Metals and alloys engineering materials

 Metals and Alloys (4 hrs)

6.1 Iron: types, properties and uses

->Iron is a chemical element with the symbol Fe (from the Latin word "ferrum") and atomic number 26. It is one of the most abundant elements on Earth and has a variety of types, properties, and uses. Here's an overview:

1. Types of Iron:

   a. Wrought Iron: It is a low-carbon iron alloy with a fibrous structure. Wrought iron is tough, malleable, and ductile. It was traditionally used for ornamental purposes, such as gates, fences, and decorative items.

   b. Cast Iron: This iron alloy contains a higher carbon content than wrought iron (typically 2-4%). Cast iron is brittle and has excellent castability. It is commonly used in the manufacturing of engine blocks, pipes, cookware, and construction materials.

   c. Steel: Steel is an iron alloy that contains a small amount of carbon (less than 2%). By varying the carbon content and adding other elements, steel can exhibit a wide range of properties. It is widely used in construction, automotive manufacturing, appliances, and many other industries.

2. Properties of Iron:

   a. High Melting Point: Iron has a melting point of 1,538 degrees Celsius (2,800 degrees Fahrenheit), making it suitable for applications requiring high-temperature resistance.

   b. Ferromagnetism: Iron is strongly magnetic and can be magnetized, which makes it useful in the production of magnets and electromagnets.

   c. Good Conductivity: Iron is a good conductor of both heat and electricity, making it valuable in electrical wiring and heat transfer applications.

   d. Ductility and Malleability: Iron can be easily shaped and formed into various shapes without breaking, which enhances its usability in manufacturing processes.

3. Uses of Iron:

   a. Construction: Iron and steel are widely used in construction, including buildings, bridges, and infrastructure. They provide structural support and are highly durable.

   b. Transportation: Iron and steel are key materials in the automotive, aerospace, and maritime industries. They are used in the manufacturing of vehicles, ships, and aircraft due to their strength and impact resistance.

   c. Machinery and Equipment: Iron is used in the production of machinery, tools, and equipment for various industries. Its high strength and wear resistance make it suitable for such applications.

   d. Household Goods: Iron and steel are found in many household items, such as appliances, cutlery, and furniture. These materials offer durability and aesthetic appeal.

   e. Energy Sector: Iron is essential in the production of wind turbines, electrical transformers, and power generation equipment.

   f. Packaging and Containers: Iron and steel cans are commonly used for packaging food and beverages due to their strength and ability to protect the contents.

It's worth noting that iron can also form various alloys by combining it with other elements like carbon, chromium, nickel, and others. These alloys, such as stainless steel, provide enhanced properties like corrosion resistance, high temperature resistance, and improved strength for specific applications.

6.2 Steel: composition and types (carbon steel and alloy steel)

⇨  Steel is an iron alloy that contains a small amount of carbon (typically less than 2%). The composition of steel can vary depending on the specific requirements and desired properties. There are two primary types of steel based on their composition: carbon steel and alloy steel. 1. Carbon Steel: Carbon steel is a type of steel that primarily consists of iron and carbon. It is the most common and widely used form of steel due to its affordability, strength, and versatility. The carbon content in carbon steel can range from 0.05% to 2.0%. a. Low Carbon Steel (Mild Steel): It contains a low percentage of carbon (usually less than 0.3%) and small amounts of other elements. Low carbon steel is easy to work with, weldable, and has good formability. It is used in construction, automotive parts, pipelines, and general-purpose applications. b. Medium Carbon Steel: With a carbon content between 0.3% and 0.6%, medium carbon steel offers higher strength and hardness than low carbon steel. It is used in applications that require increased strength and wear resistance, such as axles, gears, and railway tracks. c. High Carbon Steel: High carbon steel has a carbon content ranging from 0.6% to 2.0%. It provides excellent strength and hardness but is less ductile and more brittle than low or medium carbon steel. High carbon steel is used in applications like cutting tools, springs, and wire ropes. 2. Alloy Steel: Alloy steel is a type of steel that contains additional alloying elements apart from carbon. These elements can include elements like manganese, chromium, nickel, molybdenum, vanadium, and others. Alloying elements are added to enhance specific properties of steel, such as strength, hardness, corrosion resistance, and heat resistance. Alloy steel is commonly used in applications that require higher performance and specialized properties. Some common types of alloy steel include: a. Stainless Steel: Stainless steel is a corrosion-resistant alloy steel that contains a minimum of 10.5% chromium. It also typically contains nickel and other elements. Stainless steel is known for its excellent corrosion resistance, high strength, and hygienic properties. It is widely used in kitchenware, medical equipment, chemical processing, and architectural applications. b. Tool Steel: Tool steel is a high-carbon alloy steel that is specifically designed for use in making cutting tools, molds, and dies. It has exceptional hardness, wear resistance, and heat resistance. Tool steel often contains elements such as tungsten, vanadium, and molybdenum. c. High-Strength Low-Alloy (HSLA) Steel: HSLA steel contains small amounts of alloying elements like copper, phosphorus, and vanadium. It provides improved strength, toughness, and weldability compared to carbon steel. HSLA steel is used in structural applications, automotive components, and pressure vessels. d. Alloy Tool Steel: Alloy tool steel combines high strength and hardness with excellent wear resistance. It is commonly used in the production of cutting tools, dies, and molds. These are just a few examples of the many types of alloy steel available, each with its own unique composition and properties suited for specific applications.

6.3 Types of carbon steels and their uses

⇨  Carbon steel is a broad category that encompasses various types of steel based on their carbon content and other alloying elements. The different types of carbon steel have distinct properties that make them suitable for specific applications. Here are some common types of carbon steels and their uses: 1. Low Carbon Steel (Mild Steel): - Uses: Low carbon steel is widely used in general-purpose applications due to its affordability, formability, and ease of machining. It is used in construction, automotive parts, structural components, sheet metal, pipes, and tubes. 2. Medium Carbon Steel: - Uses: Medium carbon steel offers higher strength and hardness than low carbon steel, making it suitable for applications that require increased strength and wear resistance. It is used in axles, crankshafts, gears, railway tracks, and forging applications. 3. High Carbon Steel: - Uses: High carbon steel provides excellent strength and hardness but is less ductile and more brittle than low or medium carbon steel. It is used in applications that require strong, wear-resistant components, such as cutting tools, springs, knives, and wire ropes. 4. Ultra-High Carbon Steel: - Uses: Ultra-high carbon steel contains a very high carbon content, typically between 1.25% and 2.0%. It has exceptional hardness and wear resistance, but its brittleness limits its use in most applications. It is mainly used in specialized applications like knives, chisels, and blades. 5. High-Strength Low-Alloy (HSLA) Steel: - Uses: HSLA steel contains small amounts of alloying elements such as copper, phosphorus, and vanadium. It offers improved strength, toughness, and weldability compared to regular carbon steel. HSLA steel is used in structural applications, automotive components, pressure vessels, and bridges. 6. Dual-Phase Steels: - Uses: Dual-phase steels are a type of high-strength low-alloy (HSLA) steel. They have a microstructure consisting of both ferrite and martensite phases, which provides excellent strength and ductility. Dual-phase steels are used in automotive components, construction equipment, and high-strength structural applications. 7. Spring Steel: - Uses: Spring steel is a type of high carbon steel known for its excellent elasticity and resilience. It is used to manufacture springs and spring components in various industries, including automotive, industrial equipment, and firearms. 8. Boiler and Pressure Vessel Steel: - Uses: Boiler and pressure vessel steel is used in the manufacturing of boilers, pressure vessels, and storage tanks that contain high-pressure liquids or gases. It is designed to withstand high temperatures and pressures, ensuring safety and reliability in such applications. These are just a few examples of the types of carbon steels and their common uses. The specific type of carbon steel chosen for a particular application depends on factors like required strength, hardness, ductility, machinability, and cost considerations.

6.4 Basic introduction of heat treatment of steel

⇨ Heat treatment is a controlled process used to alter the microstructure and properties of steel by heating and cooling it under specific conditions. It involves heating the steel to a specific temperature, holding it at that temperature for a certain period, and then cooling it at a controlled rate. The heat treatment process can enhance the strength, hardness, toughness, ductility, and other mechanical properties of steel.

The basic steps involved in the heat treatment of steel are as follows: 1. Heating: The steel is heated to a specific temperature, known as the austenitizing temperature. This temperature is determined based on the type of steel and the desired properties. Heating can be done using various methods such as direct flame, induction, or electric furnaces. 2. Soaking: Once the steel reaches the austenitizing temperature, it is held at that temperature for a specified period. This soaking time allows for the complete transformation of the microstructure and the dissolution of any impurities or segregation present in the steel. 3. Cooling: After the soaking period, the steel is cooled at a controlled rate. The cooling rate is crucial in determining the final microstructure and properties of the steel. a. Annealing: Slow cooling (also known as annealing) produces a soft and ductile microstructure with improved machinability and reduced internal stresses. Annealing is often used to relieve stress, refine grain structure, and restore ductility in hardened steels. b. Normalizing: Normalizing involves cooling the steel in still air after austenitizing. It produces a fine-grained microstructure and improved mechanical properties, such as increased strength and toughness. Normalizing is commonly used to refine the structure of carbon and low-alloy steels. c. Quenching: Quenching involves rapid cooling of the steel by immersing it in a quenching medium, such as water, oil, or polymer solutions. This rapid cooling "freezes" the microstructure, resulting in a hard and brittle structure called martensite. Quenching is used to increase the hardness and wear resistance of the steel. d. Tempering: Tempering is performed after quenching to reduce the brittleness and improve the toughness of the steel. The quenched steel is heated to a specific temperature below its critical point and held for a certain time, followed by air cooling. Tempering reduces the hardness of the steel while increasing its ductility and toughness. 4. Additional Processes: Depending on the desired properties, other heat treatment processes can be performed, such as case hardening, carburizing, nitriding, and induction hardening. These processes introduce specific elements or compounds to the steel surface to improve wear resistance, hardness, and other surface properties. Heat treatment is a critical process in the manufacturing and fabrication of steel components. It allows for the optimization of steel properties to meet specific application requirements, such as in automotive parts, machinery, tools, and structural components. The selection of the appropriate heat treatment process depends on the type of steel, its intended application, and the desired properties.

6.5 Different commercial forms of rolled steel section

⇨  Rolled steel sections are produced by rolling steel ingots or billets through various rolling processes to achieve specific shapes and sizes. These sections are widely used in construction, manufacturing, and other industries due to their structural strength and versatility. Here are some different commercial forms of rolled steel sections:

1. Beams: - I-Beams: Also known as H-beams, these sections have an "I" shape with two horizontal flanges and a vertical web in the middle. I-beams are commonly used in structural applications, such as building frames, bridges, and support structures. - Wide Flange Beams: Similar to I-beams, wide flange beams have wider flanges and are often used in larger and heavier load-bearing applications. 2. Channels: - C-Channels: C-shaped sections with a flat back and two perpendicular legs. They are used for structural support, framing, and as purlins in building construction. - U-Channels: U-shaped sections with two parallel legs and a base. U-channels are commonly used for edging, support brackets, and structural components. 3. Angles: - Equal Angles: L-shaped sections with equal leg lengths. Equal angles are used for structural framing, bracing, and as corner guards. - Unequal Angles: L-shaped sections with unequal leg lengths. Unequal angles are used in applications where differing leg lengths are required, such as structural supports and framework. 4. Tubes and Pipes: - Hollow Structural Sections (HSS): Steel tubes and pipes with a hollow cross-section. HSS are used in structural applications, including columns, beams, and trusses. - Round Tubes: Steel tubes with a circular cross-section. They are used in various applications, such as furniture, handrails, and automotive components. - Square and Rectangular Tubes: Steel tubes with square or rectangular cross-sections. These sections are commonly used in construction, fabrication, and architectural applications. 5. Plates and Sheets: - Steel Plates: Flat sheets of steel with varying thicknesses. Steel plates are used in various industries, including construction, shipbuilding, and manufacturing equipment. - Steel Sheets: Thin, flat steel sections typically less than 6mm in thickness. Steel sheets find applications in roofing, cladding, and general fabrication. 6. Rails: - Steel Rails: Rolled steel sections specifically designed for railway tracks. Steel rails provide a stable and durable track surface for trains. 7. Others: - Flat Bars: Rectangular-shaped bars with a flat surface. Flat bars are used in construction, fabrication, and general structural applications. - Round Bars: Steel bars with a circular cross-section. Round bars are used in machining, construction, and for making fasteners. These are just a few examples of the different commercial forms of rolled steel sections. The specific section chosen for a particular application depends on factors such as load-bearing requirements, structural design, and industry standards. Manufacturers often offer a wide range of standard sizes and lengths for these rolled steel sections to meet various customer needs.

6.6 Reinforcing steels (TOR and TM T)

⇨  Reinforcing steels, such as TOR and TM T, are types of steel bars used in reinforced concrete structures to provide strength and enhance structural integrity. These steel bars are commonly used in construction projects, including buildings, bridges, highways, and other infrastructure. Here's an overview of TOR and TM T reinforcing steels: 1. TOR Steel: - TOR stands for "Thermo-Mechanically Treated One Reinforcement." - TOR steel bars are manufactured by subjecting mild steel billets to a series of mechanical and thermal treatments. - The process involves rolling the steel billets at a high temperature, followed by quenching them in water or other cooling mediums and then allowing them to cool naturally. - The controlled heat treatment gives TOR steel bars enhanced mechanical properties, including increased strength, ductility, and bond strength with concrete. - TOR steel bars have a characteristic ribbed pattern on their surface, which improves the grip between the steel and concrete, providing better reinforcement. 2. TM T Steel: - TM T stands for "Thermo-Mechanically Treated." - TM T steel bars undergo a similar manufacturing process to TOR steel bars, involving hot rolling, water quenching, and natural cooling. - TM T steel bars are designed to have a higher strength and better ductility compared to standard mild steel bars. - These bars also have a ribbed or deformed surface pattern for improved bond strength with concrete. - TM T steel bars are commonly used in seismic-resistant structures, high-rise buildings, and infrastructure projects where higher strength and performance are required. Both TOR and TM T reinforcing steels provide several advantages in reinforced concrete structures: - Increased Strength: The heat treatment process imparts higher tensile strength to the steel bars, ensuring they can withstand higher loads and stresses. - Improved Bond Strength: The ribbed or deformed surface pattern enhances the bond between the steel bars and the concrete, resulting in effective load transfer between the two materials. - Better Ductility: The heat treatment process improves the ductility of the steel bars, allowing them to deform without failure under excessive loads or seismic activity. - Corrosion Resistance: The ribbed surface pattern also improves the corrosion resistance of the steel bars by increasing the surface area for concrete cover and reducing the risk of corrosion-induced damages. - Compatibility: TOR and TM T reinforcing steels are compatible with commonly used concrete mixtures and construction practices, making them suitable for a wide range of construction projects. It's important to note that the specific standards and specifications for TOR and TM T reinforcing steels may vary across different regions and countries. Therefore, it is recommended to adhere to local building codes and consult relevant design and construction guidelines when using reinforcing steels in concrete structures.

6.7 Properties, advantages and uses of' stainless steel, tool steel, brass, aluminum and duraluminum

⇨ Certainly! Here are the properties, advantages, and common uses of stainless steel, tool steel, brass, aluminum, and duralumin: 1. Stainless Steel: - Properties: Stainless steel is an alloy primarily composed of iron, chromium, and other elements like nickel and molybdenum. It exhibits excellent corrosion resistance, high strength, good ductility, and durability. Stainless steel is also known for its aesthetic appeal. - Advantages: The main advantage of stainless steel is its corrosion resistance, which makes it suitable for applications in various environments, including marine, chemical, and food processing industries. It is also highly durable, easy to clean, and has good heat resistance. Additionally, stainless steel is available in different grades with varying properties to meet specific application requirements. - Uses: Stainless steel is widely used in kitchenware, cutlery, appliances, medical equipment, automotive parts, construction materials, and architectural applications. It is also extensively used in the pharmaceutical, chemical, and oil and gas industries. 2. Tool Steel: - Properties: Tool steel is a high-carbon alloy steel known for its exceptional hardness, toughness, and wear resistance. It typically contains elements like tungsten, vanadium, and molybdenum, which enhance its properties. - Advantages: Tool steel exhibits high strength and hardness, making it ideal for applications that require cutting, shaping, or forming materials. It offers excellent wear resistance and can withstand high temperatures without losing its hardness. Tool steel is also known for its dimensional stability and ability to hold a sharp edge. - Uses: Tool steel is used in the manufacturing of cutting tools, molds, dies, punches, and other tools. It is commonly employed in industries such as automotive, aerospace, metalworking, and plastic injection molding. 3. Brass: - Properties: Brass is an alloy composed primarily of copper and zinc. It exhibits good corrosion resistance, high electrical and thermal conductivity, and is easily machinable. - Advantages: Brass is known for its attractive appearance, low friction, and excellent formability. It can be easily shaped, bent, and soldered. Brass also has good acoustic properties and is resistant to tarnishing. - Uses: Brass is used in various applications, including plumbing fittings, electrical connectors, musical instruments, decorative items, coins, and ammunition casings. Its antimicrobial properties also make it suitable for applications in healthcare settings. 4. Aluminum: - Properties: Aluminum is a lightweight metal with a low density. It has good corrosion resistance, high thermal and electrical conductivity, and is highly malleable and ductile. - Advantages: Aluminum's low weight makes it attractive for applications where weight reduction is critical, such as in the aerospace and automotive industries. It is also non-toxic, non-magnetic, and has excellent reflectivity and recyclability. - Uses: Aluminum is used in a wide range of applications, including aircraft and vehicle bodies, beverage cans, building facades, electrical conductors, kitchen utensils, and packaging materials. It is also used in construction, transportation, and manufacturing industries. 5. Duralumin: - Properties: Duralumin is an aluminum alloy that typically contains copper, magnesium, and manganese. It combines the properties of aluminum, such as low density and corrosion resistance, with increased strength and improved mechanical properties. - Advantages: Duralumin offers higher strength and improved hardness compared to pure aluminum. It has good fatigue resistance and retains its strength at elevated temperatures. Duralumin is also lightweight and has good machinability. - Uses: Duralumin is commonly used in aircraft construction, where its combination of strength and lightness is critical. It is also used in automotive parts, bicycle frames, sporting goods, and in various structural applications. It's important to note that the specific properties, advantages, and uses of these materials may vary depending on the specific grades or alloys used within each category. Additionally, the selection of a particular material for a specific application should consider factors such as cost, environmental conditions, mechanical requirements, and design considerations.

6.8 Introduction to corrosion of metals and its revention

⇨ Corrosion is a natural process that occurs when metals react with their surrounding environment, resulting in the deterioration and degradation of the metal. It is a major concern in various industries, including construction, infrastructure, manufacturing, and transportation. Understanding corrosion and implementing prevention measures is crucial to prolong the lifespan and performance of metal structures and components. Here is an introduction to corrosion of metals and its prevention: 1. What is Corrosion? - Corrosion is the electrochemical reaction between a metal and its environment, typically involving the presence of moisture, oxygen, and other corrosive agents. - The most common form of corrosion is the oxidation of metals, where metal atoms lose electrons and form metal ions. - Corrosion can manifest in different forms, including rusting, pitting, galvanic corrosion, stress corrosion cracking, and crevice corrosion. 2. Factors Affecting Corrosion: - Environment: Corrosion rates are influenced by factors such as humidity, temperature, pH levels, pollutants, and exposure to corrosive substances like saltwater or chemicals. - Metal Composition: Different metals and alloys have varying susceptibility to corrosion. Some metals, like stainless steel and aluminum, form protective oxide layers that slow down corrosion, while others, like iron, are more prone to rusting. - Electrolyte Conductivity: The presence of moisture or aqueous solutions facilitates the movement of ions, accelerating the corrosion process. 3. Methods of Corrosion Prevention: - Material Selection: Choosing corrosion-resistant metals or alloys for specific applications can significantly reduce corrosion risks. For example, stainless steel is highly resistant to rusting. - Protective Coatings: Applying protective coatings, such as paints, polymers, or metallic coatings, can create a barrier between the metal and the corrosive environment. - Cathodic Protection: This method involves connecting a sacrificial anode (a more reactive metal) to the metal being protected. The sacrificial anode corrodes instead of the protected metal, safeguarding it from corrosion. - Corrosion Inhibitors: Chemical substances can be added to the environment or applied as coatings to reduce the corrosion rate. These inhibitors form a protective layer on the metal surface, slowing down the corrosion process. - Design Modifications: Modifying the design of structures or components can minimize corrosion by improving drainage, avoiding crevices where moisture can accumulate, and incorporating proper ventilation. - Environmental Control: Controlling the environment through measures such as dehumidification, proper insulation, and corrosion-resistant coatings can help prevent corrosion. 4. Regular Inspection and Maintenance: - Regular inspection and maintenance are essential to identify and address corrosion-related issues in a timely manner. This includes monitoring the condition of metal structures, conducting corrosion testing, and implementing appropriate maintenance and repair procedures. It's important to note that no corrosion prevention method is entirely foolproof. A combination of approaches, tailored to the specific application and environment, is often necessary to effectively combat corrosion. Additionally, ongoing research and advancements in materials science continue to provide new methods and technologies for corrosion prevention.