Sand hole defect of GEVO16 diesel engine cylinder block casting

GEVO16 cylinder block is the key casting of HXN5 locomotive diesel engine on the main line, with the main dimension of 3987 mm × 1 458mm × The casting quality is about 7.5 T, the maximum wall thickness is about 200 mm, and the minimum wall thickness is only 14 mm.

The technical requirements are relatively high, and the main bearing seat and other parts need to be subject to radiographic inspection with high requirements. The acceptance standard is in accordance with astm-e446-2015 and astm-e186-2010 for X-ray inspection, and it is required to reach grade II; Ultrasonic flaw detection shall be carried out on the ingate and cylinder head bolt hole.

  1. Production process

Furan resin self hardening sand core molding, molding sand strength greater than 0.6 MPa, using water-based zirconium powder coating. The lower ingate is introduced from the outside of the camshaft cavity, while the upper ingate is introduced from the outside of the horizontal bolt hole. The casting process diagram is shown in Figure 1.

  1. Existing defects

At the initial stage of trial production and small batch trial production of GEVO16 diesel engine cylinder block castings, it was found that there were sand holes in the water cavity boss of several cylinder blocks (as shown in Figure 2), which seriously affected the product quality and production progress.

  1. Defect analysis

Sand hole defect is a common defect in sand mold casting, which is a kind of hole defect wrapped with sand particles or sand blocks inside or on the surface of the casting. The existence of the defect will have a bad impact on the strength and sealing performance of the product, and it will also impact the tool in the next process, resulting in tool damage. Therefore, it should be solved as soon as possible. The cylinder block is processed continuously for 4 sets, and there are sand holes on the top of the water cavity of the cylinder block, and the position is relatively fixed. Due to the large size of the cylinder block and the core forming process, there are a large number of sand cores, and the operation of the next core process is relatively complex. The whole process is sorted out, and the root cause of the problem is carefully found

(1) The structure of GEVO16 cylinder block is complex. The boss at the bottom of the water cavity is located in the middle of the bottom of the mold cavity, and the structure of the water cavity core blocks this part, which makes it difficult to clean and inspect the residual sand in this part during the assembly of the sand core.

(2) The sand core between camshaft cavity core and waist round hole core is not reasonable. Although it is relatively easy to lower the core, there is sharp angle sand in some parts, which is easy to cause collapse when lowering the core, resulting in broken sand falling into the cavity.

(3) During core setting, the square window between the upper side plate core and the V-shaped core and the contact edge between the upper side plate core are easy to produce sand rubbing, and it is difficult to remove the broken sand after it falls into the mold cavity.