According to the process scheme optimized by previous simulation, the manufacturing process of sand casting scheme is used for sand mold manufacturing and processing, and core assembly pouring is carried out to obtain the sand casting of engine cylinder head. The cleaned sand casting is shown in Figure 1.
Shot blasting can ensure that the sand on the surface and inside of the sand casting is cleaned, and there are no casting defects such as shrinkage cavity, porosity, air hole and cold shut on the surface of the sand casting.
The dimensional accuracy of sand castings is tested by three-dimensional scanning testing equipment. The test results are shown in Figure 2. The green area indicates that the dimensional deviation is within ± 0.3mm, the blue area indicates that the deviation is less than -0.3mm, and the yellow area indicates that the deviation is more than + 0.3mm. The overall size of sand castings meets the requirements of dimensional accuracy of castings.
Dissection and flaw detection were carried out on the sand casting. There was no air hole defect inside the sand casting. Figure 3 shows the dissection and flaw detection results of key positions of the casting. The overall shrinkage and porosity level of the sand casting met the requirements of CT3.
The overall surface quality of the casting is slightly poor. Figure 4 shows the side of the engine cylinder head. The upper half is formed by laser sintering casting sand mold, which can be seen that there are obvious step lines on the surface, and the lower half is formed by digital Moldless casting sand mold. The surface quality has no step lines, which is better than that formed by laser sintering sand mold. If the surface quality requirements of some parts of sand castings are high, it needs to be solved by grinding the sand mold or selecting processing molds for individual sand molds.
| Si | Fe | Cu | Mn | Mg | Zn | Ti | Sr |
| 9.21 | 0.03 | 0.28 | 0.30 | 0.37 | 0.17 | 0.034 | 0.016 |
The chemical composition test results of casting alloy are shown in Table 1, and the alloy is controlled within the technical requirements.
| Tensile strength (n / mm2) | Yield strength (n / mm2) | Elongation (%) | Hardness (HB) |
| 320 | 295 | 1.5 | 101 |
The test results of mechanical properties of the test bar after T6 heat treatment are shown in Table 2. The tensile strength, hardness and elongation meet the performance requirements of the casting. Its metallographic structure matrix is α Solid solution + granular eutectic silicon, as shown in Figure 5.
