SUMMARY in ENGINEERING MATERIALSProperties of materialsA. Chemical properties are properties of a material that refer to the structure of a material and its formation from our elements.Factors that affect the chemical properties1. Composition means the percentage of the various elements that make up the metal.2. Corrosion resistance is the ability of the material to resist deterioration by chemical or electro-chemical reaction with its environment.3. Crystal structure is the ordered, repeating arrangement of atoms and molecules in a material.4. Microstructure is the structure of a polished and etched materials as revealed by microscope magnifications greater than ten diameters5. Stereo specificity is the tendency for polymers and molecular materials to form with an ordered, spatial, three dimensional arrangement of monomer molecules.Example of polymers rubberChemical properties These are properties that depend on the arrangement of the atoms and describe the behavior of a material in process that alter its identity. A way a substance may change or start to form other substance.

Includes1. Conductivity ability to conduct heat/electricity.2. Flammability tendency of certain substance to combust.3. Reactivity the tendency of matter to react with other substances and form new substance.Chemical change the process occur in a substance transforming it to a new substance which is undergoing chemically.Example corrosion of G.I roof, ripening of fruits

Physical properties are properties of materials that refer to the interaction of materials with various forms of energy and with other forms of matter.a. Curie point is the temperature at which ferromagnetic materials are no longer be magnetized by outside forces.b. Density is the mass per unit volumec. Dielectric strength is the maximum potential difference that an insulating material of given thickness can withstand for a specified time without occurrence of electrical breakdown through its bulk.d. Electrical resistivity is the electric resistance of a material per unit length and cross-sectional area or per unit length and unit weight.e. Heat distortion temperature is a temperature at which a polymer under a specified load shows a specified amount of deflection.f. Melting point is the point at which a material liquefies on heating or solidifies on cooling.g. Poissons ratio is the absolute value of the ration of the transverse strain to the corresponding axial strain in a band subjected to uniaxial stress.h. Refractive Index is the ratio of the velocity of light in a vacuum to its velocity in another material.i. Specific gravity is the ratio of mass or weight of a solid or liquid to the mean or weight of an equal volume at water.j. Thermal conductivity is the ratio of heat flow per unit time in a homogenous material under steady state conditions, per unit area, per unit temperature gradient in a direction perpendicular to area.k. Thermal expansion is the rate at which a material elongates when heated.

Mechanical Properties are properties of the material that are displayed when a force is applied to the material.a. Compressive strength is the maximum compressive stress that a material is capable of withstanding.b. Creep is the permanent strain under stress.c. Creep Strength is the constant stress that will cause a specified quality of creep in a given time of constant temperature.d. Endurance limit the maximum stress below which a material can theoretically endure a finite number of tress cycles.e. Flexural Strength is the outer fiber stress developed when a material is loaded as a simple supported beam and deflected to a certain value of strain.f. Hardness is the resistance of a material to plastic deformation.g. Modulus of elasticity is the ratio of stress to strain in a material loaded within its elastic range. h. Percent Elongation increase in the gage length measured after the specimen fractures within the gage length. i. Percent Reduction in Area is the difference expressed as a percentage of original area between the original CSA of a tensile test specimen and the minimum CSA measured after the fractures.

Ultimate Strength the maximum stress a material withstands when subjected to an applied load. Dividing the load at failure by the original CSA determines the value.

Elevated temperature may have 3 general effects upon metals and alloys.1. Loss of metal as a result of oxidation or exposure to contaminating media.2. The formation of surface cracks resulting from cyclic thermal stresses.3. The change in the properties of the material with increasing temperature.Elasticity is the physical property of a material that return to its original shape after the stress that made it deform or distort is removed.Modulus of elasticity mathematical description of an object or substances tendency to be deformed elastically.Modulus of Rupture is a computed strength which does not bear a specific relationship to the maximum stress the material will sustain before fracture, but provides a value from which the maximum twisting moment.Reduction Area measure of the ductility of metals defined in a tensile test. It is the difference between the original CSA of a specimen and the area to its smallest cross section after testing.

Engineering Materials1. Metals3. Glass2. Plastic4. Rubber

Metals defined as an element that possess certain properties.Properties of Metala. BRITTLENESS is the property of a metal which permits no permanent distortion before breaking.b. DUCTILITY is the ability of metal to be permanently deformed before breaking.c. ELASTICITY is the ability of the metal to return to its original shape after any force upon it has been removed.d. HARDNESS is the resistance of a metal to forcible penetration.e. MALLEABILITY - is the property of a metal which allows it to be hammered of rolled into other (wires) sizes and shape.f. TOUGHNESS is the property of a metal withstand shock or impact.g. FATIGUE FAILURE is the point at which a metal break, crack, or fails as a repeated stress.

Selection of Materials4 Factors to be considered:a) Material must satisfy the strength requirement.b) Material must be capable of being fabricated into the desired form.c) Cost of the material must be low.d) Material must be available for the use at the required time.

Two major Division of Metala. Ferrous Metal are made up principally of iron, which is magnetic.b. Non-Ferrous Metal are metals that contain little or no iron. Also resistant to corrosion and are non-magnetic.

Types of SteelI. Low Carbon Steel commonly called machine steel contains from 0.10 to 0.30% CarbonCharacteristicsUses1. Easily forged1. Chains2. Welded2. Rivets3. Machined3. Bolts4. Shafting

II. Medium Carbon Steel contains 0.30% to 0.60% CarbonUsesa) Heavy forgingb) Car axlesc) Rails

III. High Carbon Steel commonly called tool steel contains from 0.60 to 1.7% carbonCharacteristicsa) Can be hardenedb) Tempered

IV. Alloy Steel are steels which have certain metal such as chromium, nickel, tungsten, vanadium added to them to give the steel certain new characteristics. By the addition of various alloys, steel can be resistant to rust, corrosion, heat, abrasion, shock & fatigue.

V. High Speed Steels contains various amounts and combinations of tungsten, chromium, vanadium, cobalt & molybdenum.

VI. High Strength, Low Alloy Steels contains a maximum carbon content of 0.28% and small amount of vanadium, copper and columbium.Characteristica) Do not require pointingb) Developed a protective coating when exposed to the atmospherec) Have higher strength

Chemical Elements in steel1. Carbon in steel may vary from 0.01% to 1.7%Effect on steel-the amount of steel of carbon will determine the brittleness, and strength of steel

2. Manganese content usually varies from 0.39 to 0.80%a) Makes the metal more ductileb) Gives good bending qualityc) It toughen the metald) Raises its critical temperature

3. Phosphorus content does not exceed 0.05%a) Makes the steel brittleb) Reduces its ductility

4. Silicon content about 0.20%a) To remove gases and oxides thus preventing the steel from becoming ferrous and oxidizingb) Makes harder and tougher

5. Sulfur does not contain more that 0.04%a) Causes crystallization of steel when the metal is heated to a red color

6. Chromium in steel imparts hardness and wear resistancea) It gives steel a deeper hardness penetration than other alloying metals. It also increases resistance to corrosion.

7. Molybdenum it allows cutting tools to retain their hardness when hota) Improves physical structuresb) Gives a greater ability to harden

8. Nickel in steels improves its toughness, resistance to fatigue failure, and resistance to corrosion.

9. Tungsten increases the strength and toughness of steel and its ability to harden. It also give cutting tools the ability to maintain a cutting edge even at a red heat.

10. Vanadium in amount up to 0.20% increases the tensile strength and produces a finer grain structure in steel. It is usually alloyed with chromium to make parts such as spring, gears and wrenches.

Stainless SteelSteel Production one of the largest and most important in the USMost of the iron ore are used to make steel comes from the open-pit and underground mines, and is sent directly to steel mills. These are called direct shipping ores

Taconite lower grade oreIron ore huge blast furnacesBlast Furnace first step in the steel making process.Ore, coke and limestone called the charge are dumped into the top. Air is dried and heated to about 680C and blown in the near base.

The coke burns in the air, generating heat and gases which melt the charge. The limestone begin to crumble and absorb impurities in the ore and coke forming SLAG.

Purifying Processes

A. Openhearth Surface Raw materials are put into the furnace by a charging machine. Empty the box loads. A ladle pours in molten iron. After 8 12 hours of intense heat, the purified molten steel is run into the ladle.

B. Basic Oxygen Surface The furnace is first tipped on its side, and molten iron and scrap are charge into its mouth. It is then rotated into an upright position. Oxygen is blown at high speed into the furnace.

C. Electric Furnace makes super steels (3 large rods called electrodes reached through the top of the furnace) Powerful electric current jump from the ends of the electrodes to the scrap.

Molten to Finished FormContinuous Casting newest method of producing steel. Molten steel flows into a copper mold. The outside surface begins to harden forming a thin shell. Water is sprayed. Rollers and cutters.

Ingot TeemingThe ladle of fleshly made steel is made held by a crane above a row of ingot molds. A valve in the bottom of the ladle is open and the steel flows into each mold, filling it to the top.

Rolling Millsa) Plate, sheet, stripc) Structural steels and railsb) Rods, bars, seamless pipes and tubes

Identification of metals4 Method to identify metals (the most accurate are the 1st two methods)1. By manufacturers stamp2. By color code painted on the bar3. By spark testing4. By their appearance

Spark Testinga. Low Carbon or Machine Steel show sparks in long, light yellow streaks w/ a slight tendency to burst.b. Medium Carbon Steel similar to low carbon steel, has sparks that burst with a sparkler effect due to the greater percentage of carbon in the steel.c. High Carbon Steel shows yellow star bursts close to the grinding wheel.d. High Speed Test produce several interrupted spark lines w/ a dark red, ball-shaped at the end.e. Cast Iron shows a torpedo-shaped spark with a feather like effect near the end. It changes from dark red to gold color.

By AppearanceMetalCarbon ContentAppearanceMethod of ProcessingUses

Cast Iron2.5 to 3.5 %Grey, rough, sandy surfaceMolten metal poured into sand moldsParts of machines such as lathe beds

Machine Steel0.10 to 0.30 %Black scaly surfacePut through rollers while hotBolts, Rivets, Nuts

Cold Rolled or Cold Drawn0.10 to 0.30 %Dull, silver, Smooth surfacePut through rollers or drawn through dies while cold.Shafting, Bolts, Screw, Nuts

Tool Steel0.60 to 1.5%Black GlossySame as Machine SteelDrills, Taps, Dies, Tools

High Speed SteelAlloy SteelBlack GlossySame as Machine SteelDies, Tools, Taps, Drills, Toolbits

BrassYellow (various shades) rough if casts, smooth if rolledSame as Cast Iron or rolled to shapeBushing Pump parts, Ornamental Work

CopperRed Brown rough if cast, smooth if rolledSame as Cast Iron as rolled to shapeSoldering Irons, electric wire, water pipes

Metal Processing4 Major Kinds of Metal Processing in the industry1. Heat Treatment or hot working2. Casting3. Machining4. Cold Working

Heat treatment operation involving heating of metals to change its properties.

Why heat treatment of metal is needed?a. To obtain the desired propertiesb. To improve machinabilityc. To change electrical propertiesd. To change magnetic propertiese. To increase resistance to corrosionf. To reduce the grain size

Various heat treatment processes used in the industry1. Hardening2. Tempering3. Annealing4. Normalising5. Case Hardening

Normalising it is the process to make the steel part to its normal stage. Generally it is done for the ff. purposes.a) To remove internal stresses caused by workingb) To reduce grain size of steelc) To achieve desired mechanical properties

Recommended Color Coding of different materialsCast Iron GrayWrought Iron Prussian blueSteel PurpleBrass, Bronze Light YellowCopper Red BrownAluminum light green

Annealing is the process for softening the steel part. Generally it is done for the ff. purpose.a) To soften the steel for easy machiningb) To increase ductility in the steelc) To relieve internal stressesd) To refine the grain size in the steele) To change electrical and mechanical properties

Case Hardening it is the process for making outer surface harder of the steel part. Generally it is done for the ff. purposes.a) To make outer surface harderb) To utilize low carbon steelc) To bring the cost cheaper