Control system of carbon intensity distribution of low-pressure carburized layer and control method thereof

Abstract

The invention relates to a control system of the carbon intensity distribution of a low-pressure carburized layer and a control method thereof, belonging to the technical field of metal heat treatment. The control system comprises a low-pressure carburizing furnace, a controller, a pressure sensor, a thermoelectric couple, a nitrogen regulating valve, a nitrogen input pipe, a carburizing gas regulating valve, a carburizing gas input pipe, a vacuum system and a gas suction pipe. The invention simulates automatic optimized low-pressure pulse process parameters by using carburized layer concentration distribution values and realizes the control functions; the carburizing gas regulating valve executes on / off action according to an order of the controller to control carburizing section time and diffusing section time, therefore the accurate control of the intensity distribution of the carburized layer is realized; and in addition, the invention can keep high carburizing speed and prevent the tolerance of surface carbides, accurately controls the surface carbon intensity and the depth and the intensity distribution of the carburized layer, reduces the accumulated carbon black inside thelow-pressure carburizing furnace, is free from depending on a gas component sensor and has the advantages of configuration simplification, easy implementation, high reliability and easy maintenance.

Description

technical field [0001] The invention relates to a control device and a control method in the technical field of metal heat treatment, in particular to a low-pressure carburizing layer carbon concentration distribution control system and a control method thereof. Background technique [0002] Low-pressure carburizing, also known as vacuum carburizing, is a carburizing process carried out in a carburizing atmosphere below atmospheric pressure, which is carried out by decomposing and absorbing carbonitride gas on the steel surface. [0003] The carburizing reaction that occurs when methane is used is: [0004] [0005] The carburizing reaction that occurs when propane is used is: [0006] [0007] The carburizing reaction that occurs when ethane is used is: [0008] [0009] After searching the existing technology, it is found that the document [1] "Ipsen Avac Acetylene Low Pressure Carburizing Process Equipment and Its Industrial Application" Ipsen Industrial Furnac...

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Problems solved by technology

Therefore, this literature uses the average carbon flow rate to solve the diffusion partial differential equation, which has the following two disadvantages: ① Taking the average carbon flow rate as the boundary condition does not conform to the actual situation, so the process specification obtained by this method cannot achieve the correct control of the concentration distribution of the carburized layer ② "average carbon flow" is a function of the three variables of steel composition, carburizing temperature and carburizing time

The low-pressure pulse carburizing control system proposed in [5] has the following obvious defects: ①Pinela vacuum gauge is essentially a thermal conductivity measuring instrument, which itself has obvious hysteresis, and the difference between it and the film vacuum does not reflect carburization. Carbon process changes; ②The difference between the pinila vacuum gauge and the thin-film vacuum gauge can only reflect the C 2 h 2 with H 2 The ratio does not reflect the %C of the workpiece surface

In short, the existing low-pressure pulse carburizing technology is difficult to control the carbon concentration distribution of the carburized layer.

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