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Common Defects of Iron Castings

Learning the common iron casting defects is important for the iron casting purchasers. The buyers should be able to judge the common defects and give an reasonable treatment advices to the suppliers.

There are many different defects in iron castings, and knowing the defects and their causes are complex, and sometimes many different defects can be seen on the same appear on the castings.

In general, castings with a slight defects can be used directly. Castings with medium defects should be allowed to repair before use. If there are serious flaws in castings, only scrapped.

According to the working experience in Dandong Foundry, I listed the common casting defect types and causes as follows:

1. Air Hole

Air hole is the internal casting porosity or surface smooth holes of varying sizes.

It is because that molding sand has too much water, poor ventilation, sand core or sand core has bad drying, pouring temperature is too low or pouring too fast and so on.

2. Shrinkage

Shrinkage is located in section positions of castings. It is irregular shape with rough holes.

Casting shrinkage is because that gating system is incorrect, or the riser is too small; pouring temperature is too high, or the chemical composition of metal is not qualified.

3. Trachoma

Trachoma is also called sand hole, which is sand filled holes in the internal or on the surface of the castings.

Trachoma is due to the bad strength of molding sand, sand molds have part damage, gating system is irrational.

4. Slag

Slag is because the melting time is not sufficient, the cold metal left in the ladle, the filter is not good, pouring temperature is too low.

5. Staggered box

Staggered box causes the staggered positions at the parting line of the castings.

Staggered box is because that the wrong position of top sand box and down sand box, the upper and lower sand box is not aligned.

6. Sticky sand

The surface of castings is bonded by sand, so looks very rough.

Sticky sand is because the sand is not enough for fire resistance, pouring temperature is too high, no painting brush or painting too thin.

 

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