AME 1 End of Unit

B. Bronze: Due to its corrosion resistance and good bearing properties.

Explanation:

Bronze, specifically nickel-aluminum bronze, is the most common material for large marine vessel propellers. This choice is primarily due to its excellent corrosion resistance, which is crucial for components submerged in seawater. Additionally, bronze offers good bearing properties, which help to reduce wear and tear.  

1. Why nickel aluminium bronze is used for VEEM Propellers

veemmarine.com

2. A Guide to Different Types of Bronze Alloys - MetalTek International

www.metaltek.com

3. Industrial - Selecting Bronze Bearing Materials - Copper Development Association

www.copper.org

While other materials like stainless steel and aluminum alloys have their advantages, bronze remains the preferred choice for large marine propellers due to its overall performance and cost-effectiveness.

Why the other answers are incorrect:

• A. Cast iron: While cast iron is strong and inexpensive, it is not suitable for marine propellers due to its susceptibility to corrosion in saltwater environments. Corrosion can weaken the propeller over time, reducing its efficiency and safety.
• C. Stainless steel: Stainless steel is highly resistant to corrosion, but it is generally too heavy for large marine propellers. The weight of the propeller directly impacts the vessel's fuel consumption and performance.
• D. Aluminum alloy: Although aluminum alloys are lightweight and offer good corrosion resistance, they may not have the necessary strength and durability for large marine propellers, especially in demanding conditions.

Answer:

B. Kitchen cutlery

Explanation:

Austenitic stainless steel is commonly used for kitchen cutlery due to its excellent corrosion resistance, durability, and ease of cleaning. It's also non-reactive, meaning it won't alter the taste of food.

Answer:

B. Surgical instruments

Explanation:

Martensitic stainless steel is known for its high hardness and strength, making it an excellent choice for surgical instruments. It can be easily sharpened and maintains a sharp edge, crucial for precision in medical procedures.

Why the other options are incorrect:

• A. Kitchen sinks: While stainless steel is commonly used for kitchen sinks, martensitic stainless steel is not the ideal choice for this application. It's more susceptible to corrosion and staining compared to other types of stainless steel, such as austenitic.
• C. Construction beams: Martensitic stainless steel, while strong, is generally not used for construction beams due to its lower ductility compared to other types of steel. This makes it more prone to brittle fracture under stress.
• D. Electrical wiring: Martensitic stainless steel is not a good conductor of electricity and is therefore not suitable for electrical wiring. Copper is the primary material used for this purpose.

B. Copper-nickel alloy: Due to its excellent corrosion resistance and heat transfer properties.  

1. Copper-Nickel Alloys

www.copper.org

Explanation:

Copper-nickel alloys are the preferred choice for seawater cooling pipes due to their exceptional resistance to corrosion in marine environments. This is crucial for ensuring the longevity and reliability of the piping system. Additionally, copper-nickel alloys exhibit good heat transfer properties, which can enhance the efficiency of the cooling system.  

1. Cu-Ni Alloy Resistance to Corrosion and Biofouling - Copper Development Association

www.copper.org

While other materials like stainless steel offer corrosion resistance, copper-nickel alloys generally excel in this area, especially in seawater conditions. Cast iron and ductile iron are susceptible to corrosion, and while they might be cost-effective initially, the long-term costs associated with maintenance and replacement can outweigh the initial savings.

Why the other answers are incorrect:

• A. Cast iron: While cast iron is strong and cost-effective, it is highly susceptible to corrosion in the marine environment. This would quickly degrade the pipe and lead to leaks and other issues.
• C. Stainless steel: While stainless steel offers good corrosion resistance, it can be more expensive than copper-nickel alloys for large-diameter pipes. Additionally, the thermal conductivity of stainless steel is lower than copper-nickel, which can affect heat transfer efficiency in cooling systems.
• D. Ductile iron: Ductile iron is stronger than cast iron, but it is still susceptible to corrosion in seawater. It may not offer the same level of durability and longevity as copper-nickel alloys in this specific application.

Copper-nickel alloys provide the optimal combination of corrosion resistance, heat transfer properties, and durability for seawater cooling pipes in marine vessels.

B. Bronze, stainless steel, and ductile iron: Due to their combination of strength, corrosion resistance, and durability.

This is the correct answer as it accurately lists the three materials commonly used for ship's side valves and provides a concise explanation of their suitability.

Why the other options are incorrect:

• A. Cast iron: While cast iron can be used in some marine applications, it's generally not suitable for ship's side valves due to its brittleness and susceptibility to corrosion in the harsh marine environment.
• C. Aluminum and copper: While both aluminum and copper have their applications in marine engineering, they are not typically used for ship's side valves. Aluminum may lack the necessary strength and corrosion resistance, while copper is often alloyed with other metals (like tin to form bronze) to improve its properties for marine use.
• D. Plastic and rubber: These materials are not suitable for ship's side valves due to their lack of strength and durability to withstand the pressures and harsh conditions of the marine environment. They are also susceptible to degradation from exposure to saltwater and UV radiation.

Answer:

A. Iron (60-70%), Chromium (16-18%), Nickel (8-10%)

Explanation:

Austenitic stainless steel is primarily composed of iron, with chromium being the key alloying element providing corrosion resistance. Nickel is added to stabilize the austenitic structure and improve properties like ductility and toughness. While the exact percentages can vary depending on the specific grade, the general composition falls within the ranges provided in option A.

Why the other options are incorrect:

• B. Copper (50%), Zinc (30%), Tin (20%): This composition describes brass, not stainless steel.
• C. Aluminum (70%), Magnesium (20%), Silicon (10%): This composition is closer to an aluminum alloy, not stainless steel.
• D. Titanium (60%), Vanadium (25%), Molybdenum (15%): This composition describes a titanium alloy, not stainless steel.

Stainless steel is primarily an iron-based alloy with chromium as the essential element for corrosion resistance. Nickel is often added for improved properties.

Answer:

B. 70% copper, 29% zinc, 1% tin; used for heat exchanger tubes  

1. What Is Admiralty Brass Properties Uses And Composition - Munot Metalloys

www.munotmetalloys.com

Explanation:

Admiralty brass is typically composed of approximately 70% copper, 29% zinc, and 1% tin. The addition of tin significantly improves the alloy's corrosion resistance, making it ideal for marine applications, especially heat exchanger tubes.

Why the other options are incorrect:

• A. 90% copper, 10% aluminum; used for propeller blades: This composition describes aluminium bronze, not admiralty brass. While both are used in marine applications, their specific properties and applications differ.
• C. 60% copper, 40% zinc; used for engine bearings: This composition describes brass, but not admiralty brass. While brass is used in various marine components, its properties are not ideal for heat exchanger tubes, which require better corrosion resistance.
• D. 80% copper, 20% lead; used for plumbing pipes: This composition describes lead brass, which is not commonly used due to health concerns related to lead exposure. Additionally, lead brass is not suitable for marine environments due to its susceptibility to corrosion.

Admiralty brass, with the addition of tin, offers superior corrosion resistance compared to standard brass, making it a suitable choice for heat exchanger tubes in marine applications.

Answer:

A. Carbon, silicon, manganese, chromium, nickel, and molybdenum.

Explanation:

• A is correct. These elements are commonly added to steel to modify its properties, such as strength, hardness, corrosion resistance, and ductility.
• B is incorrect. While some of these elements might be used in specific steel alloys or as impurities, they are not primary alloying elements.
• C and D are incorrect. These elements are gases or alkali metals, respectively, and are not typically used as alloying elements in steel production.

Answer:

A. Cast iron: Due to its high strength and heat resistance.

Explanation:

Cast iron is the most common material for cylinder heads in small auxiliary engines due to its excellent heat dissipation properties and high strength to withstand combustion pressures. It also offers good wear resistance.  

1. Abrasion resistant Cast iron

www.emcasting.com

While aluminum alloys and copper alloys have some advantages, cast iron is generally preferred for its overall performance and cost-effectiveness in this application.

Why the other answers are incorrect:

• B. Aluminum alloy: While aluminum alloys are lightweight and have good heat dissipation, they lack the necessary strength and heat resistance for a cylinder head, which is subjected to high pressures and temperatures during combustion.
• C. Copper alloy: While copper has excellent thermal conductivity, it is generally too soft for a cylinder head and lacks the necessary strength to withstand combustion forces.
• D. Stainless steel: Stainless steel is strong and corrosion-resistant, but it lacks the heat dissipation properties required for a cylinder head. It would overheat under the high temperatures generated during combustion.

Cast iron, with its combination of strength, heat resistance, and cost-effectiveness, remains the preferred choice for cylinder heads in small auxiliary engines.

Answer:

A. 90% copper, 10% aluminum; used for propeller blades

Explanation:

Aluminium bronze typically consists of around 90% copper and 10% aluminum. It's widely used for marine applications, especially propeller blades, due to its excellent combination of strength, corrosion resistance, and resistance to cavitation.

Why the other options are incorrect:

• B. 70% copper, 30% zinc; used for electrical wiring: This composition describes brass, not aluminium bronze. While brass is used for some electrical applications, it's not the primary choice for marine environments due to its lower corrosion resistance compared to aluminium bronze.
• C. 60% copper, 40% tin; used for engine bearings: This composition describes bronze, not aluminium bronze. Bronze is used for bearings due to its good anti-friction properties, but aluminium bronze offers superior strength and corrosion resistance for marine applications.
• D. 80% copper, 20% lead; used for plumbing pipes: This composition describes lead brass, which is not commonly used in modern applications due to health concerns related to lead exposure. Aluminium bronze offers better corrosion resistance and mechanical properties for marine environments.

Answer:

A. Stainless steel is an iron alloy containing at least 10% chromium and 8% nickel.

Explanation:

• A is correct. Stainless steel is primarily an iron alloy with chromium as the essential element providing corrosion resistance. Nickel is often added to improve properties like toughness and ductility.
• B, C, and D are incorrect. While these are all alloys, they do not define stainless steel.

The minimum chromium content for stainless steel to exhibit corrosion resistance is around 10.5%, but the exact composition can vary depending on the specific type of stainless steel.