Billet finish refers to the surface condition and overall appearance of aluminum billets at the end of the casting process and prior to any further processing such as extrusion, forging, or rolling. While the internal metallurgical quality is critical, the surface finish of aluminum billets plays a key role in ensuring smooth downstream processing and final product quality.

1. Purpose of Billet Surface Finish Control

• Ensures consistent feedstock quality for extrusion or rolling

• Reduces surface defects in extruded or forged products

• Minimizes equipment wear and die damage

• Supports high-quality anodizing or coating in finished parts

2. Characteristics of Aluminum Billet Finish

a. As-Cast Finish (Standard Finish)

• Light gray metallic appearance

• Smooth to moderately rough surface depending on cooling rate and mold design

• May show minor surface marks or casting rings

• Fine oxide film naturally present on the surface

b. Homogenized Billets

• Surface remains similar in appearance to as-cast

• Improved internal microstructure but surface may appear duller due to heat treatment

• Often slightly oxidized due to high-temperature exposure

c. Scalped or Machined Billets

• Top surface layer removed to eliminate casting skin and surface imperfections

• Bright, clean metallic surface

• Ideal for critical applications (e.g., aerospace, high-quality extrusion)