General Steel Making: The Cementation Process Posted By : Sarah E. ...

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General Steel Making: The Cementation Process
The cementation process is a now-obsolete technique for makingsteel with the carburization of iron. Unlike modern steelmaking itincreased the amount of carbon in the iron. It was apparentlydeveloped before the 17th century. The process probably originatedin Bohemia in the 16th century and was in use in Bavaria in theearly 1600's. The process was patented in England by Ellyot andMeysey in about 1614.

The cementation process of making steel is also called theconverting process. This process consists in impregnating bars ofwrought iron or soft steel with carbon, at a temperature below itsmelting point, and was used (chiefly in England) for the productionof high carbon bars to be employed in the manufacture of cruciblesteel or shear steel. The bars were usually of pure Swedish ironmade by the Walloon process. They are packed in layers, separatedby charcoal (sometimes called cement) in fire-brick chambers(converting pots) heated externally by flues, and forming part ofthe cementing furnace. The top of the pot is closed with an arch ofwheel swarf, which later frits and forms an air-tight cover. Thefurnace attains its full temperature in about 3 to 4 days, at whichit is maintained about 7 to 8 days for mild heats, about 9 days formedium heats, and about 11 days for high carbon heats; the coolingdown requires about 4 to 6 days. To test the progress of theoperation, trial bars (test bars or tap bars) are drawn atintervals through a special small aperture, provided for thepurpose, and examined. If wrought iron has been employed, thefinished bars will be found covered with blisters formed by thereaction between the contained slag and the carbon, from whichcomes the name blister bar or blister steel; at one time this wassometimes termed German steel.


This phenomenon is absent when steel bars are treated; bothproducts are known as cement (cemented) bars or cement steel. Barsdesired of very high carbon may be retreated, and are known asdoubly converted bars or glazed bars. Since the carbon penetratesfrom the outside inward, the percentage will decrease progressivelyto the center. In very mild bars there is an unaltered core of mildgeneral steel called sap, and very hard bars are easilydistinguished by being what is known as flaked, as on fracture theypresent bright cleavage planes. It is important to have thetransition from one grade to the other as gradual as possible: whenthe line of demarcation is too abrupt, the process has been carriedout too rapidly, and the bars are said to be flushed. If, owing toa leak in the pot, air has entered, the outside of the bars will besomewhat oxidized, and are called aired bars. If the temperaturehas been a little too high, so the outside has fused slightly, theyare called glazed bars. Blister bars rolled or hammered down at ayellow heat are known as plated bars or bar steel.

The following are various methods suggested or tried from time totime: In Bink's process compounds of cyanogen were specified, andcurrents of nitrogen, carbonic oxide, and ammonia, or ammoniaalone, were to be passed through decarburized molten iron. InBoullet's process iron was to be cemented with a substanceconsisting of sugar, horn dust or shavings, animal fat or blood,and wood charcoal dried and pulverized. In Brooman's process ironwas to be melted in pots with compounds of cyanogen; such compoundsmight consist of charcoal, salt, brick dust or oxide of manganese,sal ammoniac, and ferrocyanide of potash. Henry Brown's processconsisted in cementing iron in a granulated condition in close potswith carbon: iron which was being puddled was taken out of thefurnace as soon as it became granulated, and before it was pasty;it was then broken up until it would pass through a 20-mesh screen,after which it was put in long pots with wood and cemented asusual. James Boydell's process was to cement the product obtainedby puddling wrought iron melted in a cupola. In Holland's processsilk waste of every kind was to be torrifled, i.e., dried at a hightemperature without being carbonized, and then ground to a finepowder and used for cementing.
By: Sarah E. Martin
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Sarah E. Martin is a freelance marketing writer specializing inconstruction, mechanical engineering, and general steel . For more information, please visit www.youtube.com/watch ?v=wdikZ-Th5Hw .
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