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A job shown in the figure is to be made from steel by casting process. The mould for this job is made from wooden pattern. Dimensions of the wooden pattern assuming machining allowance of 3 mm on each side, shaking allowance of 1 mm on length & width & shrinkage allowance of 3%.
L = 80 + 2 x 3 = 86 mm
W = 40 + 2 x 3 =46 mm
H = 30 + 2 x 3 = 36 mm
The shrinkage allowance of 3% is added to all the dimensions of pattern. Dimension of pattern after providing shrinkage allowance of 3% will be
Given shaking allowance is 1 mm on length and width. Recall that shaking allowance is a negative allowance. Hence 1 mm has to be reduced from the calculated values of length and width side.
L = 88.58  1 = 87.58 mm
W = 47.38  1 = 46.38 mm
H = 37.08 mm
The ratio of solidification times of a sphere and cube made of same materials cast under identical conditions 2:1, are , the ratio of their volumes are __________
R = 0.7071
Metal is to be poured in a cubical cavity of 100 cm side made entirely in drag. The crosssection of the cope box is 200x 150 cm and height is 100 cm. If the densities of metal and sand are 7900 kg/m^{3} and 1600 kg/m^{3} respectively. The minimum weight required to be placed on cope in kN to prevent lifting of cope box is __________.
= 7900 x 9.81 x 1
= 77499 N/m^{2}
Upward force exerted by molten metal on cope = 77499 x 1 x 1
= 77.499 kN
So, minimum weight to keep in cope box
= 77.499  4.8
= 72.699 kN
For a given volume, the ratio of height to diameter of a blind cylindrical riser with a hemispherical top for minimum cooling rate is____________.
In sand casting of hollow part of zinc, a cylindrical core of diameter 130 mm and height 200 mm is placed inside the mould cavity. The densities of core material and zinc are 1500 kg/m^{3} and 12000 kg/m^{3} respectively. The net force that tends to lift the core during pouring of molten metal will be __________ N.
Upward force buoyancy force weight of molten metal displaced
Downward force weight of core
D = density of core
= dvg
Net force upward force – downward force
= 273.441 N
A disk of diameter 40 cm and 5 cm thick is to be casted out of pure aluminium is an open mold operation. Melting temperature of Al , pouring temperature 800 . Assume that the amount of aluminium heated will be 5% more than that needed to fill the mould cavity. The amount of heat (MJ) added to aluminium starting from room temperature of 25 is__________. (Specific heat of Al (both cold and heated)= 0.88 J/g . Heat of fusion= 389 J/g. Density Al = 2.70 g/cm^{3} ).
Volume of molten metal = 5% more than volume of mould
⇒ Volume of molten metal
Mass of molten metal
_{heat supplied} _{= m}(c_{p}(T_{m}  T_{R}) +L.H + C_{p}(T_{P} T_{m}))
T_{m} = melting temperature
T_{R} = room temperature
T_{p} = pouring temperature
= 19 MJ
Two castings of the same metal have the same surface area. One casting is in form of a sphere and the other is a cube. The ratio of the solidification time for the sphere to that of the cube is____________.
Let τ = Solidification time
According to Chvorinov’s rule
But since A_{cube} = A_{sphere}
Match ListI with ListII and select the correct answer using the codes given below the lists: ListI
P. Shrinkage cavity
Q. Drop
R. Blister
S. Dross
ListII
1. This is a scar covered by thin layers of a metal
2. Lighter impurities appearing on the top surface of a casting
3. An irregularly shaped projection on the cope surface of the casting
4. An improper riser may give rise to this defect
Shrinkage cavity ➝ if shrinkage of metal is not compensated by riser this defect is caused.
Drop ➝ is an irregularly shaped projection on the cope surface of casting.
Blister ➝ A scar covered by thin layer of metal.
Dross ➝ lighter impurities appearing on the top surface of a casting.
A cylinder of 150 mm diameter & 200 mm height is to be cast without any riser. The cylinder is moulded entirely in drag of a green sand flask & is top gated. The cope of flask is 200 mm height & the height of metal pouring is 50 mm above the cope. A tapered sprue is employed & the gating ratio is 1 : 1.5 : 2. The time taken _________ (in seconds) to fill the casting cavity neglecting energy losses, if the ingate area is 400 sqmm.
Flow rate = Q = Velocity x area
A_{c} = minimum cross sectional area
Gating ratio = 1: 1.5: 2
In gate area = 400 mm^{2} ⇒ minimum area
Pouring time
A cube and sphere made of same material cast under identical conditions solidify at the same time. The ratio of length of cube to diameter of sphere is __________
In pressurized gating system with a gating ratio 2:1.5:1. The sprue area is 200mm^{2} . The time taken (in sec) to fill the cavity of volume 10^{6}mm^{3} with a 20% metal head of 200 mm assuming a 20% loss of head in gating system is __________
Given Gating Ratio = 2 : 1.5 : 1
Head of metal = 200 mm
loss of head of metal = 20%
net available head = 0.8 x 200
= 160mm
Flow rate of metal = V x A
= 5.645 sec
The size of a cylindrical side riser, whose height and diameter are equal, to feed a steel slab casting 30cm 30cm 6cm is ____________(Use modulus method)
The dimensions of the slab
= 30 cm x 30 cm x 6 cm
This can be considered as a long bar with a crosssection of (30 x 6)cm^{2}
= 2.14
D = 6 x 1.2 x 2.14 = 15.408 cm = H
The riser height, H = D = 15.408 cm
The diameter at base of a down sprue, avoiding aspiration, as shown in figure, to deliver liquid cast iron ( p_{m}=7800 kg/m^{3} ) at a rate of 10 kg/s against no head at the base of the sprue (Neglecting the friction and orifice effects) is __________.(answer should be in cm)
In order to avoid aspiration effect
Where A_{1} and A_{2} are crosssectional areas at point 1 and 2.
H_{2} = 20 + 6 = 26 cm
h_{1} = 6 cm
A cylindrical riser is attached to the side of a steel plate casting having dimensions 25cm x 12.5cm x 5cm. The volume shrinkage of steel during solidification is 3% and the volume of riser is 3 times that of dictated by the shrinkage consideration alone. The dimension of the riser in optimum conditions is ____________.
For optimum cylindrical side riser,h = d
Volume of casting, V_{c} = 25 x 12.5 x 5
Shrinkage of steel during solidification = 3%
Minimum volume of the riser necessary is,
A casting of dimension 200 x 100 x 60mm is casted in such a way that 60 mm dimension is vertical and 2/3 rd of it is in drag. If the height of cope is 100 mm and cavity is fed by a bottom gate with a crosssectional area 100mm^{2} , the time (seconds) taken to fill the cavity is _____________.
Hot chamber machine used for die casting
Muller is used for mixing sand
Die electric baker is used for making cores with bentonite as bonding material
Sand blaster is used for cleaning.
A casting of size 100cm x 100cm x 25cm was filled by top and bottom gates with manometric height in pouring basin to be 25 cm. The area of gate is 5cm^{2} . The difference in time (in s) to fill the casting by top and bottom gates is___________.
Casting area, A = 100 x 100 = 10^{4}cm^{2}
casting height, H = 25 cm
Manometric height, h_{t} = 25 cm
Gate area, A_{g} = 5 cm^{2}
Top Gate:
Bottom Gate:
The pouring basin in a sand mould is 200 mm diameter & 100 mm height. The mould cavity is a cube of 125 mm side and must be filled in 25 second. The maximum velocity must ensure laminar flow into the mould cavity and in the gates of circular cross section.
Assume:
(A) Constant temperature,
(B) No loss in the velocity head and
(C) Diameter of gate 8 times diameter of the sprue base. Properties of the molten metal are v=0.9mm^{2} per second,p= 700kg/m^{3} and c_{p}=33.6 J/molk.
The diameter of sprue to avoid aspiration effect is ____________.(fill the values of the 2 integer in between which the answer lies)
The dimension of pouring basin will not affect the pouring time
Let V = maximum velocity of molten metal in the gating system
To ensure the laminar flow in the gating system R_{e} 2000
Worst case, R_{e} = 2000
A cylindrical job with diameter of 200 mm and height of 100 mm is to be cast using modulus method of riser design. Assume that the bottom surface of cylindrical riser does not contribute as cooling surface. If the diameter of the riser is equal to its height, then the height of the riser (in mm) is
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41 videos38 docs27 tests
