Casting Processes Flashcards
What is casting?
Casting is a process in which molten metal flows by gravity or other force into a mold where it solidifies in the shape of the mold cavity.
What is an ingot?
The term ingot is usually associated with the primary metals industries; it describes a large casting that is simple in shape and intended for subsequent reshaping by processes such as rolling or forging.
What are advantages of the casting process?
- Casting can be used to create complex part geometries, including both external and internal shapes
- Some casting processes are capable of producing parts to net shape. No further manufacturing operations are required to achieve the required geometry and dimensions of the parts.
- Casting can be used to produce very large parts. Castings weighing more than 100 tons have been made
- The casting process can be performed on any metal that can be heated to the liquid state
What are disadvantages of the casting process?
They include limitations on mechanical properties, porosity, poor dimensional accuracy and surface finish for some casting processes, safety hazards to humans when processing hot molten metals, and environmental problems.
What is the difference between an open mold and a closed mold
In an open mold, the liquid metal is simply poured until it fills the open cavity. In a closed mold, Figure 2.1b, a passageway, called the gating system, is provided to permit the molten metal to flow from outside the mold into the cavity. The closed mold is by far the more important category in production casting operations.
What are the two main categories of casting?
expendable mold casting and permanent-mold casting
What is an expendable mold?
An expendable mold means that the mold in which the molten metal solidifies must be destroyed in order to remove the casting.
What is a permanent mold?
A permanent mold is one that can be used over and over to produce many castings.
What are benefits of expendable molds?
More intricate parts can be cast.
What are advantages and disadvantages of permanent molds?
Part shapes in the permanent-mold processes are limited by the need to open the mold. On the other hand, some of the permanent mold processes have certain economic advantages in high production operations.
What does Chvorinov’s rules refer to?
Equates solidification time to the volume and surface area of the casting, with a mold constant.
What does Chvorinov’s rule indicate
Chvorinov’s rule indicates that a casting with a higher volume-to-surface area ratio will cool and solidify more slowly than one with a lower ratio. This principle is put to good use in designing the riser in a mold. To perform its function of feeding molten metal to the main cavity, the metal in the riser must remain in the liquid phase longer than the casting.
What are the three steps during shrinkage?
(1) liquid contraction during cooling prior to solidification.
(2) contraction during the phase change from liquid to solid, called solidification shrinkage.
(3) thermal contraction of the solidified casting during cooling to room temperature.
What is the name of the cavity created by shrinkage?
a pipe
What are the parts of a sand casting mold?
The mold consists of two halves: cope and drag. The cope is the upper half of the mold, and the drag is the bottom half. These two mold parts are contained in a box, called a flask, which is also divided into two halves, one for the cope and the other for the drag. The two halves of the mold separate at the parting line.
