C, this formulation produced a dense interlocking structure with continuous interfacial bonding. The optimized CBHHB achieved a compressive strength above 2500 N, a reducibility index of 77.05%, an RDI_+6.3 of 96.6%, and a post-reduction strength above 900 N. However, CBHHB showed poor melting–dripping permeability. At 30% addition, the S value reached 42.41 kPa °C, 2.23 times of that of the reference burden. FactSage calculations indicated that Phase 12, comprising melilite, monoxide, slag liquid, and a'(Ca,Sr,Ba)₂SiO₄, broadened with increasing CBHHB content, consistent with the rise in gas-flow resistance. A 20% blending ratio provided the best balance between reduction performance and permeability. This study establishes an integrated framework linking binder formulation, packing structure, metallurgical performance, and phase evolution.