Q: What are the common causes of bending cracks?
A: Excessive inclusions (such as MnS), uneven microstructure, edge burrs/microcracks, improper cold bending process (too small bending mandrel, too fast bending speed).
Q: How to determine if Q235 coil is of acceptable quality?
A: Check the quality certificate (composition, mechanical properties, dimensions, surface grade); ensure there are no excessive defects in appearance; conduct random checks on mechanical/process properties and dimensional tolerances according to standards.
Q: What are the dimensional tolerance standards for Q235 coil?
A: Thickness tolerance follows GB/T 3524. For thicknesses of 2–6mm, the general precision is ±0.15mm; width tolerance is ±5mm. Specific requirements are subject to the contract/standard.
Q: What are the common edge problems and solutions for Q235 coil?
A: Edge cracks, burrs, and tapered shapes; control the quality of continuously cast billets, optimize the finishing rolling side guide plates and coiling tension, and trim or chamfer edges if necessary.
Q: How to solve the problem of excessively thick iron oxide scale on Q235 coil? A: Reduce the furnace temperature and furnace time, optimize the descaling water pressure (≥18MPa), use high-pressure water for secondary descaling, and cool and package the coiled product promptly.