In casting production, even with advanced equipment and mature processes, quality defects may still occur.

Understanding defect types, root causes, and preventive measures is essential for improving quality and reducing rejection rates.

1.Porosity

Porosity is one of the most common casting defects, appearing as small holes inside or on the surface of castings.

Causes:

·Excess gas content in molten metal.

·Severe turbulence during filling.

·Improper venting design.

Solutions:

·Optimize gating design to reduce turbulence.

·Control melting temperature and perform degassing treatment.

·Improve venting systems.

2.Cold Shut

A cold shut occurs when two streams of molten metal fail to fuse properly, leaving a visible seam.

Causes:

·Low pouring temperature.

·Insufficient filling speed.

·Improper gate location.

Solutions:

·Increase pouring temperature.

·Optimize gating layout and shorten flow paths.

·Improve mold preheating.

3.Shrinkage Cavity & Shrinkage Porosity

Shrinkage cavities usually appear in thick sections due to insufficient feeding during solidification.

Causes:

·Inadequate feeding system design.

·Large wall thickness variations.

·Improper solidification sequence.

Solutions:

·Optimize riser or pressure feeding systems.

·Adjust design for uniform wall thickness.

·Control cooling rate.

4.Inclusions

Inclusions refer to non-metallic impurities trapped inside the casting.

Causes:

·Impurities not removed during melting.

·Oxide films entrapped during pouring.

Solutions:

·Improve melt purification.

·Optimize gating to reduce air entrapment and oxidation.

5.Surface Defects

Surface defects include sand sticking, cracks, and rough surfaces.

Causes:

·Improper mold surface treatment.

·Unstable temperature control.

Solutions:

·Improve mold coating.

·Enhance temperature monitoring.

6.Defect Differences in Low Pressure vs Gravity Casting

·Low pressure casting typically reduces porosity due to smooth filling.

·Gravity casting, with faster flow, is more prone to turbulence-related defects.

·Automated control systems significantly reduce human-related defect risks.

7.Conclusion

Casting defects are not unavoidable; the key lies in understanding their mechanisms and optimizing processes and equipment.Through proper gating design, temperature control, and automation, brass casting quality can be greatly improved.