Dimensions and Shape Accuracy

Thickness Range: 0.30–3.5mm (Mainstream specifications 0.5–2.0mm)

Thickness Tolerance: According to Q/BQB 401, standard accuracy ±0.03–0.08mm, high accuracy ±0.01–0.03m

Width: 600–1500mm (Common 1000/1250mm)

Length: 2000–6000mm (Fixed length/Unfixed length)

Flatness: ≤5mm/m (Standard accuracy), ensuring fit during subsequent processing.

Surface Quality and Roughness

Surface Condition: Annealed + Smooth (S), Default is Matte (D), Glossy (B) optional

Surface Quality: FB (higher-grade finish) is the default, FC/FD can be upgraded as needed

FB: Minor scratches and indentations are allowed, do not affect molding and painting

FC: No obvious defects on the better side, the other side ≥ FB

FD: No defects affecting appearance on both sides, suitable for appearance parts

Surface Roughness (Ra): Matte 0.6–1.9μm, Glossy ≤0.9μm

Appearance Requirements: No scars, cracks, inclusions, delamination, steel strip is allowed to be delivered with defects but ≤6% of the total length.

Special Performance Requirements

Tensile Strain Marks: SPCC has no warranty period, SPCD ≥3 months, SPCE ≥6 months without Lüders bands (avoid surface tensile marks)

Oil Supply: Default is rust-preventive oil, will not rust within 6 months, oiling can be agreed upon.

Production Process and Key Control Points

Steelmaking → Continuous Casting: Low-carbon steel (C≤0.12%), LF refining to control P and S, slab homogenization annealing.

Hot Rolling → Pickling: Hot rolling temperature 900–1100℃, laminar flow cooling; hydrochloric acid pickling (HCl) to remove oxide scale, surface roughness Ra≤3.2μm.

Cold Rolling: Six-roll/four-roll mill, multi-pass reduction (total reduction 20–50%), precise control of thickness tolerance, lubricated rolling to ensure surface quality.

Continuous Annealing: 650–750℃, nitrogen-hydrogen protective atmosphere, recrystallization to eliminate work hardening and restore plasticity.

Leveling → Finishing: 0.5–2% light reduction leveling to eliminate yield plateaus and adjust surface roughness; slitting, cutting to length, surface cleaning and oiling.

Inspection and Packaging: Batch-by-batch inspection (chemical composition, mechanical properties, surface finish, dimensions). Packaging conforms to Q/BQB 400, providing moisture and rust protection.

Inspection and Acceptance Rules

Inspection Batch: Same brand, same specification, same processing condition, same heat treatment, ≤30 tons.

Sampling: Chemical composition: 1 sample per furnace; Mechanical properties, bending, hardness: 1 sample per batch, transverse sampling.

Judgment: Single item failure allows for double retesting; if retesting still fails, the entire batch is rejected.

Arbitration: Based on GB/T 228 (tensile strength), GB/T 232 (bending), and SAE J911 (roughness).

Our Factory's Internal Control Upgrade Key Points (Benchmarking Industry Advanced Standards)

Precise Composition Control: C≤0.10%, Alt≥0.025%, P, S≤0.030%/0.020% respectively, improving deep-drawing performance.

Upgraded Precision: Mainstream thickness tolerance ±0.01–0.02mm, flatness ≤3mm/m, suitable for precision structural components.

Surface Consistency: Ra stable at 0.8–1.2μm, FB surface with zero obvious defects, meeting the appearance requirements of home appliances and chassis.

Performance Stability: Yield strength fluctuation ≤15MPa, elongation ≥38%, ensuring consistency in batch processing.

Green Production: Pickling wastewater reuse rate ≥98%, waste acid and iron oxide scale fully recycled, meeting environmental protection requirements.