09Lecture-Calc - Weight of molten metal (lead) = W m =...

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ENGR3190U – Lecture 09 - Calculations Chapter 11 – 11.1.3 Buoyancy Calculations in Metal Casting During pouring, buoyancy of the molten metal tends to displace the core, which can cause casting to be defective Force tending to lift core = weight of displaced liquid less the weight of core itself F b = W m - W c F b = buoyancy force (N) W m = weight of molten metal displaced (N) W c = weight of core (N) Weights are determined as volume of core times densities of core material (see table 11.1 for densities). Density of sand = 1.6 g/cm 3 , Lead = 11.3, copper = 8.73, grey cast iron = 7.16, steel = 7.82 Example A sand core has a volume = 1875 cm 3 , determine the buoyancy force tending to lift the core during the pouring of molten lead into the sand cast. Answer : Weight of core W c = 1875(1.6) = 3000g = 3kg
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Unformatted text preview: Weight of molten metal (lead) = W m = 1875(11.3) = 21,188 g = 21.19kg Given 1kg = 9.81N, the buoyancy force = 9.81(21.19 - 3) = 178.4N Chapter 11 11.3.4 True Centrifugal Casting Calculations What rotational speed is required for a G-factor? D gGF N 2 30 = g N R GF 2 ) 30 ( = N = rotation speed (rev/min) g = acceleration of gravity (9.8 m/s 2 ) D = inside diameter of mold (m) R = inside radius of mold (m) GF = G-factor Example A true centrifugal casting operation is to be performed horizontally to make copper tube sections with OD = 25 cm and ID = 22.5 cm. What rotational speed is required if a G-factor of 65 is used to cast the tubing? Answer: Inside diameter of mold D = OD of the casting = 25 cm = 0.25 m 7 . 681 25 . ) 65 )( 8 . 9 ( 2 30 = = N rev/min...
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09Lecture-Calc - Weight of molten metal (lead) = W m =...

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