CHARACTERISTICS OF METALLIC MATERIALS Chapter 9. 6 top employment sectors per NAICS Primary metals Fabricated metal products Machinery Computers and electronics.

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Structure of Metallic Materials Metals can survive drastic changes in the environment they used in Extreme heat, can remain strong and rigid enough to support heavy loads Frigid environments, can remain flexible and still be easily formed Few materials can retain their essential properties when subjected to the same range of hot and cold
  • 2 6 top employment sectors per NAICS Primary metals Fabricated metal products Machinery Computers and electronics Transportation equipment and manufacturing Electrical equipment, appliances, and component manufacturing
  • 3 Structure of Metallic Materials Metals can survive drastic changes in the environment they used in Extreme heat, can remain strong and rigid enough to support heavy loads Frigid environments, can remain flexible and still be easily formed Few materials can retain their essential properties when subjected to the same range of hot and cold
  • 4 Pure metals Found in nature Few are used in their natural form Too hard, or too soft Too expensive Alloys Blend of metals and other elements More complex structure than pure metals
  • 5 New elements are discovered when new synthetic products are caused by artificial nuclear reactions All man-made elements are radioactive Short “half-life” Half-life – the gradual exponential decay where the element exhibits only half of it’s initial values
  • 6 Major Metals Aluminum Copper Iron Lead Tin Magnesium Nickel Titanium Zinc Major Alloys Steel Brass Bronze
  • 7 Brass Copper and zinc Steel Iron, carbon, magnesium, vanadium, nickel and chromium Carbon is not a metal
  • 8 Why is Alloying Important? Best attributes of the base metal enhanced by addition of another element Brass is stronger than copper and zinc by themselves Alloys can be created to withstand exposure to just about any environment 25,000 types of steel 200 types of copper alloys
  • 9 Physical Properties 4 basic physical properties: Weight Color Conductivity Reaction when exposed to heat Some metals can be identified by these properties Lead is dense and heavy Platinum, gold and silver can be recognized by color
  • 10 Physical properties often more important than mechanical properties (next) Specific Heat The amount of energy necessary to raise one gram of material 1°C Thermal Conductivity Ability of a substance to conduct heat Measured by the rate heat flows through a substance Good thermal conductivity means good electrical conductivity
  • 11 Thermal Expansion Change in volume of a product at different temperatures Most molten metals shrink during solidification and cooling Shrinkage, how much a material shrinks Must take into account when designing tools Superconductors Material able to conduct electricity with no resistance to the flow of current Happens at absolute zero (0 Kelvin, -273.15°C) Increase in heat increases electrical resistance
  • 12 Mechanical Properties How parts or products will withstand continued use of abuse in the user’s work environment Measured using standardized testing procedures Tensile Strength Ability of material to resist being pulled apart Hardness Resistance to penetration
  • 13 Fatigue Breaking of a metal after stress is continually removed and reapplied Fold a thin sheet of metal then straighten repeatedly until it cracks Creep Elongation that occurs when exposed to elevated temps while under stress Will eventually separate or rupture (creep failure)
  • 14 Plasticity The ability to change shape or size as a result of force being applied Helpful in shaping materials Ductility Ability to be formed plastically, without breaking. If material is not ductile, it’s difficult to form
  • 15 Classifications of Metals (4 types) 1. Ferrous Metals Contain Iron Most commonly used metals Types of iron: Wrought iron Tough and ductile Contains very little carbon Easy to bend (even without heating) Ornamental iron-work Cast Iron High carbon content Pouring molten iron into molds Hard Brittle High compression strength
  • 16 Good corrosion resistance Make engine blocks, machine parts, gear cases Gray Iron Easy to cast Less expensive than other cast irons Made from pig iron (refined wrought iron) and scrap iron or steel White Cast Iron Very hard Parts that must combat fatigue and extreme wear and abrasion Malleable Iron Made by heating white cast iron to a specific temperature then cooling it slowly (called annealing)
  • 17 Ductile Cast Iron One of the newest forms of cast iron Replaced a lot of use of white iron Heat-treatable Crankshafts, connecting rods, camshafts Steel Iron and carbon Other additives used to make harder and tougher steel
  • 18 Carbon Steels Low-carbon steel of mild steel.05%-.30% carbon Very soft Easily formed and machined Doesn’t heat treat well Medium-carbon steel.30%-.60% carbon More difficult to bend and shape Can be heat treated (can make it brittle)
  • 19 High-carbon steel (tool steel).60%-1.50% carbon Difficult to bend Very hard Can be heat treated Used to make tools, dies, molds, screwdrivers, milling cutters
  • 20 2. Nonferrous Metals Metals with no iron content Resistant to corrosion Aluminum Copper Lead Magnesium Nickel Zinc Fig 9-4 (pg 137)
  • 21 3. High-Temperature Superalloys Ability to survive, without degradation in temperatures as great as 2200°F (1200°C) for reasonable periods in nonloadbearing structures 1800°F (1000°C) under loads Developed after WWII Used in space-related industries Classified according to the base metal Usually Iron, nickel, or cobalt Sometimes chromium, titanium, aluminum or tungsten
  • 22 4. Refractory Metals High temperature metals Withstand heat and maintain strength at temps ranging from 4474°F (2468°C) for niobium, to 6170°F (3410°C) for tungsten Tungsten highest known melting point Used to make light filaments, welding rods, rocket engines
  • 23 Nature of Industrial Stock Steelmaking industry forms molten steel into many shapes Ingots for creating: Bars Plates Hot-rolled strip Round or hex rod Tubing Wire Angle stock
  • 24 Billets Feedstock for long products with small cross sections Bar stock, angles, I-beams, plates Hot-rolled steel - squeezed between rollers while hot (bluish surface coating) Cold-rolled steel – rolled while cold (shiner surface)
  • 25 Powder Used for: Casting Metal Injection Molding 3D printing Sheet form Sold by gage number, smaller the number the thicker the stock Not all sheet types have the same numbering system
  • 26
  • 27 Determining the Type of Steel Usually impossible to look at stock and determine which type of steel it is 3 basic techniques: 1. American Iron and Steel Institute (AISI) and Society of Automotive Engineers (SAE) developed a simple labeling system Tags or engraved on stock
  • 28 DesignationProperties PMild and low carbon steels FCarbon/Tungsten and special purposes steels LLow alloy/special purpose MMolybdenum alloy and high speed steel TTungsten alloy and high speed steel HHot working, chromium, tungsten, and/or molybdenum DDie steel, air-hardened, and high chromium steel AAir-hardened steel OOil-hardened steel SShock-resistant steel WWater-hardened steel
  • 29 Unified Numbering System (UNS) More accurate Also developed by AISI and SAE 4 or 5 digits Classifies steel according to their primary alloying element First number stands for the type of metal Second number indicates the percentage of alloy Last 2 digits tell how much carbon in 100 ths of a percent
  • 30 1020 Steel 1 – type = carbon steel 0 – percentage of alloy = 0% alloy 20 – carbon content =.20% carbon UNS NumberType of Steel 1Plain carbon steel (no alloy) 2Nickel steel 3Chromium and nickel steel 4Molybdenum steel 5Chromium steel 6Chromium and vanadium steel 7Tungsten steel 8Nickel, chromium, and molybdenum steel 9Silicon and manganese steel
  • 31 3. Color code system End of stock is painted Alloy steel is normally painted with 2 colors 1020 steel is painted brown
  • 32 When no information is available Sometimes identification tags or markings can be lost Then has to be identified by it’s properties Pattern and color of sparks when ground Takes training and experience
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