Which is better, casting, forging, or welding?

It depends on the purpose of the object.
After forging, metals can improve their microstructure and mechanical properties. After hot working deformation through forging method, the casting structure transforms from coarse dendrites and columnar grains to equiaxed recrystallized structures with finer and uniformly sized grains due to metal deformation and recrystallization. This compacts and welds the segregation, looseness, porosity, slag inclusions, etc. inside the steel ingot, making the structure more compact and improving the plasticity and mechanical properties of the metal.
The mechanical properties of castings are lower than those of forgings of the same material. In addition, forging processing can ensure the continuity of the metal fiber structure, keeping the fiber structure of the forging consistent with the shape of the forging, and ensuring the integrity of the metal streamline, which can ensure that the parts have good mechanical properties and long service life. The forgings produced by precision forging, cold extrusion, warm extrusion and other processes are incomparable to castings