It is difficult to control the carbon content in steel in a stirred tank, and it requires a lot of manpower. By 1856, the British H. Bessemer (1813 ~1898) invented the converter steelmaking method, which solved this problem.
Bessemer, the son of a mechanical engineer, fled to England during the French Revolution. After leaving the rural school, he became a type worker. At the age of 65,438+07, he began to produce metal alloys and bronze powder. During the Crimean War between Britain, France and Russia (65,438+0853 ~ 65,438+0856), he witnessed the gun body made of pig iron or wrought iron.
Bessemer once noticed that some solid cast iron blocks would decarburize when exposed to air before melting. Of course, this oxidation is the principle of stirring steelmaking. He didn't study chemistry and didn't understand this principle, but it made him consider blowing air into molten iron to make steel. So one day in 1856, he built a steelmaking furnace in St. Pancras, London.
This is a fixed container. It can hold 350 kilograms of cast iron. After the air was pumped into the container under pressure, the intensity of the reaction surprised Bessemer, because he didn't estimate that the reaction of carbon in cast iron with oxygen in the air and the reaction of other impurities with oxygen would release heat. Fortunately, after 10 minutes, the impurities have been removed and the flame has subsided. You can approach the container and cut off the pressurized air flow. Metal is injected into the ingot mould and determined to be low carbon steel. On August 1856, 1 1, Bessel announced the invention at the meeting of the British Society in Cheltenham, Certo. Soon, Bessemer was made into a rotatable tilting converter, each furnace can hold 5 tons of pig iron, and the smelting time was 1 hour, including the time of furnace repair and ingot casting, which greatly shortened the time of stirring steelmaking and reduced the energy spent in stirring smelting operation. As a result, steel mills at home and abroad have purchased production licenses for this method.
Bessemer was warmly praised by people from all walks of life after he announced his invention, but he was quickly criticized and ridiculed. The reason is that the ingot produced by the converter he created is over-oxidized, and the generated iron oxide exists in the steel. At the same time, the phosphorus in pig iron can not be removed, which makes the quality of steel poor, either loose or hard and brittle, and breaks when forging.
The problem of excessive iron oxide in steel was later solved by mouchette, an Englishman with rich steelmaking experience. He added an alloy of iron, manganese and carbon to molten metal, called mirror iron, because manganese can reduce the formation of iron oxide.
Phosphorus removal from iron ore is a long-term unsolved problem in steelmaking. Like all other builders of steelmaking furnaces, Bessemer uses silicon-containing materials as furnace lining. This lining will not combine with oxides produced by phosphorus oxidation, and this stable compound cannot be removed from steel. Before making steel, Bessemer can only use ore with phosphorus content below 0.05% (mass fraction) to make iron.
However, the problem of phosphorus removal was later solved by Thomas (1850~ 1885), a clerk of a British court, and 1878 succeeded.
Although Thomas is a court clerk, he loves chemistry. In his spare time, he went to Birkbeck College of University of London to study chemistry, and passed the metallurgical and chemical examinations of the Royal Institute of Mining and Technology. After learning that Bessemer needed to solve the problem of phosphorus removal in steelmaking, he experimented with various chemicals, including magnesium oxide and lime. With the help of his cousin, P.C.Gilchrist, he conducted converter experiments at Blaenavon Steelmaking Plant in Bleiner, where his cousin is a chemist. The two of them carried out experiments from 1877 to 1878 for 9 months, which proved that using calcined dolomite bonded with lime as converter lining can satisfactorily remove phosphorus and produce valuable phosphate fertilizer at the same time, and was called Thomas phosphate fertilizer in memory of him.
Dolomite is a kind of rock containing magnesium carbonate and calcium carbonate. After roasting, magnesium oxide and calcium oxide are generated. It can combine with phosphorus oxides to produce magnesium and calcium phosphate, which is a good phosphate fertilizer.
Thomas won the medal of Bessemer in 1883, but unfortunately he died of tuberculosis at the age of 35. The converter steelmaking method invented by Bessemer, improved by Thomas and others, has been used to this day. The converter used now can rotate around the horizontal axis, which is convenient for charging and discharging. There are air holes at the bottom of the stove, from which air is blown in. It takes about ten minutes to smelt a furnace of steel with a capacity from one ton to dozens of tons.
With the development of industry, a large number of scrap steel and scrap iron have appeared in production, construction and daily life. These wastes can't be used in converter, so open hearth steelmaking and converter steelmaking appear at the same time.
In converter steelmaking, the heat required to keep metal in liquid state is provided by the heat generated by chemical reaction, while in open hearth steelmaking, the heat generated by chemical reaction is not enough to keep metal in molten state, so the heat must be provided by external heat source.
1856, Frederic Siemens of Germany manufactured an AC heat exchanger based on the principle of thermal regeneration. In this way, heat storage checker brick chambers are built on both sides of the combustion furnace, and the hot combustion exhaust gas of the combustion furnace transfers heat to the checker brick through one side of the checker brick chamber, and then the air for combustion passes through the heated checker brick chamber, and then enters the combustion chamber for combustion after being heated, thus improving the furnace temperature. Every once in a while, the flow direction of air and exhaust gas will be exchanged, so that the heat accumulators on both sides can be used alternately. This kind of furnace was originally used to burn glass, and later it was used to make steel. This is an open hearth furnace.
Initially, solid fuel was burned in an open-hearth furnace. 186 1 year, William (1823 ~ 1883), the younger brother of Siemens Frederick, founded a gas producer to produce producer gas. This is to pass a certain amount of air and a small amount of water vapor through burning coal or red-hot coke, so that the carbon dioxide produced by it can be converted into combustible carbon monoxide as much as possible. Steam reacts with carbon to produce combustible carbon monoxide and hydrogen.
Siemens William is an engineer who came to Britain after receiving formal technical education in Germany. Siemens Frederic runs an electrical company in Dresden, Germany, and has also been to Britain. The two brothers think it is more convenient for Britain to encourage engineers and inventors to apply for patents in Britain. In 1866, they set up a Siemens steel plant in Birmingham, England, using open hearth steelmaking.
Siemens brothers * * * four people, are excellent inventors. William is the second child and Frederick is the third. The boss Werner Siemens (18 16 ~ 1892) is an electrochemical scientist who invented the principle of generator and founded Siemens in Germany. Carl Siemens, the youngest brother, started a business in Russia. In this way, Willer is called "Siemens in Berlin"; William is called "Siemens of London"; Friedrich is called "Siemens of Dresden"; Karl is called "Siemens of Russia".
Almost at the same time, French metallurgist Martin (P.Martin, 1824 ~ 19 15) and his brother (B.Martin) also used the principle of thermal regeneration to build an open hearth furnace and set up a factory in Siley, France. The steel they produced was exhibited at the Paris Expo in 1867 and won a gold medal. Martin was awarded the Bessemer Medal by the British Iron and Steel Association in 19 15.