Inclusions modification and improvement of machinability in a non-quenched and tempered steel with Mg treatment

Abstract

To explore the effect of Mg on the inclusions and machinability in a non-quenched and tempered steel, the industrial tests and machining experiments were carried out. The evolutions of the inclusions after Mg treatment were described and the machining effects between Mg addition and non-addition were compared. The results show that with Mg addition of 13 ppm, most of the long-strip inclusions above 50 µm were transformed into spindle and spherical inclusions with the sizes below 50 µm, and the density of inclusions increased from 197 to 356 mm2. The percentage of composite inclusions increased from 9.23 to 28.38%. The machining experiments show that the surface roughness of steel decreased from 4.64 to 2.81. After Mg–Ca treatment, the tool wear decreased from 0.164 to 0.113 mm, and the percentage of C-type chips increased from 24.37 to 79.03%.