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EN
This article deals with the effect of selected machining parameter values in hard turning of tested OCHN3MFA steel in terms of SEM microstructural analysis of workpiece material, cutting forces, long-term tests, and SEM observations of flank wear VB and crater wear KT of used changeable coated cemented carbide cutting inserts in the processes of performed experiments. OCHN3MFA steel was selected as an experimental (workpiece) material. The selected experimental steel was analyzed prior to hard turning tests to check the initial microstructure of bulk material and subsurface microstructure after hard turning and chemical composition. Study of workpiece material’s microstructure and worn cemented carbide cutting inserts was performed with Tescan Vega TS 5135 scanning electron microscope (SEM) with the X-Ray microanalyzer Noran Six/300. The chemical composition of workpiece material was analyzed with Tasman Q4 surface analyzer. All hard turning experiments of the used specimens were performed under the selected machining parameters in the SU 50A machine tool with the 8th selected individual geometry of coated cementite carbide cutting inserts clamped in the appropriate DCLNR 2525M12-M type of cutting tool holder. During the hard turning technological process of the individual tested samples made of OCHN3MFA steel, cutting forces were measured with a Kistler 9257B piezoelectric dynamometer, with their subsequent evaluation using Dynoware software. After the long-term testing, other experiments and results were also realized, evaluating the influence of selected machining parameters with different cutting insert geometry on the achieved surface quality.
EN
Machining of materials is recognized as removing unwanted materials by using different cutting inserts. In this research, cutting inserts used are CBN inserts and treated cryogenically at -196°C in liquid nitrogen chamber. The inserts are subjected to 30 hours of treatment in controlled atmosphere. The materials used are Titanium and AISI 440 C hard Martensitic Stainless steel. The cutting parameters are cutting velocity 30, 40 and 50 m/min with feed rate of 0.05, 0.10 and 0.15 mm/rev and depth of cut of 0.05, 0.75 and 1.00 mm. The performance evaluated was tool wear, surface roughness. Cryogenically treated CBN inserts produced less tool wear on titanium than AISI 440 C Martensitic stainless steel. The roughness produced was low at high cutting speed with low feed rate. Flank wear was not progressive and varied. In turning AISI 440 C stainless steel, built up edge formed in all cutting speed which is a common phenomena and lead to crater wear formation. The chips produced were saw tooth chips by both materials.
EN
Purpose: The experiments with different operating parameters using CBN and PCBN tools on hard AISI 440 C material were investigated in this paper. Design/methodology/approach: In this research AISI 440 C stainless was used under hard condition. The cutting tools are having three cutting edges and each edge repeated for 5 times. The test conducted by each cutting edge was termed as trail 1, 2, 3, 4 & 5. The length of cutting was 150 mm and each trail. The surface roughness and flank wear, crater wear and BUE were measured by SEM. Findings: The surface roughness was low by CBN at high turning cutting speed and the flank wear was high. The surface roughness was high by PCBN tool than CBN tool and flank wear recorded was low for PCBN tool than CBN tool. The chips produced were saw tooth in all operating parameters. The CBN tool was unable to withstand heat at cutting zone and hence more flank wear occurred. The PCBN tool sustained the temperature and less tool wear occurred. More crater wear formed on PCBN tools where as CBN tool produced less crater wear. The formation of crater wear on the rake face was due to rough surface of the saw tooth chips. Practical implications: The investigation results will provide useful information to applying CBN and PCBN cutting tools in hard turning stainless steels. Originality/value: Hard turning is a latest technology and possible to turn all hard materials. The hard turning produce net shaped products and reduces machining time, low cost per products, etc. The difficult to cut materials like stainless steels was turned by super hard cutting tools like CBN and PCBN to achieve good urface roughness, dimensional control and reduced tool wear.
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