Rejection Rate Minimization of Cast Iron Components …
59
and mechanical properties of cast iron such as yield strength (YS), tensile strength
(TS) and percentage of elongation are studied with help of ultimate tensile machine
and fractography using scanning electron microscopy (Tescon Vega 3 SBH model).
Phases present in grey and ductile cast iron are confirmed by employing XRD (Rigaku
Miniflux 600 model).
3 Results and Discussion
Table 2 shows the various test result of casting sand for ductile and grey cast iron
[9]. The optimum moisture content is necessary for quality moulds and good casting
[10]. Moisture content for all the three components lies within expected range such
as 2.8–4.6% for effective moulding practice. Compatibility of green sand for casting
grey cast iron lies below the expected range. This shows that the binder efficiency is
less than the required limit. On the other hand, though ductile cast iron lies within
the expected range, the compatibility valve is marginal.
The optimum permeability of mould is 120–150 which is necessary to maintain
within the range to avoid blowholes, pinholes expansion defects and rough surface
finish. Present results show that permeability is slightly higher than the optimum
valves such as 161 and 159. It shows that one of the causes for blow holes in grey cast
iron (non-return value) and porosity issues in ductile cast iron (harvester cup) which
is due to high permeability valves of the mould. In casting processes, pressurized
gating system ensures a short filling time and full sprue during casting. For sand
casting, Sprue:Runner:Ingate ratio should be 4:8:3 and 1:1.5:0.75 as per ASM and
Indian standard, respectively. In non-return value design, Sprue:Runner:Ingate ratio
is 1:1.75:0.75 which deviates from ASM and also Indian standard.
Table 2 Testing result of casting sand quality
Name of sand test
Expected range Ductile cast iron Grey cast iron
Moisture test
2.8–4.6%
3.23%
3.21%
Compatibility test
40–50%
41%
37%
LOI test
<8%
4.63%
0.45%
Permeability test
120–150
161
159
Mould hardness test (B-scale)
60–70
82.67
80
American finesse number (AFN)
55–60
55.99
56.17
Green compression strength (kg/cm 2 ) 0.87–0.94
0.803
0.76
Core sand moisture test
3.50%
Refractoriness test
1683 °C
Silica (raw) sand
1644 °C
Green sand
59
and mechanical properties of cast iron such as yield strength (YS), tensile strength
(TS) and percentage of elongation are studied with help of ultimate tensile machine
and fractography using scanning electron microscopy (Tescon Vega 3 SBH model).
Phases present in grey and ductile cast iron are confirmed by employing XRD (Rigaku
Miniflux 600 model).
3 Results and Discussion
Table 2 shows the various test result of casting sand for ductile and grey cast iron
[9]. The optimum moisture content is necessary for quality moulds and good casting
[10]. Moisture content for all the three components lies within expected range such
as 2.8–4.6% for effective moulding practice. Compatibility of green sand for casting
grey cast iron lies below the expected range. This shows that the binder efficiency is
less than the required limit. On the other hand, though ductile cast iron lies within
the expected range, the compatibility valve is marginal.
The optimum permeability of mould is 120–150 which is necessary to maintain
within the range to avoid blowholes, pinholes expansion defects and rough surface
finish. Present results show that permeability is slightly higher than the optimum
valves such as 161 and 159. It shows that one of the causes for blow holes in grey cast
iron (non-return value) and porosity issues in ductile cast iron (harvester cup) which
is due to high permeability valves of the mould. In casting processes, pressurized
gating system ensures a short filling time and full sprue during casting. For sand
casting, Sprue:Runner:Ingate ratio should be 4:8:3 and 1:1.5:0.75 as per ASM and
Indian standard, respectively. In non-return value design, Sprue:Runner:Ingate ratio
is 1:1.75:0.75 which deviates from ASM and also Indian standard.
Table 2 Testing result of casting sand quality
Name of sand test
Expected range Ductile cast iron Grey cast iron
Moisture test
2.8–4.6%
3.23%
3.21%
Compatibility test
40–50%
41%
37%
LOI test
<8%
4.63%
0.45%
Permeability test
120–150
161
159
Mould hardness test (B-scale)
60–70
82.67
80
American finesse number (AFN)
55–60
55.99
56.17
Green compression strength (kg/cm 2 ) 0.87–0.94
0.803
0.76
Core sand moisture test
3.50%
Refractoriness test
1683 °C
Silica (raw) sand
1644 °C
Green sand