6.1.7. Carbide bandThe carbide band of raw material should below requirementAccording to SEP1520, the qualified grade should≤CZ6.2/7.3 (material for roller), ≤CZ6.2/7.4 (material for ring)6.2 Forging Annealing should be taken after forging to get fine metallographic structure for heat treatment.6.3 Heat treatment6.3.1. HardnessHardness on rings’ raceway surface ≥58HRC and ≤ 63HRC; hardness on roller, ≥59HRC and ≤ 63HRC. Specific requirements are specified by drawings or technical specifications. hardness deviation on Raceway surface shall ≤2HRC.6.3.2. MicrostructureNo matter the rings and rollers of bearing case hardened, martensitic or bainitic hardened, the metallographic structure and control criteria should be agreed by Envision. 6.3.3. Others