Multi-Objective Optimization of the Hot Stamping Process for B1500HS Ultra-High-Strength Steel Based on a Four-Dimensional Quality Evaluation Framework

This study establishes a closed-loop chain of evaluation, optimization, and capability assessment for the hot stamping of 1.2 mm B1500HS ultra-high-strength steel. A four-dimensional quality framework (appearance, geometry, mechanics and microstructure) was established, and FMEA identified hardness non-uniformity, necking and cracking as priority risks. An L16(45) orthogonal dataset (heating 870–930 °C; forming 720–780 °C; speed 40–70 mm/s) was re-analyzed by ANOVA. Heating temperature dominated all responses (contribution > 91%), whereas stamping speed was insignificant. Run 16 (930 °C, 780 °C, 40 mm/s) ranked first by Min–Max weighting and by equal-/entropy-weight GRA (Kendall τ ≥ 0.650, p < 0.001); because speed was insignificant, 70 mm/s is equally acceptable and preferable for productivity. Two-stage validation (merged n = 10) gave Rm = 1515.6 MPa, Rp0.2 = 1145.8 MPa, A = 7.8%, HV = 568.4 and ≈ 97.5% martensite. Preliminary capability indices were excellent for Rm (Cpk = 2.12), A (2.46) and HV (2.29), and acceptable for Rp0.2 (1.13). The framework links laboratory optimization with batch-production quality control.