ME 251 Fundamentals of Metal Casting

Steps required to produce a product

1) Design 2) Material selection 3) Process selection 4) Manufacture 5) Inspection & evaluation 6) Feedback

If a solid metal melts at 400C and the temperature of nucleation is 385C the undercooling is what degrees C?

15

𝑡𝑠=𝐵 (V/A)^n where n=1.5 to 2.0 • ts is total solidification time • B is the mold constant • V is the volume of the casting • A is the surface area of the casting

Chvorinov's rule

_____ is used to make material removal from a casting mold easier.

Draft

True/False: Metals that are difficult to machine will also be difficult to cast.

False

True/False: The crystals in the equiaxed zone are spherical and vertically oriented.

False

True/False: The surface finish of metal castings is ideal for final production.

False

True/False: When designing a mold it is best to use cores for hollow areas of the casting.

False

_______ can be used in gating systems to trap foreign material.

Filters

____ _______ is one of the most common casting methods. This method uses an expendable mold.

Sand casting

_______ _________ can cause (1) warping, (2) cracking, and (3) sunk in areas in a mold.

Section thickness

The end of solidification is represented by the equilibrium ________ ___________.

freezing temperature

____________ is the difference between the melting point and the temperature of nucleation.

Undercooling

Define temperature of nucleation

When crystals first form.

When casting metal there is higher ________ between the mold and the ________.

adhesion, material

The columnar zone is highly directional making it __________.

anisotropic

A(n) _____ riser cannot be seen from the outside of the mold.

blind

Filters are typically made of ________ materials.

ceramic

Metal casting involves the selection of mold material. Mold materials talked about in class include ________, ____ and other ______.

ceramic, sand, metals

The _____ zone is the fastest cooling zone, resulting in the _______ ________.

chill, highest strength

The ________ zone is the _______ region. In this zone there is rapid growth that is _____________ to the casting surface.

columnar, weakest, perpendicular

One advantage of metal casting is creating _______ ______ or __________.

complex shapes, geometries

Thicker areas of a mold ________ more causing sunk in areas.

contract

Extra space in the mold pattern is added for ___________ of the metal.

contraction

The top flask of a mold is the ____. The bottom flask of a mold is the ____.

cope, drag

Thermal expansion/contraction can cause ________.

cracking

With a ____ or ____ riser, the metal flows through the mold cavity before entering the riser.

dead, cold

Out of these three which has the fastest cooling rate: permanent mold, sand cast, die cast

die cast

Direction, rate, and type of grain growth is determined by _________ and rate of ____ _______.

direction, heat removal

The ________ zone is centered in the middle of the casted metal.

equiaxed

Casting requires an __________ or a ________-___ mold.

expendable, multiple-use

The two parts of a mold are called ______.

flasks

What determines (1) minimum section thickness, (2) maximum length of a thin section, (3) fineness of detail, (4) ability to fill mold extremities

fluidity

What do the following processes prevent 1) Melting in a vacuum or covered with flux 2) Melting in environments with low-solubility gases 3) Minimizing turbulence

gas porosity

Four casting defects that can occur during solidification are ___ ________, _________ reactions, thermal _________ and thermal ___________. (each term separated by ,)

gas porosity, oxidation, expansion, contraction.

The ______ ______ delivers molten metal to the mold cavity.

gating system

Each nucleation event produces a _____. These _____s determine the __________ properties of the material.

grain, grain, mechanical

Casting metal requires ____ temperature and ___ pressure.

high, low

Casted parts can have ______ sections or ________.

hollow, cavaties

Metal casting can be used to produce _____ parts.

large

A(n) ____ riser does not flow through the mold cavity.

live

Unlike metals, casting plastics require ___ temperate and ____ pressure.

low, high

The solidification process determines the final ________ properties.

material

Chemical reactions can occur between molten metal and its surroundings causing _____ ______ to form.

metal oxides

High superheat has the disadvantage of degrading the ____ faster.

mold

To begin the molding process we must create the ____ ______. Then we will ____ the ________. The molten metal is ______ into the ____ ______. The material is then cooled and allowed to ________. The material is _______ from the ____and is ready for these secondary operations - _________ and __________. (terms in each sentence separated by ,)

mold cavity, melt material, poured mold cavity, solidify, removed mold, finishing inspection

Draft is mainly used for ________-___ molds.

multiple-use

On a graph, superheat is the portion of the curve before the __________ point.

nucleation

The two stages of solidification are __________ and _______ ______. These two stages affect the _____ _________ of the casted material.

nucleation, crystal growth, grain structure

A(n) ____ riser can be seen from outside the mold.

open

The chill zone is located on the _____ most parts of the material.

outer

Unlike plastics, metals tend to _______ at high temperatures.

oxidize

The _______ ____ is the area where the mold is divided into two pieces.

parting line

A mold _______ is typically larger than the final part.

pattern

These are the 3 stages of _____ ______ shrinkage. 1) Contraction of liquid 2) Solidification shrinkage 3) Solid metal contraction

phase change

Two types of finishing for metal castings include secondary _________ and _________.

polishing, machining

Metal casting has different _______ _______ including gravity fed, high pressure, vacuum.

pouring methods

The gating system of a mold includes three parts the _______ cup, the _____, and the ______.

pouring, sprue, runner

The crystals in the equiaxed zone are ________ oriented.

randomly

Filters ________ liquid flow rate and can cause __________.

reduce, turbulence

A _____ is a reservoir of liquid metal that feeds extra metal into the mold to compensate for shrinkage.

riser

Metal casting produces material waste primarily from the use of _____s and ______ ______s.

riser, gating system

A _____ holds excess metal. When the metal casting begins to ________ the metal _________. The excess metal from the _____ is pulled into the mold cavity to avoid surface ______ and other defects. (each term separated by ,)

riser, solidify, contracts, riser, cracks

The first metal is likely oxidized so it is diverted to the ______ and _____ wells to keep it out of the mold.

runner, sprue

Out of these three which has the slowest cooling rate: permanent mold, sand cast, die cast

sand cast

Casting is a _____-producing process

shape

Cooling is ______ in thicker sections.

slower

The _____________ process is a critical step in metal casting as it determines the _____ properties of the material.

solidification, final

When melted, metal absorbs gas in the atmosphere. After pouring, metal solidifies and gas becomes less _______ which forms _____ in the solid metal.

soluble, pores

How much warmer the liquid metal is to the melting temp is called _________.

superheat

To increase fluidity we want to increase this.

superheat

Proper design of the gating system reduces __________.

turbulence

Solidification shrinkage is ________ on the phase change diagram.

vertical

Chvorinov's rule states that total solidification time is proportional to the ______ to _______ ____ ratio. If a material has low surface area and high volume it will cool ______ than a material with a higher surface area of the same volume.

volume, surface area, slower