Metals Flashcards
(27 cards)
Types of steel
steel advantages = high strength + ductility, ease/speed/precision
disadvantages = melts when heated, will corrode
low carbon steel = .06-.3%
medium carbon = .3-.5%
high carbon = .5-.8%
as carbon increases, strength increases, but ductility decreases, so medium is ‘best’
weathering steel = corten/has copper added to form patina
A36/A992 = common in W shapes (.25-.29 carbon)
A440 = high strength, for bolting, riveting
A441 = low alloy for welding
Ornamental metals
handrails, guardrails, elevator interiors, metal panels, door/partition facings, signs, light fixtures, ceilings, meshes and perforations, etc.
most common: SS, Cu alloys, bronze, brass, Al
less common: carbon steel, Cu, iron, porcelain enamel
10 gauge min. in lg. sheets to avoid oil canning, unless back laminated, or embossed
Metal fabrications
non-structural, like stairs, expansion jts. (both structural and seismic), gratings, ladders, etc.
Types of stainless steel
302: Cr, Ni added, very strong, hard corrosion resistant
304: like 302, but more weldable, commonly used
301: less Cr, Ni, better tensile strength
316: for extremely corrosive environments
430: no Ni, less corrosion resistance, interiors only
W_x_
nominal depth x weight lbm/ft
Cast iron first reasonable
1709, Abraham Darby used coke not charcoal in production, decreased impurities, increased strength
Steel first reasonable
1856 Henry Bessamer process makes steel inexpensive, stronger
Types of Steel Shapes
wide flanges (W), I-beams (S), channels (C), structural tees (WT or ST), angles (L), tubes (TS) - round/square/rectangle, plates (PL) (more than 6”), bars (less than 6”)
Non-ferrous metals
Al: soft, so alloyed w Mn, Zn, Mg, Cu, usu. extruded, high stength to wt., but high embd. energy
Cu: very non-corrosive bc of patina (oil or wax can slow this process), v. conductive, used for wiring, pipes, ornament
Bronze: Cu + Sn
Brass: Cu + Zn
Zn: non corrosive, for roofing/flashing
Pb: good acoustics, easy to form, non-corrosive, poisonous
Types of metal decking
Most often steel, sometimes aluminum; composites ats structurally with concrete infill; cellular allows raceways
Metal finishing
bending, brake forming, spinning, embossing
annealing = reheated + slowly cooled to make more ductile
quenching = reheated + cooled quickly in water to strengthen
tempering = reheated + medium coolest to strengthen + increase ductility
case hardening = harder surface, softer core
anodizing = electrolytic bath that does surface chemistry to help corrosion resistance
painting/coating = for protection or aesthetics
Steel channels used for:
framing openings, stringers, where flush side is needed - buckle easily bc of asymmetry
Light gauge metal framing
10-25 gauge; usu galv. steel, sometimes aluminum; used for interior partions, exterior walls (bearing or non), joist, rafters, etc.; NONCOMBUSTIBLE; doesn’t shrink with age
Cast iron common
1876, used in roofs in France
1850-1880 = Cast Iron Age
Levels of metal finish
No. 3 = dull, coarse
No. 4 = general purpose, still dull/coarse, common
No. 6 = sull satin
No. 7 = reflective
No. 8 = mirror-like
Cast iron showcased
1851; Crystal Palace, Joseph Paxton
1889; Eiffel Tower, Halle des Machines
Open-web steel joists
bottom chord & webs = bent rods
top chord = angles w/ bearing plate attached
Types of open-web steel joists
K-series (2” increments) (spans 8-60 ft), LH-series (4” incr.) (spans 25-96 ft), DLH-series (4”) (spans 89-144 ft), e.g. 36LH13 (36” depth, LH-series, type 13 chord). Chord number increases as strength increases.
Metal fabrication types
casting (molds), hot rolling (W-shapes, finer, less strong, more flexible), cold rolling (stronger, more brittle), extruding, drawing (stronger)
Galvanic Action Index
Most reactive metals: Mg, Zn, Al, Mild Steel, Cast Iron
Medium: Cu, Ni, Cr, Pb, Sn, Stainless Steel (active)
Least reactive: Brass, Bronze, Stainless Steel (passive)
Types of iron
wrought = low carbon, has slag, soft/ductile, corrosion resistant
cast = ~2% carbon, hard & brittle
grey cast iron = high silicon content, for plumbing uses
Cast iron + Steel = 1st skyscraper
1885, cast iron int/ext cols., Bessamer girders, William LeBaron Jenny, 10-story, Home Insurance Bldg., Chicago
Cast iron first used in buildings
By 1779, common in bridges and columns
Metal joining
bolts, screws, welding (>800 deg F), brazing (800-500 deg F - only filler melts), soldering (used for lower melting pt. metals, only filler melts)
