8 The Casting Process Flashcards
NDT method used for service examination of castings
Penetrant PT
Testing methods that may be needed to detect internal defect’s regardless of the material or type of casting
Radiographic RT
Ultrasonic testing UT
The rough surfaces of any casting also can produce problems in this ultrasonic device
Transducer coupling
This method is used extensively in the examination of critical coolant passages in turbine engine blades to measure thickness
Ultrasonic UT
Methods used to detect leading and trailing edge cracks before and during service of turbine blades
Eddy current ET
Penetrant PT
The first step in the casting process is to create this which represents the finished product
Pattern
The pattern may have attachments or grooves in the mold to serve as channels for flow of material into the cavity these are called
Runners
In some casting processes this is made to flow into close contact with the pattern and that has sufficient strength to maintain that position
Mold
An opening to the outside of the mold is called
Spruce
Pinetree shaped structures in solidification seals a small pockets of liquid to freeze later
Dendrites
Large grains in castings cause diffraction effect with which method
Radiografic RT
In castings reflection from grain boundaries cause problems with this method
Ultrasonic UT
Low melting or fusing alloys are known as
Eutectic Alloys
Some of the most important problems connected with the casting process are those of
Shrinkage
The freezing of a liquid from the outside toward the center
Progressive solidification
The freezing from one part of a casting to another, such as from one end to the other end is known as
Directional solidification
The point where metal is poured into the mold is known as
Feed head
In casting, the highest temperature areas immediately after pouring are called
Hot Spots
In a casting isolated sections that freeze early, that may disturb good directional solidification result in
Shrinks, porosity, cracks, ruptures, or warping
Usually located at points of greatest sectional dimension in castings
Hot spots
Used to pour and transport hot molten metal from the melting equipment to the molds
Ladle
Drops of splashing metal lose heat, freeze, and are then entrapped as globules that cannot join completely with the metal which freezes later and are held partially by mechanical bond
Cold shots
Thin sections that cool to rapidly in contact with the mold walls may freeze off before the metal travels it’s complete path, or metal flowing in one direction may solidify and then be met by metal flowing through another path to form a defect known as a
Cold shut
Metal is fed into the cavity that shapes the casting through a system consisting of pouring basins, a down spruce, runners, and ingates
Gating system
Used to replace the contraction of solidification and to promote good directional solidification
Risers
Heat absorbing devices inserted in the mold near the cavity to help and directional solidification
Chills
Fast cooling during and after solidification retards grain growth and thus produces a harder, stronger structure using these
Chills
The bottom part of the flask is called
Drag
The upper part of the flask is known as
Cope
A mixture of sand, clay, and moisture is
Green sand
Used to facilitate the removal from the mold medium
Draft angles
Where the largest two dimensions are in a single plane is this kind of pattern
Flat back
Require separation along two or more planes for removal of the pattern to produce the casting cavity
Irregular parting
Open face containers that hold the molten medium as it is packed around the pattern.
Flasks
Snap, pop off, and slip are all types of these
Flasks
When molds are constructed with removable flasks these are placed over them to maintain alignment during pouring
Jackets
Bodies of mold material, usually in the form of inserts that exclude metal flow to form internal surfaces in a casting
Cores
When a substantial portion of a core is enclosed in a casting, this method is frequently used to determine whether or not the core shifted during casting, or to be certain that all the core material has been successfully removed after casting
Radiography RT
Very large or long slender cores that might give way under pressure of the flowing metal or sometimes give additional support by the use of
Chaplets
This method used to examine the finished casting can reveal discontinuities surrounding chaplet regions and indicate whether the chaplet completely fused with the base metal
Radiography RT
With the mold open, the inside surfaces are subjected to heat from torches, radiant lamps, hot dry air, or electric heating elements to form a dry insulation around the mold cavity this is known as
Skin Drying
A mold made by covering the heated metal pattern with sand that it’s mixed with small particles of a thermosetting plastic
Shell Mold
Mold casting that is used mostly for the shaping of aluminum, copper, magnesium, and zinc alloys
Permanent mold casting
Mold casting when pressure is applied to the liquid metal to cause it to flow rapidly and uniformly into the cavity of the mold, or die
Die Casting
Investment casting is also known as
Lost wax casting
Investment castings of high-strength alloy turbine buckets for gas turbines require NDT methods of
Radiographic RT and penetrant PT
Casting procedure makes use of the rotating mold to develop forces acting on the metal to improve its density towards the outside of the mold
Centrifugal Casting
Method used to produce cast bar
Continuous casting
This melting equipment is charged through a door above the melting zone with layers of coke, iron, and limestone and maybe operated continuously by taking off melted iron is it accumulates in the well at the bottom
Cupola
Fractured forming in metal during solidification resulting from restrained contraction is called
Hot tear
