Professional Introduction to Stainless Steel BA Surface

1. Definition of BA Products

The JIS standard defines BA (Bright Annealed) as a surface that has been bright annealed after cold rolling. The national standard also defines it similarly, but the product standard for BA is no different from 2B, such as JIS, ASTM, and national standards.

2. Surface Classification of BA Products

BA products have varying surface grades, affecting glossiness. Unlike 2B, which is classified based on surface defects and maintains the same surface color, BA grades differ in both defects and surface states. The cold rolling rate determines the gloss, with thinner materials generally being glossier than thicker ones.

3. Gloss of BA Products

The gloss of BA products is determined by three factors:

Resolution: The clarity of an image reflected on the strip’s surface. Higher resolution means clearer images.
Haze: A whitish appearance due to surface roughness, causing random light reflection. SUS430 steel requires specific haze standards, unlike SUS304.
Coloring: The surface can appear brown or blue due to variations in the oxide film’s thickness. Consistent coloring is generally maintained unless unit errors occur.

Good gloss is achieved when resolution and haze are both optimal. High-resolution applications include watch straps, mirrors, battery tubes, and car window frames. Lower resolution is acceptable for sinks, pipes, and utensils. High-resolution requirements for SUS430 include heater reflectors, washing machine drums, and car light reflectors. White mist requirements are also high in applications like panel materials and home appliance panels.

4. Material Properties of BA Products

Whitening: Unique to SUS430, where surface unevenness is corrected during processing. Lower whitening requirements apply to general utensils and home appliance panels.
Buff Quality (BQ): BA products have better polishing quality than 2B. If 2B does not meet polishing needs, BA is recommended. SUS430 has slightly lower BQ than SUS304.
Grain Size (GS): Smaller grain size means coarser grains, softer material, and better bending and deep drawing properties, but rougher surfaces after processing. Larger GS improves polishing.
Soft Material: Slightly softer than JIS and national standards.
Gold Dust: Characteristic of SUS430, where surface roughness before rolling creates a shiny, gold dust appearance after processing. For lamination uses, indicate during ordering to increase inspection.
Anisotropy: Different R values (plastic deformation) along the rolling direction affect stamping performance and can cause lugging in deep-drawn parts. Controlled cold rolling rates improve anisotropy.

5. Examples of BA Product Uses

High-resolution applications: Watch straps, mirrors, battery tubes, car window frames.
Low-resolution applications: Sinks, pipes, utensils.
SUS430 specific applications: Heater reflectors, washing machine drums, car light reflectors, bicycle fenders, beer caps.