Metals Flashcards
Alloy:
a combination of pure metals to give greater strength or resistance to corrosion
Ferrous Alloy:
alloys that contain a lot of iron (e.g.: stainless steel, galvanized iron)
rolling
process of passing metal through rollers to produce the needed shape
- can be done while metal is hot or cold
- hot rolling eliminates flaws in the metal
- cold rolling inceases metal’s strength and elastic limit, but decreases ductility
Non Ferrous Alloys:
doesn’t contain much iron (e.g.: aluminum, copper, zinc)
Cast Iron:
hard brittle alloy of iron and 2.1 - 4% carbon that can be readily cast in a
mold, use for pipes, plumbing fixtures, hardware, castings, etc. (Crystal Place made of it)
Wrought Iron:
iron that has been purified by beating it repeatedly with a hammer, used
for ornamental work, grilles, pipes, and outdoor furniture (Eiffel Tower made of it)
Steel:
any range of alloys of iron and carbon that contain less than 2% carbon, the most
widely used structural metal in construction, used for framing, concrete, rebar, lathing,
conduit, pipes, fixtures, connectors like nails, bolts, and pins.
Aluminum:
Light weight metal with good thermal/electrical conductivity and resistance
to corrosion, used for lightweight framing, railings, grills, siding, curtain walls, doors/
windows, flashings, roofing, hardware, etc
Galvanic Corrosion:
an electrochemical process where one metal corrodes preferentially to another when they both are in electrical contact and immersed in an electrolyte (which is a liquid or gel that contains ions and can be decomposed by electrolysis)
Purpose of Galvanizing:
When metal is going to be used in an environment where corrosion is likely, it is often galvanized so that it will be able to withstand the conditions.
Galvanizing:
coating iron or steel with a protective layer of zinc by immersing it in a molten bath.
Anodizing:
process of coating aluminum with a protective oxide layer by an electrolytic process
galvanic series
zinc
glavanized steel
aluminum
steel and iron
stainless steel
lead
tine
copper alloys (brass, bronze)
copper
-listed in order of sesceptibility to corrosion; the farther apart the metals are, the more likely corrosion will occur when the metals are in direct contact
As carbon is added to steel…
strength increases but ductility deacreases
Copper:
Metal that resists corrosion, electrical and thermal activity, used for electrical
work, water pipes, roofing/flashing, and mesh
Brass:
metal that resists corrosion, used for finish hardware, plumbing, HVAC
components and fittings
Lead:
Metal that resists corrosion and is workable, but also toxic, heavy, soft, and weak,
used for foundations, rough hardware, roofing and flashing
Zinc:
Metal used for roof coverings, flashings, and protective coatings for steel
Monel:
Metal used for roofing, flashing, countertops, sinks
Bessemer Process:
steelmaking procedure where carbon, silicon, and other impurities
are removed from iron to make steel.
Basic Oxygen Process:
steelmaking procedure where a hollow, water-cooled lance is
lowered into a container of molten iron/recycled steel scrap and a stream of pure oxygen
is blown in at high pressure from the lance to burn off the excess carbon/impurities.
Light Gauge Steel:
steel that is cold rolled and lighter than .018”
Bulb Tees:
a steel reinforcing member used when constructing pre-stressed, poured
gypsum deck. When the gypsum is poured, it surrounds the Bulb-Tee.
terneplate
an alloy of 75% lead and 25% tin used to plate steel for roofing
Wide Flanges:
used for beams and columns (took the place of American Standard (aka I Beam) shapes)
3 standard series for open web steel joists
K- standard
LH - long span
DLH - DLH
• Galvanic Action or electrolysis occurs …
…when different metals are in contact and moisture is present.
• One metal corrodes as its ions are deposited onto
the other metal
• When two metals are close to each other on the
galvanic scale (right) they have a lessor tendency to
corrode.
• Cathodes are stable metals not prone to corrosion
• Anodes are less stable and more likely to corrode • So keep Cathodes and Anodes away from each
other!! They don’t place nice.
Cathode and Anode diagram
Angles:
versatile, used for short beams supporting small loads (e.g.: as lintels
spanning doors and windows in masonry construction)
• Primarily used in steel construction connect wide flange beams, girders, and
columns
• Used as diagonal bracing and as members of trusses when paired back to back
with flat gusset plates at the joints of the truss
• Channels:
used with truss members and bracing as well as for short beams/lintels
Open Web Steel Joist
• A lightweight steel truss used to provide direct support for roof or floor decks and
to transfer the load imposed on the deck to the structural frame (column or beam)
• Selected based on the span between bearing points, joist spain, slope, live/dead
loads, collateral loads, wind up lift, deflection criterial, and max depth allowed
• Spacing is commonly ranges from 2’ - 10’ on center
Joist Girders
are beefier versions designed to carry heavier loads…usually bays of the open web steel joists. These bear on columns and structure.
• Remember: columns hold up joists, which hold up beams, which hold up decking
• Rivets:
steel fasteners consisting of a cylindrical body and formed head that is brought to a a high heat inserted through holes matched in members to be joined and then worked with a special hammer to make another head on the other side.
• As it cools is shrinks and clamps the jointed pieces together
• Was originally the most used technique, but is very labor intensive compared to
bolting and welding
Common bolts:
easy to find in hardware stores, and installed for less than high-
strength bolts. Used in joints where lower strength is sufficient enough to carry the load
• Act primarily in bearing and shear
• High Strength Bolts:
heat treated during manufacture to develop necessary
strength
• Can get connecting ability from sheer resistance or from being tightened to the
point hat the members they join are kept from slipping by the friction between
them (know as slip critical connections)
• Inserted into holes slightly larger than the diameter of the bolt
• Washers may or may not be required, depending on if load needs to be bread
over a larger area
• Tightened with an electric wrench to 70% of its ultimate tensile strength if used
to connection by friction
• Hard to verify if necessary tension has been met
Welding:
joints the members of a steel frame as if they were a monolithic whole, and connections are stronger than members they join in shear and moment force resistance.
• Welding and bolting can be combined in the same connection to take advantage of the unique qualities of each
- Arc welding: an electrode is held close to a seam between steel members and an electric arch generates heat to melt both and form a single puddle which then cools and solidifies
- A complex science in the field, air must be kept away to prevent quick oxidation
- Required thickness/length of weld is determined by designer
What is the designation for the most commonly used structural steel for beams?
A36
A36 refers to the ASTM Standard A36/A36M, Standard Specification for Carbon Structural Steel
-Steel meeting this standard has a minimum yeld point of 36,000 psi
A36 is one of ht ecommonly used steels for riveted, bolted, and welded construction for bridges and buildings and for general structural purposes.
A153 steel is the standard for
hot dip zonc coating on iron and steel hardware
A441 steel is
a high strength strucutral steel used for welded construction
A501 steel is the designation for
hot formed welded and seamless carbon steel structural tubing
Which of the following is NOT a standard designation for open web steel joists
DLH
K
LH
ML
ML is not a designation
DLH - deep long span
K-standard open web joists
LH-long span joists
the depths in K series for steel joists range from
8 in - 30 in and increase in increments of 2 in
the depths in LH and DLH series for steel joists range from
18 in - 96 in and increase in increments of 4 in
The stringers of prefabricated steel utility stairs are normally constructed of
a. angle iron
b. channel sections
c. steel plate
d. tube sections
b. channel sections
any of hte listed forms can be used, but stringers are normally constructed of steel channel sections with the flanges turned away from the stair
Which type of brass finish would best prevent tarnish and require the least maintenance?
An organic finish woul dbest prevent tarnish and require the least maintenance
anodized finished are used on what type of metal
aluminum
Which of the following is not a copper alloy?
a. austenitic stainless steel
b. monel metal
c. muntz metal
d. nickel silver
a. austenitic stainless steel
stainless steel is an alloy of iron, carbon, and chromium
-austentic stainless steel is the most common type;also contains some nickel and/or manganese; nonmagnetic and not heat treatable
monel is a trade name for a metal alloy of…
copper and nickel
muntz metal is a common alloy of …
…60% copper and 40% tin
nickel silver is name given to an alloy of
65% copper, 25% zinc, and 10% nickel
Which of the following additives is NOT added to steel to improve corrsion resistance?
a. chromium
b. copper
c. tungsten
d. molybdenum
c. tungsten
tungsten is added to steel to improve the material’s ability to retain its strength when exposed to high temperatures
what are additives added to steel to improve its corrosion resistance?
chromium, copper, molybdenum, nickel
two advantages of using a copper roof are its
workability
resistance to corrosion
disadvantages of copper roofing include
easily dented
expsnsive material for roofing
what percentage of carbon does structural steel typicall contain
0.2%-0.5% ; considered medium carbon steel; most common
steel with over 2.0% carbon is classified as
cast iron
galvanic action can be avoided by…
…using neoprene spacers between dissimilar metals
Dissimilar metals should be physically separated by
nonconducting materials such as neoprene in order to prevent galvanic action
increasing the thickness of dissimilar metals will not prevent galvanic action; it will only prostpone complete deterioration
true or false. Direct contact with water will spped up galvanic action
true
moisture in that air is enough to cause galvanic action
joining metals with heat and a filler metal with a metling point above 800 deg F is called
brazing
welding is joining two metals by heating them above…
their metling points
soldering is joining two metals with
lead based or tin based alloys as a filler metal that melt below 500 deg F
Oil canning is …
…a perceived waviness across the flat areas of sheet metal panels. It is a naturally-occurring phenomenon that is inherent in all light-gage sheet metal. SMACNA’s new “Architectural Sheet Metal Manual,” 6th edition, provides methods from design to installation to mitigate its occurrence.
Oil canning is more apparent under shallow cross lighting so its presence is more discernible during certain seasons or times of day. Also, differing thermal forces can create waviness–either temporary or sustained–as the sun moves across the sky.
Oil canning is an aesthetic issue, not a structural problem or a defect. It is unrealistic to expect any architectural roof or similar wide-metal element to be totally free of some degree of oil canning.
in steel manufacturing what do manganese, molybdenum, vanadium, nickel and chromium do?
manganese - resistance to abrasion and impact
molybdenum - gives strength
vanadium - imparts strength and toughness
nickel and chromium - strength toughness and corrosion resistance
american standard beams are known as…
S shapes
which of the following are characteristics of stainless steel?
a. it cannot be welded
b. it should not be in contact with copper
c. it is an alloy of steel and chromium
d. it is only available with mecahnical and coated finishes
e. it corrodes easily if exposed to oxygen
e. it is approximately as strong as bronze
B, C, D
which of the following types of metal should NOT be specified for connection hardware and flashing for use with wood treated with ACQ preservative?
a. aluminum
b. copper
c. stainless stell
d. hot dip galvanized
a. aluminum
ACQ (alkaline copper quat) is a wood preservative that contains up to 96% copper.
- it has taken the place of CCA (chromated copper arsenic)
- any metals used in proximity to ACQ treated woof must be compatible with copper accorgin tot he galvanic series
- aluminum flashing or connectors should never be used with treated lumber
- copper is the best choice, but while copper flashing is readily available, not all fasteners are made of copper
sherardizing
in the selection of exposed flashing, stainless steel doesn’t require additional proteective coating, true or false
true
copper and stainless steel expand and contract at about the same rate. true or false
true
