6 Common Investment Casting Defects: Causes, Prevention and Solutions
Jun 12, 2026
6 Common Investment Casting Defects:
Causes, Prevention and Solutions
When procuring industrial castings such as pump housings, valve bodies, agricultural machinery parts, or construction machinery components, many quality issues originate in the casting process—long before assembly begins.
Defects such as shrinkage cavities, porosity, sand inclusions, cold shuts, uneven casting, cracks, and dimensional deviations can affect: product performance, processing efficiency, assembly accuracy, and delivery schedule.
Some defects are subtle and may not be detected during basic visual inspection. They typically only become apparent during CNC machining, pressure testing, or final on-site installation.
Understanding these defects helps you evaluate suppliers and mitigate project risks early on.
I. Six Common Fundición a la cera perdida Defects
1. Shrinkage
Shrinkage porosity refers to irregular, rough-surfaced voids forming inside a casting.
Causes: Inadequate casting structure, improper gating and riser design, excessively high pouring temperature, high shrinkage rate of the molten metal, high levels of gas and oxide inclusions in the molten metal reducing fluidity and feeding capacity, improper mold assembly, poor heat dissipation of the mold shell, and incomplete filling of the riser and pouring cup during pouring.
Prevention: Improve casting structure to minimize hot spots; design a proper gating and riser system for sequential solidification; select an appropriate pouring temperature; improve the smelting process to reduce gas and oxide content in the molten metal; ensure proper assembly and improved heat dissipation; ensure the riser and pouring cup are completely filled with molten metal during pouring.
2. Centralized pores
Causes: Poor mold permeability, preventing gas from escaping the mold cavity during casting; Insufficient mold firing, leaving residues in the mold material and gas-generating substances in the shell-making material; Cold mold casting, or mold being damp; High gas content in the molten steel and poor deoxidation; Inadequate gating system design, leading to gas entrapment during casting.
Prevention: Improve mold permeability, adding vents if necessary; Thoroughly fire the mold; Use hot mold casting to prevent mold from becoming damp; Improve deoxidation methods; Optimize the gating system structure.
3. Sand inclusions
Cause: Localized delamination of the inner shell layer occurs, and during pouring, molten metal fills the delaminated areas, causing surface bulges in the casting.
Prevention: Measures such as controlling sand application quality, optimizing coating viscosity and uniformity, shortening the interval between coating and sand application, appropriately matching hardening and drying temperatures, improving fusible mold wettability, and selecting low-linear-modification refractory materials can prevent delamination and thus avoid defects.
4. Incomplete casting (undercasting), cold shut
Incomplete filling of the mold cavity by molten metal results in missing castings.
Causes: Low pouring and mold temperatures; severe oxidation of the molten steel; excessively thin casting walls; poor gating system design; insufficient mold firing/poor permeability; slow pouring speed/interruption; insufficient pouring volume.
Prevention: Increase pouring/mold temperature; optimize smelting process to improve molten metal quality; design a suitable gating system for thin-walled parts; ensure adequate firing and improve mold permeability; increase pouring speed and avoid interruptions; ensure sufficient pouring volume.
5. Hot Cracking
Hot cracking refers to intergranular cracks that form during the high-temperature solidification stage of a casting, with an oxidized surface.
Causes: Caused by factors such as unreasonable casting structure, inadequate gating system design, poor mold shell collapse, high levels of metallic impurities, and improper temperature control during pouring and mold shelling.
Prevention: Prevented by optimizing the casting structure and gating system, reducing the high-temperature strength of the mold shell, improving the smelting process, properly controlling the pouring and mold shelling temperatures, and improving cooling conditions for crack-prone areas.
6. Cold Cracking
Cold cracking is a penetrating crack that occurs after the casting has cooled to an elastic state, caused by casting stress exceeding the material strength or external impact, resulting in a bright fracture surface.
Causes: Related to unreasonable casting structure and gating system, excessive residual stress, and poor metal quality.
Prevention: Prevented by optimizing the structural design, improving the mold shell collapse, avoiding severe impacts to the casting, and improving the quality of the molten metal.
II. Longway Real-World Project Case Studies
In one of our recent pump casing manufacturing projects, we encountered a pump casing with a complex structure and significant variations in wall thickness, making it highly susceptible to problems such as porosity, sand inclusions, and cold shuts. To address the porosity issue, we implemented measures such as adding vents to improve the permeability of the mold shell and using hot-casting to prevent moisture absorption. To prevent sand inclusions, Longway adopted measures such as shortening the interval between coating and sand application, appropriately matching the hardening and drying temperature, improving the wettability of the fusible mold, and selecting low-linear-change refractory materials. For cold shut defects, we improved the quality of the molten metal by increasing the casting temperature and speed and optimizing the smelting process. Ultimately, after the first batch of trial production, all parameters of the pump casing products met the customer’s production standards, and the overall pass rate increased to over 98%.
Are you planning a new casting project?
Our engineering team can review your drawings and identify potential manufacturing risks before production begins. We can provide: process recommendations, material recommendations, tolerance assessments, machining assistance, feasibility analysis, and quotation support.
Please send us your drawings or specifications so we can discuss your project.