Effect of Total Residual Content (Cu+Cr+Ni) on the Machinability of AISI 1215 Steel

Abstract

The effect of total residual content (Cu+Cr+Ni) on the machinability of American Iron and Steel Institute (AISI) 1215 (UNS G12150) low carbon resulfurized free-machining steel was investigated jointly between Inland Steel Company in the United States and Nippon Steel Corporation in Japan. Three different machinability tests were used. At Inland, the automatic screw machine test using a modified version of the test method outlined in ASTM Method for Evaluating Machining Performance of Ferrous Metals Using an Automatic Screw/Bar Machine (E 618-81) was used. At Nippon, the automatic screw machine test with its own methodology and the cyclic plunge test were used. Three levels of total residual contents were obtained through addition of copper, chromium, and nickel in ingots. The amounts of these three elements were changed simultaneously to simulate practical conditions. The total residual contents obtained were 0.07, 0.20, and 0.28 wt%. The automatic screw machine test at Inland revealed that rough form tool life, based on part growth, deteriorates slightly when residual content is high. Poor surface finish is occasionally observed in medium and high residual content heats in the automatic screw machine tests carried out both at Inland and Nippon. On the other hand, no deterioration of surface finish was observed in the cyclic plunge test. Overall, the authors conclude the machinability of AISI 1215 steel deteriorates slightly when the total residual content becomes very high; however, it is not affected significantly within the range of normal total residual contents observed in these steels made in the BOF, that is, 0.05 to 0.12%.