1) A casting is a material that is integrally cast in a mold, with uniform stress distribution and no restriction on the compression direction.

The forging is pressed by the force in the same direction. The internal stress is directional and only can afford the directional pressure.

With the same material and wall thickness of the part, forgings are better than castings from material and crystal structure.

2) For valves, the wall thickness of castings of the same pound grade and material shall be greater than the forgings, and the compressive strength shall be equal to the forgings.

3) Castings have high requirements for casting process and can make complex shapes. The valve body structure and flow path are irregular,casting can be formed at one time. As long as the casting process arrangement is reasonable, large-diameter valve body can be casted successfully.                                     

Forging have a good compactness of the final product. but for too complex flow path and shape, they cannot be formed at one time, so they need to be forged in modularization separately and welded together for the final product, So the size of forging parts are limited.

4) Forgings cannot be processed into complex and streamlined flow channels. The flow channels are processed by turning, and many sharp corners are formed inside the part. These sharp corners are easy to cause uneven stress and cracking.

5) And the same time for the modular welding design, the diameter of the forged valve seat is relatively fixed. For some valve sizes, the diameter should be too small,it will affect the flow capacity which increases the valve flow resistance and reduces the efficiency of the whole system.

6) Due to the limitations of the forging process for the large-size valves and in order to save costs at the same time, many manufacturers currently adopt the  castings in the center structure of the valve body and forgings for both end structure.

7) No matter castings or forgings, there may be product defects during processing. The main defects of castings are sand holes and blowholes etc. and the main defects of forgings are large grains, cold hardening, cracks and crazings etc. in order to obtain the qualified product , correspondingly the castings need a heat treatment to eliminate the stress inside the part which obtained during the casting process, and other X-ray, magnetic particle inspection and penetrant inspections etc.                                                                                           For forgings,  that need strict heat treatment for the weld line and the corresponding detection methods. Forgings often need ultrasonic inspection. In addition, the welding process need formulate very strictly. The qualification of welding engineer is also the key to ensure product quality.

8) No matter what kind of raw materials are used for the valve, strict quality controls are required, and there should be standard testing procedures to ensure the quality of the valve.