20 Types of Casting Defects [Their Causes & Remedies] PDF

In this article, you’ll learn what are Casting Defects? How do they occur? what are the causes and remedies for the casting defects.

You can also download the PDF file of this article at the end.

What are Casting Defects?

Casting is the process by which a liquid material is poured into a mold containing a hollow cavity of a desired shape, and then cooled. The cooled part, also known as a casting, is removed or broken from the mold to complete the process.

This process involves applying high pressure to the molten metal. Due to this, it is prone to several unwanted phenomena which may compromise the quality of the final products. These are called casting defects, causing significant problems for manufacturers.

Castings can contain a variety of defects, each with its own characteristics, causes, and remedies. Identifying the causes and defects of casting is crucial. Therefore, you can prevent these imperfections proactively and deliver high-quality products.

Here are specific examples of defects that can appear in casting process, along with the causes and remedies of each type of defect. So let’s get started.

Read Also: Different Types of Pattern in Casting Process (Explained)

Types of Casting Defects

Following are the major types of casting defects:

1. Mismatch
2. Swell
3. Pinholes
4. Blow holes
5. Open holes
6. Cut and washes
7. Fusion
8. Drops
9. Metal penetration
10. Shrinkage defect
11. Run out
12. Slag inclusion
13. Hot or hard spot
14. Hot tear or crack
15. Col shut
16. Dirt
17. Misruns
18. Honeycombing or Sponginess
19. Fins and burns
20. Warpage

#1 Mismatch

Also known as shift, it is a casting defect usually caused by misalignment of the mold’s top (cope) and bottom (dope) parts. Sometimes it may occur due to misalignment of the core at the parting line.

There are mainly two types of mismatch: mold shift and core shift. Mold shift indicates mold misalignment and is often visible as horizontal displacement. Whereas core shift is caused by misalignment of the core, which appears as a vertical displacement.

#2 Swell

Swell refers to the enlargement of the mold cavity. This is due to the pressure of the molten metal, resulting in local or overall elongation of the casting product. It usually takes the shape of a slight, smooth bump on the surface of the casting. Consequently, its feeding and machining requirements will increase, resulting in wasted metal.

#3 Pinholes

Pinholes are also casting defect that occurs at the top of a die-cast part. These are small holes of about 2 mm, usually found in poorly ventilated pockets on the upper surface of the workpiece.

These holes are clearly visible, meaning that no special equipment is required to identify them. Generally, they appear in large numbers either on top of the casting or just below.

#4 Blow Holes

Blow holes are large holes that form inside a cast workpiece. Blowholes are formed when gases entrapped on a casting’s surface after solidifying form a rounded or oval cavity. These holes are not visible to the naked eye. To detect them, you will need X-ray, ultrasonic, harmonic, or magnetic analysis.

Read Also: 23 Types of Metals: Their Properties & Applications [Explained]

#5 Open Holes

When the metal is cast into a mold, open holes appear on the surface of the metal due to the entrapment of air. This type of casting defect is round or oval on the surface of the casting. It often has a smooth surface with a bright yellow or white color.

After casting, you can identify gas porosity defects by visual inspection. In addition, to check for this defect on non-machined surfaces, you need an X-ray device.

#6 Cut and Washes

Cuts and washes are areas of excess metal that appear when molten metal erodes the molding sand. In castings, cuts are low projections that decrease in height as they extend along the drag face.

In this case, the sand does not have enough strength to resist erosion. Cuts and washes usually tend to the side where the liquid metal pressure is higher.

#7 Fusion

It is also a casting defect usually observed when grains of sand mix with the flowing liquid metal. As a result, a thin layer of hard, vitreous crust forms firmly attached to the casting. This is mainly due to the low refractoriness of sand. The low refractoriness of sand prevents it from resisting the liquid metal’s high temperatures.

#8 Drops

This mainly occurs when the casting is still in liquid condition. A drop-casting defect occurs when cracks appear on the top surface of the sand, causing sand pieces to fall into the melting metal.

Thus, an unusual and irregularly shaped projection is formed on the surface of the casting. In addition, it can also cause the metal surface to be dirty and unusable.

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#9 Metal Penetration

These defects can be observed in situations where molten metal enters openings or gaps in the molding sand. As a result, this results in a rough and uneven surface finish of the casting, which is clearly visible.

It is mainly because the grain size of the molding sand is too coarse, which prevents the proper flow of the liquid metal to the mold. Thus, it will acquire a rough and irregular surface, reducing its aesthetics.

#10 Shrinkage Cavity

When holes are created in the casting due to volumetric contraction, this is sometimes referred to as shrinkage cavities.

#11 Run Out

There is a phenomenon known as run out, which occurs when liquid metal leaks out of the mold, causing a casting to be incomplete or missing.

#12 Slag Inclusion

As a result of the pouring of molten metal containing slag particles into the mold cavity and the solidification of the molten metal, slag inclusions occur. The defect is usually found on the surface of the casting. This lowers the mechanical properties of the final product.

The appearance of the defect is a ribbon-like entrance or pocket with sharp edges and irregular shapes. Many other types of inclusions are available to look for, such as sand, nails, dirt, or oxides. It is only a few millimeters thick. You can easily see them without using any tools.

Read Also: 10 Different Types of Corrosion in Metals [Prevention Methods]

#13 Hot or Hard Spot

These types of casting defects occur when an area on the casting cools faster than the surrounding material. A hot spot refers to a part of the casting that is harder than its surrounding area. It is also referred to as a hard spot in some cases.

#14 Hot Tear or Crack

During the cooling process of the molten metal, residual stress (tensile) in the material causes the casting to fail. In this case, the failure of the casting looks like a crack, which is called a hot tear or crack.

This defect is usually observed during the solidification of the metal casting. Some cracks are obvious and can easily be seen with the naked eye, while others may require specialized equipment. This is commonly noticed as irregular or linear patterns on die-cast parts.

#15 Cold Shut

Cold shut is also a type of crack with rounded edges. Two streams of molten metal enter the mold from two gates, and when these streams meet at a junction with low temperatures, they do not fuse and form a cold shut. It is visible with the naked eye and often causes the cast to reject, creating a weak spot.

#16 Dirt

Dirt can also cause serious casting defects. Dirt defects result from the embedding of dust and sand particles in the casting surface.

Read Also: Understanding Different Types of Welding Joints

#17 Misruns

Misruns are related to cold shut which occurs when the liquid metal is too cold to flow to the ends of the mold cavity before freezing and solidifying. In this case, the liquid metal does not fill the mold cavity. Misruns refer to the empty part or space in the mold.

#18 Honeycombing or Sponginess

A type of casting defect that occurs when there is a collection of small cavities present within the metal casting that are close to each other, and appear in close proximity to one another.

#19 Fins and Burns

Fins and burns are one of the most commonly occurring casting defects. Also known as flash, it is unwanted and additional material attached to the casting metal. It is typically formed by a thin sheet of metal that forms at the edges of the parting line. It is a waste material that turns into slag after melting.

#20 Warpage

In casting, warping refers to an undesirable deformity that can occur over the course of time, which can impact the shape and dimensions of the final product as a result. This usually occurs during or after solidification. It causes the metal to be rolled into flat or large sections.

Closing It Up

I hope I have covered everything about this article “Casting Defects“. If I missed something, or if you have any doubts, let me know in the comments. If you liked this article, please share it with your friends.

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