Behavior of nonmetallic inclusions in front of the solid-liquid interface in low-carbon steels

Abstract

The present study is concerned with the interaction phenomena of nonmetallic inclusions in front of a moving solid-liquid interface. The in situ observation was done in a high-temperature experiment by using a laser microscope. Alumina inclusions in an aluminum-killed steel with low oxygen content exhibited the well-known clustering behavior. The velocity of the advancing interface first increased while approaching the particle, but became stagnant during engulfment and increased again after that. Alumina-magnesia complex inclusions in a magnesium-added steel with high oxygen content were very finely dispersed in the molten pool. These inclusions escaped from the advancing interface during solidification, but gathered again at the retreating interface during remelting. The tiny inclusions were thought to behave just as tracer particles of a local flow. The velocity of particles was measured on a video image, and the significant acceleration or deceleration was found near the interface. It was concluded that the flow was induced by the Marangoni effect due to the local difference in temperature and oxygen content in front of the interface, particularly in the case of a higher oxygen content. However, the flow was weak in the case of a low oxygen content.

Effect of Mg Addition on the Evolution of Inclusions in Al–Ca Deoxidized Melts

“…4,32,33) By using in-situ CSLM observation, Kimura et al found that alumina-magnesia complex inclusions on the surface of molten steel have a much weaker tendency to aggregate and to form clusters than alumina inclusions. 34,35) It is probably a good idea that the inclusions after calcium treatment can be refined through magnesium addition. Once the addition time is appropriate, the residual large inclusions are refined, which can improve the final quality of steel.…”

“…The size of inclusions reduces to 2 μm probably due to the modification of the contact angle and interfacial tension between inclusions and molten iron. The work of Kimura et al 34,35) can approve it indirectly. The reason for this interesting phenomenon is complicated, and it should be paid more attention in the following research.…”

Precipitation Behavior of Copper, Tin and Manganese Sulfide at High Temperature in Fe-10%Cu-0.5%Sn Alloys

“…The principle and the method of operation of the laser microscope have been described in detail elsewhere. 7,[18][19][20][21][22][23][24][25] Fe-10mass%Cu alloys 7,18) and Fe- (Received on August 29, 2005; accepted on October 6, 2005 ) Tramp elements such as Cu or Sn cause a severe hot shortness. Any tramp elements have been rejected and diluted below a certain limit by the use of virgin iron source.…”

Interaction mechanism of non-metallic particles with crystallization front

“…refinery products in the ladle (mainly deoxidation), which were not sufficiently removed from the liquid metal and which moved with the liquid metal to the mould, as well as the secondary precipitates, which were generated while casting. The final distribution of precipitates in the ingot is a consequence of the co-existing processes of precipitation, agglomeration and interaction with the crystallization front [1][2][3][4][5]. These processes are responsible for a non-homogeneous distribution of non-metallic inclusions, which mainly manifests itself in the concentration of contaminants in the central part of the ingot.…”