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10.2. What is meant by allotropic behaviour?Allotropic behaviour is the property possessed by certain elements to exist in two or more

distinct forms that are chemically identical but have different physical properties. In the case of iron the crystal structure has one form at room temperature and another at high temperature. When heated above 910 °C the atomic structure changes from body centered cubic to face centered cubic but reverts again when cooled. The allotropy of iron modifies the solubility of carbon, and it is because of this that steel can be hardened. the possibility of existence of two or more different crystal structures for a substance (generally an elemental solid). 10.5. Why is the “fatigue” an improper term as it applies to metals ?

Because Metal fatigue is the progressive and localized structural damage that occurs when a

material is subjected to cyclic loadings. In materials science, fatigue is the weakening of a material

caused by repeatedly applied loads. It is the progressive and localised structural damage that occurs

when a material is subjected to cyclic loading. The nominal maximum stress values that cause such

damage may be much less than the strength of the material typically quoted as the ultimate tensile

stress limit, or the yield stress limit.

Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads

are above a certain threshold, microscopic cracks will begin to form at the stress concentrators such

as the surface, persistent slip bands (PSBs), and grain interfaces.Eventually a crack will reach a

critical size, the crack will propagate suddenly, and the structure will fracture. The shape of the

structure will significantly affect the fatigue life; square holes or sharp corners will lead to elevated

local stresses where fatigue cracks can initiate. Round holes and smooth transitions or fillets will

therefore increase the fatigue strength of the structure.

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11.3 Why is carbon so important in steel ?Carbon is so important in understanding a steel’s characteristics. Carbon is the most

important indicator or predictor of a steel’s properties and response to processing. So in that 1018 steel, 0.18 weight % carbon (on average) is implied; in 1137, 0.37 wt % carbon (on average) is implied; in 1144, the average carbon content we expect is, you guessed it, 0.44 wt.%.Very low carbon. Grade 1008-1010. The low carbon content makes these steels low strength and very ductile. Typically used for cold heading. Cold forming. The machinist would characterize these as gummy. Chips are stringy, continuous, and soft.Low carbon. Grade 1018; 1022. Low carbon means low strength. The non alloys in this range are weldable, and all of these grades are cold formable with out the need for an anneal. Grades in this carbon range are often carburized to achieve a high surface hardness. Not a good choice for machining, difficult to get chip to break. Chips are somewhat continuous, and soft to semi-soft. Parts made from these grades tend to have low stock removal, and look like the bar that they were made from- bolts, light duty shafts, tie rods, pins.Medium carbon. 1045, 1137, 1144. Medium carbon means medium strength. Usually cold drawn. Can be heat treated. Not recommended for cold heading. Welding requires special practices and residual control. (Do not weld 11XX grades due to high sulfur content!)Chips are continuous and semi hard (1030), continuous and tough (1035), and continuous and start to become springy or hard (1045-1050). Small shafts, forgings, and kingpins are typical of these grades. Not usually annealed. Heavy draft (cold work) followed by a stress relief operation can get

yield strengths into the 100,000 psi minimum. ASTM A 311 class B is one such designation, Stressproof (TM) is Niagara LaSalle’s trademarked name for a similar product.High carbon. Above 0.50 carbon, most of us start to describe steels as “high carbon.” Depending on the application, and carbon content, an anneal may be required for processing. My rule of thumb for carbon grades is at 0.60 and above, an anneal is required prior to cold drawing. ( For alloys, generally annealing is required at 0.40% carbon.) So a 1060 bar would be annealed prior to cold drawing. The type of anneal for these steels would be called a lamellar pearlitic anneal. It would help to develop a predominately coarse lamellar pearlitic structure in the steel. Chips are continuous and range from hard (1060) to tough (1070) to springy (1080 and above).Very high carbon. At 0.90 carbon and above, (drill rod and bearing steels) a different kind of anneal is called for. It is called spheroidize annealing, and results in a greater mean free path of ferrite between the hard carbide particles in these steels. Very high carbon steels are most machinable in the spheroidize annealed condition.Adding sulfur to carbon steels is called resulfurizing. This addition provides a way to break up the chip, thus escaping the continuous chip that we get from 10XX steels. This is why 11XX and 12XX steels are so machinable.

11.4 Discuss briefly the use of nonferrous metal that are alloyed with steelThe characteristics of non-ferrous metal

Non-ferrous metals include aluminum, brass, copper, nickel, tin, lead, and zinc, as well as precious metals like gold and silver. While non-ferrous metals can provide strength, they are primarily used where their differences from ferrous metals can provide an advantage.

For instance, non-ferrous metals are much more malleable than ferrous metals. Non-ferrous metals are also much lighter, making them well-suited for use where strength is needed, but weight is a factor, such as in the aircraft or canning industries. Because they contain no iron, non-ferrous metals have a higher resistance to rust and corrosion, which is why you’ll find these materials in use for gutters, water pipes, roofing, and road signs. Finally, they are also non-magnetic, which makes them perfect for use in small electronics and as electrical wiring.

As far as recycling goes, aluminum is the third most recycled material in the world. However, many other non-ferrous materials like copper, brass and lead are relatively scarce, and metallurgists rely heavily on scrap material recycling to make new ones.

Precious metals and their alloys are rare metallic elements and alloys such as silver, gold, platinum, palladium, iridium, osmium, rhodium, and ruthenium. They tend to be costly and in high demand due to their special properties including conductivity and resistance to corrosion. Aluminum and its alloys are lightweight metals with good corrosion resistance, ductility, and strength. Aluminum is renowned for its low density and is the most widely used non-ferrous metal. Relatively pure aluminum is used only when corrosion resistance is more important than strength or hardness.           Copper is a reddish orange, soft, and malleable (low hardness) metal that is a good conductor of heat and electricity. Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. Bronze is an alloy of copper and (usually) tin that is much harder and more brittle than brass.  Nickel and its alloys are metals with high strength and toughness, excellent corrosion resistance, and superior elevated temperature properties. They are able to withstand an assortment of extreme operating conditions involving environments that are corrosive, high temperature, high stress, and combinations of these factors.  Zinc and its alloys are metals that are used widely in the production of die cast components. Zinc-based alloys are used for casting and wrought applications Pure or unalloyed zinc is used in non-structural applications and to galvanize metals such as iron in order to prevent corrosion. It is also used in batteries and as an alloy with copper to make brass. Other nonferrous materials used in their pure form and in alloys include cobalt, lead, magnesium, molybdenum, titanium, and tungsten. 

These are the non ferrous metals and their uses: Aluminium – An alloy of aluminium, copper and manganese. Very lightweight and easily worked.

Used in aircraft manufacture, window frames and some kitchen ware.

Copper – Copper is a natural occurring substance. The fact that it conducts heat and electricity means that it is used for wiring, tubing and pipe work.

Brass – A combination of copper and zinc, usually in the proportions of 65% to 35% respectively. Is used for ornamental purposes and within electrical fittings.

Silver – Mainly a natural substance, but mixing with copper creates sterling silver. Used for decorative impact in jewellery and ornaments, and also to solder different metals together.

Lead – Lead is a naturally occurring substance. It is heavy and very soft and is often used in roofing, in batteries and to make pipes.