1. FUNDAMENTALS OF METAL CASTING
Overview of Casting Technology
Heating and Pouring
Lecture from M.P. Groover

2. Solidification Processes
Starting work material is either a liquid or is in a highly plastic condition, and a part is created through solidification of the material
Solidification processes can be classified according to engineering material processed:
Metals
Ceramics, specifically glasses
Polymers and polymer matrix composites (PMCs)
Lecture from M.P. Groover

3. Figure Classification of solidification processes.
Lecture from M.P. Groover

4. Casting Melt the metal Pour it into a mold Let it freeze
Process in which molten metal flows by gravity or other force into a mold where it solidifies in the shape of the mold cavity
The term casting also applies to the part made in the process
Steps in casting seem simple:
Melt the metal
Pour it into a mold
Let it freeze
Lecture from M.P. Groover

5. Capabilities and Advantages of Casting
Can create complex part geometries Can create both external and internal shapes Some casting processes are net shape; others are near net shape Can produce very large parts Some casting methods are suited to mass production
Lecture from M.P. Groover

6. Disadvantages of Casting
Different disadvantages for different casting processes:
Limitations on mechanical properties
Poor dimensional accuracy and surface finish for some processes; e.g., sand casting
Safety hazards to workers due to hot molten metals
Environmental problems
Lecture from M.P. Groover

7. Parts Made by Casting
Big parts
Engine blocks and heads for automotive vehicles, wood burning stoves, machine frames, railway wheels, pipes, church bells, big statues, pump housings
Small parts
Dental crowns, jewelry, small statues, frying pans
All varieties of metals can be cast, ferrous and nonferrous
Lecture from M.P. Groover

8. Overview of Casting Technology
Casting is usually performed in a foundry
Foundry = factory equipped for making molds, melting and handling molten metal, performing the casting process, and cleaning the finished casting
Workers who perform casting are called foundrymen
Lecture from M.P. Groover

9. The Mold in Casting
Contains cavity whose geometry determines part shape
Actual size and shape of cavity must be slightly oversized to allow for shrinkage of metal during solidification and cooling
Molds are made of a variety of materials, including sand, plaster, ceramic, and metal
Lecture from M.P. Groover

10. Open Molds and Closed Molds
Figure Two forms of mold: (a) open mold, simply a container in the shape of the desired part; and (b) closed mold, in which the mold geometry is more complex and requires a gating system (passageway) leading into the cavity.
Lecture from M.P. Groover

11. Two Categories of Casting Processes
Expendable mold processes – uses an expendable mold which must be destroyed to remove casting
Mold materials: sand, plaster, and similar materials, plus binders
Permanent mold processes – uses a permanent mold which can be used over and over to produce many castings
Made of metal (or, less commonly, a ceramic refractory material
Lecture from M.P. Groover

12. Advantages and Disadvantages
More intricate geometries are possible with expendable mold processes Part shapes in permanent mold processes are limited by the need to open the mold Permanent mold processes are more economic in high production operations
Lecture from M.P. Groover

13. Sand Casting Mold
Figure Sand casting mold.
Lecture from M.P. Groover

14. Sand Casting Mold Terms
Mold consists of two halves:
Cope = upper half of mold
Drag = bottom half
Mold halves are contained in a box, called a flask
The two halves separate at the parting line
Lecture from M.P. Groover

15. Forming the Mold Cavity
Mold cavity is formed by packing sand around a pattern, which has the shape of the part When the pattern is removed, the remaining cavity of the packed sand has desired shape of cast part The pattern is usually oversized to allow for shrinkage of metal during solidification and cooling Sand for the mold is moist and contains a binder to maintain its shape
Lecture from M.P. Groover

16. Use of a Core in the Mold Cavity
The mold cavity provides the external surfaces of the cast part In addition, a casting may have internal surfaces, determined by a core, placed inside the mold cavity to define the interior geometry of part In sand casting, cores are generally made of sand
Lecture from M.P. Groover

17. Gating System
Channel through which molten metal flows into cavity from outside of mold
Consists of a downsprue, through which metal enters a runner leading to the main cavity
At the top of downsprue, a pouring cup is often used to minimize splash and turbulence as the metal flows into downsprue
Lecture from M.P. Groover

18. Riser
Reservoir in the mold which is a source of liquid metal to compensate for shrinkage of the part during solidification
The riser must be designed to freeze after the main casting in order to satisfy its function
Lecture from M.P. Groover

19. Questions
Advantages of Shape casting process. Difference between a pattern and a core in sand casting? Difference between open and closed mold
Lecture from M.P. Groover

20. Heating the Metal Heat to raise temperature to melting point
Heating furnaces are used to heat the metal to molten temperature sufficient for casting
The heat required is the sum of:
Heat to raise temperature to melting point
Heat of fusion to convert from solid to liquid
Heat to raise molten metal to desired temperature for pouring
Lecture from M.P. Groover

21. Total Heat required to raise Temperature of metal to the pouring temperature
Lecture from M.P. Groover

22. Question:
One cube meter of certain eutectic alloy is heated in a crucible from room temperature to 100 degree Celsius above its melting point for casting. The alloy's density = 7.5g/cm3 , melting point = 8000 C, Specific heat = 0.33 J/g C in solid state and 0.29 J/g C in liquid state; and heat of fusion = 160 J/g. How much heat energy must be added to accomplish the heating, assuming no losses?
Lecture from M.P. Groover

23. Pouring the Molten Metal
For this step to be successful, metal must flow into all regions of the mold, most importantly the main cavity, before solidifying
Factors that determine success
Pouring temperature
Pouring rate
Turbulence
Lecture from M.P. Groover

24. Engineering Analysis of Pouring
Lecture from M.P. Groover

25. Engineering Analysis of Pouring
Continuity Law:-
Q = v1 A1 = v2 A2
Q = Volumetric flow rate
v = Flow Velocity
A = Cross sectional area of Liquid
Lecture from M.P. Groover

26. Engineering Analysis of Pouring
Lecture from M.P. Groover

27. Question
A mold sprue is 20cm long and the cross-sectional area at its base is 2.5cm2 . The sprue feeds a horizontal runner leading into a mold cavity whose volume is 1560cm3 . Determine: (a) velocity of molten metal at base of the sprue (b) Volume rate of flow and (c) time to fill the mold.
Lecture from M.P. Groover

28. Summary
Formulas please …….
Lecture from M.P. Groover