In the first two parts of this series, we examined the basic definition of grain flow and described the anisotropic properties in metals because of it. The mechanical properties that require the sample to fracture or break will be enhanced when the crack needs to propagate perpendicular to grain flow. The crack is microstructurally diverted when this happens, requiring more energy to propagate, thus enhancing the properties. The second article showed that the raw material that arrives into a forge shop already possesses a grain flow from the suppliers’ operations. We also examined how forging imparts additional changes to grain flow. In this part of our series, we will examine in more detail the effect of forging on grain flow and look at the parameters that affect it.
During the forging process, the metals (and the underlying grains) will plastically deform in the path of least resistance. The metal will flow in the direction and manner that requires the least amount of work. This principle is fundamental. During this deformation, the forging process will impart some grain flow into the metal and the grains. The primary forging parameters that affect grain flow are: