Production Process, Surface Finishes and Main Grades of Cold Rolled Stainless Steel Sheets

 

1. Core Production Process

Raw Material Pretreatment: Hot rolled coils (3–6 mm thick) are shot-blasted and pickled to remove oxide scale for qualified surface quality in subsequent rolling.

Multi-high Cold Rolling: Mainly processed by 20-high rolling mills for low deformation resistance and high precision. Rolling is conducted at room temperature to reduce the thickness to 0.3–3.0 mm, with thickness tolerance controlled within ±0.01 mm.

Annealing for Softening: Cold working leads to work hardening, which increases strength but reduces ductility. Continuous annealing is applied for recrystallization to eliminate internal stress and restore ductility. Measures are taken to prevent carbide precipitation for austenitic stainless steel.

Temper Rolling & Straightening: Temper rolling improves surface gloss and flatness to form 2B or BA finishes. Flattening corrects plate shape, ensuring flatness no more than 1 mm per meter.

Finishing & Protection: Products are cut to fixed lengths and inspected. Protective films are applied to avoid scratches before labeling and warehousing. Extra polishing is required for high-end mirror finishes.

2. Surface Finishes & Key Parameters

2B (Standard Matte Finish, Most Widely Used): Processed via cold rolling, annealing, pickling and temper rolling. Silver-grey uniform matte surface with surface roughness Ra 0.1–0.5 μm. Ideal for general decoration and stamping.

BA (Bright Annealed Finish): Annealed under protective atmosphere to achieve mirror-like bright surface with Ra ≤ 0.05 μm. Applied to high-end home appliances, elevator interiors and medical devices.

2D (Dull Finish): Cold rolled, annealed and pickled without temper rolling. Rough surface with Ra 0.5–1.5 μm, suitable for deep drawing and internal industrial components.

8K Mirror Finish: Polished based on 2B or BA surface, Ra ≤ 0.01 μm. Used for architectural curtain walls and luxury products.

Specifications: Thickness 0.3–3.0 mm; Common width 1000/1219/1500 mm; Length 2000–6000 mm.Typical Mechanical Properties (304, 2B): Yield strength ≥240 MPa, Tensile strength ≥550 MPa, Elongation ≥45%.Executive Standards: GB/T 708, ASTM A240, EN 10088, JIS G4305.

3. Main Grades & Features

304 (18-8 Austenitic Steel): The most versatile grade with excellent corrosion resistance, good stamping performance and weldability. Used for home appliance panels, kitchen utensils and elevator interiors.

316L (Low-carbon Molybdenum-containing Steel): Outstanding resistance to acid, alkali, seawater and chloride ions. Suitable for heat exchangers, medical devices and marine decorative parts.

430 (Ferritic Steel): Nickel-free material with good thermal conductivity and cost advantages. Widely used for gas cooker panels, washing machine drums and decorative strips.

201 (Nickel-saving Austenitic Steel): Low nickel and high manganese design with high strength and cost-effectiveness. Applied to decorative panels, furniture and elevator door casings.

301 (High-carbon Austenitic Steel): Remarkable work hardening capacity and good elasticity, perfect for spring strips, precision stampings and electronic components.

4. Differences Between Cold Rolled and Hot Rolled Stainless Steel

Comparison Items	Cold Rolled Stainless Steel Sheet	Hot Rolled Stainless Steel Plate
Processing Temperature	Room temperature (no recrystallization)	1150–1250°C (above recrystallization temperature)
Thickness Range	0.3–3.0 mm (thin gauge)	3.0–200 mm (heavy gauge)
Surface Condition	2B / BA / Mirror (highly smooth)	No.1 (matte and rough)
Dimensional Accuracy	Thickness tolerance ±0.01 mm, excellent flatness	Thickness tolerance ±0.5 mm, ordinary flatness
Material Performance	High strength, good ductility and stamping performance	Low internal stress, good weldability and structural rigidity
Production Cost	Relatively high due to complex processes	Relatively low for mass production
Main Applications	Decoration, home appliances, precision parts	Structural components, storage tanks, industrial equipment