The experimental planning was elaborated to be accomplished through a complete factorial analysis with one replicate in two levels and four factors (cutting speed, feed rate, cutting depth, tool nose radius), with the objective of evaluating which were the most significant factors and its respective interactions in the answers: cutting forces (cutting force, feed rate cutting force and penetration force), residual stress and microstructure of the material。

The used items in the experiments were [25]:

● 32 bodies test of DIN 100 CrMn6 steel, temper and quenched with 60 to 64 HRc hardness。 The chemical composition of the material was: 0。93 C, 0。49 Si, 1。02 Mn, 1。48 Cr, 0。018 P,

0。012 S, 0。12 Ni, and 0。15 Cu。

● Insert with VNMA 160404(08)–BCN 200 geometry, with 4 cutting faces, covered with ceramic and TiAlN base, Sumitomo;

● Machine turning center: CNC–OKUMA LB300;

● Piezoelectric dynamometer PCB-206A1, with maximum scale measurements of 4。45 kN for the feed rate cutting force and cutting force, and 5。87 kN for penetration cutting force;

● Acquisition signal system data, HBM Spider 8 operating with the Catman 4 data acquisition software, under a frequency of 200 Hz;

The tests were conducted without cutting fluid utilization and the used cutting parameters were: cutting speed: 150 and 210 m/mim; feed rate: 0。05 and 0。15 mm/rev; cutting depth: 0。05   and

0。20 mm and tool nose radius: 0。4 and 0。8 mm。

The internal ring of the conical bearing used on the tests is illustrated in the Fig。 1。

For the residual stresses measurements, the X - ray diffraction technique was used, with the sin2method with the variation of the measurement angle from - 60° to + 60°, being irradiated CrK in the cristalografics planes (2 1 1)。 The used equipment was the DMAX model from RIGAKU–I。 The obtained residual stresses values were circunferentials, that is, in the tangential direction to the bearing ring cone, and sixteen bodies of machined tests were measured (complete factorial planning without replicate) and another one body in the precedent state to the machining [25-28]。

Some metallographic analyses were conducted in some pieces before machining and the microstructure was typically formed by martensite with high carbon content and dispersed primary carbonetes in all the mass, with of 5 to 10% of retained austenite。

Fig。 1。 Internal conical bearing ring used on the tests

Table 1。

Cutting force measurements

Test cs [m/min] f [mm/r] p [mm] radius [mm] Ff [N] Fc [N] Fp [N] Resultant [N]

1 150 0,05 0,05 0,4 26,3 33,9 59,9 73,68

2 210 0,05 0,05 0,4 17,9 17,3 28,5 37,84

3 150