抄録
It is imperative that one should observe, how various defects in iron and steel occur while manufacturing or using them. The present writer, taking 15 cases, tested and explained in a metallographical and mechanical way. The causes of breaks or cracks, as they were observed, were mainly due to the poor chemical composition of the materials, the un-uniformity of its distribution, the crystalsegregation, the segregation of blowholes or slags. the incompetency of working or treating temperature, the un-uniform distribution of internal stress, the overworking, etc. Therefore, test should always be made of each individual case, considering the property and employment of each material.
