A Methodology for Establishing a Machinability Database for Hot Rolled Steel Bar

A single point turning test method for establishing a generalized machinability database for bar steels is proposed by the Bar Application Group of the American Iron and Steel Institute. A unique aspect of this work is the large number of participants including steel companies, steel users, machining laboratories, and a tool manufacturer. The proposed test methodology to evaluate steel machinability, based on ISO 3685, is outlined. Variability in tool life data has been evaluated through a controlled round-robin test program for three steel grades: SAE1141, SAE1541, and SAE4140. Major factors contributing to variability in tool life studies include (1) machine dynamics, (2) tool wear measurement methods, and (3) premature tool failure prior to reaching a specified wear criterion. After addressing these factors, it is felt that the proposed test method can provide adequate single point turning test results to aid in the material selection process. Although work is ongoing to further understand and reduce the variability among the test laboratories, fourteen additional steel grades are currently being evaluated using the proposed guidelines.