The room temperature crushing strength was tested for the metallised iron pellets obtained by hydrogen reduction of six kinds of self-fluxing pellets and two kinds of acid pellets under rising temperatures at a rate of 0.19 K/s up to 1273 K.
The degree of swelling during the reduction was small for the all pellets compared with that under isothermal reduction, but the strength was unexpectedly low. This was found to be due to the formation of large cracks in some pellets. The formation of microcrack in the remaining slag phase also appeared to have further decreased the strength.
The strength tended to increase as the basicity of the pellets increases up to about unity and above this it decreased remarkably. This was attributed to the strength of the slag phase at low temperatures where the reduction step from hematite to magnetite was almost completed with the development of considerable stresses.
The effect of the increase in the slag content was cancelled out by the appearance of relatively large macropores in such pellets.
The acid pellets also resulted in low crushing strengths because they had little slag phase and hence the number of the remaining bonding between the iron particles in the pellets became small.
(Received September 19. 1980)
*Department of Metallurgical Engineering, Faculty of Engineering, Osaka University, Suita, Osaka 565, Japan.
**Department of Metallurgical Engineering, Faculty of Engineering, Osaka University. Now, Murata Machinery, Ltd., Kyoto 601, Japan.
© 2002 The Japan Institute of Metals
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