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Fireproof and Disaster-resistant Door Technology
Published Time:
2025-09-25
Material & Gauge Selection
Door leaf and frame components are fabricated from hot-dipped galvanized steel sheet to EN 10346 or ASTM A653, typically 1.2 mm – 1.5 mm thick for integrity and 0.8 mm – 1.0 mm for stiffeners. Zinc coating ≥ Z275 g/m² guarantees corrosion resistance after bending without micro-cracking.
C N C Press-Brake Setup
• Machine: 6-axis C N C press brake (±0.1° repeatability, 320 kN – 500 kN).
• Tooling: 28 mm gooseneck punch paired with 60° die opening; tip radius 0.8 t to avoid stress concentrators that could compromise fire resistance.
• Back-gauge: Servo-driven fingers with ±0.05 mm positioning to maintain cumulative tolerance ≤ 0.3 mm on leaf perimeter—critical for intumescent seal compression.
Bend Sequence & Spring-Back Compensation
• Air-bending at 85° to counter 3–5° spring-back (typical for 1.5 mm Z275 steel).
• Sequence: outer frame → hinge reinforcement channels → lock pocket. Each bend is under-cut 0.2 mm on flange length to guarantee positive fit-up before MIG welding, minimizing weld distortion that could jeopardize fire seal alignment.
Compliance Checks
• Dimensional: diagonal difference ≤ 1 mm (EN 1634-1).
• Micro-cracking: 10× magnified visual inspection on outer radius; zinc layer intact, no substrate exposure.
• Angle: sampled 1 per 50 parts; SPC chart maintained for CE/UL traceability.
Post-Bend Treatment
Edges are vibratory-deburred to remove shear burrs < 0.1 mm, preventing hot-spot corrosion and ensuring uniform intumescent seal adhesion. Parts are then alkaline cleaned and zinc-phosphate pretreated prior to epoxy-powder coating (min. 60 µm) for 240 min fire rating compatibility.
Outcome
The above protocol yields leaf and frame components that maintain < 1 mm gap under 500 °C deflection tests, satisfying EN 1634-1 (120 min) & UL 10C (90 min) requirements while enabling clean intumescent seal closure.
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