10 Fatal Mistakes Overseas Buyers Make When Ordering Heavy Steel Structures(Section 1-5) - Knowledge
1. Replace high-strength Q355/Q460 steel with thin Q235 material Many small processing factories cut cost by using Q235 thin H beam for heavy crane column and crane girder. Q235 poor impact toughness under dynamic lifting load, crack appears within 1–2 years of crane use. Solution...
Many small processing factories cut cost by using Q235 thin H beam for heavy crane column and crane girder. Q235 poor impact toughness under dynamic lifting load, crack appears within 1–2 years of crane use. Solution: Sign contract clause requiring third-party material test report before shipment, forbid material grade substitution without buyer approval.
2. Integrate crane load on roof rafter without independent crane beam
Unprofessional designers share roof beam to bear crane force, no independent crane corbel. Long-term lifting vibration causes roof frame deflection, roof panel leakage and bolt loosening. Standard heavy industry design: Separate crane beam system independent of main portal frame.
3. Skip NDT non-destructive welding inspection for key nodes
Ordinary light steel only needs visual welding check, while heavy steel box column, crane girder full penetration weld must pass UT ultrasonic flaw detection. Hidden welding crack will expand under dynamic load and break components.
4. Ignore fatigue load calculation for frequent lifting workshop
Static load calculation cannot meet heavy crane demand. Factories without professional structural engineers omit fatigue check, resulting in hidden danger for 24-hour continuous production workshop.
5. Low-grade anti-corrosion coating for high temperature/chemical workshop
Ordinary single-layer anti-rust paint fails in smelting, chemical plant within 2 years. High-temperature workshops need special heat-resistant coating; chemical corrosive environment requires multi-layer heavy-duty anti-corrosion system.