1. Metals and Metal Alloys
Describe Gamma Iron in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
Gamma iron also known as Austenite.
Describe the following factors relating to the manufacture of steel: d. Adverse effects of sulphur (1)
Sulphur causes steel to be brittle when rolled or forged and therefore it must be removed in the refining process. If all the sulphur cannot be removed its effects can be countered by adding manganese. The manganese combines with the sulphur to form manganese sulphide which does not harm the finished steel. Manganese improves a metals forging characteristics by making it less brittle at rolling and forging temperatures
Describe the purpose, composition, uses and cold-working properties of martensitic stainless steel. (1)
The 400 series of stainless steel is a martensitic steel. These steels are alloyed with chromium only and therefore are magnetic. martensitic steels become extremely hard if allowed to cool rapidly by quenching from elevated temperature.
Describe the purpose, composition, uses and cold-working properties of 18-8 stainless steel. (1)
The corrosion resistant steel most used in aircraft construction is known as 18-8 steel because it contains 18 percent chromium and 8 percent nickel. One of the distinctive features of 18-8 steel is that its strength may be increased by cold working.
Describe the properties and characteristics of steels having chrome-molybdenum alloying agent. (1)
(chrome-moly) steel is the most commonly used alloy in aircraft. Its SAE designation of 4130 denote its alloy of approximately 1 percent molybdenum and 0.30 percent carbon. It machines readily, is easily welded by either gas or electric arc and responds well to heat-treatment. heat-treated SAE 4130 steel has an ultimate tensile strength about for time that of SAE 1025 steel, making it an ideal choice for landing gear structures and engine mounts. Chrome molly's toughness and wear resistance make it a good material for engine cylinders and other highly stressed parts.
Describe Cementite in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- AKA iron carbide - Fe3C - hard, brittle material, normally classified as a - It forms directly from the melt in the case of white cast iron. - In carbon steel, it either forms from austenite during cooling or from martensite during tempering.
Describe Alloying Agents In respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- Alloying agents are small quanities of elements added to a base metal to form an ALLOY. - e.g. steel is an alloy of iron (the base metal) with an alloying agent of carbon
Describe Medium carbon steels in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- Balances ductility and strength - good wear resistance - used for large parts - forging and car parts.
Describe Ferrite in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- Basically solid iron, or a solid solution with iron as the main constituent. - gives steel and cast iron their magnetic properties - example of a ferromagnetic material. - Practically speaking, it can be considered pure iron.
Describe Ferritic in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- Ferritic stainless steel is a type of chromium alloy - has ferritic, body-centered cubic crystal structures. - no more than 30 percent chromium contain no nickel or carbon therefore do not respond to heat treatment.
Describe High carbon steels in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- Less strong - cheap - easy to shape - surface hardness can be increased through carburizing High carbon steel: approximately 0.55% to 0.95% carbon content with 0.30 to 0.90% manganese content. Very strong, used for springs and high-strength wires Steel can be heat-treated which allows parts to be fabricated in an easily-formable soft state. If enough carbon is present, the alloy can be hardened to increase strength, wear, and impact resistance. Steels are often wrought by cold-working methods, which is the shaping of metal through deformation at a low equilibrium or metastable temperature.
Describe the properties and characteristics of steels having a Carbon (low, medium and high carbon steels) alloying agent. (1)
- Mild (low carbon) steel: approximately 0.05% to 0.25% carbon content with up to 0.4% manganese content (e.g. AISI 1018 steel). Less strong but cheap and easy to shape; surface hardness can be increased through carburizing. - Medium carbon steel: approximately 0.29% to 0.54% carbon content with 0.60 to 1.65% manganese content (e.g. AISI 1040 steel). Balances ductility and strength and has good wear resistance; used for large parts, forging and car parts. - High carbon steel: approximately 0.55% to 0.95% carbon content with 0.30 to 0.90% manganese content. Very strong, used for springs and high-strength wires. - Very high carbon steel: approximately 0.96% to 2.1% carbon content, specially processed to produce specific atomic and molecular microstructures. Steel can be heat-treated which allows parts to be fabricated in an easily-formable soft state. If enough carbon is present, the alloy can be hardened to increase strength, wear, and impact resistance. Steels are often wrought by cold-working methods, which is the shaping of metal through deformation at a low equilibrium or metastable temperature.
Describe Martensitic in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- The 400 series of stainless steel is martensitic steel. - Tempered martinsite gives steel good hardness and high toughness. - Untempered martinsite is low in toughness and therfore brittle. - Used in aircraft landing gear and structural sections
Describe Low carbon steels in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- Very strong - used for springs - high-strength wires
Describe Austenite in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- a metallic non-magnetic allotrope of iron - exists when iron heated above 912 °C and up to 1,394 °C. - SOFT and DUCTILE form of iron. - can dissolve considerably more carbon (as much as 2.04% by mass at 1,146 °C) than ferrite. - most commonly used type of stainless steel for making hospital and food-service equipment.
Describe Pig iron in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- intermediate product of smelting iron ore with coke, usually with limestone as a flux. - very high carbon content .˙. very brittle. - generally remelted in a furnace & excess carbon is burnt off to form steel.
Describe Austenitic in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- non-magnetic metal alloys primarily used in the production of STAINLESS STEEL. - contain a high percentage of NICKEL and CHROMIUM - VERY RESISTANT TO CORROSION. - used to make highly stressed aerospace parts e.g. TURBINE DISCS. - Hardened by cold working - H Grade L Grade (high and low)
Describe Pearlite in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- two-phased, layered structure composed of alternating layers of FERRITE and CEMENTITE that occurs in some steels and cast irons. - common microstructure occurring in many grades of steels.
Describe Martensite in respect of steels and steel alloys and give typical examples of where each may be used in aircraft construction or maintenance. (1)
- very hard form of steel crystalline structure. - formed by rapid cooling (quenching) of austenite which traps carbon atoms that do not have time to diffuse out of the crystal structure. - also form by application of stress. - easily destroyed by the application of heat. - Too much martensite leaves steel brittle, too little leaves it soft.
Describe the characteristics, properties, compositions and uses of K-monel as used in the construction of aircraft or aircraft components. (2)
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Identify the metals that are commonly alloyed with magnesium for aircraft use. (1)
A - Aluminium E - Rare Earth H - Thorium K - Zirconium M - Manganese Z - Zinc
Describe the following factors relating to the manufacture of steel: a. Manufacturing processes for pig iron, cast iron and steel (1)
A blast furnace is charged with iron ore, charcoal or coke and limestone. Huge quantities of air blast in at the bottom of the furnace and the calcium in the limestone combines with the silicates in the iron ore to form slag which floats to the top of the molten metal. Liquid iron collects at the bottom of the blast furnace. The liquid iron is then poured out and flows through a channel and into a bed of sand. Once it cools, this metal is known as pig iron. Pig iron contains 4 to 5 percent carbon and is hard and brittle and is of limited use as it is. Pig iron can be remelted and mixed with slag and hammered out to eliminate most of the carbon (down to 0.3 percent) to create strong, malleable wrought iron. Another process involving pig iron is to to melt the pig iron and combine it with scrap iron, smelt out impurities and add alloys to form cast iron. This metal contains 2 to 4 percent carbon, along with quantities of silicon, manganese and trace impurities. Cast iron, as the name implies, is typically cast into molds to form a wide variety of parts and products. Pig iron is also further processed to produce steel.
State the four digit numbering series for aluminium alloys: (2) a. Copper - 2000 series b. Manganese - 3000 series c. Silicon - 4000 series d. Magnesium - 5000 series e. Magnesium and Silicon - 6000 series f. Zinc - 7000 series
Aluminium alloys are classified using a four digit index system. The first digit identifies the major alloying ingredient. The second digit represents a specific alloy modification. For example if this digit is zero, it indicates that there were no special controls over individual impurties. The last two digits indicate the hundreths of a percent above the 99% pure aluminum. Example: If the last two digits are 75 the alloy contains 99.75 pure aluminium. Wrought aluminum alloys can be divided into two categories: non-heat treatable and heat treatable. Non-heat-treatable alloys, which include the 1xxx, 3xxx, 4xxx and 5xxx series alloys, derive their strength from solid solutioning and are further strengthened by strain hardening or, in limited cases, aging. Heat-treatable alloys include the 2xxx, 6xxx and 7xxx series alloys and are strengthened by solution heat treatment followed by precipitation hardening (aging).
Describe the characteristics, properties, compositions and uses of Aluminium bronze as used in the construction of aircraft or aircraft components. (2)
Aluminium bronze is a type of bronze in which aluminium is the main alloying metal added to copper. A variety of aluminium bronzes of differing compositions have found industrial use, with most ranging from 5% to 11% aluminium by weight, the remaining mass being copper; other alloying agents such as iron, nickel, manganese, and silicon are also sometimes added to aluminium bronzes. Aluminium bronzes have good tearing qualities, great strength, hardness and resistance to both shock and fatigue. Because of these properties they are used for diaphragms, gears and pumps. These alloys are useful in areas exposed to salt water and corrosive gasses
Using heat-treatment diagrams, describe how the desired grain structures are obtained during the steel manufacturing process. (1)
As relatively pure iron experiences changes in temperature the microstructure of the iron goes through changes, called 'phase transitions' and forms different allotropes. Allotropes are different structural forms of the same element and can exhibit quite different physical properties and chemical behaviours. Iron has three allotropic forms known as: - Alpha iron or ferrite. This is the stable form of iron at normal temperatures. It is a fairly soft metal that can dissolve only a small concentration of carbon (no more than 0.021% by mass at 910 °C). - Gamma iron or austenite. Alpha iron undergoes a phase transition to gamma iron above 912 °C and up to 1394 °C. This is non magnetic, soft and ductile form of iron but it can dissolve considerably more carbon (as much as 2.04% by mass at 1146°C). - Delta-ferrite. This allotrope forms above 1,390 °C up to the melting point of iron at 1,539 °C. The crystal structure is similiar to Alpha iron. Iron, of course, is of most importance when mixed with certain other metals and with carbon to form steels. Like iron, the microstructure of plain carbon steel also changes as a result of extreme changes in temperature as well as the amount of carbon is present in the alloy. The phase transition diagram shows the relationship between temperature and carbon content. As the carbon content increases, cementite, also known as iron-carbide a hard brittle substance forms. An increasing ratio of cementite to other allotropes also increases the hardness and brittleness of the alloy. Steel is generally considered to have a carbon content of 0.2 - 2.1%, above this the alloy is considered to be cast iron.
Describe the purpose, composition, uses and cold-working properties of austenitic stainless steel. (1)
Austenitic steels are also referred to as 200 and 300 series stainless steels, contain a large percentage of chromium and nickel and in the 200 series, some manganese. When these steels are heated to a temperature above there critical range and held there, a structure known as austenite forms. Austenite is a solid solution of pearlite, an alloy of iron, carbon and gamma iron, which is a non magnetic form of iron. Austenitic stainless steels can be hardened only by cold working while heat treatment serves only to anneal them.
Identify the relative disadvantages of titanium when subjected to very high temperatures. (1)
Because of the high melting point of titanium, high temperature properties are disappointing. The ultimate yield strength of titanium drops rapidly above 425°C. The absorption of oxygen and nitrogen from the air at temperatures above 530°C makes the metal brittle on long exposure that it soon becomes worthless. However titanium does have some merit for short time exposure up to 1650°C where strength is not important. Aircraft firewalls demand this requirement
Describe the characteristics, properties, compositions and uses of Beryllium copper (including the effects of using nickel as an alloying agent) as used in the construction of aircraft or aircraft components. (2)
Beryllium copper is one of the most used copper alloys. It consists of approximately 97 percent copper, 2 percent beryllium and sufficient nickel to increase its strength. Once heat treated beryllium copper achieves a tensile strength of 200,000 psi and 70,000 psi in its annealed state. This makes beryllium extremely useful for diaphragms, precision bearings, bushings, ball cages and spring washers.
Describe the characteristics, properties, compositions and uses of Brass as used in the construction of aircraft or aircraft components. (2)
Brass is copper alloy containing zinc and small amounts of aluminium, iron, lead, manganese, magnesium, phosphorous and tin. Brass with zinc content of 30 to 35 percent is very ductile, while brass containing 45 percent zinc has relatively high strength.
Describe the characteristics, properties, compositions and uses of Bronze as used in the construction of aircraft or aircraft components. (2)
Bronze is a copper alloy that contains tin. A true bronze consists of up to 25 percent tin and along with brass is used in bushings, bearings, fuel metering valves and valve seats. Bronzes with less than 11 percent tin are used in such items as tube fittings
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) e. Chrome-molybdenum
Chrome molly's toughness and wear resistance make it a good material for engine cylinders and other highly stressed parts
Describe the properties and characteristics of steels having chromium agent. (1)
Chromium is alloyed with steel to increase strength and hardness as well as improve its wear strength and corrosion resistance. Because of its characteristics, chromium steel is used in balls and rollers of antifriction bearings.
Specify the effects of Copper when alloyed with aluminium. (1)
Copper Alloys with the 2xxx series utilise copper as the principal alloying agent. When aluminium is mixed with copper certain metallic changes take place in the resultant alloy's grain structure, these changes are beneficial and produce greater strength. A major drawback to aluminium-copper alloys is their susceptibility to inter-granular corrosion when improperly heat-treated. Most aluminium alloy used in aircraft structures is aluminium-copper alloy. Two of the most commonly used in the construction of skins and rivets are 2017 and 2024.
Describe the characteristics, properties, compositions and uses of Copper as used in the construction of aircraft or aircraft components. (2)
Copper alloys are metal alloys that have high resistance against corrosion. The best known traditional types are bronze and brass, The similarity in appearance of the various alloys, along with the different combinations of elements used when making each alloy, can lead to confusion when categorizing copper alloys. Copper-based alloys have lower melting points than steel or iron, and are more readily produced from their constituent metals Copper and its alloys have a huge variety of uses that reflect their versatile physical, mechanical, and chemical properties. Some common examples are the high electrical conductivity of pure copper, the excellent deep drawing qualities of cartridge case brass, the low-friction properties of bearing bronze, the resonant qualities of bell bronze, and the resistance to corrosion by sea water of several bronze alloys.
Describe the characteristics, properties, compositions and uses of Copper tubing as used in the construction of aircraft or aircraft components. (2)
Copper tubing was once used extensively in aircraft fluid lines but because of its weight and tendency to become brittle when subjected to vibration it has been almost entirely replace with aluminium alloy. Brass fittings for fluid lines have also been replaced either aluminium or steel fittings.
Describe the purpose, composition, uses and cold-working properties of ferritic stainless steel. (1)
Ferritic steels are primarily alloyed with chromium but many also contain small amounts of aluminium. However they contain no carbon and therefore, do not respond to heat treatment.
Describe the characteristics, properties, compositions and uses of Inconel as used in the construction of aircraft or aircraft components. (2)
Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys. Inconel alloys are typically used in high temperature applications. Inconel is often encountered in extreme environments. It is common in gas turbine blades, seals and combustors as well as turbocharger rotors and seals because of their ability to maintain strength and corrosion resistance under extremely high temperature conditions. Inconel contains approximately 80 percent nickel and 14 percent chromium and small amounts of iron and other elements.
Specify where each of the following steel alloys could be b. Silicon
Increases strength, Magnetisim and used for spring steels.
Describe the following factors relating to the manufacture of steel: b. Treatment of impurities including slag (1)
Iron is produced by mixing iron ore with coke and limestone and submitting it to hot air. The coke burns and forms superheated carbon monoxide which absorbs oxygen from the ore causing the molten iron to sink to the bottom of the furnace. The limestone reacts with the impurities in the iron and coke and forms slag which floats on top of the molten iron. The slag is removed and the refined metal is poured from the furnace.
Describe the characteristics, properties, compositions and uses of Lead as used in the construction of aircraft or aircraft components. (2)
Lead is a chemical element in the carbon group with symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft and malleable metal, which is regarded as a heavy metal and a post-transition metal. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid. It is also the heaviest non-radioactive element. Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield.
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) a. Carbon (low, medium and high carbon steels)
Low: Used in safety wire, cable bushings and threaded rod ends. Easily welded and machined but does not easily accept heat treatment Medium: Improved heat treatment capabilites while retaining ductility High carbon steels: Very hard steel, used in springs, files and cutting tools
Describe the characteristics, properties, compositions and uses of Magnesium and Dow metal alloys as used in the construction of aircraft or aircraft components. (2)
Magnesium alloy is one of the lightest metals with sufficient strength to be used in aircraft structures. It is typically alloyed with the following elements: - Zinc - Aluminium - Thorium - Zirconium - Manganese Magnesium has some serious drawbacks as an aircraft alloy. Magnesium is highly reactive and readily corrodes as well as being prone to cracking. This limits magnesium alloy use in thin sheet metal and metal forming and is the reason why most magnesium components are cast. Magnesium also burns readily, and caution must be taken when grinding or machining. If a fire does occur, dry powder fire extinguishers must be used as putting water on a magnesium fire only intensifies the blaze. DOW METAL: A trademark name applied to any of various magnesium alloys containing more than 85 percent magnesium, characterized by extreme lightness.
Identify the advantages of magnesium over other metals for aircraft use. (1)
Magnesium alloys are used for castings and in their wrought form are available in sheets, bars, tubing, and extrusions. Magnesium is one of the lightest metals having sufficient strength and suitable work characteristics for use in aircraft structures. It has a density of 1.74 compared with 2.69 for aluminium. It weighs only about 2/3 as much as aluminium.
Specify the effects of Magnesium and Silicon when alloyed with aluminium. (1)
Magnesium and Silicon are added to aluminium the resultant alloy carries the 6xxx series designation. in these alloys the silicon and manganese form magnesium silicide which makes the alloy heat-treatable. The 6xxx series has medium strength and good forming and corrosion resistance properties.
Describe the limitations on the use of magnesium in aircraft construction, with particular regard to corrosion, cracking, burning and machining. (2)
Magnesium has some serious drawbacks that have to be overcome before it can be used successfully. For example, magnesium is highly susceptible to corrosion and tends to crack. The cracking contributes to its difficulty in forming and limits its use for thin sheet metal parts. This tendency is largely overcome by forming parts while the metal is hot. Treating the surface with chemicals that form an oxide film to prevent oxygen from reaching the metal minimises the corrosion problem. When oxygen is excluded from the surface no corrosion can form. Another important step in minimising corrosion is to always use hardware such as rivets, nuts, bolts and screws that are made of a compatible material. In addition to cracking and corroding easily, magnesium burns readily in a dust or small particle form. For this reason caution must be exercised when grinding and machining magnesium. If a fire should occur, extinguish it by smothering it with dry sand or some other dry material which excludes air from the metal and cools its surface. If water is used it will only intensify the fire.
Specify the effects of Magnesium when alloyed with aluminium. (1)
Magnesium is used to produce 5xxx series alloys. These alloys possess good welding characteristics and corrosion resistance. If the metal is exposed to high temperature or excessive cold working its susceptibility to corrosion increases.
Specify the effects of Manganese when alloyed with aluminium. (1)
Manganese alloys with the 3xxx series utilise manganese as the principal alloying agent, and are generally considered non heat-treatable. The most common variation is 3003 which offers moderate strength and has good working characteristics.
Describe the characteristics, properties, compositions and uses of Monel as used in the construction of aircraft or aircraft components. (2)
Monel is a trademark of Special Metals Corporation for a series of nickel alloys, primarily composed of nickel (up to 67%) and copper, with some iron and other trace elements. In the 1960s, Monel metal found bulk uses in aircraft construction, especially in making the frames and skins of experimental rocket planes, such as the North American X-15, to resist the great heat generated by aerodynamic friction during extremely high speed flight. Monel metal retains its strength at very high temperatures, allowing it to maintain its shape at high atmospheric flight speeds, a trade off against the increased weight of the parts due to Monel's high density.
Describe the cladding process and precautions when using, storing, handling and identifying ALCLAD (2)
Most external aircraft surfaces are made of clad aluminium. ALCLAD consists of a pure aluminium coating rolled onto the surface of heat-treated aluminium alloy. The thickness of this coating is approximately 5 percent of the alloys thickness on each side. For example, if an ALCLAD sheet of aluminium is .040 inch thick, then 5%, or 0.020 inches of pure aluminium is applied to each side. This results in an alloy thickness of 0.036 inch. This clad surface greatly increases the corrosion resistance of an aluminium alloy. However if it is penetrated, corrosion agents can attack the alloy within. For this reason sheet metal must be protected from scratches and abrasions. In addition to providing a starting point for corrosion abrasions create potential stress points. Precautions when handling and storing ALCLAD: Sheets stored on edge in rack Do not remove protective paper Don't cut off corner ID markings Keep work area clean Have assistance when handling large sheets Aluminium sheets are identified across the sheet in rows as follows Four digit designation e.g. 2024 Federal specification no e.g. QQ-A-50/5 Military specification e.g. MIL-A-8902 Aeronautical material spec e.g. AMS 4049 Material thickness e.g. .032
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) h. Vanadium
Most wrenches and ball bearings are made of chrome-vanadium steel.
Describe the following factors relating to the manufacture of steel: c. Importance of fluxes (1)
Much of the steel used in aircraft construction is made in electric furnaces which allow better control of alloying agents than gas fired furnaces. An electric furnace is loaded with scrap steel, limestone and flux. Carbon electrodes are lowered into the steel producing electric arcs between the steel and the carbon. The intense heat from the arcs melts the steel and the impurities mix with the flux. Once the impurities are removed, controlled quantities of alloying agents are added and the liquid metal is poured into molds.
Describe the characteristics, properties, compositions and uses of Muntz metal as used in the construction of aircraft or aircraft components. (2)
Muntz metal is a form of alpha-beta brass with about 60% copper, 40% zinc and a trace of iron. It is named after George Fredrick Muntz who commercialised the alloy following his patent of 1832. The alloy must be worked hot and is used today for corrosion resistant machine parts.
Describe the characteristics, properties, compositions and uses of Nickel as used in the construction of aircraft or aircraft components. (2)
Nickel adds strength and hardness to steel and increases its yield strength. It also slows the rate of hardening when steel is heat-treated, which increases the depth of hardening and produces a finer grain structure. The finer grain structure reduces steel's tendency to warp and scale when heat-treated. SAE 2330 steel contains 3 percent nickel and 0.03 percent carbon, and is used in producing aircraft hardware such as bolts, nuts, rod ends and pins.
Describe the properties and characteristics of steels having a Nickel alloying agent. (1)
Nickel adds strength and hardness to steel and increases its yield strength. It also slows the rate of hardening when steel is heat-treated, which increases the depth of hardening and produces a finer grain structure. The finer grain structure reduces steel's tendency to warp and scale when heat-treated. SAE 2330 steel contains 3 percent nickel and 0.03 percent carbon, and is used in producing aircraft hardware such as bolts, nuts, rod ends and pins.
Describe the properties and characteristics of steels having a Nickel/Chromium alloying agent. (1)
Nickel toughens steel and chromium hardens it, therefore when both elements are alloyed they give steel desirable characteristics for use in high strength structural applications. Nickel-chrome steels such as SAE 3130, 3250 and 3435 are used for forged or machined parts requiring high strength, ductility, shock resistance and toughness.
Describe the properties and characteristics of steels having a Molybdenum alloying agent. (1)
One of the most widely used alloying elements for aircraft structural steel is molybdenum. It reduces the grain size of steel and increases both impact strength and elastic limit. molybdenum steels are extremely wear resistant and possess a great deal of fatigue strength. This accounts for its use in high strength structural members and cylinder barrels.
Describe the properties and characteristics of steels having a Phosphorus alloying agent. (1)
Phosphorus raises the yield strength of steel and improves low carbon steel's resistance to atmospheric corrosion. However, no more than 0.05 percent phosphorus is usually used in steel, since higher amounts cause the alloy to become brittle when cold.
Describe the characteristics, properties, compositions and uses of Pure aluminium as used in the construction of aircraft or aircraft components. (2)
Pure aluminium while being exceptionally light , lacks sufficent strength for aircraft structural applications, but when it is alloyed with other compatible metals it gains considerable strength while retaining it low weight and some of its corrosion resistant properties carries over to the newly formed alloy. When aluminium is mixed with copper or zinc, the resultant alloy is strong as steel with only one third the weight.
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) c. Phosphorus
Raises yield strength and improves resistance to corrosion
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) d. Nickel
SAE 2330 steel contains 3 percent nickel and 0.03 percent carbon, and is used in producing aircraft hardware such as bolts, nuts, rod ends and pins
Specify the effects of Silicon when alloyed with aluminium. (1)
Silicon alloys with the 4xxx series utilise silicon which lowers a metals melting temperature. This results in an alloy that works well for welding and brazing.
Describe Stainless Steel
Stainless steel is a classification of corrosion resistant steels that contain large amounts of chromium and nickel. Their strength and resistance to corrosion make them well suited for high temperature applications such as firewalls and exhaust system components.
Describe the characteristics, properties, compositions and uses of Tin as used in the construction of aircraft or aircraft components. (2)
This silvery, malleable other metal is not easily oxidized in air and is used to coat other metals to prevent corrosion. The first alloy, used in large scale since 3000 BC, was bronze, an alloy of tin and copper. After 600 BC pure metallic tin was produced. Pewter, which is an alloy of 85-90% tin with the remainder commonly consisting of copper, antimony and lead, was used for flatware from the Bronze Age until the 20th century. In modern times tin is used in many alloys, most notably tin/lead soft solders, typically containing 60% or more of tin.
Describe the characteristics, properties, compositions and uses of Titanium (Alpha, Alpha-beta, Beta) as used in the construction of aircraft or aircraft components. (2)
Titanium falls between aluminium and stainless steel in terms of elasticity, density, and elevated temperature strength. It has a melting point of from 1500 °C to 1735 °C, low thermal conductivity, and a low coefficient of expansion. It is light, strong, and resistant to stress corrosion cracking. Titanium is approximately 60 percent heavier than aluminium and about 50 percent lighter than stainless steel. • A (alpha) — all around performance; good weldability; tough and strong both cold and hot, and resistant to oxidation. • B (beta)—bendability; excellent bend ductility; strong both cold and hot, but vulnerable to contamination. • C (combined alpha and beta for compromise performances) — strong when cold and warm, but weak when hot; good bendability; moderate contamination resistance; excellent forgeability
Describe the properties and characteristics of steels having a Tungsten alloying agent. (1)
Tungsten has an extremely high melting point and adds this characteristic to steel it is alloyed with. Because tungsten steels retain their hardness at elevated operating temperatures, they are typically used for breaker contacts in magnetos and for high speed cutting tools.
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) i. Tungsten
Typically used for breaker contacts in magnetos and for high speed cutting tools.
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) f. Nickel/Chromium
Used for forged or machined parts requiring high strength, ductility, shock resistance and toughness.
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) e. Chromium
Used in balls and rollers of antifriction bearings
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) g. Molybdenum
Used in high strength structural members and cylinder barrels
Describe the properties and characteristics of steels having a Vanadium alloying agent. (1)
When combined with chromium, vanadium produces a strong tough ductile steel alloy. Amounts up to 0.20 percent improve grain structure and increase both ultimate tensile strength and toughness. Most wrenches and ball bearings are made of chrome-vanadium steel.
Describe the properties and characteristics of steels having a Silicon alloying agent. (1)
When silicon is alloyed with steel it acts as a hardener. When used in small quantities, it also improves ductility.
Specify the effects of Zinc when alloyed with aluminium. (1)
Zinc is added to aluminium alloy to produce 7xxx series alloys making it harder and stronger. Some widely used zinc-aluminium alloys are 7075 and 7178. The aluminium-zinc alloy 7075 has a tensile of 77 KSI and a bearing strength of 139 KSI. However the alloy is very difficult to bend. An even stronger zinc alloy is 7178 which has a tensile strength of 84 KSI and a bearing strength of 151 KSI.
Describe the characteristics, properties, compositions and uses of Zinc as used in the construction of aircraft or aircraft components. (2)
Zinc is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C. Above 210 °C, the metal becomes brittle again and can be pulverized by beating. Zinc is a fair conductor of electricity. For a metal, zinc has relatively low melting (419.5 °C) and boiling points (907 °C). A widely used alloy which contains zinc is brass, in which copper is alloyed with anywhere from 3% to 45% zinc, depending upon the type of brass. Brass is generally more ductile and stronger than copper and has superior corrosion resistance. Zinc is most commonly used as an anti-corrosion agent. Galvanization, which is the coating of iron or steel to protect the metals against corrosion. The 7xxx series aluminium alloys are made harder and stronger with the addition of zinc. Some widely used forms of zinc aluminium alloys are 7075 and 7178
Describe the characteristics, properties, compositions and uses of Clad aluminium as used in the construction of aircraft or aircraft components. (2)
a new corrosion resistant aluminum product which is markedly superior to the present strong alloys. Its use should result in greatly increased life of a structural part. Alclad is a heat-treated aluminum, copper, manganese, magnesium alloy that has the corrosion resistance of pure metal at the surface and the strength of the strong alloy underneath. The clad surface protects the underlying aluminium alloy from corrosive attack, however if it is scratched it loses this protective property. The thickness of the pure aluminium layer is approximately 5% of the alloys total thickness.
Specify where each of the following steel alloys could be used in aircraft or aircraft component construction. (1) a. Carbon (low, medium and high carbon steels) b. Silicon c. Phosphorus d. Nickel e. Chromium and chrome-molybdenum f. Nickel/Chromium g. Molybdenum h. Vanadium i. Tungsten
a. Carbon Low: Used in safety wire, cable bushings and threaded rod ends. Easily welded and machined but does not easily accept heat treatment Medium: Improved heat treatment capabilites while retaining ductility High carbon steels: Very hard steel, used in springs, files and cutting tools b. Silicon: Increases strength, Magnetisim and used for spring steels. c. Phosphorus d. Nickel e. Chromium and chrome-molybdenum f. Nickel/Chromium g. Molybdenum h. Vanadium i. Tungsten
State the approximate percentage of the following alloying agents to achieve the desired properties of the steel. (1) a. Carbon (low, medium and high carbon steels) b. Silicon c. Phosphorus d. Nickel e. Chromium and chrome-molybdenum f. Nickel/Chromium g. Molybdenum h. Vanadium i. Tungsten
a. Carbon (low, medium and high carbon steels) (0.10 - 0.30%), (0.30 - 0.50%) 0.50 - 1.05%) b. Silicon (0.2 -2 .0%) c. Phosphorus (0.05%) d. Nickel (0.3%) e. Chromium (3 - 5%) and chrome-molybdenum 0.4 - 1.10% Cr 0.08 - 0.35% Mo f. Nickel/Chromium (1.25 - 3.5% Ni 0.8 - 1.5% Cr) g. Molybdenum (0.2-5%) h. Vanadium (0.2%) i. Tungsten (Up to 18%)
