What are different types of Casting defects - Causes and Remedies

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1. Mould Shift or mismatch

In The sand casting when upper and lower part do not aligned together properly, the path will be shifted from it's desired position. it causes due to inappropriate making or preparation of mould cavity.

Causes

1. Misalignment of cope and drag part of mould cavity while preparing mould. Samsung
2. defective tools used for preparation which causes the improper making of mould cavity.

Remedies

That tools should not be defective and should align properly.
2. The Cope and drag part should be mounted properly.
3. Correct placement of the pattern.
4. Molten material should be poured carefully.

2. Misrun

Sometimes when the molten metal is poured in the cavity, the solidification of the metal takes place in a quick manner. the metal solidifies so quickly that the metal can't occupy the whole cavity and some part of the cavity is not filled by the molten metal. this defect is known as mis- Run

Causes

1. Narrow parts of sections of the mould.
2. Low temperature of molten metal.

Remedies

1. Narrow sections should be avoided otherwise temperature of the molten metal should be sufficient for these fractions.
2. Temperature and fluidity should be analysed. If we keep these two factors correct the problem of Misrun can be overcome.

3. Cold shut

This defect in casting often occurs when two gates to pour the molten metal is employed. when molten material is filled with two gates the material meets inside the cavity. at the place of junction, a proper fusion of these materials is required. if the temperature of the metal is not appropriate, the fusion of the molten metal can be improper. a line or edge at the junction will be formed this line or edge indicates the defect of cold shut in the casting.

Causes

1. Low Temperature of molten metal
2. Lack of fluidity of molten metal.

Remedies

1. Higher temperature of molten metal should be achieved
2. Fluidity of the metal should be controlled by pressure and temperature.

4. Shrinkage of molten metal

After Pouring the molten metal solidification takes place. During  the solidification the shrink in the material occurs, and because of this shrinkage in the metal the cavity is not filled up to the requirement and casting remains shorter.

Causes

1. Higher temperature of the metal is main reason behind this defect.
2. Miscalculation of allowances.
3. Improper solidification of molten metal

remedies

1. Shrinkage allowance should be provided to the pattern during its preparation.
2. The temperature of molten metal should not be very high.

5. Microporosity

This defect is hard to detect as it occurs at microscopic level. But this weakens the final casting. This porosity left when the solid station is about to be completed. It generally occurs at near the walls or sand edges the microporosity is detected product undergo for testing processes.

Causes

1. Higher solidification time.
2. Gases  entrapped in the cavity.

Remedies

1. Solidification time should be reduced.
2. Gating system should be improved for the gases to be removed from the cavity.

6. Metal Penetration

This defect takes place when the grain size of the casting sand is thick. The molten metal combines or fused together with the sand at the surfaces. This results the surface to be very rough and uneven. The appearance of the product is bad.

Causes

1. Large or thick size of sand grains.
2. Improper ramming of sand while preparing mould.
3. Lower strength of the sand.
4. Temperature of the molten metal aise high

Remedies

1. Casting sand of fine grain size should be used.
2. The extra material due to metal penetration on the surfaces can we chipped off later.
3. Higher temperature should be avoided.
4. Ramming of the moulding sand should be proper.

7. Blow holes

The mould cavity contains some gases inside before pouring the molten metal. When we pour the molten metal some part of these gases get entrapped inside the material. After solidification of molten metal the round cavities is formed on the surface of the final product these cavities are called blowholes.

Causes

1. Sand is rammed to hard.
2. Sand contains excess moisture
3. The grains of sand is too fine.
4. Inappropriate use of organic binders
5. Venting of the mould is not proper.
6. The tools like chills, chaplets contains moisture.

Remedies

1. Ramming of the mould should be less hard.
2. Excess moisture should be removed from the sand.
3. Use the sand of thicker grains.
4. Proper venting should be provided to the mould.
5. The tools used like chills and chaplets should not have impurities.

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