Flank wear in turning of hardened steel 42CrMo4.

Zeqiri, Hakif ; Salihu, Avdi ; Bunjaku, Avdyl 等

1. INTRODUCTION

During the technological projection process, an important role has the knowledge of mechanism of consumption of the metal cutting instrument in function of cutting regime, the geometry of the cutting instrument, time of processing and the cooling equipment. The process of cutting plate's consumption is as a result of different forms of proceeding energy and mechanical, chemical, electrical, and magnetically properties.

Evaluation of the condition of torpidity of cutting plates is done with the help of consumption indicators which can bee divided in three groups (Bodinaku, 2006):

* Technological indicators, which determine the change of production quality. Here we have included as first the exactness of dimensions, shape and position, and profile parameters of the roughness of the processed surface. fig.1.

* Geometrical indicators of the cutting edge, fig.2.

* Energetic indicators which belong to the change of energetically relations on the process of de-cohesion. Here is the subject of the increase of cutting forces what results with higher cutting power, increase of the temperature on the cutting process, increase of vibrancy in system: processing equipment-machine and metal cutting instruments.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

2. CONDITIONS DURING THE EXPERIMENTATION

2.1. For research there have been used cutting plates P30, produced by Sintal-ZAGREB, ISO SNMM120404, SNMM120408, and SNMM120412. Reinforcing have been done on the body of instrument with a sign ISO PSDNN2525P12, on a standard supporter with an outlet 25mm and cutting geometry: [chi]=[60.sup.0], [chi].sub.1] = [45.sup.0], [gamma]= -[6.sup.0], [alpha]=[6.sup.0], [lambda]= -[6.sup.0], [r.sub.[epsilon]] =0.4mm, [b.sub.f]=0.2mm, [[gamma].sub.f] =-[20.sup.0].

Researching material -- Hardened Steel 42CrMo4 (cylindrical shape) with dimensions [PHI]68x750/048.5x750mm, and with strength Rm=880 N/[mm.sup.2] / 1080 N/[mm.sup.2]. Processing with cutting have been realized with horizontal late IK62: P=10 kW, maximal working diameter 400 mm, n = (12.5 / 2000) rev/min, feed s = (0.035 / 2.08) mm/rev.

Measuring of the radial consumption [V.sub.B], has been realized with Microscope JLC680148, with a zooming 25 times, measuring exactness 0.01mm. A special attention have been taken to the way of holding the piece being processed, since on the character of consumption of cutting plates from the hard metal. Specially caution was dedicated to the mode of processing part tightening, because the character of hard metal cutting plate consumptions depend on system rigidity machine-auxiliary equipment-processing part-cutting tool (Salihu, 2001).

Processing with cutting have been realized with a holding of the processing piece, with new edge, without cooling equipment, with changing of parameters v, s, a, r & t (table 1), with applying the experimental plan of five factors of a first order y = [2.sup.k] + [N.sub.0]. The criterion for measuring of the consumption have been taken the course from 1km length of circular cutting, increasing the cutting regime, until the first rate of consumption have been obtained.

2.2. Plan of experimental research-Based on the scaled number of rotations done by the machine, the literature taken in use, professional experience, dimensions, chemical content and mechanical properties of the piece being processed and metal- cutting instrument, we have been decided on cutting regimes:

3. ANALIZING OF RESEARCH RESULTS

With defining of the input and output data, selection of the proper method for measuring for measuring and the measuring gauge, selection of the shape of function for definition of space for experiment, statistical processing of researched data and the verification of the mathematical model, is determined the impact of adopted (v, s, a, r & t) on the size of the consumption. During the research we have followed the change of consumption VB on cutting plates from the hard metal P30. For the description of this change there has been adopted the mathematical model of exponential shape (1):

[V.sub.B] = C x [v.sup.x] x [s.sup.y] x [a.sup.z] x [r.sup.k] x [t.sup.q] (1)

The analyze of the mathematical model (1) shows the impact of cutting speed v on the consumption size [V.sub.B], whereas it is necessary that the mathematical model (1) to be transformed into another mode which will enables the analyzing of the cutting course of the cutting edge. The time for cutting will be eliminated based on well known relation t=L/v, if this relation will be replaced on equation (1) with mathematical calculation of obtained results during the experiment tab.2. where is obtained the mathematical model (1.1), chart interpretation is given in the fig. 3

[V.sub.B] = 0.0506[v.sup.0480] [s.sup.0.174] [a.sup.0.0474] [r.sup.0.088] [L.sup.0.754] (1.1)

[FIGURE 3 OMITTED]

From the mathematical model (1.1) it is obvious that in the consumption size [V.sub.B], dominant influence has the taken course L, cutting speed v & feed s, whereas the cutting depth a & radius line of the cutting edge r has a smaller influence (Zeqiri, 2005). With increasing of the cutting speed, the conditions in the cutting zone will change, metal shaving will be removed fast from the cutting zone, which reduces plastic deformations in the zone of the metal shaving deformation and in the zone of creation of surface layers which impacts in reducing of roughness.

Increasing of the cutting speed v causes diminution of contact surface between metal shavings and cutting plates. With this mechanical and heating impact will be displaced in direction of the cutting edge, causing higher specific pressure and bigger gradient of speed. Friction gradient between metal shavings and front surface, the compression gradient of metal shavings and cutting forces will be decreased.

So, the increasing of the cutting speed v causes increasing of the operation from the friction of metal shavings with front surface of the cutting tool. From this we can conclude that: important influence in consumption size has cutting speed v, because the concentration of big hardness in the cutting edge causes changes not only in the mechanical properties of the processing material but as well in the cutting tool. Increasing of the cutting step s causes increase of the thickness of the removed layer (s sin%), and with this it is necessary a higher energy for transformation of the layer into metal shaving.

4. CONCLUSION

Based on analysis of output results with experimental research tab.2, mathematic model (1.1) and chart interpretation we can conclude that: MODELIT1.1

1. Changing of the consumption size can be described with function of the exponential shape;

2. The consumption increases evidently with the increase of cutting speed, cutting time & cutting length.

3. Visible Interaction was shown through the cutting speed v and cutting time t. This indicates that with increasing of the cutting time the influence of the cutting speed in the consumption size is decreased.

4. The presented function can be applicable for determination of limited fields, optimal solutions of cutting regimes, for achievement required exactness and useful economical relations.

5. REFERENCE

Bodinaku, A. (2006). Mechanical technology, Volume 2, Faculty of Mechanical Engineering, Tirana, Albania

Salihu, A. (2001). Research of machinability of cutting material with increased speed, doctoral dissertation, Faculty of Mechanical Engineering, Prishtina

Zeqiri, H. (2005). Research of machinability by turning of 42CrMo4 steel, doctoral dissertation, Faculty of Mechanical Engineering, Prishtina

Tab. 1. Conditions for experiment realization
Independent variables with levels and coding identification

Nr Note Level Maximal Average Minimal
 code 1 0 -1

1 v[m/min] [X.sub.1] 67.000 53.000 42.000
2 s[mm/rev] [X.sub.2] 0.042 0.038 0.035
3 a[mm] [X.sub.3] 1.000 0.707 0.500
4 r[mm] [X.sub.4] 1.200 0.800 0.400
5 t[min] [X.sub.5] 8.000 2.828 1.00

Tab. 2. Derived results during experiment realization

 Design cutting condition results

 v s a r t [V.sub.B]
Nr m/min mm/rev mm mm min

1 42 0.035 0.500 0.4 1.00 2.900
2 67 0.035 0.500 0.4 1.00 9.600
3 42 0.042 0.500 0.4 1.00 3.300
4 67 0.042 0.500 0.4 1.00 10.800
5 42 0.035 1.000 0.4 1.00 3.400
6 67 0.035 1.000 0.4 1.00 9.100
7 42 0.042 1.000 0.4 1.00 3.200
8 67 0.042 1.000 0.4 1.00 11.800
9 42 0.035 0.500 1.2 1.00 3.750
10 67 0.035 0.500 1.2 1.00 4.580
11 42 0.042 0.500 1.2 1.00 6.505
12 67 0.042 0.500 1.2 1.00 13.380
13 42 0.035 1.000 1.2 1.00 4.125
14 67 0.035 1.000 1.2 1.00 9.035
15 42 0.042 1.000 1.2 1.00 7.100
16 67 0.042 1.000 1.2 1.00 13.100
17 42 0.035 0.500 0.4 8.00 15.780
18 67 0.035 0.500 0.4 8.00 22.630
19 42 0.042 0.500 0.4 8.00 17.060
20 67 0.042 0.500 0.4 8.00 24.253
21 42 0.035 1.000 0.4 8.00 16.278
22 67 0.035 1.000 0.4 8.00 23.225
23 42 0.042 1.000 0.4 8.00 18.630
24 67 0.042 1.000 0.4 8.00 24.301
25 42 0.035 0.500 1.2 8.00 17.743
26 67 0.035 0.500 1.2 8.00 24.273
27 42 0.042 0.500 1.2 8.00 20.740
28 67 0.042 0.500 1.2 8.00 25.072
29 42 0.035 1.000 1.2 8.00 17.216
30 67 0.035 1.000 1.2 8.00 25.548
31 42 0.042 1.000 1.2 8.00 21.463
32 67 0.042 1.000 1.2 8.00 25.132
33 53 0.038 0.707 0.8 2.828 11.780
34 53 0.038 0.707 0.8 2.828 11.630
35 53 0.038 0.707 0.8 2.828 10.960
36 53 0.038 0.707 0.8 2.828 11.055
37 53 0.038 0.707 0.8 2.828 11.066
38 53 0.038 0.707 0.8 2.828 11.066