Optimization of turning cutting parameters for casting austenitic stainless steel CF8M used in industrial ball valves

Abstract

Ball valves are widely used in industrial applications due to their high sealing efficiency and operational simplicity.Their performance depends on the contact between a metallic ball and a PTFE sealing element, making the surface finish of theball critical to ensure tightness and prevent leakage. In this context, this study investigates the optimization of cuttingparameters in the turning of ball valve components using the Box–Behnken Design (BBD). Twenty-one balls made of castaustenitic stainless steel ASTM A351 CF8M were machined by varying the depth of cut, feed rate, and cutting speed. Surfaceroughness was evaluated using a contact profilometer, adopting an average roughness criterion of < 0.4μm, required toguarantee proper sealing performance. Statistical analysis revealed that the feed rate was the most influential parameter,contributing 77.38% to surface roughness variation. Optimal machining conditions were identified as cutting speed between200 and 240 m/min, feed rate of 0.08 mm/rev, and depth of cut between 0.3 and 0.5 mm, resulting in values below 0.4μm.Experimental validation confirmed a significant improvement in surface finish compared to the current process. The proposedoptimization provides a practical reference for machining parameter selection in the turning of an austenitic stainless steelvalve ball.