Fig. 3. Shown is the comparison of the total average drilling forces.
holes drilled for each alloy is shown in Table 4. The addition of tin to the G2 and G12 alloys provided the desired drilling results in terms of holes drilled. For both alloys, the targeted number of 2,016 holes was achieved, with the exception being the special solid carbide drill that only drilled 1,809 holes in the 396- G2 alloy. The values marked with an asterisk in the table indicate the drills broke before the end of the test. The only drills affected were the special solid carbide drill when used with the 396-G2 alloy and the solid carbide drill when used with the 396-G3 alloy.
On the other hand, the 396-G3
alloy, which contains sludge intermetal- lic particles, was more sensitive to tool wear than the 396-G2 and B319.2-G12 alloys. In this case, the maximum num- ber of holes drilled was 1,728, with the exception of the solid carbide drill that broke down after 971 holes. Te sludge phase—which has a high
Fig. 4. Shown is the comparison of the total average drilling torques.
the 396-G3 alloy presents greater fluctuations in drilling force and torque values. In the case of the special solid carbide drill, the drill broke after 1,728 holes in the 396- G3 alloy and after 1,809 holes in the
Alloy code
G2 G3
G12
Particle Area (µm2)
Av
17.07 9.10 7.44
SD
18.60 12.10 10.60
396 G-2 alloy, without completing the targeted goal of 2,016 holes. The targeted goal had been met by the cobalt grade and high precision solid carbide drills in the drilling process. The four tools’ lives in terms of
Table 3. Characteristics of Eutectic Silicon Particles
Particle Length (µm)
Av
8.16 4.87 4.33
SD
6.68 4.12 3.73
Roundness Ratio (%)
Av
39.97 51.60 60.00
SD
20.83 20.90 18.90
Table 4. Total Number of Holes Drilled and Total Number of Samples Drilled for Each Alloy Drill
G2 396 + 0.15%Sn
Holes drilled
Solid Carbide
Special Solid Carbide Cobalt Grade
High Precision Solid Carbide 1,980
1,809* 2,016 2,016
Samples drilled
14
12.56* 14 14
Holes drilled
971* 1,728 1,728 1,728
G3 396+ 0.25%Fe + 0.25%Mn
Samples drilled
6.74* 12 12 12
Note: The values marked with an asterisk (*) indicate it was a case of the drill breaking January 2014 MODERN CASTING | 51
Holes drilled
2,000 2,016 2,016 2,016
Av
2.76 2.02 2.07
Aspect Ratio
SD
1.65 1.06 1.05
41,071 67,114 12,000
Density (particles/mm2)
hardness value, high melting point and high specific gravity compared to the matrix—is clearly capable of damag- ing cutting tools. Te sludge phase may cause rapid tool wear and introduce problems accompanying a dull tool, which was confirmed upon drill wear examination.
Tis article is based on a paper (12-079) published in AFS Proceedings 2012.
G12 B319.2 + 0.15%Sn
Samples drilled 14
14 14 14
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