錻力原鈑の表面疵に就いて

Abstract

The bad coating of the tin-plates are due to improper pickling and tinning operations. But in many cases, the surface defects of the iron base are found none the less the grave cause to be counted for these failures.The defects commonly seen on the surface of the iron base are those called "nebulous appearances, " the characteristic aspects of which are given in the shapes of seams, segregation, and recesses of which the embedded oxides have been pickled out.The Writer has investigated these surface defects in every step of the operation i.e. from the ingot making to the finishing of sheet, and come to the following conclusions.1) "Ingot seams" which are found in "cold cast" ingot carry oxides, blow holes, and segregations in the columnar crystal zone of the ingot.when the ingot is rolled to sheet bar, the lateral seams run stretched in broken succession towards the direction of rolling of the sheet bar as thin pencil lines. And this bar is again rolled in its turn in cross wise to the former rolling direction. So these longitudinal seams are extended to the wide parabolical zigzag bands developing the inclusions in the seams. These defective surfaces are washed off by pickling, leaving the rough and heterogeneous appearances.2) The thick dendritic structure grown in the columnar crystal zone of ingot is found in "hot cast" ingot. Such ingot of dendritic structure is liable to give rise to cracks in the ingot being reduced in the blroming mill, and the cracks, like ingot seams, cause bar mill seams and "nebulous appearances". While the ingot of dendritic structure is liable to form a very scaly sheet, and corrosion pits or sandy rough surface are formed after the sheet has been pickled.3) Generally, the above mentioned defects in sheet iron can be prevented by merely removing all adhesives and defective parts, if possible, before the ingot or sheet bars are reduced in the mill. Now open hearth heats of stabilizing chemical analysis together with a close watch of the temperature at which the steel is poured, regulating the rate of casting, will help to overcome these defects.