The hydraulic valve is an essential component in the hydraulic system. The performance of the hydraulic valve determines the performance of the whole hydraulic system. As the main part of the hydraulic valve, the valve body casting bears the high pressure load, and is also affected by the temperature and oil erosion. The quality of the valve body casting has become an important factor affecting the hydraulic technology.

(1) A model of a hydraulic valve body with casting defects is established to calculate the stress values of the ideal valve body and the valve body with shrinkage cavity under different pressures. The results show that the shrinkage not only leads to stress concentration, but also changes the structure of the valve body, greatly reduces the local effective wall thickness, reduces the effective pressure bearing area, reduces the bearing capacity of the valve body, weakens the strength of the valve body, and makes the maximum stress of the valve body with the shrinkage larger than the maximum stress of the ideal valve body.

(2) For the one-piece hydraulic valve body, when the pressure is 25MPa, although the maximum stress value of the valve body with shrinkage cavity before improvement is less than the yield limit, the fatigue safety factor is less than 1, which does not meet the fatigue strength; when the valve body structure is improved, the volume of defects in the valve body decreases, and the weakening of defects on the valve body strength decreases. When the pressure is 30MPa, the improved valve body has The valve body with shrinkage cavity can still meet the strength requirements. Therefore, the yield limit and fatigue safety factor should be considered when analyzing the strength of valve body.

(3) In the whole basin of multi way valve under different working conditions, because of the throttling effect of the valve port, the oil pressure at the throttle port is relatively low, and the speed at the valve port is relatively large; and because the flow direction of the oil flows through the valve port changes, the speed gradient at the valve port is relatively large, and the speed gradient near the valve core wall is greater than that near the valve body wall; and The temperature rise of the valve body and the valve core wall is higher than that of the valve body wall.

(4) Because of the existence of the shrinkage cavity, the change of oil flow area is smaller than that of the ideal valve body, which leads to the smaller pressure and velocity gradient in the area where the shrinkage cavity exists, so the temperature rise in the area where the shrinkage cavity exists is smaller.

(5) The strength of multi way valve body under different working conditions is calculated by the method of fluid structure coupling. The results show that the maximum stress value of the valve body is concentrated at the inlet of the middle oil passage of the valve body bucket coupling when the bucket is turning up and the boom is lifting, and meets the strength requirements when the load pressure is 16MPa.

(6) There are casting shrinkage holes between the oil passage and bolt hole, as well as on the middle oil passage of the valve body, which reduces the effective wall thickness, weakens the bearing capacity of the valve body, causes the stress concentration, greatly increases the stress of the valve body at the shrinkage hole, and weakens the strength of the valve body.