Causes of cracking during the forging of bars

Conclusions

• 1. The columnar zone in forged billets of alloy ÉI 437B results in anisotropic plastic properties. In upsetting along the ingot (billet) axis, the metal is more plastic in the direction of the long axis of the columnar crystals than in the direction normal to it. The lower the temperature and the higher the amount of deformation, the more pronounced is the anisotropy. It is apparently a result of the difference in plasticity between the interior of the grains and the rigid intergranular skeleton.

• 2. Such an anisotropy leads to microcracks during upsetting of ingots and bars with traces of columnar structure.

• 3. To eliminate the anisotropic plasticity of columnar grains and the danger of cracking during forging, the process must be conducted within narrow temperature and deformation limits. These conditions, however, are not always applicable to the central equiaxed zone. Hence, the presence of traces of columnar structure in bars intended for upsetting to heavy-duty parts of complex configuration, is highly undesirable.