EXPERIMENTAL INVESTIGATIONS OF NITROGEN ALLOYED DUPLEX STAINLESS STEEL IN DRY MILLING PROCESS

Duplex stainless steels are generally more difficult to cut because of their high toughness, low heat conductivity, more strain hardening rate and more built-up edge formation. Milling is an important machining process for manufacturing flat, curved and profiled surfaces. In this work, an attempt has been taken to investigate the machining performance of two different types of cast duplex stainless steels in dry milling operation using coated tungsten carbide tools. A 15 run experiment was designed to investigate the effect of spindle speed and feed rate on the surface roughness and cutting force. The end milling experiments were conducted with five different spindle speeds and three different feed rates with a constant axial depth of cut. The result revealed that the increasing spindle speed decreased the surface roughness and the cutting force values up to 1000 rpm and then increased. The increase of feed rate increased the surface roughness and cutting force values. The presence of higher austenite in 5A grade duplex stainless steel was responsible for higher surface roughness and cutting force values compared with 4A grade duplex stainless steel.