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Wednesday, 13 November 2013

Case Hardening Process - Gas Carburizing

Gas Carburizing
Points : Gas Carburizing, Definition Definition In gas carburizing, the gas may be generated from suitable liquids, as done in certain processes, or the gas such as methane or propane may be led directly into the container in which the work is placed. Some city’ gasses are quite suitable. Some source of oxygen is necessary for best results, either as air or CO2. but usually it is not necessary to add any oxygen:
there are explosive ranges of gas composition, which should be avoided. The work is placed in a gas-tight container, which can be heated, in a suitable furnace, or the furnace itself may be the container. The carburizing gas is admitted to the container, and the exit gas is vented. It should be apparent that there are certain advantages in the gas carburizing process. The steel does not have to be packed, and there is no handling and storage problem of the solid carburizer with which to contend. The time required to bring the work to the carburizing temperature is less than is necessary with solid carburzers. On the other hand, the pack method requires less expensive equipment, and control of the composition of the gases is simple. Continuous furnaces can be used in either process. Continuous gas-carburizing furnaces have been developed only recently. In continues gas carburizing, the quenching and tempering cycles take place in the same unit, that is , the carburizing, quenching, and tempering processes are carried out in sequence in the same closed furnace as the work progresses on a conveyer from one operation to the next. There are several variations of gas carburizing; For example, small parts are frequently placed in a retort, which can be rotated; the retort is heated externally, carburizing gas led into the retort, and the exit gas is burned. Case depths in relation to time and temperature.

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