Compression tests were performed on as-cast and heat-treated specimens of the alloys Nos. 1∼12 in report No. 6. The summarized results were as follows: (1) As the hardness of primary crystal increased, the yielding stress increased from 30 to 140 kg/mm2, but was not affected so much by C% of alloys. (2) At about constant strain of 1%, the compressive stress increased almost in proportion to the hardness of the specimens, but at 0.3% strain the compressive stress varied markedly for the specimens having the same hardness. The factors causing this variation seemed to be the S, C contents, the melting and the casting conditions and the heat-treatment of the alloys. (3) The specimens having hardness of above 60HRC fractured vertically or were crushed to pieces, at about 1% strain and the stress of about 320 kg/mm2. On the other hand,the specimens below about 55HRC fractured on the plane about 45° to the compressed axes, at the stress of 160∼280 kg/mm2 and about 3∼30% strain.
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