Research Journal of Applied Sciences, Engineering and Technology 2(5): 487-491, 2010
ISSN: 2040-7467
© M axwell Scientific Organization, 2010
Submitted Date: May 27, 2010
Accepted Date: June 15, 2010
Published Date: August 01, 2010
Performance Study of Cryogenically Treated HSS Drills in Drillilg Gray
Cast Iron Using Orthogonal Array Technique
1
1
B.R . Ram ji, 2 H.N . Narasimha M urthy, 2 M. Krishna and 2 M.J. Raghu
Departm ent of Manufacturing Engineering, BM S College of Engin eering, Bangalore, India
2
Departm ent of Mechanical Engineering, RV College o f Engineering, Bangalore, India
Abstract: The objective of this research was to study the performance of cryogenically treated HSS drills for
drilling gray cast iron. Drilling experiments were conducted with cutting speeds: 560, 710, 900, 1120 rpm,
feeds: 0.05, 0.08, 0.12, 0.19 mm/rev and a constant drill diameter: 8 mm. The cry ogenic treatment cycle
consisted of coo ling the test sam ples from roo m tem peratu re to cryogenic tem peratu re of -17 8.9ºC in 3 h,
soaking at cryogenic temperature for 24 h and w armin g to roo m tem peratu re in about 5 h. The thrust force and
torque were measured using drill tool dynamometer. The surface roughness (Ra, Rz, Rq and R t) of the drilled
specimens were measured using talysurf. The experimental lay-out was designed using Taguchi’s Orthogonal
Array technique. S ignal-to-Noise Ratio analysis was performed to identify the effect of the parameters on the
response variables. The treated drills we re foun d sup erior to the non -treated in all the test conditions in terms
of lesser thrust force, torque and also superior surface roughness of the specimens. The tool wear was studied
u sin g SEM .
Key w ords: Cryogenic, drilling, gray CI, surface roughness, Taguchi
INTRODUCTION
The challen ge of m odern ma chinin g indu stries is
mainly focused on achieving high quality in terms of
work-piece dimensional accuracy, surface finish and less
tool wear. The harde r the material, the more difficult it is
to machine. Cast iron has been used in large quantities for
years because of desirable properties as good castability,
good ma china bility and low cost.
A wide variety of gray cast iron is used in industries
for various applications. M achin ability of C ast Iron is
affected by the amount of carbon. The tool lives may
increase significantly after being sub mitted to subze ro
temperatures. Cryogenic treatment involves the soaking of
cutting tools at very low temperatures, -184ºC or below.
The results can be surprisingly good depending upon the
application. Reports of 92-817% increases in tool lives
after they are treated at -196ºC are found (Paulin, 1993).
The tool steels submitted to conventional heat
treatment presented only a small amount of retained
austenite, but those submitted to cryogenic treatment
showed better wear perfo rman ce du ring m achin ing. This
is due to a new mechanism besides the transformation of
the retained austenite into martensite. The new
mechanism is time and temperature dependent during the
long hours of dwelling in cryogenic treatment. The
carbide particles smaller in sizes are found after the
treatment, which w ould c ontribu te to the wear resistance
of the tools (Gruman Aircraft Engineering, 1965;
Barron, 1974; A hmed , 2004).
Chatterjiee (1992) reported the cryogenically treated
high speed drills yielded higher tool life compared than
that of with untreated ones, for different cutting speeds
and for different work materials.
Firouzdor et al. (2008) reported the influence of deep
cryogenic treatment on wear resistance and tool life of
M2HSS drills in high-speed dry drilling of carbon steels.
The researchers observed 77 and 126% im proveme nt in
cryogenic treated and cryogenic and temper treated drill
lives, respectively. The improvement in wear resistance of
the drills was mainly attributed to the resistance of
cryogenically treated drills against diffusion wear
mechanism, due to the formation of fine and
homogeneous carbide particles during cryogenic
treatment. Additionally, transformation of retained
austenite to martensite played an effective role, i.e.
improved hardn ess va lues. C arter (1956), Shaw (1986)
and Adler et al. (2006) reported results of tool
performance in case of cryogenically treated tools used
for drilling, milling, turning, etc.
Based on the literature review it was concluded that
experimental studies on the effect of cryogenic treatment
on drilling gray cast iron has not been reported yet. Finite
Element Analysis for the performance of cryo genically
treated drills has been very scarcely repo rted. Th us, this
research was aimed at studying the performance of
Corresponding Author: B.R. Ramji, Department of Manufacturing Engineering, BMS College of Engineering, Bangalore, India
Tel: 9844348421
487
Res. J. Appl. Sci. Eng. Technol., 2(5): 487-491, 2010
Table 1: Experimental conditions used for drilling exercises
Machine tool
Sensitive drilling machine
Wo rkpiece
Gray Cast Iron (C-3.266 % , M n-0.329%, P0.407, S-0.120, Si-1.806 %)
Size
N50 X 40 mm
Cu tting to ol
HSS drills
Working tool geo metry Diameter: 8 mm, Flute length: 75 mm , Ov erall
length: 117 mm
Lip angle: 118°, Helix angle: 20°
Drilling parameters
Cutting velocity, A: 560, 710, 900, 1120 rpm
Feed rate, B: 0.05, 0.08,0.12, 0.19 mm/rev
Depth of drilled blind hole: 15 mm
Tool co nd ition , C: Cry oge nica lly treated (C T),
non-treated (NT)
M easu ring in strum ents Talysu rf (SJ-201) for surface roughn ess (Ra,
Rz, Rq, Rt)
Drill tool dy nam ome ter for m easuring thrust
force in Kgf and Torque in Kg-m, Scanning
Electron Microscope: JOEL
Place of study
R V College of Engineering, Bangalore, Ind ia
Time of study
September 2009
cryogenically treated HSS drills in terms of thrust force,
torque and the surface roughness in drilling of gray cast
iron expe rimen tally based on Tagu chi’s Orthogonal array
technique and FEA.
MATERIALS AND METHODS
Experimental-drilling studies: The drilling exercises on
gray cast iron and the study of the influence of cryo genic
treatment of the inserts on the thrust force, torque and the
surface roughness of the work piece were undertaken
under the experimental conditions presented in Table 1.
The experim ents were conducted at RV College of
Engineering Bangalore, India during September 2009.
The cryogenic treatment involved cooling the inse rts
from room temperature to cryogenic temperature
(-178.9ºC) in 3 h, soaking at this temperature for 24 h and
warming to room temperature in 5 h. Drilling exercises
were carried out for each experimental condition to cut
15 mm dep th blind hole in the w ork-piece an d for each
experimental condition five holes were drilled.
Table 2: Parameters, levels and orthogonal array
Factor code
Parameter
A
Cu tting v eloc ity
B
Feed rate
C
Tool condition
No. of levels considered for study
Orth ogo nal A rray c hos en c orres pon ding to
fou r para mete rs an d fo ur lev els
Design of experiments using taguchi’s orthogonal
array technique: The factor level combinations selected
for the design of experiments is shown in Table 2. An
L'16 OA layou t was selected to satisfy the minimum
number of experiments condition. The experimental
results are shown in Table 3 and 4.
No. of levels
4
4
2
4
L'16
The calculation of the SN for the first experiment in
the array above is shown below for the case of a specific
target value of the performance characteristic.
Signal-to-Noise ratio analysis of the responses: The
signal-to-noise ratio analysis based on the responses
obtained in the drilling exercises is shown in Table 5, 6
and 7 for thrust force. To determine the effect each
variab le has on the output, the signal-to-noise ratio, or the
SN number, has been computed for each experiment
conducted.
(1)
Stl = 602 + 59 2 + 60 2 + 62 2 + 61 2 = 18246
Stl = Stl-Sml = 18246-18240.8 = 5.2
(2)
(3)
Table 3: Experimental lay-out and results for thrust force as response
S.No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Cutting speed (rpm)
560
560
560
560
710
710
710
710
900
900
900
900
1120
1120
1120
1120
Feed mm/rev
0.05
0.08
0.12
0.19
0.05
0.08
0.12
0.19
0.05
0.08
0.12
0.19
0.05
0.08
0.12
0.19
T o o l c o nd it io n N T /C T
NT
CT
NT
CT
CT
NT
CT
NT
NT
CT
NT
CT
CT
NT
CT
NT
488
Thrust force (Kg f)
---------------------------------------------------------------------------------------T1
T2
T3
T4
T5
60
59
60
62
61
59
57
60
62
63
114
114
115
115
116
92
95
93
97
98
55
55
56
58
59
75
77
75
76
78
82
81
80
89
87
173
172
172
170
167
73
73
72
74
75
65
63
57
58
56
126
129
130
127
122
122
123
121
119
120
65
64
66
67
69
90
91
90
92
93
96
95
92
94
92
199
201
206
210
208
Res. J. Appl. Sci. Eng. Technol., 2(5): 487-491, 2010
Table 4: Experimental results for torque and surface roughness as responses
Torque (Kg-m)
-------------------------------------------------------------------------S.No.
T1
T2
T3
T4
T5
1
5.08
5.12
5.11
5.33
5.27
2
5.36
4.78
5.12
4.38
4.98
3
5.77
6.10
5.82
5.63
5.97
4
5.31
4.86
5.14
4.93
5.42
5
5.42
5.19
4.63
5.62
5.89
6
5.58
6.21
5.24
4.91
4.47
7
4.33
5.60
4.20
4.72
4.80
8
6.44
6.31
6.10
5.98
5.82
9
5.96
6.11
6.24
5.87
6.06
10
4.82
5.11
5.15
4.11
4.92
11
6.50
6.53
6.16
6.34
5.40
12
5.91
5.24
5.92
5.88
6.41
13
4.66
4.92
5.57
5.36
4.73
14
6.88
6.11
6.30
6.14
6.23
15
5.35
4.90
5.11
5.32
5.42
16
5.14
5.79
5.23
5.63
5.09
S u rf ac e r ou g hn e ss – Ra ( :m)
------------------------------------------------------------------------------------T1
T2
T3
T4
T5
0.13
0.12
0.13
0.13
0.13
0.11
0.10
0.11
0.09
0.12
0.17
0.17
0.16
0.16
0.17
0.15
0.16
0.15
0.16
0.17
0.11
0.13
0.15
0.16
0.16
0.14
0.15
0.14
0.15
0.15
0.15
0.13
0.13
0.18
0.14
0.29
0.29
0.29
0.29
0.32
0.14
0.13
0.12
0.14
0.14
0.11
0.10
0.11
0.09
0.08
0.22
0.21
0.22
0.23
0.24
0.21
0.18
0.16
0.16
0.18
0.14
0.11
0.11
0.12
0.13
0.18
0.19
0.21
0.21
0.21
0.15
0.14
0.16
0.18
0.21
0.36
0.40
0.43
0.45
0.41
Table 5: SN number for each experiment conducted for thrust force
S.No.
Speed A
Feed B
Tool condition C
1
560 -1
0.05-1
NT -1
2
560 -1
0.08-2
CT -2
3
560 -1
0.12-3
NT -3
4
560 -1
0.19-4
CT -4
5
710 -2
0.05-1
CT -2
6
710 -2
0.08-2
NT -1
7
710 -2
0.12-3
CT -4
8
710 -2
0.19-4
NT -3
9
900 -3
0.05-1
NT -3
10
900 -3
0.08-2
CT -4
11
900 -3
0.12-3
NT -1
12
900 -3
0.19-4
CT -2
13
112 0-4
0.05-1
CT -4
14
112 0-4
0.08-2
NT -3
15
112 0-4
0.12-3
CT -2
16
112 0-4
0.19-4
NT -1
Sm1
18 24 0.8
18 12 0.2
65 89 5.2
45 12 5.1
16 01 7.8
29 03 2.2
35 11 2.2
14 58 63 .2
26 93 7.8
17 88 0.2
80 39 1.2
73205
21 91 2.2
41 58 7.2
43 99 2.2
20 97 15 .2
Table 6: Computed average SN values
SN A 1
34.17
SN B 1
32.81
SN A 2
32.20
SN B 2
30.95
SN A 3
32.40
SN B 3
33.96
SN A 4
33.72
SN B 4
34.76
)=
1.97
)=
3.81
SN C 1
SN C 2
SN C 3
SN C 4
)=
S t1
18246
18143
65898
45151
16031
29039
35175
145886
26943
17943
80430
73215
21927
41594
44005
209802
S e1
5.2
22 .8
2.8
26
13 .2
6.8
62 .8
22 .8
5.2
62 .8
38 .8
10
14 .8
6.8
12 .8
86 .8
V e1
1.3
5.7
0.7
6.5
3.3
1.7
15 .7
5.7
1.3
15 .7
9.7
2.5
3.7
1.7
3.2
21 .7
SN 1
34.48
28.03
42.75
31.42
29.87
35.33
26.50
37.09
36.17
23.56
32.19
37.68
30.73
36.89
34.39
32.86
After computing the SN ratio for each experimen t,
the average SN value is calculated for each factor and
level as shown in Table 6. Where:
33.72
32.49
38.23
28.05
10.17
(6)
Tab le 7: Range and rank for thrust force, torque and surface roughn ess
Speed
Feed
Tool condition
Thrust force
Ra ng e, )
1.97
3.81
10.17
Rank
3
2
1
Torque
Ra ng e, ) 5.27
1.96
8.28
Rank
2
3
1
Surface rough ness Ra ng e, ) 6.80
5.33
7.04
Rank
2
3
1
Similarly SN B1, SN C1 were computed and
) = SN Amax – SN Amin = 34.17-32.20 = 1.97
(7)
Table 7 shows the range R ( ) = high SN - low SN) of
the SN compu ted for each parameter for each of the
response factors. Larger the R value for a parameter, the
larger the effect the variable has o n the process. This is
because the same change in signal causes a larger effect
on the output variable being measured.
It can be seen that the tool condition has the largest
effect on the thrust force, torque and surface roughness.
Speed has the smallest effect on the thrust force and feed
has the smallest effect on the torque and the surface
roughness.
(4)
(5)
Similarly SN 2, SN 3, SN 4 … etc. have been computed.
489
Res. J. Appl. Sci. Eng. Technol., 2(5): 487-491, 2010
lack of matrix strength indicating the absence of carbide
particles i.e., martensitic matrix. The treated drills showed
(Fig. 1d) micro damages at the chisel edge indicating the
presence of carbide particles i.e., martensitic matrix. The
cryogenic treatment of HSS drills toughened the tool
material and increased its strength, which was also
indicated by the increase in hardness. The treated drills
showed decreased thrust force and torque and better
surface roughness than that obtained by non-treated drills.
RESULTS AND DISCUSSION
Thrust force and torque are indicators of tool
performance. Greater the thrust force and torque, greater
is the tool w ear and hen ce low er drill tool life. T he drill
tool wear is caused by abrasive, diffusive and adhesive
wear mechanisms. The heat generated during drilling also
affects drill tool life. At higher speeds and feeds, the
thrust force and torque of the drill tool increases for a
given depth of hole drilled.
Surface finish is an impo rtant index of m achin ability
because life and performance of the machined
com ponents are influenced by their surface finish, residual
stresses and surface defects (Paul et al., 2001). The
signal-to-noise ratio analysis indicated that, the cryogenic
treatment has the largest effect on the thrust force, torque
and surface roug hness. Speed h as the smallest effect on
the thrust force and feed has the smallest effect on the
torque and surface roughness (R a).
CONCLUSION
Drilling exercises w ere performed using
cryogenically treated and non-treated HSS drills to study
the tool performance. Based on the study the following
conclusions were drawn:
The extents of influence of cutting velocity, feed and
the condition of the inserts were examined by conducting
drilling exercised based on O rthogona l Array
Experimentation technique.
Cryogenic treatment resulted in lesser thrust force,
torque and y ielded superior surface finish com pared to
that of non -treated drills. The response s obtained after
drilling were analyzed using signal-to-noise ratio
analysis.The tool condition had the largest effect on the
Scanning electron microscopy: The scanning electron
micrographs of the HSS drills are shown in Fig 1. Figure
1a and c show non treated and treated drills respectively.
In this after drilling condition Fig. 1(b), the non-treated
drills showed plastic deformation, which was due to the
Fig. 1: SEM of HSS drills (a) Non-treated before drilling, (b) Non-treated after drilling showing excessive wear on cutting edge,
(c) treated before drilling and (d) treated drill after drilling showing less wear of the cutting edge
490
Res. J. Appl. Sci. Eng. Technol., 2(5): 487-491, 2010
thrust force, torque and surface roughness. Speed had the
smallest effect on the thrust force and feed had the
smallest effect on the torque and the surface roughness.
Based on the resu lts it was conc luded that cryogenic
treatment can yield significant improvemen t in both
productivity and p roduct quality and henc e ove rall
machining economy offsetting the cost of cryogenic
cooling.
Carter W .A., 1956. Metal Machining, Part VI, Overseas
Edition, Cutting Fluids, Machinery Lloyd.
Chatterjee, S., 1992. Performance characteristics of
cryogenically treated high-speed drills.Int. J. Prod.
Res., 32(4): 773-786.
Firouzdor, V., E. Nejati and F. Khomamizadeh, 2008.
Effect of deep cryogenic treatment on wear resistance
and tool life of M 2 HSS drill. J. Mater. Process.
Technol., 206(1-3): 46 7-472.
Gruman Aircra ft Engineering, 196 5. Cry ogenic coolants
speed titanium machining. Machinery, pp: 101-102.
Paul, S., N.R. Dhar and A.B. Chattopadhyay, 2001.
Beneficial effects of cryogen ic cooling over dry and
wet machining on tool wear and surface finish in
turning AISI 1060 steel. J. Mater. Process. T ech.,
116(1): 44-48.
Paulin, P., 1993. Frozen gears. Gear Technol., pp: 26-29.
Shaw, M.C., 1986. Metal Cutting Principles. Oxford
University Press, Oxford.
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