Over 60 of all metal castings are produced via a sand casting process

Over 60 of all metal castings are produced via a sand

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Over 60% of all metal castings are produced via a sand casting process Disadvantages: Various heat treatments may be applied to relieve stresses from the initial cooling and to add hardness When casting with metals like iron or lead, which are significantly heavier than the casting sand, the casting flask needs to be covered with a heavy plate to prevent a problem known as floating the mold. TA 201 Dr. Shashank Shekhar
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2014-15 Semester-I Sand Casting Steps Sand making (Sand Plant) Mold making Pattern making (Pattern shop) Core making (core shop) Core assembling on mold Pouring Shake out raw casting out Sand blasting and Machining (finishing) Metal making (Melting shop) Transfer of metals To Pouring station Pouring ladle Sent to supplier Design section TA 201 Dr. Shashank Shekhar 21
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2014-15 Semester-I TA 201 Dr. Shashank Shekhar 22 Patterns Taper in patterns for ease of removal from the sand mold Typical metal match-plate pattern used in sand casting Pattern types: (a) single (b) split (c) match plate Lost form casting: where the pattern is lost after casting
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2014-15 Semester-I Possess: Strength Permeability Thermal stability Collapsibility Anchored by core prints (buoyancy of molten metal tends to displace core) Chaplets are used to keep the core from moving TA 201 23 Dr. Shashank Shekhar Cores made of sand aggregates
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2014-15 Semester-I Sand making 24 Green Sand: Plastic mixture of sand grains, clay, water and other materials such as graphite powder Sand muller TA 201 Dr. Shashank Shekhar Binders General water and clay Organic resin Inorganic binder sodium silicate and phosphate Types of sand mold Green sand mold - moisture is high Dry sand mold organic binders rather than clay and good strength Skin dried mold mold cavity surface of green sand mold heated to 10 to 25 mm
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2014-15 Semester-I Heating Analysis Heating to a desired temperature Heat energy requirement 1. The heat to raise the temperature to the melting point. 2. The heat of the fusion to convert it from solid to liquid. 3. The heat to raise the molten metal to the desired temperature for pouring- Super heat . H = V{C s (T m - T o ) + H f + C l (T p -T m )} = density of metal = gm/cm 3 V= volume of metal = cm 3 Cs= Specific heat of solid metal (J/gm/ o c) C l = Specific heat of liquid metal (J/gm/ o c) H f = Heat of fusion on unit mass (J/gm) Tp= Pouring Temperature ( o C) Tm= Melting temperature ( o C) To= Starting/ ambient temperature ( o C) TA 201 25 Dr. Shashank Shekhar
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2014-15 Semester-I Pouring Analysis Care: 1. Pouring Temperature 2. Pouring rate 3. Turbulence Engineering analysis of pouring Bernoulli’s Theorem: Sum of the energies (head, pressure, kinetics and friction) at any two points in a flowing liquid are equal. h = head (cm) P = pressure on the liquid (N/cm 2 ) = density (gm/cm 3 ) F = head loss due to friction (cm) v = velocity of liquid (cm/sec) g = gravitational acceleration (cm/s 2 ) 1 and 2 are any two locations in the flowing liquid 2 2 2 2 2 1 2 1 1 1 2 2 F g v P h F g v P h TA 201 26 Dr. Shashank Shekhar
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2014-15 Semester-I
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