Operating conditions of cupola by low grade coke and properties of molten metal were investigated. Results obtained were summarized as follows: (1) The temperature of molten metal is rised with increasing of charge coke ratio and blast volume. (2) CO₂% in gases taken at the top of cupola is lowered when the temperature of molten metal is higher. (3) The position of melting zone is lowered to CO₂ rich atmosphere and the molten metal is more oxidized on the condition of too low height of bed coke and low charge coke ratio or too much blast volume. (4) The melting velocity increases with increasing of blast volume and diecreases with increasing of charge coke ratio. (5) The best operating condition by our low grade coke was concluded as follows; (a) Height of bed coke on tuyere level; same as internal diameter of cupola, (b) charge coke ratio; 16, 15 or 14% respected to the capacity of cupola 1/2, 3 or 5 ton. (c) Blast volume; 11, 55 or 80 m³/min. respected to the capacity of cupola 1/2, 3 or 5 ton.

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1) Types of fractures by tensile test of quenched and tempered steel vary from cup-, radial-, cone types and these correspond increasing Charpy values. By steel not quenched, for instance only normalised, such regulalities are not found.
2) By low carbon steels, such as case hardening steel, radial fractures are not seen, even in the case where the Charpy value is such as to produce radial fractures in structural steels.
3) The results have shown that there is little or no difference between the types of fractures of Cr- and Cr- Mo steel.
4) The comparison between water- and oilquenched case hardehing steels shows that the edge of watcr quenched steel is more apt to be broken off, where the both water- and oil quenched shows cup type fractures.

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