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Construction Materials & Methods > Steel Material > Flashcards

Steel Material Flashcards

1
Q

What are some pros of steel as a building material? (4)

A
  • Homogeneous properties
  • Light in proportion to its strength
  • Well-suited for rapid construction
  • Plentiful and relatively inexpensive
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2
Q

What are some cons of steel as a building material? (2)

A
  • prone to corrosion

- loss of strength in fires

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3
Q

What is steel?

A

steel is basically an alloy of iron and carbon, but several other elements are used in various proportions and combinations to give steel different properties

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4
Q

What two groups do ferrous alloys come in?

A
  • steel

- cast iron

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5
Q

What are the three main types of steel?

A
  • low carbon steel
  • medium carbon steel
  • high carbon steel
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6
Q

What are the characteristics of low carbon, or mild steel? (3)

A
  • soft, good ductility and weldability
  • employed in cold-rolled or hot-rolled condition
  • used for pressed work and where welding is required
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7
Q

What are the characteristics of medium carbon steel? (3)

A
  • high strength
  • ductility or toughness may be obtained by heat treatment
  • used mostly in machinery components
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8
Q

What are the characteristics of high carbon steel? (3)

A
  • very high strength and hardness
  • used in heat-treated conditions
  • used mainly for tools and dies
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9
Q

How does carbon content affect iron alloys?

A

greater proportions of carbon generally increase the hardness and decrease the ductility of the iron alloy

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10
Q

Describe the microstructure of A36 steel grade. (2)

A
  • ferrite grains

- pearlite grains

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11
Q

Describe the microstructure of a pearlite grain. (2)

A
  • ferrite layer (light gray)

- iron carbide layer (dark gray)

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12
Q

How is iron found in its natural state?

A

not as a pure metallic material, but as a mineral in the form of iron oxides

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13
Q

How much iron does the mined material contain?

A

between 20% and 60%

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14
Q

What is ore containing more than 60% iron called, and why?

A

reduced ore, since it does not require additional refining

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15
Q

What are the three basic raw materials needed in the production of iron?

A
  • iron ore
  • coal
  • limestone
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16
Q

How is coal used in iron production?

A

coal is converted into coke and used as burning fuel for the blast furnace

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17
Q

How is limestone used in iron production?

A

limestone is used as a flux material in the blast furnace

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18
Q

What do coal, limestone, and iron ore work together to produce?

A

pig iron, the basic material used in the production of all ferrous metals and alloys

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19
Q

What is pig iron?

A

a metallic iron material containing a small percentage of carbon and traces of silica, manganese and phosphorus

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20
Q

How is carbon content reduced in a basic-oxygen furnace?

A

by blowing oxygen through molten carbon-rich pig iron, producing an alloy with desired chemistry for low-carbon steel

21
Q

What may be added to a basic-oxygen furnace?

A

a carefully controlled amount of scrap steel

22
Q

How does an electric arc furnace work?

A

scrap metal and/or direct reduced ore, pig ore, molten blast furnace steel are heated by means of an electrical arc current to desired melting point

23
Q

What are the advantages of an electric arc furnace? (3)

A
  • may use scrap metal only
  • reduced energy requirement in comparison to other furnaces
  • may be stopped and restarted easily, giving flexibility of production for various grades of material
24
Q

What is the disadvantage of an electric arc furnace?

A

must be near abundant electrical grid

25
Q

What is the next step in iron production after blasting?

A

molten steel is then transported to be poured into molds or cast into slabs, blooms, or billets

26
Q

What is the next step in iron production after molding/casting?

A

these are then transported to be cooled slowly till room temperature is achieved prior to rolling in desired shape and size

27
Q

How is hot-rolled steel made?

A

billets or blooms are heated above recrystallization point and then rolled into desired shape and length

28
Q

How is hot-rolled steel cooled?

A

after, they are slowly cooled to room temperature

29
Q

What are wide-flanged shaped (W-shapes) used for?

A

the most commonly used shape for beams and columns

30
Q

What are channels, angles and tees used for?

A

trusses, lighter-weight framing, and other miscellaneous uses

31
Q

What size are angle shapes?

A

4”x3” nominal legs with 3/8” thickness

32
Q

What are WT shapes?

A

T-shape cut from a W-shape

33
Q

What shapes do hollow structural sections (HSS) come in?

A

hollow square, rectangular, round, and elliptical shapes

34
Q

How are HSS made?

A

made by cold or hot-forming steel strip and welding longitudinally

35
Q

What are HSS resistant to?

A

especially suitable for structural members subject to twisting or buckling stresses

36
Q

What are HSS used for?

A

trusses, structurally efficient column sections, and where the simple external profile is desirable

37
Q

What does strengthening steel improve?

A

strength, ductility and durability

38
Q

What are the three methods used to alter steel’s microstructure?

A
  • heat treatment: formation of additional grain boundaries
  • strain or work-hardening: generation of dislocations
  • alloying: introduction of interstitial and/or substitutional atoms
39
Q

How is steel weathering prevented?

A

surface oxidation adheres to base metal, limiting further rusting

40
Q

Where is weathering steel used?

A

highway and bridge structures, eliminating the need for a protective coating

41
Q

How is stainless steel made?

A

added nickel and chromium

42
Q

What is the purpose of stainless steel?

A

forms self-protecting oxide layer that provides long-lasting protection against corrosion

43
Q

What is a downside of stainless steel?

A

much more expensive

44
Q

What products are made from cold-formed steel? (3)

A
  • corrugated steel decking
  • light-gauge metal studs and joists
  • high-strength wire for concrete prestressing strands
45
Q

What is cold-working?

A

working or shaping at near-ambient temperatures

46
Q

How is cold-working unique?

A

plastic flow of the material increases the number of dislocations which pile/tangle up on intersecting slip planes

47
Q

What is the advantage of cold-working?

A

the increase in deformation during the fabrication processes results in an increased resistance to further deformation while in service

48
Q

What is the disadvantage of cold-working?

A

increases strength, but decreases toughness

Construction Materials & Methods (29 decks)

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