Anatomically take samples from the same area of several cylinder head sand castings cast in different process schemes. The sampling position and number are shown in the figure. Conduct high/low power inspection on the samples respectively, and then conduct tensile test after heat treatment with the same solution aging treatment system. The average mechanical properties of the sand casting body samples under different structures and pinhole grades are obtained. Under the condition of no pinhole defect, With the secondary dendrite arm distance from 21 μ M increased to 56 μ m. The tensile strength and yield strength of the alloy are reduced by 25 MPa and 6 MPa, and the elongation is also reduced from 8% to 4.5%. The secondary dendrite arm distance has a great impact on the tensile strength and elongation of the alloy.
Secondary dendrite arm distance 40~45 μ When the pinhole of sand mold casting rises from 0 to 5, the tensile strength, yield strength and elongation of the alloy gradually decrease, with the maximum decrease of 25 MPa, 29 MPa and 3.5% respectively.