Roughness evaluation of 4340 steel with two types ceramic tools in milling.

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The study evaluated roughness obtained in milling ABNT 4340 steel hardened with two types of cutting tools based on aluminum oxide with magnesium oxide addition (Al2O3 + MgO) and another with zirconium oxide (ZrO2). The experimental procedure adopted was the complete orthogonal arrangement with four parameters (input factors) and 10 levels. The behavior of two types of experimental ceramic inserts (Al2O3 + MgO) and (Al2O3 + ZrO2) were tested at three cutting speeds (200; 300; 400 m.min-1), in three feeds (0.05; 0.10; 0.15 mm.rev-1), in two machining depths (0.10 and 0.20 mm) and dry milling. The response factors were the surface roughness (Ra) and (Rt). 36 tests were carried out for each type of insert, 18 in the forward direction and 18 in the return direction, totaling 72 tests with roughness measurements in both paths, both in the outward and in the return path along the length of the insert. milled region. The milling was concordant in both paths. The average values of roughness (Ra) and (Rt) (surface quality) found in milling with the two types of ceramic tools are compatible with the usual field of application for finishing and usually obtained with grinding. The roughness (Ra) was 0.753 μm and (Rt) was 5.57 μm in milling with the Al2O3 + MgO insert and with the Al2O3 + ZrO2 insert, the roughness (Ra) was 0.957 μm and the (Rt) of 6.88 μm. The lowest roughness values were obtained with cutting speeds of 300 m.min-1 for Ra and 200 m.min-1 for Rt with 0.05 mm/rot feed and 0.10 mm depth.