AME 1 End of Unit

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.

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:

B. 90% copper, 10% nickel; used for heat exchanger tubes

Explanation:

Cupro-nickel alloys typically contain around 90% copper and 10% nickel. They are widely used for heat exchanger tubes in marine applications due to their excellent resistance to saltwater corrosion.

Why the other options are incorrect:

• A. 70% copper, 30% nickel; used for engine blocks: While copper alloys are used in some engine components, this specific composition is not typically used for engine blocks. The properties required for engine blocks, such as heat resistance and strength, are better suited to other alloys.
• C. 60% copper, 40% zinc; used for propeller shafts: This composition describes brass, not cupro-nickel. Brass is often used for marine applications, but propeller shafts typically require higher strength and corrosion resistance than brass can provide.
• D. 80% copper, 20% tin; used for electrical wiring: This composition describes bronze, not cupro-nickel. While bronze has good conductivity, it's not the primary choice for electrical wiring due to its cost compared to copper. Additionally, copper is a more efficient conductor.

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.

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:

C. 93% aluminum, 4% copper, 3% magnesium; used for superstructure components

Explanation:

Duralumin is primarily an aluminum alloy containing approximately 93% aluminum, 4% copper, and 3% magnesium. Its key properties are high strength-to-weight ratio and good corrosion resistance, making it suitable for superstructure components on marine vessels like decks, bulkheads, and frames.

Why the other options are incorrect:

• A. 90% copper, 10% aluminum; used for propeller blades: This composition describes aluminium bronze, not duralumin. While both are used in marine applications, their specific properties and applications differ.
• B. 70% copper, 29% zinc, 1% tin; used for heat exchanger tubes: This composition describes admiralty brass, not duralumin. Brass alloys are primarily copper-zinc based, while duralumin is an aluminum alloy.  
  1. Resources: Standards & Properties - Copper & Copper Alloy Microstructures: Brasses

  

  www.copper.org

• 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. Duralumin is an aluminum alloy, not a copper-based alloy.

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, specifically those containing copper and nickel, are the preferred choice for seawater-cooled heat exchangers in marine vessels. These alloys offer exceptional corrosion resistance, which is crucial for components in direct contact with seawater. Additionally, copper-nickel alloys have excellent heat transfer properties, ensuring efficient heat exchange.  

1. Corrosion resistance of copper-nickel alloys

nickelinstitute.org

2. Copper Nickel Heat Exchangers: Benefits & Suitable Applications - YouTube

www.youtube.com

While other materials like stainless steel and aluminum alloys have some advantages, copper-nickel alloys provide the optimal combination of properties for this specific application.

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 heat exchanger's performance.
• C. Stainless steel: Stainless steel offers good corrosion resistance, but it is generally less efficient at heat transfer compared to copper-nickel alloys. This can impact the overall efficiency of the heat exchanger.
• D. Aluminum alloy: Although aluminum alloys have good heat transfer properties and are lightweight, they are susceptible to corrosion in seawater, especially in the presence of salts and other impurities. This would significantly reduce the heat exchanger's lifespan.

Copper-nickel alloys provide the optimal combination of corrosion resistance and heat transfer efficiency for seawater-cooled heat exchangers in marine applications.

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.

Answer:

B. 304: Interior fittings, railings; 316: Hull components, bilge pumps

Explanation:

• 304 stainless steel is often used for interior fittings and railings on marine vessels due to its good corrosion resistance in less severe environments.
• 316 stainless steel is better suited for external components exposed to saltwater, such as hull components and bilge pumps, due to its superior resistance to chloride-induced corrosion.

Options A, C, and D contain incorrect pairings of steel grade and application.

Why the other options are incorrect:

• A. 304: Kitchen sinks, electrical wiring; 316: Propellers, engine components: While both 304 and 316 have their applications, electrical wiring is typically not made from stainless steel due to cost and conductivity considerations. Additionally, propellers often require materials with higher strength and specific corrosion resistance properties, which 316 might not fully provide.
• C. 304: Propellers, rudder; 316: Kitchen appliances, decorative trim: Propellers and rudders are exposed to harsh marine environments and require superior corrosion resistance, which is better provided by 316 stainless steel. 304 is more suitable for interior applications like kitchen appliances and decorative trim.
• D. 304: Engine components, structural beams; 316: Interior lighting, ventilation ducts: Engine components often require materials with specific heat resistance and mechanical properties, which 304 might not fully provide. Interior lighting and ventilation ducts are generally not exposed to the same level of harsh conditions as external components and can be adequately served by 304 stainless steel.

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.