Controlled atmosphere in sealed multi-purpose furnace of classification and application
Sealed box multi - purpose furnace production line is suitable for mass production, such as automotive industry. Domestic manufacturers are more close to the user requirements, targeted to launch a variety of moderate prices, various styles, superior performance controllable box-type atmosphere furnace. Most of the process parameters can be optimized, predicted and accurately control the distribution of carbon concentration to obtain the ideal concentration distribution and layer structure; Can achieve computer management, with a simple menu design, friendly man-machine interface.
Today, the controllable atmosphere is classified into three categories: endothermic gas, exothermic gas, nitrogen-based atmosphere, ammonia decomposition gas, drip decomposition gas, hydrogen and charcoal gas.
1. Endothermic gas
In the generator, natural gas, liquefied petroleum gas and other gases are mixed with a certain proportion of air (when the air volume is relatively small, the mixed gas is partially burned first), and then heated to a high temperature (above 1000℃) by the catalyst, so that the unburned part of the mixed gas pyrolysis (endothermic reaction) and made. Endothermic gas is a controlled atmosphere for application. It is used as a carrier gas, and an appropriate amount of enriched gas (methane or propane) can be brought into the heating furnace to carburize the surface of low carbon steel parts, so that the carbon content can meet the specified requirements. The carbon potential of furnace gas can be controlled by controlling the amount of enriched gas added. The carbon potential of furnace gas is the amount of carbon at a certain temperature when furnace gas is in equilibrium with the amount of carbon in austenite on steel surface, which can be simply understood as the carburizing capacity of furnace gas. Endothermic atmosphere is widely used in chemical heat treatment processes such as carburizing, carburizing and gas carburizing, etc. It can also be used for the bright quenching of medium carbon steel, high carbon steel, alloy tool steel, bearing steel and high speed steel.
2. Exothermic gas
In the generator, a gas produced by mixing a gaseous fuel such as natural gas liquefied petroleum gas or a liquid fuel such as alcohol or diesel with more air to make it close to full combustion (exothermic reaction) and then by initial purification (water removal) or high purification (water removal, carbon dioxide and carbon monoxide) of the combustion products. Exothermic gas can be used in the bright annealing of low carbon steel, the decarburization of silicon steel sheet, the bright quenching of medium carbon steel and high carbon steel, the sintering of powder metallurgy and the gas nitrocarburizing, etc. Purifying exothermic atmosphere can also be used for annealing and brazing protection of stainless steel, or as carburizing carrier gas, etc.
3. Nitrogen based atmosphere
It is commonly used to purify the industrial nitrogen produced in the process of oxygen production (oxygen removal or air) and obtain high-purity nitrogen, or it can be the gas obtained by evaporation of liquid nitrogen. Nitrogen-based atmosphere can be used for heating protection, but also can be added methanol to make its composition close to the endothermic atmosphere, as the carrier gas when carburizing, then add enriched gas (such as propane) can be carburized. It has the advantages of saving natural gas, LPG, etc., and controlling carbon potential.
4. Ammonia decomposes gas
Under the action of certain temperature and catalyst, ammonia can be completely decomposed into 3 volumes of hydrogen and 1 volume of nitrogen, forming ammonia decomposition gas. Ammonia can also be mixed with air for partial combustion, and then purified by water purification to obtain ammonia combustion gas (the main component is nitrogen). Both atmospheres contain hydrogen, a mixture of hydrogen-water types. It is mainly used for heat treatment of stainless steel and sintering of powder metallurgy. Because ammonia is more expensive, the preparation cost is higher.
5. Drip decomposition gas
The decomposition gas produced by drip carburizing which makes the carbon concentration of steel surface controllable also belongs to controllable atmosphere. This is the Cabomagh method that was introduced in the early 1960s. Its principle is: to drip into the two kinds of organic liquid in the furnace, thermal cracking occurred in the furnace, with a liquid (such as methanol) of pyrolysis gas as a carrier gas, in another (such as acetic acid ethyl ester) of pyrolysis gas as the enriched gas to realize the steel carburizing, and by regulating the amount of the second liquid drip into the control of carbon potential of furnace to to achieve. The advantage of this method is no gas generator furnace, simple equipment structure, suitable for mass production.
Hydrogen 6.
Hydrogen is a reducing gas. Dry hydrogen is difficult to prepare, so the hydrogen used is actually a tiny mixture of water and hydrogen. Whether a metal is oxidized or reduced when heated in hydrogen depends on the ratio of water to hydrogen. But protective heating with hydrogen does not prevent the decarbonization of steel. Annealing of stainless steel and silicon steel sheets and reduction of sintered iron powder from powder metallurgy can all be carried out in hydrogen.
7. The charcoal
With a blower to blow air into the furnace, the air and hot charcoal reaction produced by the gas is charcoal gas. Its main components are carbon monoxide and carbon dioxide. Carbon monoxide is a reducing gas, and carbon dioxide is an oxidizing gas.
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On 2018-08-08 11:45:46
