The role of columnar crystals in scab formation during stainless steel ingot rolling

At high-temperature deformation the cast metal exhibits mechanical anisotropy. The role of columnar crystals in the formation of the defects on the stainless steel ingots manifests itself in the fact that, owing to geometric buckling, they turn to angle of 45 deg to the axis of the ingot as the maximum tangential stresses, which aid the formation of these defects, act along their joint lines. This mechanism is typical to the ingots obtained with open electric arc melting. In order to reduce the effect of the above factor it will be necessary to provide for the orientation of the columnar crystals such that the corresponding angle is close to 90 deg. In this case the ''dangerous'' 45 deg angle of the joint line would occur after the metal has already been deformed to some extent and aquired the appropriate plastisity margin. As far as the geometric buchling factor is concerned, the required processing plastisity of the ingot can be ensured if the inclination angles of the columnar crystals to the axis are under 45 deg, which can be obtained by controlling the process of crystallization, for example in electroslag or vacuum arc remelting