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This study attempted to find a simpler method for modifying hydrogen storage alloys that are used as anodes in Ni‐MH batteries to prolong their cycle life. The alloy was modified by mechanical grinding with cobalt metal powder. A short grinding time yielded samples with a higher discharge capacity and longer cycle life than those of the alloy which was mixed with the cobalt powder without the mechanical treatment. However, prolonged grinding caused a decrease in the discharge capacity because of amorphization of the alloy by mechanical stress. We believed the formation of a cobalt compound on the alloy surface plus closer contact between particle enhanced the cyclic durability and discharge capacity of metal hydride anodes.

L arge nonmetallic inclusions in the slabs cast continuously by the bow-/..ype machine accumulated within the upper part of slab, that is, the inside radius /m rt of casting machine. Nl ost of such nonmetallic inclusions were caused mainly by the erosion of tundish immersion nozzle and by the reoxidation of molten steel secondly. The characteristic accumulation of large non metallic inclusion were caused by the inclination of the upper shell of steel from the vertical during casting and these phenomena were eX/llained theoreticall),. T herefore, the bow-type machine had the disadvantage of trap/ling large nonmetallic inelusions compared with the vertical type and the vertical ty/le with bendillg. In order to decrease the ' in/JUt of nonmetallic inclusiolls. the following /JI'ecau tions are necessmy,' 1) Sealing of molten steel stream with AI' gas from ladle to tUlldiJh 2) Right selection of tem/lerature alld com/los it ion of molten steel, in the case 'if using twulish immersion lIo:::)e made of fu sed silica 3) Selection of material ~r tlllu/ish immersion no ::::le which excels in alltierosion to molten steel. III order to remove large nonmetallic inclusions as much as /lOssibie, the following measures are im/lortant ; 4) The slow s/Ieed ~r molten steel stream at the outlet of tundish immersion nozz le 5) Selection of the shape of tundish immersion lIo::::le advantageous to accomJllish the good floala lion qf inclusions i" mollen sleel

Solidification behaviours in the continuolls(y cast slabs of mild steel were determined by addition of radioactive gold and solute distribution in the slabs under various casting conditions was analysed, comparing with lhe solidification stmctures. From these experimental data, the flow velocity in Ihe liquid jlool and solute segregation in the cenler of the slab s were estimated mathematically, using the boundary layer Ihe01Y and partial mixing model in liquid. The liquid f low along the shell is comjlosed of the nou le jet, the natural convection and the bulging flow , the amount of its velocity being 10 to 40 Clll /sec, 1 to 2.5 clll/sec and 2 to 4 cm/sec. The cenler segregation is mainly caused of solule redistribution during uni-directiollal solidification in colulIlnar Cly stal reg ion , which inlensity is strongly dependent on the rate of solidification and Ihe liquid flow, especially the bulging flow. T o reduce the center segregation , increasing Ihe equiaxed c,ystals and minimiz ing the bulging were eifective, which are relaled to lhe amount of cooling water, casting speed, casting temjlerature , slab Ihickness and Ihe machine arrangement .

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