Carbon Cleaning Research And Process Optimization For Remanufactured Parts With Molten Salt

Remanufacturing engineering, as a thriving developing direction of manufacturing industry, can not only save the energy but also protect the environment, etc., this consists with the national policy of the circular economy. In the process of remanufacturing engineering, cleaning is a key factor in subsequent inspection and reparation. Molten salt has the advantages of low viscosity, good liquidity and strong chemical stability. Salt bath cleaning can be comprehensively applied to get rid of various kinds of organic pollutant, such as carbon deposition, oil contamination, thread lock, besides, it is not restricted by the shape and hole of the workpieces. Salt bath cleaning will perform perfect within just 3-10 min. What’s more, molten salt has the function of the self-clean, which means that the soiling in the molten salt pool can decompose by itself so that it can be reused many times, and the abandoned molten salt turns to be massive, so the waste residue is easy to treatment.Because the molten salt cleaning has many advantages, abroad have developed the corresponding equipment and process parameters. But it is rarely researched at home. In this paper, we study the formation and adsorption process of carbon deposition, and then explore the effect of formula, temperature and time on molten salt decontamination ability and cleaning effect. According to the above analysis, the molten salt composition and proportion is optimized to provide a basis for the industrial production of molten salt cleaning.Firstly, the chemical composition and the microstructure of carbon deposition were observed; the formation and adsorption Process of carbon deposition were explored; formation Process is verified by experiment. It’s chemical composition and microstructure was analysis by SEM and IR-Raman spectroscopy, to get the microscopic structure of carbon deposition; formation reaction and adhesion process were analyzed; the contribution of different forces on the formation of carbon deposition was investigated, the formation reasons was explained from the Process; the molten salt cleaning carbon deposition experiment proved the formation Process of carbon deposition.In order that the problem that carbon deposition was difficult to be removed in the process of remanufacturing cleaning, the paper is trying to provide the basis theoretical about the carbon removal. Method The removal Process of molten salt cleaning technology was analyzed from thermal expansion effect, chemical action, surface tension, and the combination effect of these three parts.The paper analyzed the clean effects of formulation and temperature on the decontamination ability by weighing method. And the paper analyzed the effects of the formulation、temperature、cleaning time on cleaning effect using expert scoring method. Result It shows that the decontamination ability improves constantly with the decrease of KNO3 contents meanwhile the increase of cleaning temperature, but after the temperature rising to 320℃,the decontamination ability was no longer obvious improvement. the cleaning effect was better with the cleaning time longer, the KNO3 content reduced, and the cleaning temperature increased, while the cleaning temperature was between 270-330℃, but when the temperature was higher than 360℃, the cleaning effect would be reduced.The optimal operating temperature of the original formula is higher than the decomposition point of NaNO2, so it will produce large amounts of toxic gas while working. After consulting the study of solar heat storage medium, propose a new formula of molten salt. Researching the thermophysical properties of the new formula by DSC-DT, find it in a very stable state between 250℃ to 300℃. Then research the proportion of ingredients in the new formula according to the mixture design and obtain the optimal process parameters which consist of 10% KNO3,55% NaNO2,35% NaNO3 and the cleaning temperature of 290℃. Besides, compared with the original formula, kerosene and water-based cleaning agent, the new process has a better performance in removing pollutants on valve, bolt and tappet within the stable range.