Nickel Alloys and Molding Processes Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the purpose of drawing spikes when removing the split pattern from the drag?

To measure the depth of the mold cavity

To tighten the pattern into the sand

To loosen the pattern from the sand (correct)

To create additional molds in the sand

What is the function of the gate and runner in the mold assembly?

To stabilize the cope during pouring

To hold the pattern in place

To increase the cooling time of the metal

To connect the mold cavity to the sprue opening (correct)

Why is the sand around the pattern moistened before withdrawal?

To ensure that the mold remains intact (correct)

To facilitate the introduction of core prints

To accelerate the drying process of the sand

To improve the bonding of the sand particles

What role do core prints play in the molding process?

They assist in locating the core within the mold Signup and view all the answers

What must be done if the lifting force on the cope exceeds its weight due to hydraulic pressure during pouring?

Weights must be placed on the cope or it must be clamped Signup and view all the answers

Which nickel alloy is specifically known for its excellent corrosion resistance and high strength at elevated temperatures?

Monel Metal Signup and view all the answers

What is the primary element in the German Silver alloy?

Copper Signup and view all the answers

Which nickel alloy has a very low coefficient of heat expansion?

Invar Signup and view all the answers

What addition to K-Monel enhances its strength and hardness?

Aluminium Signup and view all the answers

What is the primary use of Nichrome alloy?

Resistance wire Signup and view all the answers

Which of the following nickel alloys is described as hard, white, and ductile?

German Silver Signup and view all the answers

What percentage of nickel does Inconel contain?

79.5% Signup and view all the answers

What is the primary advantage of malleable iron over grey cast iron?

Malleable iron has better ductility and toughness. Signup and view all the answers

How does an increase in carbon content typically affect steel?

It increases hardness while decreasing toughness. Signup and view all the answers

In what situations are alloys of cast iron most commonly utilized?

For components requiring high tensile strength. Signup and view all the answers

Which alloying element is primarily responsible for corrosion resistance in cast iron?

Chromium Signup and view all the answers

When are cast steels preferred over cast iron for applications?

When high impact resistance is necessary. Signup and view all the answers

Which of the following materials is commonly used in the construction of a crankshaft?

Cast iron Signup and view all the answers

What are the typical components of Babbit metal?

Tin and antimony Signup and view all the answers

What is the main advantage of using plastic materials over metals in engineering applications?

Plastic materials can be more lightweight and corrosion-resistant. Signup and view all the answers

What is the main component of yellow brass?

Copper and zinc Signup and view all the answers

What is a limitation of using permanent mould casting?

It has high costs associated with moulds. Signup and view all the answers

Which type of sand mould casting accounts for approximately 80% of total output?

Sand-mould casting Signup and view all the answers

In the two flask system of sand mould casting, what are the names of the upper and lower flasks?

Cope and Drag Signup and view all the answers

What is one of the primary materials used in semi-permanent mould casting?

Graphite Signup and view all the answers

What occurs to the pattern in the expendable pattern process of sand mould casting?

It remains in the mould and melts. Signup and view all the answers

What is the most common design used for sand mould casting?

Two flask system Signup and view all the answers

Which section of an iron foundry does NOT belong to the prominent sections listed?

Casting Detection Signup and view all the answers

What defines the moulding material used in sand mould casting?

It is primarily made of sand. Signup and view all the answers

Which of the following is true regarding cores in casting methods?

Cores can be either permanent or expendable. Signup and view all the answers

What is a key characteristic of sand moulds in the sand-mould casting process?

They are single-casting and destroyed after use. Signup and view all the answers

What is the primary difference between hypoeutectoid and hypereutectoid steel?

Hypoeutectoid steel contains less carbon than the eutectoid composition. Signup and view all the answers

Which of the following is NOT a type of cast iron?

Carbon cast iron Signup and view all the answers

What is the purpose of tempering steel?

To reduce internal stresses and improve toughness. Signup and view all the answers

Which materials are primarily involved in the composition of stainless steels?

Nickel and chromium Signup and view all the answers

What distinguishes age hardening from precipitation hardening?

Age hardening is a subtype of precipitation hardening. Signup and view all the answers

What is the primary purpose of surface hardening?

To improve the fatigue resistance on the surface. Signup and view all the answers

What is flame hardening primarily used for?

To achieve specific surface hardness. Signup and view all the answers

Which of the following is an advantage of nitriding over carburizing?

Nitriding does not significantly alter the dimensions of the part. Signup and view all the answers

What process is used to enhance the resistance of aluminum to corrosion?

Oxidation Signup and view all the answers

What is the main characteristic that differentiates brass from bronze?

Brass contains copper and zinc, while bronze contains copper and tin. Signup and view all the answers

What is a key advantage of using dry sand moulds compared to green sand moulds?

They yield a better surface finish in castings. Signup and view all the answers

Which of the following describes the inherent risks associated with dry sand moulds?

Increased risk of hot tearing in castings. Signup and view all the answers

What disadvantage is commonly associated with dry sand core moulding?

Requires careful setting of cores. Signup and view all the answers

What is a notable feature of Furan and CO2 moulds?

They eliminate the need for flasks. Signup and view all the answers

Why is distortion more common in dry sand moulds than in green sand moulds?

The thermal expansion properties differ significantly. Signup and view all the answers

What is the primary reason for using vacuum or protective atmosphere methods for processing refractory metals?

To prevent rapid oxidation Signup and view all the answers

Which element is primarily used as nuclear fuel due to its radioactive properties?

Uranium Signup and view all the answers

What is a significant drawback of pure uranium when used in nuclear applications?

Weak structural integrity Signup and view all the answers

Which refractory metal has the highest melting point?

Tungsten Signup and view all the answers

What role do alloying elements like chromium and molybdenum play in uranium?

Increase strength and suitability for nuclear applications Signup and view all the answers

Why are specialized melting techniques, like electron beam melting, necessary for refractory metals?

To prevent oxidation during processing Signup and view all the answers

Which property of uranium oxide makes it suitable for certain nuclear applications?

No phase change in inert atmosphere Signup and view all the answers

What is a significant disadvantage of using plastic materials compared to metals?

Plastics can exhibit embrittlement with age. Signup and view all the answers

Which characteristic distinguishes thermosetting plastics from thermoplastics?

They undergo a permanent chemical change when heated. Signup and view all the answers

How do the thermal expansion properties of plastics generally compare to those of metals?

Plastics expand five to ten times more than metals. Signup and view all the answers

Which of the following trade names corresponds to a thermoplastic material?

Tenite Signup and view all the answers

What is the common loading behavior of plastics at room temperature when subjected to small loads?

They show continuous creep behavior. Signup and view all the answers

Which of the following is NOT a characteristic of thermoplastic materials?

They retain their shape permanently after cooling. Signup and view all the answers

What is a reason for the decreasing cost of plastic materials?

Advancements in recycling technologies. Signup and view all the answers

Which of the following applications is most appropriate for cellulose acetate?

Covers and guards in machinery. Signup and view all the answers

What is a primary characteristic of thermoplastic materials after they have been molded?

They can return to a solid state upon cooling. Signup and view all the answers

Which thermosetting plastic is known for its usage in electrical applications?

Bakelite Signup and view all the answers

What is the main advantage of using stellite in cutting tools?

Excellent abrasive resistance Signup and view all the answers

What properties of stellite make it suitable for use in corrosion-prone environments?

Corrosion resistance Signup and view all the answers

Which stellite material has the highest ultimate tensile strength?

Forged stellite Signup and view all the answers

What is the typical range for the coefficient of friction on dry metals?

0.15 to 0.24 Signup and view all the answers

Which of the following properties is NOT characteristic of stellite?

Excellent machinability Signup and view all the answers

In which of the following applications is stellite NOT typically used?

Electrical wiring components Signup and view all the answers

Which mechanical property of forged stellite is specifically mentioned?

Can be rolled, forged, and punched at 1000°C Signup and view all the answers

What is the primary composition of stellite?

Cobalt base with chromium and tungsten Signup and view all the answers

What is one of the limitations of using welded stellite?

High cost Signup and view all the answers

What is a primary characteristic of ‘no-bake’ moulds?

They harden through a chemical reaction without baking. Signup and view all the answers

Why might dry sand core moulds be preferred over other types of moulds?

They allow for the production of large castings without excessive costs. Signup and view all the answers

What major advantage do composite moulds provide compared to traditional moulds?

They combine the advantages of multiple materials for better performance. Signup and view all the answers

What is a disadvantage of using cold-box moulds compared to green sand moulds?

They require more intricate manufacturing processes. Signup and view all the answers

What is the effect of using a very low water content in moulds?

It enhances the hardness of the mixture at room temperature. Signup and view all the answers

Which characteristic makes cold-box moulds more accurate than green sand moulds?

They bond sand grains through chemical processes. Signup and view all the answers

What is a common limitation of green sand moulds?

They require extensive manipulation to maintain sand control. Signup and view all the answers

What temperature is typically used for baking sand cores?

175 to 230°C for 4 to 24 hours. Signup and view all the answers

What is a key advantage of composite moulds in casting complex shapes?

They inherently provide better strength and surface finish. Signup and view all the answers

What type of materials are typically used in the ‘no-bake’ systems?

Furfuryl alcohols, urea, and formaldehyde. Signup and view all the answers

Study Notes

Casting Process

Casting is one of the oldest methods of producing metal components.
It involves melting the metal and pouring it into a mold that has the desired shape.
The solidified metal in the mold is the casting.
The foundry is the place where castings are produced.
Two main types of foundries are: Jobbing and Captive.

Types of Casting Processes

Expendable Mould Casting: The most common; uses a mould formed from a mixture of sand, additives and water. The pattern is destroyed after the metal cools and hardens.
Permanent Mould Casting: The mould, made of metal, is reusable. This method works with lower weight non-ferrous metals and for mass production.
Semi-Permanent Mould Casting: Uses a more durable than permanent molds, made of high refractory material. This is used for a small number of castings and not mass production.

Sand Mould Casting

Most common type of casting: Accounts for 80% of cast parts.
Mould Materials: Sand mixed with additives (such as clay) and water is the most common material that forms the mould.
Types of Sand Mould Casting: Green sand, dry sand, skin-dry sand, loam sand, and cement-bonded sand. Mould surface coatings help protect the mold (avoid penetration by the liquid metal).

Pattern Materials

Wood: Relatively inexpensive but susceptible to warping and requires maintenance. Used for small and short-run production.
Metal: More durable and accurate in size than wood. Used for large scale and mass production or large quantity parts.
Plastic : Easily worked and built up, though more expensive.
Metal inserts: Used to increase strength in specific areas.

Cores

Use of cores: Creates internal cavities or shapes in the casting
Materials for cores: Sand, chemically coated sands, and/or metal inserts.
Important parameters to consider:
- Number of castings
- Size and complexity of the casting
- Molding method
- Type of pattern

Gating System

Need for gates: Molten metal is introduced into the mold cavity through a system of channels called 'gates'.
Types of gates: Include pouring basins, sprues, runners, feeders, gates (top, bottom, wedge), and chills.
Function: Ensures controlled and even flow of metal into the cavity.
Design concerns:
- Avoid metal turbulence
- Minimize gas entrapment during pouring
- Minimize surface erosion
- Ensure efficient feeding of molten metal.

Risers

Purpose of risers: Maintain fluidity of metal to compensate for shrinkage during cooling of casting.
Location: Placed in areas where solidification starts first (usually in thicker sections).
Functions:
- To compensate shrinkage porosity
- To feed the molten metal to the casting to prevent freezing problems.

Defects in Castings

Blow holes: Cavities filled with gas, arising from inadequate venting. Causes can be excess moisture in the sand, inadequate venting, or high gas content of the melt.
Misruns: Incomplete filling of mold due to insufficient metal supply, incorrect gating design, or low-temperature melts.
Cold shuts: Non-fusion defects caused by two streams of metal solidifying separately, caused by poor gating design, inadequate metal temperature or solidification conditions, and improper metal mixing.
Flashes: Extrusion of metal from the die, arising from inadequate tooling or process conditions. Metal from the die cavity that solidifies on the outer edges of the piece.
Penetration: Metal penetrating into the mold, caused by excessive pouring temperature or insufficient mould refractoriness.
Hot tears: (cracks) caused by high internal stresses during solidification of the metal when it has a lower yield strength. Incorrect cooling rate is also a factor. Hot spots due to poor die casting or design can cause this issue.
Soldering. Adhesion of casting metal to the die due to excessive temperature.
Scars and blisters. Small blow-holes caused by gas.

Repair techniques

Cold welding: Employed to correct cracks and cavities on surfaces.
Hot welding: For repairing complex cavities or holes.
Liquid metal welding: For larger cavities on the casting surface.
Metal spraying: Coating on surface.
Luting and impregnation: Sealing agents for surface imperfections.

###Casting Processes, Other than Sand Casting

Permanent mold casting: The metal mold is reused, for mass production and complex or high quality parts.
Die casting: The molten metal is injected into the mold under considerable pressure. Used for intricate or thin-walled parts of nonferrous metals, and produces a dense grain structure.
Investment casting: A shell of refractory material is used around a pattern. Used for small, intricate parts or components or large shapes.
Centrifugal casting: Molten metal is poured into a rotating mold, allowing centrifugal force to distribute the metal properly. Suitable for rotational symmetry.
Continuous casting: Molten metal is poured and solidified continuously, rather than in separate ingots. Used for large shapes of metal.

Foundry Furnaces

Crucible or pot furnace: Simplest and most economical, used for melting ferrous and nonferrous metals.
Electric furnace: More precisely controlled, used when high quality or alloying is necessary.
Cupola: Economical for ferrous metals, and for mass production of castings. This is the main furnace in most foundries.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the intricacies of molding processes and the properties of various nickel alloys. This quiz covers topics ranging from mold assembly components to alloy characteristics and their applications. Ideal for students studying materials science or engineering.