IMPROVEMENTS IN STEEL MACHINABILITY DEPENDING ON MATERIAL PROPERTIES.

CORRELATION BETWEEN METALLURGICAL PROPERTIES AND MACHINABILITY (M) OF STEELS IS DISCUSSED. AMONG THE FACTORS INFLUENCING M ANALYZED ARE: CHEMICAL COMPOSITION OF STEEL, ITS HEAT-TREATED STRUCTURE, COLD WORKING, IMPURITIES, ETC. TYPES OF FREE-CUTTING STEELS ARE CLASSIFIED WITH ATTENTION PAID TO STEELS INCLUDING SULFUR AND SULFUR COMPOUNDS, STEELS FOR MACHINE CONSTRUCTION AND STEELS WITH IMPROVED M. EXAMPLES OF CONCRETE STEELS WIH IMPROVED M ARE PRESENTED. IT IS POSSIBLE TO IMPROVE MACHINABILITY BY ADEQUATE COLD WORKING AND HEAT TREATMENT. OTHER IMPROVEMENTS SUCH AS THE REDUCTION OF GEAR HOBBINGTIME IN SCM440 WITH HB300 BY ADDING A SMALL AMOUNT OF S, AND THE IMPROVEMENT OF MACHINED SURFACE ROUGHNESS BY ADEQUATE COLD WORKING ETC. ARE ALSO INTRODUCED IN THIS PAPER. IN JAPANESE WITH ENGLISH ABSTRACT.