Characteristics of crack cold partitions in castings
1. Cold cracking. A crack formed at a lower temperature […]
1. Cold cracking. A crack formed at a lower temperature after solidification of the casting. The split often extends through the grain to the entire section.
2. Hot cracking. A crack formed at a higher temperature in the late stage of solidification or after solidification of the casting. The section is severely oxidized, has no metallic luster, and the crack is generated and developed along the grain boundary, and the shape is tortuous and irregular.
3. Shrinkage (shrinkage crack). Cracks caused by improper filler shrinkage, shrinkage resistance, or uneven shrinkage. May appear just after solidification or at a lower temperature.
4. Heat treatment cracks. A penetrating or non-penetrating crack produced by a casting during heat treatment. Its section has oxidation.
5. Reticulated cracks (cracks). The metal type and the die-cast type are subjected to thermal fatigue due to the alternating thermo-mechanical action, and fine shell-like cracks formed on the surface of the cavity. Cast cracks form moiré defects on the surface of castings
6. Cold separation. Penetration or non-penetration on the casting, the edge is a rounded gap. It often appears on the wide f surface or thin wall away from the gate, the junction of the metal flow, and the chilled parts such as cold iron and core support.
7. White spots (split). Defects in steel mainly due to the precipitation of hydrogen. In the longitudinal section, it presents a silvery white spot that is approximately circular or elliptical, so it is called a white point; on a cross-section macro-grinding piece, it appears as a capillary crack after corrosion.
8. Casting is interrupted. A highly visible seam on the surface of the casting. Some parts of the seam are not well fused or separated. Caused by a break in the casting.
9. Heavy skin. During the filling process, due to the splash of molten metal or the fluctuation of the liquid surface, the solidified metal on the surface of the cavity cannot be fused with the subsequent metal, and the defect of the casting skin is folded.