By studying the composition, constitution size distribution and time of occurrence, the author has found out sand marks to be the product of reaction between ladle brick and molten steel. The reaction, considered theoretically, gives explanation on occurring procedure and its composition.

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The authors have examined burning condition in the small cupo1a. The results of experiment is as follows:
(1) It produces CO₂ and CO gases at the same time.
(2) Melting zone sohows concave state.
(3) The wall is exceedingly fused by materialsm slag and gases.

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The authors have found below gains by the improvement of charging.
(1) Reduction of fuel. (about 15%). (2) Got rid of hanging shelf of the wall.
(3) Shortening of melting time. (4) Elevation of tapping temperature.
(5) Reduction of the wall erosion (about 50%).

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The main cause of deficiencies in a cupola operation followed by the use of low grade coke has been consumed as the reducing action of coke for CO₂ of furnace gas to CO.
To prevent this undesirable action of low grade coke, the coating of coke with the calcium carbide slime was taken in the present study. 1/2t cupola was operated by those coated coke. The effect of the coating on the reducing action of coke was investigated.
Results obtained were summarized as follows:
(1) The coating of coke with calcium-carbide slime shows a decreasing of the reducing action for CO₂ to CO.
(2) The temperature of molten metal is rised 20-50°C by the coated coke.
(3) CO₂% in the furnace gas taken at the top of cupola and the amount of coke consumption are lowered.

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In order to determine the effects of oxygen-acetylene gas-cutting on steel plate, we have measured the temperature distribution in steel plates during the cutting procedure of steel plates 10mm thick of various carbon contents under equivalent conditions.
We have examined also the variation of micro structures as well as mechani calproperties, and how the latter being improved by the heat treatment after cutting procedure.

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