Dependence between Workpiece Material Hardness and Face Lapping Results of Steel C45

摘要

The high demands required today by manufacturing engineers for machine parts and tools necessitate very precise machining. The finishing processes are an important perspective to be considered today for meeting the goals like parallelism, tolerances, flatness, and smooth surface. These processes are high-precision abrasiye processes used to generate surfaces of desired characteristic such as geometry, form, tolerances, surface integrity, and roughness characteristics. A leading importance in this perspective has the lapping process. It leads to a surface with low roughness and high precision. The topographical structure resulting from lapping is very advantageous in sliding joints, because of the high ability of lubricant retention, as well as in nonsliding joints because of the high load-carrying ability. Many materials can be lapped, including glass, ceramic, plastic, metals and their alloys, sintered materials, satellite, ferrite, copper, cast iron, steel, etc. This paper reports the observations of steel C45 elements lapping process results. Workpieces were rollers with diameter 17 mm and height 10 mm placed in the conditioning rings with use of workholdings. Samples were divided to three groups according to their Vicker's hardness: 160, 440, and 650 HV. After grinding, lapping process was conducted. Experiments were carried out with an angular speed of the lapping plate set at 65 RPM, and lapping velocity was v = 49 m/min. The lapping pressure was provided by dead weights and during experiments executing p = 0.04 MPa. Samples were lapped during 10, 15 and 20 minutes. Abrasive slurry was composed of silicon carbide grains mixed with kerosene and machine oil. Abrasive grains size was F400/17. The material removal rate (MRR) and specimens surface characteristic are studied in the light of workpiece material hardness. Test results show that applied process parameters are the best for steel which hardness is 440 HV. In that case, the lowest values of Ra parameter were obtained in conjunction with satisfactory values of material removal rate. It can be also seen, as could be predicted, that lapping time influenced on lapping results. MRR increases and surface roughness decreases with time. The worst lapping results were obtained for normalized steel (160HV). It can be the effect of surface damage, like scratching and grooving by harder abrasive grains.