A two-stroke engine is a type of internal combustion engine which completes a power cycle with two strokes of the piston during only one crankshaft revolution. This is in contrast to a "four-stroke engine", which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen with the intake and exhaust functions occurring at the same time. Two-stroke engines have a high power-to-weight ratio, power being available in a narrow range of rotational speeds called the "power band". Compared to four-stroke engines, two-stroke engines have a reduced number of moving parts, so can be more compact and lighter; the first commercial two-stroke engine involving in-cylinder compression is attributed to Scottish engineer Dugald Clerk, who patented his design in 1881. However, unlike most two-stroke engines, his had a separate charging cylinder; the crankcase-scavenged engine, employing the area below the piston as a charging pump, is credited to Englishman Joseph Day.
On 31 December 1878, German inventor Karl Benz produced a two-stroke gas engine, for which he received a patent in 1879 in Germany. The first practical two-stroke engine is attributed to Yorkshireman Alfred Angas Scott, who started producing twin-cylinder water-cooled motorcycles in 1908. Gasoline versions are useful in lightweight or portable applications such as chainsaws and motorcycles. However, when weight and size are not an issue, the cycle's potential for high thermodynamic efficiency makes it ideal for diesel compression ignition engines operating in large, weight-insensitive applications, such as marine propulsion, railway locomotives and electricity generation. In a two-stroke engine, the heat transfer from the engine to the cooling system is less than in a four-stroke, which means that two-stroke engines can be more efficient. Crankcase-compression two-stroke engines, such as common small gasoline-powered engines, create more exhaust emissions than four-stroke engines of comparable power output because their two-stroke oil lubrication mixture is burned in the engine, due to the engine's total-loss oiling system, because the combined opening time of the intake and exhaust ports in some 2-stroke designs can allow some amount of unburned fuel vapors to exit in the exhaust stream.
Two-stroke petrol engines are preferred when mechanical simplicity, light weight, high power-to-weight ratio are design priorities. With the traditional lubrication technique of mixing oil into the fuel, they have the advantage of working in any orientation, as there is no oil reservoir dependent on gravity. A number of mainstream automobile manufacturers have used two-stroke engines in the past, including the Swedish Saab and German manufacturers DKW, Auto-Union, VEB Sachsenring Automobilwerke Zwickau, VEB Automobilwerk Eisenach; the Japanese manufacturer Suzuki did the same in the 1970s. Production of two-stroke cars ended in the 1980s in the West, due to stringent regulation of air pollution. Eastern Bloc countries continued with the Trabant and Wartburg in East Germany. Two-stroke engines are still found in a variety of small propulsion applications, such as outboard motors, high-performance, small-capacity motorcycles and dirt bikes, scooters, tuk-tuks, karts, ultralight airplanes, model airplanes and other model vehicles.
They are common in power tools used outdoors, such as lawn mowers and weed-wackers. With direct fuel injection and a sump-based lubrication system, a two-stroke engine produces air pollution no worse than a four-stroke, it can achieve higher thermodynamic efficiency. Therefore, the cycle has also been used in large diesel engines large industrial and marine engines, as well as some trucks and heavy machinery. There are several experimental designs intended for automobile use: for instance, Lotus of Norfolk, UK, had in 2008 a prototype direct-injection two-stroke engine intended for alcohol fuels called the Omnivore which it is demonstrating in a version of the Exige. Although the principles remain the same, the mechanical details of various two-stroke engines differ depending on the type; the design types vary according to the method of introducing the charge to the cylinder, the method of scavenging the cylinder and the method of exhausting the cylinder. Piston port is the most common in small two-stroke engines.
All functions are controlled by the piston covering and uncovering the ports as it moves up and down in the cylinder. In the 1970s, Yamaha worked out some basic principles for this system, they found that, in general, widening an exhaust port increases the power by the same amount as raising the port, but the power band does not narrow as it does when the port is raised. However, there is a mechanical limit to the width of a single exhaust port, at about 62% of the bore diameter for reasonable ring life. Beyond this, the rings will wear quickly. A maximum 70 % of bore width is possible in racing engines. Intake duration is between 160 degrees. Transfer port time is set at a minimum of 26 degrees; the strong low pressure pulse of a racing two-stroke expansion chamber can drop the pressure to -7 PSI when the piston is at bottom dead center, the transfer ports nearly wide open. One of the reasons for high fuel consumption in two-strokes is that so
The Diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel, injected into the combustion chamber, is caused by the elevated temperature of the air in the cylinder due to the mechanical compression. Diesel engines work by compressing only the air; this increases the air temperature inside the cylinder to such a high degree that atomised Diesel fuel injected into the combustion chamber ignites spontaneously. With the fuel being injected into the air just before combustion, the dispersion of the fuel is uneven; the process of mixing air and fuel happens entirely during combustion, the oxygen diffuses into the flame, which means that the Diesel engine operates with a diffusion flame. The torque a Diesel engine produces is controlled by manipulating the air ratio; the Diesel engine has the highest thermal efficiency of any practical internal or external combustion engine due to its high expansion ratio and inherent lean burn which enables heat dissipation by the excess air.
A small efficiency loss is avoided compared with two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed Diesel engines can reach effective efficiencies of up to 55%. Diesel engines may be designed as either four-stroke cycles, they were used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in ships. Use in locomotives, heavy equipment and electricity generation plants followed later. In the 1930s, they began to be used in a few automobiles. Since the 1970s, the use of Diesel engines in larger on-road and off-road vehicles in the US has increased. According to Konrad Reif, the EU average for Diesel cars accounts for 50% of the total newly registered; the world's largest Diesel engines put in service are 14-cylinder, two-stroke watercraft Diesel engines. In 1878, Rudolf Diesel, a student at the "Polytechnikum" in Munich, attended the lectures of Carl von Linde.
Linde explained that steam engines are capable of converting just 6-10 % of the heat energy into work, but that the Carnot cycle allows conversion of all the heat energy into work by means of isothermal change in condition. According to Diesel, this ignited the idea of creating a machine that could work on the Carnot cycle. After several years of working on his ideas, Diesel published them in 1893 in the essay Theory and Construction of a Rational Heat Motor. Diesel was criticised for his essay, but only few found the mistake that he made. Diesel's idea was to compress the air so that the temperature of the air would exceed that of combustion. However, such an engine could never perform any usable work. In his 1892 US patent #542846 Diesel describes the compression required for his cycle: "pure atmospheric air is compressed, according to curve 1 2, to such a degree that, before ignition or combustion takes place, the highest pressure of the diagram and the highest temperature are obtained-that is to say, the temperature at which the subsequent combustion has to take place, not the burning or igniting point.
To make this more clear, let it be assumed that the subsequent combustion shall take place at a temperature of 700°. In that case the initial pressure must be sixty-four atmospheres, or for 800° centigrade the pressure must be ninety atmospheres, so on. Into the air thus compressed is gradually introduced from the exterior finely divided fuel, which ignites on introduction, since the air is at a temperature far above the igniting-point of the fuel; the characteristic features of the cycle according to my present invention are therefore, increase of pressure and temperature up to the maximum, not by combustion, but prior to combustion by mechanical compression of air, there upon the subsequent performance of work without increase of pressure and temperature by gradual combustion during a prescribed part of the stroke determined by the cut-oil". By June 1893, Diesel had realised his original cycle would not work and he adopted the constant pressure cycle. Diesel describes the cycle in his 1895 patent application.
Notice that there is no longer a mention of compression temperatures exceeding the temperature of combustion. Now it is stated that the compression must be sufficient to trigger ignition. "1. In an internal-combustion engine, the combination of a cylinder and piston constructed and arranged to compress air to a degree producing a temperature above the igniting-point of the fuel, a supply for compressed air or gas. See US patent # 608845 filed 1895 / granted 1898In 1892, Diesel received patents in Germany, the United Kingdom and the United States for "Method of and Apparatus for Converting Heat into Work". In 1894 and 1895, he filed patents and addenda in various
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or obstructing various passageways. Valves are technically fittings, but are discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure; the word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll. The simplest, ancient, valve is a hinged flap which drops to obstruct fluid flow in one direction, but is pushed open by flow in the opposite direction; this is called "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems. Valves have many uses, including controlling water for irrigation, industrial uses for controlling processes, residential uses such as on/off and pressure control to dish and clothes washers and taps in the home. Aerosols have a tiny valve built in. Valves are used in the military and transport sectors.
Valves are found in every industrial process, including water and sewage processing, power generation, processing of oil and petroleum, food manufacturing and plastic manufacturing and many other fields. People in developed nations use valves in their daily lives, including plumbing valves, such as taps for tap water, gas control valves on cookers, small valves fitted to washing machines and dishwashers, safety devices fitted to hot water systems, poppet valves in car engines. In nature there are valves, for example one-way valves in veins controlling the blood circulation, heart valves controlling the flow of blood in the chambers of the heart and maintaining the correct pumping action. Valves may be operated manually, either by a handle, pedal or wheel. Valves may be automatic, driven by changes in pressure, temperature, or flow; these changes may act upon a diaphragm or a piston which in turn activates the valve, examples of this type of valve found are safety valves fitted to hot water systems or boilers.
More complex control systems using valves requiring automatic control based on an external input require an actuator. An actuator will stroke the valve depending on its input and set-up, allowing the valve to be positioned and allowing control over a variety of requirements. Valves vary in form and application. Sizes range from 0.1 mm to 60 cm. Special valves can have a diameter exceeding 5 meters. Valve costs range from simple inexpensive disposable valves to specialized valves which cost thousands of US dollars per inch of the diameter of the valve. Disposable valves may be found in common household items including mini-pump dispensers and aerosol cans. A common use of the term valve refers to the poppet valves found in the vast majority of modern internal combustion engines such as those in most fossil fuel powered vehicles which are used to control the intake of the fuel-air mixture and allow exhaust gas venting. Valves may be classified into a number of basic types. Valves may be classified by how they are actuated: Hydraulic Pneumatic Manual Solenoid valve Motor The main parts of the most usual type of valve are the body and the bonnet.
These two parts form the casing. The valve's body is the outer casing of most or all of the valve that contains the internal parts or trim; the bonnet is the part of the encasing through which the stem passes and that forms a guide and seal for the stem. The bonnet screws into or is bolted to the valve body. Valve bodies are metallic or plastic. Brass, gunmetal, cast iron, alloy steels and stainless steels are common. Seawater applications, like desalination plants use duplex valves, as well as super duplex valves, due to their corrosion resistant properties against warm seawater. Alloy 20 valves are used in sulphuric acid plants, whilst monel valves are used in hydrofluoric acid plants. Hastelloy valves are used in high temperature applications, such as nuclear plants, whilst inconel valves are used in hydrogen applications. Plastic bodies are used for low pressures and temperatures. PVC, PP, PVDF and glass-reinforced nylon are common plastics used for valve bodies. A bonnet acts as a cover on the valve body.
It is semi-permanently screwed into the valve body or bolted onto it. During manufacture of the valve, the internal parts are put into the body and the bonnet is attached to hold everything together inside. To access internal parts of a valve, a user would take off the bonnet for maintenance. Many valves do not have bonnets. Many ball valves do not have bonnets since the valve body is put together in a different style, such as being screwed together at the middle of the valve body. Ports are passages. Ports are obstructed by disc to control flow. Valves most have 2 ports, but may have as many as 20; the valve is always connected at its ports to pipes or other components. Connection methods include threadings, compression fittings, cement, flanges, or welding. A handle is used to manually control a valve from outside the valve body. Automatically controlled valves do not have handles, but some may have a handle anyway to manually override automatic control, such as a stop-check valve. An actuator is a mechanism or device to automatically or remotely control
A connecting rod is a rigid member which connects a piston to a crank or crankshaft in a reciprocating engine. Together with the crank, it forms a simple mechanism that converts reciprocating motion into rotating motion. A connecting rod may convert rotating motion into reciprocating motion, its original use. Earlier mechanisms, such as the chain, could only impart pulling motion. Being rigid, a connecting rod may transmit either push or pull, allowing the rod to rotate the crank through both halves of a revolution. In a few two-stroke engines the connecting rod is only required to push. Today, the connecting rod is best known through its use in internal combustion piston engines, such as automobile engines; these are of a distinctly different design from earlier forms of connecting rod used in steam engines and steam locomotives. Evidence for the connecting rod appears in the late 3rd century Hierapolis sawmill in Roman Asia, it appears in two 6th century Byzantine-era saw mills excavated at Ephesus, Asia Minor and Gerasa, Roman Syria.
The crank and connecting rod mechanism of these Roman-era watermills converted the rotary motion of the waterwheel into the linear movement of the saw blades. Sometime between 1174 and 1206 in the Artuqid State, the Arab inventor and engineer Al-Jazari described a machine which incorporated the connecting rod with a crankshaft to pump water as part of a water-raising machine, though the device was complex. In Renaissance Italy, the earliest evidence of a − albeit mechanically misunderstood − compound crank and connecting-rod is found in the sketch books of Taccola. A sound understanding of the motion involved is displayed by the painter Pisanello who showed a piston-pump driven by a water-wheel and operated by two simple cranks and two connecting-rods. By the 16th century, evidence of cranks and connecting rods in the technological treatises and artwork of Renaissance Europe becomes abundant; the first steam engine, Newcomen's atmospheric engine, was single-acting: its piston only did work in one direction and so these used a chain rather than a connecting rod.
Their output rocked forth, rather than rotating continuously. Steam engines after this are double-acting: their internal pressure works on each side of the piston in turn; this requires a seal around the piston rod and so the hinge between the piston and connecting rod is placed outside the cylinder, in a large sliding bearing block called a crosshead. In a steam locomotive, the crank pins are mounted directly on one or more pairs of driving wheels, the axle of these wheels serves as the crankshaft; the connecting rods, run between the crank pins and crossheads, where they connect to the piston rods. Crossheads or trunk guides are used on large diesel engines manufactured for marine service; the connecting rods of smaller steam locomotives are of rectangular cross-section but, on small locomotives, marine-type rods of circular cross-section have been used. Stephen Lewin, who built both locomotive and marine engines, was a frequent user of round rods. Gresley's A4 Pacifics, such as Mallard, had an alloy steel connecting rod in the form of an I-beam with a web, only 0.375 in thick.
On Western Rivers steamboats, the connecting rods are properly called pitmans, are sometimes incorrectly referred to as pitman arms. In modern automotive internal combustion engines, the connecting rods are most made of steel for production engines, but can be made of T6-2024 and T651-7075 aluminum alloys or titanium for high-performance engines, or of cast iron for applications such as motor scooters, they are not rigidly fixed at either end, so that the angle between the connecting rod and the piston can change as the rod moves up and down and rotates around the crankshaft. Connecting rods in racing engines, may be called "billet" rods, if they are machined out of a solid billet of metal, rather than being cast or forged; the small end attaches to the piston pin, gudgeon pin or wrist pin, most press fit into the connecting rod but can swivel in the piston, a "floating wrist pin" design. The big end connects to the crankpin on the crank throw, in most engines running on replaceable bearing shells accessible via the connecting rod bolts which hold the bearing "cap" onto the big end.
There is a pinhole bored through the bearing on the big end of the connecting rod so that pressurized lubricating motor oil squirts out onto the thrust side of the cylinder wall to lubricate the travel of the pistons and piston rings. Most small two-stroke engines and some single cylinder four-stroke engines avoid the need for a pumped lubrication system by using a rolling-element bearing instead, however this requires the crankshaft to be pressed apart and back together in order to replace a connecting rod. A major source of engine wear is the sideways force exerted on the piston through the connecting rod by the crankshaft, which wears the cylinder into an oval cross-section rather than circular, making it impossible for piston rings to seal against the cylinder walls. Geometrically, it can be seen that longer connecting rods will reduce the amount of this sideways force, therefore lead to longer engine life
USS Pompano (SS-181)
USS Pompano, a United States Porpoise-class submarine, was the second ship of the United States Navy to be named for the pompano. Her keel was laid down on 14 January 1936 by the Mare Island Navy Yard in California, she was launched on 11 March 1937, sponsored by Mrs. Isaac I. Yates, wife of Captain Isaac I. Yates, manager of Mare Island Navy Yard; the boat was commissioned on 12 June 1937, Lieutenant Commander Lewis S. Parks in command. Six boats were built in this group, with three different diesel engine designs from different makers. Pompano was fitted with H. O. R. 8-cylinder double-acting engines that were a license-built version of the MAN auxiliary engines of the cruiser Leipzig. Owing to the limited space available within the submarines, either opposed-piston or, in this case, double-acting engines were favoured for being more compact. Pompano's engines were a complete failure and were wrecked during trials before leaving the Mare Island Navy Yard. Pompano was laid up for eight months until 1938.
The engines were regarded as unsatisfactory and were replaced by Fairbanks-Morse opposed piston engines in 1942. Pompano's engines were a unique prototype of the H. O. R. Engine, having 8 cylinders. An inherent problem with double-acting cylinders, owing to the piston rod reducing the piston area on one side, is an imbalance in the force on each side of the piston; the H. O. R. Engines were plagued by other problems as a result. While Pompano was still being built, the Salmon-class submarines were ordered. Three of these were built by Electric Boat, with a 9-cylinder development of the same H. O. R. Engine; the 9-cylinder arrangement was an attempt to re-balance the engine, so reducing the overall effect of vibration across the engine. Although not as great a failure as Pompano's engines, this version was still troublesome and the boats were re-engined with the same General Motors 16-248 two-stroke V16 Diesel engines as their sister boats. Other Electric Boat constructed submarines of the Sargo and Seadragon classes were built with these 9-cylinder H.
O. R. Engines, but re-engined. In the years preceding World War II, Pompano operated out of Mare Island off the West Coast of the United States, training her crew and patrolling in a constant state of readiness. Although the submarine was awarded a battle star for the attack on Pearl Harbor, she had not yet arrived from Mare Island. Reaching port shortly after the attack, she sailed from Pearl Harbor on 18 December 1941 for her first war patrol, devoted to reconnoitering the eastern Marshall Islands for an aircraft carrier strike in January. Aircraft from Enterprise bombed her in error on 20 December. Pompano arrived off Wake Island on 1 January 1942 to gather intelligence, approaching close enough to see Japanese machine gun posts. On 8 January, "bedevilled by breakdowns in her temperamental H. O. R. Engines" she subsequently viewed several other islands of the group, she sighted several large ships protected by patrol craft in the harbor at Wotje. On 12 January, one of these stood out: Yawata, with four escorts.
Pompano fired four Mark 14 torpedoes for two hits, the target broke up, disappearing from view. Five days when one of the patrol boats steamed out of the harbor, Pompano worked her way between him and the channel. Both torpedoes exploded prematurely. With the enemy charging directly for her, the submarine waited until her target was 1,000 yards away before firing two more torpedoes "down the throat", the first attack of its kind by a United States submarine; the torpedoes missed, the destroyer delivered an ineffective depth charging. After reconnoitering Maloelap, Pompano departed on 24 January, arriving at Pearl Harbor on 31 January. On the same day, aided by her reports, the fast carriers of the Pacific Fleet struck the Marshall Islands. On her next patrol, to Japanese home waters, Pompano left Pearl Harbor on 20 April 1942, refueled at Midway Island, entered her area 7 May patrolling the sea lanes west of Okinawa and in the East China Sea. Shipping was scarce. On the next day, after chasing for seven hours and fighting a motor fire in the process, she torpedoed Tokyo Maru, which exploded and sank.
As Pompano shifted her patrol area to the main route between Japan and the East Indies, a large transport escorted by one destroyer caught her eye on 30 May. Running to a position ahead of the convoy, she waited until her victim was only 750 yd away, scoring solid hits which sank Atsuta Maru two and a half hours later. With her fuel getting low and a strong possibility of not being able to refuel at Midway Island on the way back because of the Japanese attempt to invade the island, Pompano began to work eastward. On the morning of 3 June, she found a small inter-island steamer, setting the vessel afire with gunfire. On 5 June, while on the shipping route between Japan and the Mariana Islands, the submarine caught a trawler and sank it with gunfire. Two days word arrived the Japanese fleet, decisively defeated in the Battle of Midway, was fleeing toward Japan. Pompano made no contact. On 13 June 1942, she put into Midway for refueling, on 18 June arrived in Pearl Harbor, she was credited with sinking five ships for a total of 16,500 tons.
After a refit - and a change of command, to Willis M. Thomas - she sailed from Pearl Harbor again on 19 July, bound for
The firm of Hooven, Owens and Company manufactured steam and diesel engines in Hamilton, Ohio. Because the firm was known by its initials, H. O. R; the Hooven is sometimes incorrectly rendered as Hoover, the Owens may be mistaken for Owen. The firm was the successor to the firm of Owens, Ebert & Dyer which went into receivership in 1876. In 1882, George A. Rentschler, J. C. Hooven, Henry C. Sohn, George H. Helvey, James E. Campbell merged the firm with the iron works of Sohn and Rentschler, adopted the name Hooven, Rentschler Co. In 1883 the firm began the manufacture of Corliss steam engines, producing a total of 700 such engines by 1901. By World War I, the Hooven-Owens-Rentschler Company operated the largest exclusive Corliss Engine plant in the country, employing nearly 800 men. In 1928 the company merged with the Niles Tool Works to form the General Machinery Corporation. However, it continued to make diesel engines under the H. O. R. Brand, supplied many of the powerplants for United States submarines and liberty ships during World War II.
General Machinery Corporation ranked 91st among United States corporations in the value of World War II military production contracts. In the 1930s H. O. R. Developed a double-acting two-stroke diesel engine based on the German cruiser Leipzig's MAN engines but with eight cylinders instead of seven, expanded to nine cylinders in the final submarine version; the double-acting design produced more power from a physically smaller engine than conventional designs. However, H. O. R.'s double-acting engines those of USS Pompano, gained notoriety for their unreliability in the submarine force, where they were nicknamed "whores." Owing to the limited space available within the submarines, either opposed-piston or, in this case, double-acting engines were favored for being more compact. An inherent problem with double-acting cylinders, owing to the piston rod reducing the piston area on one side, is an imbalance in the force on each side of the piston; the H. O. R. Engines were plagued by other problems as a result.
This in turn overstressed the drive train and caused the gears to shed teeth, create torsional vibration, rendered the engine and gear train inoperable. As an example of the problems caused by the unreliability of the H. O. R. Engines, Captain Charles Herbert Andrews of the USS Gurnard recalled concerning a war patrol in support of Operation Torch, "I only used three, saving the fourth for a spare; when two of them broke down in the Bay of Biscay, I cut the patrol short and limped back to Scotland."During World War II, all submarine H. O. R. Engines were replaced by early 1943 with General Motors Cleveland Division engines or Fairbanks-Morse Model 38 engines; the wartime performance of the H. O. R. Engines was so poor that Captain Tommy Dykers of the USS Jack said, "The H. O. R. Engines saved the Japanese thirty or forty ships." In 1947, General Machinery Corporation merged with Lima Locomotive Works to form Lima-Hamilton Corporation, which, in turn, merged in 1950 with Baldwin Locomotive Works to form the Baldwin-Lima-Hamilton Corporation.
BLH, Hamilton Div. moved to the Eddystone Pa. plant of BLH in 1959. BLH went out of business around 1966. An HOR combination steam engine is preserved in the Henry Ford Museum in Michigan, it is one of 12 units that were made for Mr. Ford for his Highland Park assembly plant where he produced the Model T from 1908 until its production demise in 1927; this engine was removed from the Highland Park facility and placed in storage after the Ford Motor Company took up permanent residence at the giant River Rouge facilities to produce the Model A. Mr. Ford donated the steam engine to his Edison Institute as the cornerstone display in 1929; the Edison Institute was renamed the Henry Ford Museum and is known today as "The Henry Ford"
Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its low melting temperature; the alloy constituents affect its colour when fractured: white cast iron has carbide impurities which allow cracks to pass straight through, grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing. Carbon ranging from 1.8 to 4 wt%, silicon 1–3 wt% are the main alloying elements of cast iron. Iron alloys with lower carbon content are known as steel. While this technically makes the Fe–C–Si system ternary, the principle of cast iron solidification can be understood from the simpler binary iron–carbon phase diagram. Since the compositions of most cast irons are around the eutectic point of the iron–carbon system, the melting temperatures range from 1,150 to 1,200 °C, about 300 °C lower than the melting point of pure iron of 1,535 °C.
Cast iron tends to be brittle, except for malleable cast irons. With its low melting point, good fluidity, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes and automotive industry parts, such as cylinder heads, cylinder blocks and gearbox cases, it is resistant to weakening by oxidation. The earliest cast-iron artifacts date to the 5th century BC, were discovered by archaeologists in what is now Jiangsu in China. Cast iron was used in ancient China for warfare and architecture. During the 15th century, cast iron became utilized for cannon in Burgundy, in England during the Reformation; the amounts of cast iron used for cannon required large scale production. The first cast-iron bridge was built during the 1770s by Abraham Darby III, is known as The Iron Bridge. Cast iron was used in the construction of buildings. Cast iron is made from pig iron, the product of smelting iron ore in a blast furnace.
Cast iron can be made directly from the molten pig iron or by re-melting pig iron along with substantial quantities of iron, limestone and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this burns out the carbon, which must be replaced. Depending on the application and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are added to the melt before the final form is produced by casting. Cast iron is sometimes melted in a special type of blast furnace known as a cupola, but in modern applications, it is more melted in electric induction furnaces or electric arc furnaces. After melting is complete, the molten cast iron is poured into ladle. Cast iron's properties alloyants. Next to carbon, silicon is the most important alloyant. A low percentage of silicon allows carbon to remain in solution forming iron carbide and the production of white cast iron.
A high percentage of silicon forces carbon out of solution forming graphite and the production of grey cast iron. Other alloying agents, chromium, molybdenum and vanadium counteracts silicon, promotes the retention of carbon, the formation of those carbides. Nickel and copper increase strength, machinability, but do not change the amount of graphite formed; the carbon in the form of graphite results in a softer iron, reduces shrinkage, lowers strength, decreases density. Sulfur a contaminant when present, forms iron sulfide, which prevents the formation of graphite and increases hardness; the problem with sulfur is. To counter the effects of sulfur, manganese is added because the two form into manganese sulfide instead of iron sulfide; the manganese sulfide is lighter than the melt, so it tends to float out of the melt and into the slag. The amount of manganese required to neutralize sulfur is 1.7 × sulfur content + 0.3%. If more than this amount of manganese is added manganese carbide forms, which increases hardness and chilling, except in grey iron, where up to 1% of manganese increases strength and density.
Nickel is one of the most common alloying elements because it refines the pearlite and graphite structure, improves toughness, evens out hardness differences between section thicknesses. Chromium is added in small amounts to reduce free graphite, produce chill, because it is a powerful carbide stabilizer. A small amount of tin can be added as a substitute for 0.5% chromium. Copper is added in the ladle or in the furnace, on the order of 0.5–2.5%, to decrease chill, refine graphite, increase fluidity. Molybdenum is added on the order of 0.3–1% to increase chill and refine the graphite and pearlite structure. Titanium is added as a degasser and deoxidizer, but it increases fluidity. 0.15–0.5% vanadium is added to cast iron to stabilize cementite, increase hardness, increase resistance to wear and heat. 0.1–0.3% zirconium helps to form graphite and increase fluidity. In malleable iron melts, bismuth is added, on the scale of 0.002–0.01%, to increase how much silicon can be added. In white iron, boron is added to aid in the production of malleable iron.