After the sand casting is cleaned, the fluorescent wet magnetic particle flaw detection is carried out. The total number of flaw detection cracks is more than 30, the longest crack is about 50mm and the depth is about 10mm. The flaw detection cracks on the outer surface of sand castings are shown in Figure 1.
There are generally 2 cracks on the outer surface at this position, with a crack length of 6mm and a depth of about 2mm. The number of sand castings with cracks accounts for 50% of the total number of castings, and 1-3 cracks are occasionally found in other positions. Cracks on the inner surface 1# core are generally found at the cold iron joint or behind the cold iron. The crack length is 20 ~ 50mm and the depth is 5-10mm, which is uncertain.
The sand castings with cracks account for about 90% of the total number of sand castings. The flaw detection of sand casting 1# core is shown in Figure 2. The cracks at the 2# core of sand mold casting are shown in Figure 3. There are more than 10 cracks at the 2# core, which are generally concentrated under the riser and at the small arc where the stiffener intersects the plane. The length of the crack is 20 ~ 50mm and the depth is 3-8mm.
The sand castings with cracks account for more than 95% of the total number of sand castings. The peripheral crack of cold iron and the crack of No. 2 core need to be solved from the aspects of casting process design, casting fillet, chemical composition control and pouring process.