In the die-casting industry, surface defects are common, with varying terminology across regions. For instance, flow marks (also called striations) are a typical issue. But what exactly are they, and how can they be resolved?
What Are Flow Marks?

Flow marks appear as smooth, recessed streaks on the casting surface, aligned with the molten metal's flow direction. Key characteristics:

    No progressive worsening (non-developing defect)

    Can be removed via polishing

Causes of Flow Marks

    Asynchronous Metal Flow

        Two metal streams fill the cavity unevenly, leaving visible traces.

    Low Mold Temperature

        Zinc alloys: <150°C

        Aluminum alloys: <180°C

    Excessive Injection Speed

        High-speed filling causes turbulent flow, leading to streaks.

    Excessive Mold Release Agent

        Over-application of lubricant disrupts metal flow.

Solutions to Eliminate Flow Marks

✅ Adjust Gate Design

    Modify ingate cross-section or position to ensure synchronized metal flow.

✅ Optimize Mold Temperature

    Increase mold temp to recommended range.

    Enlarge overflow wells to trap impurities.

✅ Control Injection Speed

    Reduce filling speed to achieve laminar flow.

✅ Apply Lubricant Properly

    Use thin, uniform coatings—avoid excess spray.