| 摘要 |
<p>The present invention is particularly to Tungsten Carbide as tool insert with 24 hours holding time of cryogenic treatment for performing turning operation on carbon steel EN8 round bars. Cryogenic processing has become a widely used heat treatment technique for a number of products, including industrial cutting tools, automotive brake and engine system components. Deep cryogenic treatment of tungsten carbide tool inserts gives better tool life during machining process. Cryogenic treatment or cryo treatment was done on Tungsten Carbide cemented insert for 24 hours. Then the inserts were then tempered at 200°C for 2 hours. The Vickers Micro-hardness for the insert was determined. The hardness value for cemented carbide untreated insert was 1493.8 hv. The turning tests were conducted for EN8 round bars at four different cutting speeds 80 m/min., 100 m/min., 120 m/min. and 140 m/min. and four different feed rates 0.05mm/rev, O.lOmm/rev, 0.15mm/rev, 0.20mm/rev and four different depth of cut rates 1.4mm, 1.6mm, 1.8mm and 2mm respectively. The inserts were studied for wear, after the machining process was completed by using an optical microscope. The microstructure images for the cryo treated inserts were studied with the help of the scanning electron microscope. The 24 hour cryo treated inserts with the cutting speed of 80m/min and depth of cut 1.4mm was found to have produced the least tool wear. The particles formed in the 24 hours cryo treated inserts were found to be denser and larger, and the matrix was found to be coherent and much tougher. With the cryogenic treatment, coarser and randomly distributed particles had refined into the most stable and fine particles. Also, the Vickers Micro-hardness was determined for the tungsten carbide 24 hour cryo treated insert to be 1868 hv. Thus, the Micro-hardness value for the cryo treated tool insert had increased by 20%, thus providing it low tool wear and low surface roughness.</p> |
