the influence of inclusion in casting

Inclusions in castings mainly affect the fatigue strength, processing performance, and structural properties of the castings, and are also one of the reasons for casting cracks. Everything has advantages and disadvantages, the same to the inclusions. Excessive quantities affect the quality of castings and cause casting defects, controlling within a certain range is conducive to solidification and nucleation of castings.


In casting, the sources of inclusions are mainly endogenous and exogenous sources:

Endogenous inclusions (The type and composition of endogenous inclusions depend on the smelting process and alloy composition of the alloy.)

1.Degassing and desulfurization products, especially some high-density deoxidation products, are not removed in time.

2.As the temperature of the alloy decreases, the solubility of elements such as sulfur, oxygen, and nitrogen decreases correspondingly, and reaches supersaturation. These supersaturated precipitated components remain in the casting in the form of low-melting eutectic or compound.

Exogenous inclusions

1.The sticky sand, rust, slag on the surface of the alloy liquid and the metal material, as well as the non-metallic inclusions generated by the interaction with the furnace lining, cladding lining, etc.

2.The alloy liquid is oxidized by the atmosphere to produce oxides. The exogenous inclusions are mostly oxides with complex composition, their size is large, the shape is mostly polygonal, and the distribution is irregular.

The influence of inclusions on castings.

The bad influence

1.Affect mechanical properties such as impact absorption and fatigue limit. A certain amount of inclusions inevitably exist in various castings. Oxidation inclusions in these inclusions have a great influence on the impact absorption energy of steel castings. Inclusions will reduce the fatigue strength limit of the material. The larger the inclusions, the lower the fatigue limit of the material. Inclusions are often the source of cracks in part fracture. Sharp-angled inclusions cause stress concentration and accelerate the destruction of parts.

2.Affect casting performance. When the alloy contains solid inclusions, its fluidity decreases. The low melting point inclusions distributed on the grain boundaries are one of the reasons for the cracks in the castings. Low melting point inclusions can also promote microscopic shrinkage and porosity in castings.

The good influence

In some cases, non-metallic inclusions have a good effect on the quality of cast iron. For example, the oxides and sulfides in steel and the phosphorus eutectic in cast iron can increase the hardness of the material and increase the wear resistance. Some refractory non-metallic inclusions can become the core of non-spontaneous crystallization and refine the structure of the casting.

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