Transcript Document
Metals 1 Major Topics History Classification of Metals Iron Steel Steel pipe, Tubing, and Wire Steel Fasteners Rivets Structural Bolts Welding Steel Floor & Roof Framing Major Topics con’t Aluminum Lead Zinc Copper and Alloys Nickel, Chromium, Cadmium & Titanium Clad Metals History of Metal Used as early as 8000 B.C. Early civilizations mainly used metal for weapons, tools, and body armor Metal has been used for construction material ranging from simple fasteners to main structural members Classification of Metals 2 main classifications Ferrous- metals containing a large percentage of iron (Fe) Cast iron Wrought iron Steel Non-Ferrous- metals which do NOT contain iron Aluminum Lead Copper Brass Bronze Alloys Alloy – a substance composed of two or more metals Blanking- in sheet metalwork, the cutting out of a piece of metal (using a press) Braking- a mechanical bending operation usually performed on sheets and plates Casting- an article formed by solidification of molten metal in a mold Cold drawing- drawing metal through a die without the application of heat Cold-rolled- metal rolled at room temperature, below the softening point, usually harder, smoother, and more accurately dimensioned that hot-rolled material. Drawing- forcing metal to flow into a desired shape without melting by pulling it through dies Embossing- creating a raised surface (design) on metal by die pressure or by stamping or hammering on the reverse surface Extrusion – forcing a molten metal through a die by pressure Forging- heating and hammering or pressing metal into a desired shape Iron One of the most abundant metals on earth Commercial iron is composed of carbon, manganese, silicon, phosphorus, and sulfur Materials Used to Make Iron Iron ore Coke- fuel used to melt iron; derived from coal Limestone- used as a flux Flux – a material added to react chemically with impurities and remove them from molten metal Pig Iron- initial molded product from a blast-furnace; weak & brittle, but very hard Types of Iron Cast iron (and gray cast iron)- brittle metals with high compressive strength and capacity to absorb vibration. Lack ductility and therefore should not be hammered or beaten. Relatively corrosion resistant. Contains 2-4 % carbon Used for gratings, stair components, manhole covers, some piping Wrought iron- soft, corrosion and fatigue resistant, and easily machined. Contains < 1 % carbon Used for railings, grilles, fences, screens, and various ornamental work Steel A malleable alloy of iron and carbon with substantial quantities of manganese 3 main methods for making steel Open-hearth process Oxygen process Electric furnace process Mill Output Ingot- molded square or rectangular blocks of cast metal Ingots are further squeezed between rollers to produce: Bloom- a rectangular solid of steel formed from an ingot as an intermediate step in creating rolled steel structural shapes (over 36” square) Billet- a large cylinder or rectangular solid of metal (smaller then 36” square) Slab – if the width is 2x the thickness or more Standard Mill Products Angle- a section of metal rolled, drawn, or extruded through LShaped rolls or dies Bar- round, square, rectangular, hexagonal, or solid stock of drawn, rolled, or extruded metal. A rod. Channel – a rolled, drawn, or extruded metal section having a U shape. Flat- a rectangular bar whose width is greater than its thickness Pipe, round- a hollow, round section of metal, the size of which is determined by the nominal inside diameter in inches Pipe, square- a hollow, square section of metal, the size is determined by the nominal outside diameter in inches Plate- a flat piece of metal; various metals are defined as plate by the following thickness criteria: Aluminum==1/4” or more; Copper==.188” or more; Steel (including stainless)== 3/16” or more Designations of Rolled Steel Shapes W – wide flange S -- beams C –channels L – angles (may be equal or unequal legs) WT or MT – structural tees Example of Designation W 36 x 300 W === a wide flange beam 36 === indicates a beam 36” deep 300 === weight in lbs/ linear feet Samples of Steel Shapes Channel Angle Wide Flange S-Beam Square & Rectangular Tubing Tee Steel Wire 6 million tons of wire produced in the U.S. annually Shapes are not only round, but may also include: square, rectangular, and polygonal Wire is used as the starting material to form nails, bolts, screws, rivets, and welding electrodes Temper- wires hardness, stiffness, and strength is affected by the amount of carbon and alloying agents, number of passes through dies, and the final heat treatment Wire may be produced with different finishes and coated, painted, or plated depending on its intended use Classification of Steel Four main specifications Method of manufacture Heat treatment Chemical composition Reference to a recognized standard Stainless Steel To be considered stainless a steel must contain 11.5 % chromium There are basic series of stainless steel: 200, 300, 400, & 500 series Available in many finishes ranging from matte to highly reflective (mirror) Structural Steel Consists of hot-rolled steel section, shapes, and plates not less than 1/8” thick The most commonly used strength grade is 36,000 psi yield strength (ASTM 36) For heavily loaded members such as columns, girders, or trusses, a high strength, low alloy steel with a yield strength of 50,000 psi Steel Construction 3 basic types: Wall bearing Skeleton framing Long-span Large industrial buildings, auditoriums, sports arenas Often use steel trusses, steel arches, or rigid bents in this type of construction (see figures 5-17, 5-18, and 5-19 on page 127) Steel Fasteners 3 main types of fasteners: Rivets Bolts Unfinished (common, machine) High-strength structural bolts- resist vibration (ASTM 325 or A490 are stamped on bolt head) Welds In some application (based on code requirements) more than one method may be used Welding A process of joining metals by applying heat and pressure, with or without filler material, to produce an actual union through fusion. There are several methods of welding used in specific situations (shielded metal arc is the most common in steel work). Welding symbols and basic joints are standardized by AWS (American Welding Society) – see figure 5-28 on page 132 Steel Floor and Roof Framing Considerations for systems used: Span Load to be applied Depth Weight Fire resistance (code) Sound transmission Heating/Cooling system Appearance Cost/Time Open Web Steel Joists Widely used because of the long spans See figure 5-29 on page 133 for types Ends of open web joists (hung from the top chord) are extended a minimum of 4 “ in masonry/concrete, and a minimum of 21/2 “ over steel supports. Corrugated or ribbed steel decking many times used in combination with the joists. Aluminum Bauxite, the major source of aluminum, is still very abundant in the earth (Jamaica) Highly resistant to weather and corrosive environments Aluminum can be economically extruded to many shapes (mouldings, edgings, window mullions) It is very malleable, quite ductile, non-corrosive, and strong in proportion to its weight. Lead Important physical properties include: resistance to corrosion, its plasticity, and its malleability Used for waterproofing, sound and vibration isolation, and radiation shield. Can be combined with a tin alloy to plate iron or steel (called “terneplate”) Use extreme care where and how lead is used because lead vapors or dust are toxic if ingested. Zinc Is brittle and low in strength Major use is in galvanizing (dipping hot iron or steel in molten zinc) May also be used for roofing, flashing, and hardware Copper Resistant to corrosion, impact, and fatigue; very ductile Primary use is electrical wiring, roofing, flashing, and piping The oxidization of copper produces what is called a green “patina” Bronze Originally a copper-tin alloy, but now aluminum or silicon added to copper Now may be “phosphor bronze”, “aluminum bronze” or “silicon bronze” Widely used for casting delicate mold impressions (Cathedral doors) Brass Copper with zinc to form an alloy Used for doors, windows, railings, trim, grilles and for finish hardware Nickel, Chromium, and Monel Chromium and nickel are used primarily as alloying elements, however, both can take a bright polish and do not tarnish in air, making them ideal for use in plating. Monel, a nickel-copper alloy, is mostly used to make fasteners and anchors, and has excellent corrosion resistance. Clad Metals Combines the best qualities of 2 or more different materials The intent is to create a metallurgical bond between layers of materials Galvanic Action Corrosion occurs between dissimilar metals when sufficient moisture is present to carry an electric current. The galvanic series, a list of metals arranged from “least noble (anode)”, most reactive, to “most noble” (cathode), is an indicator of corrosion susceptibility. The farther apart the metals are on the list, the greater the deterioration of the least noble one.