Materials Science Chapter 2
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Questions and Answers

Which type of furnaces are used for refining pig iron to steel?

  • Basic oxygen
  • Electric arc
  • Both a and b (correct)
  • None of the above

    • What are some deoxidizing agents used in the steel production process?

  • Aluminum
  • Ferrosilicon
  • Manganese
  • All of the above (correct)

    • Cold-formed steel is produced by heating sheets or coils of hot rolled steel.

    False

    What is the maximum carbon content in structural steels?

    <p>less than 0.3%</p> Signup and view all the answers

    Iron carbide is __% carbon by weight.

    <p>6.7%</p> Signup and view all the answers

    What is the primary purpose of normalizing steel?

    <p>Produce a uniform, fine-grained microstructure</p> Signup and view all the answers

    Why is tempering performed on hardened steel?

    <p>To improve ductility and toughness</p> Signup and view all the answers

    What is the main purpose of adding alloy agents to steel?

    <p>To improve corrosion resistance</p> Signup and view all the answers

    Stainless steel has been used in corrosive applications due to its resistance to corrosion.

    <p>True</p> Signup and view all the answers

    In what year were the two types of structural steel used in the United States combined into a single specification?

    <p>1938</p> Signup and view all the answers

    The specifications for A7 and A9 included detailed chemical composition requirements.

    <p>False</p> Signup and view all the answers

    ___ shapes are doubly symmetric wide-flange shapes with parallel flanges.

    <p>W</p> Signup and view all the answers

    What is the maximum solubility limit of carbon in ferrite at 727°C?

    <p>0.022%</p> Signup and view all the answers

    What is the phase that remains as primary ferrite just above the eutectoid isotherm?

    <p>Ferrite</p> Signup and view all the answers

    Proeutectoid ferrite forms at temperatures above 727°C in steel.

    <p>False</p> Signup and view all the answers

    Moderate cooling rates produce _________ without a proeutectoid phase.

    <p>bainite</p> Signup and view all the answers

    Match the following heat treatments with their objectives:

    <p>Annealing = Refine the grain, soften the steel, remove internal stresses Normalizing = Improve machinability or mechanical properties Hardening = Increase strength and hardness Tempering = Increase ductility and toughness</p> Signup and view all the answers

    Explain how spreading salt on ice causes the ice to melt.

    <p>Salt lowers the freezing point of water, causing the ice to melt. This is because the presence of salt disrupts the crystal structure of ice, making it harder for the ice to maintain its solid form.</p> Signup and view all the answers

    At a salt composition of 10%, what is the temperature at which ice will start melting?

    <p>Below 0 degrees Celsius.</p> Signup and view all the answers

    What is the eutectic temperature of the ice and salt combination?

    <p>Depends on the specific salt composition.</p> Signup and view all the answers

    What are the five classes of ceramic materials?

    <p>Oxides, nitrides, carbides, borides, and silicates.</p> Signup and view all the answers

    Name two common ceramic materials used in Civil Engineering structures. Are they organic solid or inorganic solids?

    <p>Concrete and bricks. They are inorganic solids.</p> Signup and view all the answers

    What are the four types of organic solids used in engineering applications?

    <p>Polymers, rubbers, composites, and adhesives.</p> Signup and view all the answers

    What are the main components of the structural steel industry mentioned in the content?

    <p>Producers of structural steel, service centers, structural steel fabricators, and erectors.</p> Signup and view all the answers

    What is the process involved in reducing iron ore to pig iron?

    <p>The process involves using coal, limestone, and iron ore to create pig iron. Carbon from coal reduces iron oxides in the ore, with limestone helping to remove impurities.</p> Signup and view all the answers

    Cold-formed steel is used for structural framing of floors, walls, and roofs as well as interior partitions and exterior curtain wall applications. The thickness of cold-formed steel framing members ranges from _ to _.

    <p>0.455 mm</p> Signup and view all the answers

    Which steel type is primarily used for interior applications?

    <p>409</p> Signup and view all the answers

    304 stainless steel contains 8% chromium and 18% nickel.

    <p>True</p> Signup and view all the answers

    What is the recommended thickness range for cold-formed steel framing members?

    <p>0.455 mm to 3.000 mm</p> Signup and view all the answers

    What are the three forms in which reinforcing steel (rebar) is manufactured?

    <p>plain bars, deformed bars, plain and deformed wire fabrics</p> Signup and view all the answers

    What are the purposes of using deformed bars in reinforcing concrete? Choose the correct option:

    <p>Preventing slipping and allowing the concrete and steel to work as one unit</p> Signup and view all the answers

    In prestressed reinforcement, the steel is under continuous ________.

    <p>tension</p> Signup and view all the answers

    Match the following marking symbols to their meanings:

    <p>Letter code for manufacturer = 1 Numerical code for bar size = 2 Letter code for type of steel = 3</p> Signup and view all the answers

    What is the minimum Yield Strength of A615 steel with Grade 420?

    <p>414 MPa</p> Signup and view all the answers

    What types of steel are used for prestressed concrete reinforcement?

    <p>Both a and b</p> Signup and view all the answers

    Relaxation properties in steel refer to the percent of stress reduction that occurs when constant strain is applied over time.

    <p>True</p> Signup and view all the answers

    Breaking strength of Grade 270 Grade Seven-Wire Strand is _____ MPa.

    <p>1860</p> Signup and view all the answers

    What is the primary method of manufacturing steel framing members?

    <p>Roll forming</p> Signup and view all the answers

    Which industry standards govern the fabrication of cold-formed steel construction materials?

    <p>American Iron and Steel Institute’s Specification for the Design of Cold-Formed Steel Framing Members</p> Signup and view all the answers

    Cold-formed steel shapes can only be produced in limited varieties.

    <p>False</p> Signup and view all the answers

    The designator system for a 6" C-shape with 1 5/8" flanges and made with 0.054" thick steel is ____.

    <p>600S162-54</p> Signup and view all the answers

    Match the fastening product with its description:

    <p>Conventional bolts = Traditional fasteners used for joining structural elements Twist-off-type tension control bolt assemblies = Bolts designed for precise tension control through twisting off at a specific point Anchor rods = Rods used for anchoring structures to the ground Threaded rods = Rods with a helical structure for secure attachment</p> Signup and view all the answers

    Study Notes

    Chapter 2: Nature of Materials

    • Spreading salt on ice causes the ice to melt due to the lowering of the freezing point of water
      • At a salt composition of 10%, the temperature at which ice will start melting is lower than 0°C
      • The eutectic temperature of the ice and salt combination is the lowest temperature at which the mixture will freeze
    • Ceramic materials are classified into five classes
    • Two common ceramic materials used in Civil Engineering structures are
      • Not specified in the text, but examples include brick, concrete, and ceramics
      • They are inorganic solids
    • The four types of organic solids used in engineering applications are
      • Not specified in the text, but examples include polymers, plastics, and rubbers
    • Properties of 15 metals, including lead, zirconium, sodium, and others, can be found in a table
      • Properties include crystal structures, atomic radius, atomic mass, and atomic packing factor

    Chapter 3: Steel

    Steel Production

    • Steel production involves three phases: reducing iron ore to pig iron, refining pig iron to steel, and forming the steel into products
    • The materials used to produce pig iron are coal, limestone, and iron ore
    • The iron is magnetically extracted from the waste, and the extracted material is formed into pellets and fired
    • Reduction of the ore to pig iron is accomplished in a blast furnace
    • The molten iron, with an excess of carbon in solution, collects at the bottom of the furnace

    Iron-Carbon Phase Diagram

    • The iron-carbon phase diagram shows the relationship between steel properties and carbon content
    • The diagram extends only to 6.7% carbon, which corresponds to 100% iron carbide
    • Pure iron undergoes two transformations as temperature increases: ferrite (BCC) to austenite (FCC) at 912°C, and austenite to delta ferrite (BCC) at 1394°CHere are the study notes in markdown format:

    Iron-Carbon Phase Diagram

    • Carbon goes into solution with ferrite at temperatures between 400°C and 912°C
    • Solubility limit is very low, with a maximum of 0.022% at 727°C
    • At temperatures below 727°C, ferrite and iron carbide coexist as two phases
    • From 727°C to 1148°C, solubility of carbon in austenite increases from 0.77% to 2.11%

    Eutectoid Reaction

    • Occurs when carbon content is 0.77% and temperature is 727°C
    • Results in formation of pearlite, a two-phase material consisting of ferrite and iron carbide
    • Ferrite has 0.022% carbon, and iron carbide has 6.7% carbon
    • Forms as thin plates, with a lamellae structure

    Hypoeutectoid and Hypereutectoid Alloys

    • Hypoeutectoid alloys: carbon content less than 0.77%, formed below 727°C
    • Hypereutectoid alloys: carbon content greater than 0.77%, formed above 727°C

    Properties of Steel

    • Ferrite has low strength but is ductile
    • Iron carbide has high strength but is brittle
    • Combining ferrite and iron carbide in different proportions alters mechanical properties of steel
    • Increasing carbon content increases strength and hardness, but reduces ductility
    • Modulus of elasticity of steel does not change with carbon content

    Heat Treatment of Steel

    • Annealing: refines grain, softens steel, removes internal stresses, and increases ductility
    • Normalizing: similar to annealing, but with faster cooling rate
    • Hardening: heating above transformation range, then quenching to form martensite
    • Tempering: heating to improve ductility and toughness of hardened steel

    Steel Alloys

    • Alloying agents can improve hardenability, corrosion resistance, machinability, ductility, and strength
    • Examples of alloying agents include aluminum, sulfur, chromium, nickel, copper, manganese, silicon, molybdenum, and vanadium

    Structural Steel

    • Used in hot-rolled structural shapes, plates, and bars

    • ASTM specifications define grades, types, and classes of structural steel

    • Examples of structural steel grades include ASTM A7 and ASTM A992### Steel Classification and Properties

    • ASTM steel specifications identify the yield strength, while in other specifications, the term grade indicates requirements for both chemical compositions and mechanical properties.

    • The Unified Numbering System (UNS) is based on chemical composition, using a letter to identify the broad class of alloys and a five-digit number to define specific alloys within the class.

    • Table 3.2 summarizes the designations, properties, and composition of ASTM structural steel.

    Steel Types and Applications

    • A36, A53 Gr.B, A500, A501, A529, A572, and A618 are types of structural steel used in various applications.
    • High-strength low-alloy steel is used for structural applications, such as bridges and buildings.
    • Corrosion-resistant steel is used for structural applications exposed to environmental factors.

    Sectional Shapes

    • W, HP, M, S, C, MC, and L shapes are commonly used in structural applications.
    • Figure 3.9 illustrates these structural cross-sectional shapes.
    • Shapes are designated by a letter, followed by two numbers separated by an asterisk, indicating the nominal depth and weight per linear unit length.

    Specialty Steels

    • High-performance steels (HPS) are special products with optimum combinations of properties required for cost-effective, safe, and durable structures.
    • HPS 50W and HPS 70W are weathering steels with corrosion barriers that reduce maintenance needs.
    • HPS 70W has stronger tensile properties than traditional steel used for bridge construction, allowing for reduced material usage.

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    Description

    This quiz covers the nature of materials, including the effect of salt on ice, ceramic materials, and their applications in Civil Engineering.

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