Tutorial: Engineering technology Topic: Castings defects Prepared by: Ing. Elena Nová Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/ je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

Castings defects

 Defects are divided according to activity where they originated: 1. Defects at casting and solidifying 2. Forming defects

Defects at casting and solidification 1. Slag inclusions – At casting slag has not been retained -> surface faults, inner defects

 Structure precipitation – Casted material does not solidify equally (solidification goes from outside to inside) -> on a thicker walls maybe created cavities, -> called shrinkages (these will not happen if the casting walls are of equal thickness).  Babbles in casting structure – Wet forming sand releases hydrogen and oxygen at the cast temperature and if not properly removed the gasses will enter the structure of  the casting

 Cast tearing – Diameter of transitions have been constructed too short (solidification of thicker parts have been slower) -> a bigger metal cooler parts are inserted into moulds with bigger diameter -> managing of cooling process  Segregation – Starts segregating of casted parts at solidification and uneven distribution of alloying parts -> different properties of material inside and outside of the cast.

 Residual stress – Shrinkage cavity is hollow parts initiated at the cooling process.

 Faults initiated at forming 1. Offset, reject casting – Is caused if forms don’t matched exactly 2. Edge or oval thickening – if the form is not sufficiently rammed -> hydrogen and oxygen recede under the casted material pressure.

 strojirenstvi.studentske.cz/2008/10/kontrola -vady-odlitk.html