Dimensional Changes and Shrinkage Behavior of STS630 Bent-Sheet Components During Aging Heat Treatment

Paired coordinate measuring machine (CMM) measurements documented dimensional changes in sixteen STS630 bent-sheet components aged in one batch at 480 ± 10 °C for 3 ± 0.5 h. The same CMM and feature-specific styli were used before and after treatment in a room maintained at 20 °C. All 64 longitudinal distances, four per component, decreased. The confidentiality-scaled mean and sample standard deviation of the sixteen component-mean shrinkage values were 0.5888 and 0.0231 mm, respectively. The scale-invariant mean shrinkage ratio was 0.0461%. Comparison with the representative 0.045% H900 contraction concerns magnitude because the reference hold is 1 h. A companion coupon processed in the same batch had a mean Rockwell C hardness of 46 HRC from five readings, within the production requirement of 42–50 HRC. Cross-sectional distances, coordinates, and angles showed quantity-dependent signed changes. Small feature differences are interpreted descriptively because task-specific uncertainty has not been quantified. Precipitation-related reference-length change, forming-stress redistribution, and fixture interaction are discussed as hypotheses. The contribution is a paired component-level account of longitudinal contraction and cross-sectional inspection quantities, providing an empirical basis for subsequent dimensional assessment.