Casting Basics-> Sand Molds (A) Flashcards
What is CASTING?
Turning metal into a molten form and then pouring it into a cavity of the desired shape
Advantages of CASTING
Create complex shapes(“organic”), and cavities and passageways
Disadvantages of CASTING
Poor material properties causes large grain formation during cooling and defects. Hard dimensional control. Slow and energy intensive
Expandable mold methods
The mold is destroyed and rebuilt every time it is used
Permanent mold methods
The mold can be used multiple times
What is “Charge material”?
The material that is initially fed into the process. (RAW MATERIAL, SCRAP METAL, PRE-ALLOYED METALURGICAL)
FURNACES
Responsible for all molten metal production
ELECTRIC-ARC
electric discharges
INDUCTIVE
electricity induced by coils
What is SLAG?
impurity that results when high temperature molten metal is exposed to atmospheric oxygen
IRON ORE + COKE fuel make
Oxygen in the air react with the coke fuel, producing carbon monoxide
SAND CASTING PROS
- Readily Available and Cheap
- Refractory properties
- Reusable
- Supports Heavy Loads
- Conforms to Any Shape
- Collapses for Part Shrinkage
- Permeable to Steam and Gas
Which sand is vastly used for SAND CASTING?
SILICA SAND (SiO2).
(abundant and inexpensive and high melting point)
Three ingredients that BLEND for the perfect molding medium
CLAY, WATER and SAND
What is BANK SAND?
20% CLAY, just add water, naturally occurring
What is LAKE OR SHARP SAND?
processed sand, uniform pure silica sand
What do CEREALS do?
added to help wick the water for a uniform moisture distribution
What are MULLING MACHINES?
machines that mix sand, water, and clay
What are alternative SANDS for SAND CASTING?
Zircon (ZrSiO4) (high thermal conductivity)
Chromite (FeCr2O4)
Olivine (MgFe)2SiO4
What are PRE-TREATMENTS?
treatments done before the metal pour to improve performance
What blend does the GREEN SAND MOLD use?
(most common)
SAND+CLAY+MOISTURE
green = moist
What are the SKIN DRIED MOLDS?
Molds which have a heated surface layer of about 1/2 in. Improves surface finish.
DRY SAND MOLDS
Baked in the oven after forming
COLD CURE MOLDS
Uses a chemical binder rather than heat ton improve strength and surface finish
What is a PATTERN?
3D representation of the final desired part.
Usually 3D PRINTED and made of plastic
FLASK
the molding box. Top half is called COPE, bottom half is called DRAG. Held by LOCKING/LOCATING PINS
Other components for SAND MOLD
TURNOVER BOARD and TAPERED DOWELS
Parts of the FLASK
MOLD CAVITY, POURING BASIN, SPRUE, RUNNER, GATES, RISER, VENTS
What is the purpose of the BLIND RISER?
To catch any SLAG(impurity) and slow down metal flow. Improves material properties/
