Taking the simplified one hydraulic valve body and the two multi way valve body for loader as the research object, the position and size of the defects in the casting process of the valve body were simulated and analyzed, and the strength of the hydraulic valve body with casting defects was analyzed and calculated, and the following conclusions were obtained:

(1) During the filling process of the casting, when the liquid metal just enters the cavity, the filling is not stable, resulting in splashing; and because the cavity of the multi-channel valve body casting is complex, the flow resistance is large, the phenomenon of multiple streams of liquid intersection occurs, but in the later filling process, the pouring is gradually stable, which can effectively prevent the formation of air entrainment and slag inclusion defects.

(2) When the valve body casting material is nodular cast iron 500-7, with the increase of pouring temperature, the maximum porosity increases gradually, and the most suitable pouring temperature is 1360 ℃; compared with steel-304 stainless steel, when the valve body material is nodular cast iron QT500-7, the volume of shrinkage cavity in the valve body casting is relatively small due to the expansion of graphite which makes up part of volume shrinkage during solidification.

(3) In view of the problem of shrinkage in the casting process of valve body, the structure of valve body was improved. The maximum porosity of the improved valve body was 31.4%. Compared with the valve body before the improvement, the shrinkage defects of the improved valve body were reduced, and the porosity was reduced by 2.9 times.

(4) For the two-way hydraulic multi-channel valve, due to the complex structure of the multi-way valve body, there are many narrow and long special-shaped holes and grooves in the complex inner cavity valve body with high integration degree, forming hot spot, which makes the shrinkage resistance of the casting larger during solidification. There are many shrinkage positions in the valve body, and the maximum porosity is 72.7%.

(5) In the solidification process of multi-channel valve, there are many narrow and long special-shaped grooves intersecting in the complex inner cavity valve body with high integration degree, forming hot spot, which makes the casting have large shrinkage resistance during solidification. There are many positions of shrinkage holes in the valve body, and the maximum porosity is 72.7%.