STUDY ON SOLIDIFICATION PROCESS OF INGOTS (I)

Sampling method of molten steel near the solidus in the large ingot during solidification process

Abstract

The defects that appear in an ingot such as flakes, ghóst streaks and sand marks are produced the moment the steel solidifies from liquid into solid by the difference of physical and chemical properties between molten and solid steel. But even if physical and chemical properties both in liquid and solid steel were known completely, yet it would be very difficult to grasp the actual situations of what were going on during each of the various processes which manifold kinds of molten steel must go through in actual casting operation until they became solidified.
Then the author wished to investigate the variation of chemical element and gases content of molten steel near the solidus in the large ingot during solidification process. For the purpose of this investigation the author established a method of sampling of molten steel near the solidus.
A sampler as shown in Fig. 2 and Photo. 4 was immersed into molten steel in a mold and let it approach nearly to solidus, then was kept for a certain period of time in that position.
The copper plate would soon melt away to fill the molten steel into the guartz tube which was then withdrawn.
The author collected the molten steel from the position without failure by dipping the sampler in the molten steel for between 35 and 75 seconds under the conditions of the temperature at 1480-1510°C at the sinkhead part of an ingot of 9-20 tons below surface of the molten steel 1-2.5m.
The molten steel in the tube was water-cooled and used for analytical samples of chemical components including hydrogen, oxygen, nitrogen and various oxides.