Recieved:

16/07/2026

Accepted:

05/09/2026

Page: 

–

doi:

http://dx.doi.org/10.17515/resm2026-1894im0716rs

Views:

18

High-precision blanking process and die technology for zirconium alloy nuclear fuel assembly spacing grid strips

Guangwei Cao1, Huaping Duan 1, Fei Qian1, Jian Feng1

1Ningbo Kangdi Purui Mould Technology Co., Ltd, Ningbo, 315000, China

Abstract

Zirconium alloy spacing grid strips constitute critical structural components in pressurized water reactor fuel assemblies, where dimensional precision directly influences reactor safety and operational efficiency. The hexagonal close-packed crystal structure of zirconium alloys presents significant challenges in achieving the required blanking accuracy of ± 0.005 mm due to pronounced anisotropic deformation behavior and springback characteristics. This study establishes an integrated process-die system through finite element simulation, precision die manufacturing, and industrial validation. DEFORM-3D simulations identified optimal blanking parameters: single-side clearance of 0.035 mm (7.65% of sheet thickness) and 120 mm per second punch velocity, yielding 61.9% shear zone ratio and 0.023 mm dimensional deviation. A modular four-plus-one die structure incorporating AFA-2G and AFA-3G guide systems achieved ± 0.001 mm assembly accuracy. ASSAB 88 steel with double cryogenic treatment and TAC (tetrahedral amorphous carbon) coating extended single-regrind tool life to 2.0–2.5 million strokes and total tool life beyond 80 million strokes, representing a 4-fold improvement over uncoated dies and a 2.5-fold improvement over conventional DLC coatings. Industrial validation across 16,000 parts demonstrated a 98.6% pass rate with Cpk greater than 1.33, meeting the dimensional and process-capability acceptance criteria of the fuel manufacturer’s quality plan. Complete nuclear qualification of the finished assembly is outside the scope of this study.

Keywords

Zirconium alloy; Blanking process; Die technology; TAC coating

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