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Steel MakingHardness TestingThe word hardness is used to express various properties of me... Short Method Of Treatment In the new method, the packed pots are run into the case-har... Cyanide Bath For Tool Steels All high-carbon tool steels are heated in a cyanide bath. Wi... Correction For Cold-junction Errors The voltage generated by a thermo-couple of an electric pyrom... Hardening The forgings can be hardened by cooling in still air or quen... Carbon-steel Forgings Low-stressed, carbon-steel forgings include such parts as car... Conclusions Martien was probably never a serious contender for the honor ... Properties Of Steel Steels are known by certain tests. Early tests were more or l... Heat-treating Department The heat-treating department occupies an L-shaped building. ... Introduction Of Carbon The matter to which these notes are primarily directed is the... Tempering Round Dies A number of circular dies of carbon tool steel for use in too... For Milling Cutters And Formed Tools FORGING.--Forge as before.--ANNEALING.--Place the steel in a ... Pyrometers Armor plate makers sometimes use the copper ball or Siemens' ... Hardening Carbon Steel For Tools For years the toolmaker had full sway in regard to make of st... Heat Treatment Of Axles Parts of this general type should be heat-treated to show the... The Forging Of Steel So much depends upon the forging of steel that this operation... Crankshaft The crankshaft was the most highly stressed part of the entir... Using Illuminating Gas The choice of a carburizing furnace depends greatly on the fa... Carbon Steels For Different Tools All users of tool steels should carefully study the different... Properties Of Alloy Steels The following table shows the percentages of carbon, manganes... |
Carburizing MaterialCategory: CASE-HARDENING OR SURFACE-CARBURIZING The simplest carburizing substance is charcoal. It is also the slowest, but is often used mixed with something that will evolve large volumes of carbon monoxide or hydrocarbon gas on being heated. A great variety of materials is used, a few of them being charcoal (both wood and bone), charred leather, crushed bone, horn, mixtures of charcoal and barium carbonate, coke and heavy oils, coke treated with alkaline carbonates, peat, charcoal mixed with common salt, saltpeter, resin, flour, potassium bichromate, vegetable fibre, limestone, various seed husks, etc. In general, it is well to avoid complex mixtures. H. L. Heathcote, on analyzing seventeen different carburizers, found that they contained the following ingredients: Per cent Moisture 2.68 to 26.17 Oil 0.17 to 20.76 Carbon (organic) 6.70 to 54.19 Calcium phosphate 0.32 to 74.75 Calcium carbonate 1.20 to 11.57 Barium carbonate nil to 42.00 Zinc oxide nil to 14.50 Silica nil to 8.14 Sulphates (SO3) trace to 3.45 Sodium chloride nil to 7.88 Sodium carbonate nil to 40.00 Sulphides (S) nil to 2.80 Carburizing mixtures, though bought by weight, are used by volume, and the weight per cubic foot is a big factor in making a selection. A good mixture should be porous, so that the evolved gases, which should be generated at the proper temperature, may move freely around the steel objects being carburized; should be a good conductor of heat; should possess minimum shrinkage when used; and should be capable of being tamped down. Many secret mixtures are sold, falsely claimed to be able to convert inferior metal into crucible tool steel grade. They are generally nothing more than mixtures of carbonaceous and cyanogen compounds possessing the well-known carburizing properties of those substances. Next: Quenching Previous: Rate Of Absorption
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