Cold Drawn Rectangular Steel Bar Carbon Steel Flat Square Bar for Construction

Cold drawn flat steel is produced by cold drawing hot rolled flat steel, with high dimensional precision (h9-h11), smooth surface, high strength, good straightness, but price 30-50% higher, and size limited (generally <=50mm thick, <=100mm wide). Hot rolled has lower precision, scale surface, but wider size range (3-60mm thick, 10-200mm wide), lower price. Selection: high precision/surface requirement -> cold drawn; large size/cost sensitive -> hot rolled.

Yes, but note: 1) Cold drawn has work hardening, weld heat affected zone softens, strength decreases; 2) Clean oil and rust from weld area before welding; 3) Q235 uses E43 electrode, 45# uses J507, 40Cr requires preheating (150-200C) and post-weld tempering; 4) Important load-bearing parts recommend post-weld stress relief annealing.

Per GB/T 905, cold drawn flat steel precision grades: h8 (high precision, thickness +/-0.02mm), h9 (higher precision, +/-0.03-0.05mm), h10 (normal precision, +/-0.05-0.1mm), h11 (lower precision, +/-0.1-0.2mm). Commonly h9 and h10. Special h8 available on request. We can produce per customer precision grade and provide dimensional inspection reports.

Cold drawn flat steel has smooth surface without scale protection, exposed to humid air rusts more easily than hot rolled (no scale as barrier). Storage: 1) Store in dry ventilated warehouse, relative humidity <=60%; 2) Wrap with anti-rust paper or film; 3) Apply anti-rust oil; 4) Avoid contact with acids, alkalis, corrosives; 5) FIFO, storage period <=6 months. Rusted parts can be cleaned with sandpaper/wire brush then coated with anti-rust oil.

Stock sizes (Q235/45#, common dimensions): 500kg MOQ, 3-7 days. Special materials (40Cr/20Cr) and sizes: custom production, MOQ 2 tonnes, 15-30 days (including die making and cold drawing). Large orders can lock capacity for batch delivery per schedule.