1.What are the core evaluation indicators of surface finish?
Ra (Arithmetic Mean Deviation): The arithmetic mean (μm) of the absolute distances from each point on the profile to the baseline within the sampling length. The smaller the value, the smoother the surface.
Rz (Ten-Point Average Roughness): The sum of the averages of the five largest profile peak heights and the five largest profile valley depths within the sampling length (μm). This measure better reflects the macroscopic surface roughness.
2.How are European standard surface finish grades divided?
Normal Skin Pass:
Ra Range: 1.0-3.0 μm
Features: Surface with a slight rolling texture and no noticeable defects. Suitable for general structural parts (such as automotive chassis and building supports).
Smooth Skin Pass:
Ra Range: 0.5-1.0 μm
Features: Smooth surface with a fine rolling texture. Suitable for applications requiring painting or moderate appearance requirements (such as appliance housings and automotive interiors).
Super Smooth Skin Pass:
Ra Range: ≤0.5 μm
Features: Surface with a near-mirror finish and no noticeable texture. Suitable for applications requiring high appearance requirements (such as high-end appliance panels and decorative parts).
3.How are Japanese standard surface finish grades divided?
Normal Rolling (No. 1): Unfinished, with noticeable milling streaks on the surface, Ra ≈ 3.0-5.0 μm. Used for structural parts with low aesthetic requirements.
Bright Rolling (No. 2D/2B):
No. 2D (cold-rolled, annealed, matte): Ra ≈ 1.5-3.0 μm. Suitable for pre-painting.
No. 2B (cold-rolled, bright annealed): Ra ≈ 0.8-1.5 μm. Smooth surface with a slight gloss. Used for home appliances, automotive exterior panels, etc.
Mirror Rolling (BA): Super-finished, Ra ≤ 0.5 μm, with a mirror-like finish. Used in high-end decorative applications (such as elevator panels and precision instrument housings).
4.How are American standard finish grades divided?
Regular Skin Pass: Ra ≈ 1.0-2.5 μm, suitable for structural parts, pipes, etc.
Smooth Skin Pass: Ra ≈ 0.5-1.0 μm, used in applications requiring painting or a high-quality appearance (such as automotive bodies and electrical appliance housings).
5.What are the differences in lightness requirements for different scenarios?
For the architectural/structural sector (such as photovoltaic racks and steel structures):
For applications requiring low appearance, a standard finish grade of Ra = 1.5-3.0 μm is typically selected, with the focus on corrosion resistance rather than surface smoothness.
For the home appliance sector (such as refrigerator side panels and washing machine housings):
For applications requiring both appearance and paint adhesion, a finish grade of Ra = 0.8-1.5 μm is often used to ensure a uniform coating with no noticeable grain.
For the automotive sector (such as exterior body panels and door frames):
For high-end vehicles, a super-finish grade of Ra ≤ 0.5 μm is required to ensure a mirror-like finish after painting; for standard vehicles, this requirement can be relaxed to Ra = 0.5-1.0 μm.
For the decorative sector (such as elevator panels and furniture fittings):
For applications requiring a mirror-like finish, a super-finish or polished finish of Ra ≤ 0.3 μm is selected, and some may even require secondary polishing (e.g., Ra ≤ 0.1 μm).