Macrostructure of a VIM (vacuum induction melted) ingot of Fe-52% Ni alloy. A slice was cut transverse to the ingot axis and hot acid etched (50% HCl at 70 °C) revealing the solidification pattern. There is a very thin surface zone of small grains. Below the surface, there is a zone of columnar grains and the central portion is equiaxed but coarse. The scale is in inches.
Transverse Concast Discs, 430 SS
Macrostructure of 5-inch square (127 mm) continuously cast billets of type 430 stainless steel (Fe – 0.03% C – 0.34% Mn – 0.48% Si – 17.78% Cr – 0.26% Ni – 0.05% Mo – 0.07% Cu) taken at three random locations along the strand. The discs were cut transverse to the growth direction and were hot acid etched. Note the thin region of fine grains at the surface, the large columnar zone and the central equiaxed zone (of varying coarseness). Note that there are some fine cracks present.