Aluminium and aluminum alloy billets surface defects: Cinch marks and pull cracks

Aluminium and aluminum alloy billets surface defects: Cinch marks surface defects of aluminium billets

Cinch marks surface defects of aluminium billets

Cinch marks, pull cracks

When the frictional resistance between the solidified shell formed during the casting and the mold wall exceeds the strength of the ingot log itself, a cinch mark is formed on the surface of the ingot log.

In severe cases, transverse cracks on the surface of the ingot log are called cracks.

Features of  cinch marks and pull cracks:

Sometimes the sagging occurs at the cracks. This defect destroys the continuity of the ingot log structure and should be scrapped in severe cases.

Milling or turning can be performed only when the depth of the cinch marks and cracks does not exceed the machining allowance of the billet log.

Causes of cinch mark and pull cracks:

1.The inner surface of the mold is not smooth, has burrs, scratches, and poor lubrication;

2.The casting mold installation is skewed, which causes a great frictional resistance on the side when the ingot log is lowered

3. During the casting, the metal melt level uneven will be caused liquid aluminum leakage, thus suspension;

4.The casting speed is fast, the casting temperature is high, and the large casting water pressure is likely to cause cinch marks and pull cracks;

5. Casting mold cooling water scaling;

6.The casting mold is annealed or overfired.

Solution for cinch mark and pull cracks:

1. Ensure that the graphite ring is smooth, and the sludge is applied tightly and evenly;

2. Install the casting mold correctly and control the liquid level reasonably;

3.Reduce the casting speed and temperature appropriately;

4. Regularly clean the scale in the mold;

5. Do not use casting mold that has been burned by the melt materials.

6. Properly increase the cooling water pressure to ensure uniform cooling along the periphery of the billet log.

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