Basic Study On Making Non-Oxidizing Atmosphere For Hot-Work By Circulating

The heating technology in a non-oxidation state is one of the main development directions for hot-work. To produce a non-oxidizing atmosphere for hot-work by removing oxygen by the gas circles, which is a key technology of the non-oxidation workshop for hot-work, is in the first time studied in theory and by experiments in this thesis.As well known, heating steel without oxidation can be realized if the pressure of oxygen in the atmosphere is no more than the decomposing pressure of FeO, and heating steel without decarburization can be realized if the pressure of oxygen in the atmosphere is so few that decarburization rate is very slow.A test device to produce the protective atmosphere for hot-work by removing oxygen by the gas circles has been made. The device mainly includes the portion for removing the oxygen, the portion for drying, the portion for gases running, the portion for the temperature control, the portion for the pressure control and the portion for the atmosphere control.A kind of non-oxidizing atmosphere has been made by the means of displacing ah- with nitrogen at first, then removing oxygen by circulating with hydrogen and drying by circulating. The main component of this kind of atmosphere is nitrogen.It is proved by the experiments of the removing oxygen by gas circles, that the gas with more than 1% hydrogen can be used to produce the atmosphere with a very low oxygen pressure, which is lower than 3.7253 X 10~23atm. The atmosphere meets the condition of non-oxidation and non- decarburization. The higher hydrogen percent in the gas, the fewer needed times of circulating.It is proved by the experiments that the quality of air-proof of the device is very important for realizing the non-oxidation healing. Decarburization of heated sample is no relation with the fall rate of gas pressure if the fall rate is no more than 300Pa/h.TC105(ISO) will be decarbonized when they are heated up in this device, even if the atmosphere from the device meets the condition of non-oxidation and non-decarburization. The main reason is the oxygen and water absorbed by the furnace. The decarbonizing will not be decreased markedly if a little butane is added into the atmosphere. It is one of key factors for the realization of the non-oxidation workshop for hot-work to avoid the oxygen and water absorbed by the furnace rightly.