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Common Defects in Casting Components and the Causes

1. Slag holes in casting components

Features: The slag hole is an open hole or a dark hole on the casting components, all or part of which is filled with slag, and the shape of which is irregular.

Reasons for formation: The slag hole is mainly caused by the alloy smelting process and the pouring process. The mold itself will not cause the slag hole, and the metal mold is one of the effective methods to avoid the slag hole.

Prevention methods of slag holes in casting components:

1) The pouring system is set correctly and the cast fiber filter is used.

2) Adopt inclined pouring method.

3) Choose flux and strictly control quality.

2. The cracks on casting components

Features: The appearance of the crack is a straight line or an irregular curve. The surface of the hot crack fracture is strongly oxidized, which is dark gray or black, and with no metallic luster. While the cold crack fracture surface is clean and has a metallic luster.

Reasons for formation: The metal mold itself is not regressive, and the cooling rate is fast, which easily increases the internal stress of the casting components. If the opening of the mold is too early or too late, or the pouring angle is too small or too large, it is also easy to cause cracks.

Prevention methods: 

1) Pay attention to the craftsmanship of the casting components structure, so that the parts with uneven wall thickness of the casting components will be uniformly transitioned, and the appropriate fillet size should be used.

2) Adjust the thickness of the coating to make every part of the casting components reach the required cooling rate as much as possible, which can avoid the formation of too much internal stress.

3) Pay attention to the working temperature of the metal mold, adjust the inclination of the mold, and timely pull the core to crack, and take out the casting to cool down slowly.

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