| Stainless steel has been applied widely, but it is a kind of hard-to-cut materials and work hardening of this steel is very severe when cutting. AISI 440C stainless steel is considered as martensitic stainless steel, which is characterized with high carbon content, strength, hardness and wear resistance but poor in machinability. AISI 440C stainless steel has been widely used in engineering for steam valves, water valves, bumps, turbines, compressor components, shafting, cutlery, surgical tools, plastic moulds and nuclear applications etc. To widen the applications of AISI 440C stainless steel, the optimization of the machinability for AISI 440C stainless steel is a problem to be solved.A new method for cutting AISI 440C stainless steel forms as the flexibility of hardened turning expands. In this research, AISI 440C stainless steel is directly turned for finishing after heat treatment. During the experiment, cutting forces, surface roughness and residual stress are measured. The feasibility of hard cutting AISI 440C stainless steel is verified by taking surface roughness and residual stress as evaluating indicators.Cutting force is one of the most important physical parameters, which directly influence machining precision and machining quality. In this research, operations are experimented under orthogonal design by considering the characteristics of tool material and AISI 440C stainless steel and the test shows that lower cutting force can be obtained under cutting conditions of high cutting speed, low feed and small cutting depth.Surface roughness is an evaluating indicator of surface integrity, which has been found to influence wear resistance, corrosion resistance and fatigue strength of workpieces. In this research, single factor turning operation is experimented and the test shows that lower surface roughness can be obtained under cutting conditions of high cutting speed, low feed and small depth of cut. A mechanical model is established in order to study the mechanism of surface roughness generation.Residual stress is another evaluating indicator of surface integrity. It has been found that residual stress and its distribution under the surface influence the fatigue life of workpieces. In this research, AISI 440C stainless steel is cut under single factor test and surface residual stress is measured. The results show that surface residual stress of hardened turning by PCBN tool is residual compressive stress and the magnitude ofresidual stress changes with cutting parameters. The maximum residual stress isdistributed in a layer 25 to 30μm below the surface. The results also show that cuttingparameters influence the magnitude of maximum residual stress but not the distributioncharacteristics.
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