Molten Salt Cleaning Process Research Of Remanufacturing Engine Typical Fouling

As country to strengthen ceaselessly that energy saving and emission reduction, people paid more attention to remanufacture engineering day by day. Remanufacturing cleaning process is to ensure that in the process of remanufacturing machining, heat treatment, coating, plating, assembly, rust and other essential quality.Remanufacturing type dirt on the surface of the billet is complex, pollution degree is big, wide distribution; Size billet structure is diverse; In addition, remanufacturing blank of cleaning engineering are often the main source of pollution in the process of remanufacturing. The traditional cleaning technology is far cannot meet the requirement of the development of remanufacturing. Therefore, we need to research and develop new remanufacturing cleaning technology, so as to obtain better cleaning effect, effectively reduce the cost of cleaning and reduce the impact on the environment.Molten salt cleaning is an important branch of remanufacturing cleaning it can efficiently remove various pollutants from metal surface, but molten salt cleaning both in academic research and in practical application is limited at home. For this shortage, this article obtaining from the cleaning mechanism of the molten salt cleaning, separately studied salt bath cleaning technology of remanufacturing type dirt on the surface of the billet, and got the optimum parameters of the salt bath cleaning through the test and explore the suitable material of salt bath cleaning.Detailed analysis of the common remanufacturing blank surface dirt (oil, carbon deposition, incrustation, corrosion, organic coating, etc.) of the formation mechanism and the molten salt cleaning mechanism of all kinds of dirt, cleaning mechanism of molten salt mainly include thermal shock effect, physical dissolution, surface tension, wetting, emulsification, flocculation and chemical reaction.Using the surface response method analyzes cleaning ability of molten salt cleaning carbon deposition by changing the formulation and temperature, The test shows that with temperature and the mass fraction of sodium nitrite formula increasing, the ability of cleaning the carbon deposition enhancement. A cycle model and 2 min clearing power model of molten salt cleaning carbon deposition are established. By means of molten salt cleaning carbon deposition cycle test and 2 min clearing power test, molten salt cleaning process parameters of carbon deposition temperature in 330-360℃, control the NaOH mass fraction 30%, NaNO2 mass fraction in more than 40% is strongly recommended, in this process under the condition of molten salt cleaning carbon deposition is less than 5 minutes can be cleaned completely.Using orthogonal experiment analyzes cleaning effect of molten salt cleaning incrustation and corrosion by changing the formulation and temperature, and compared with dilute hydrochloric acid cleaning corrosion. The test shows that with temperature and the mass fraction of sodium hydroxide increasing, the ability of cleaning the incrustation enhancement, but with increasing of the mass fraction of sodium hydroxide the amount of corrosion is not obvious change. Using orthogonal experiment by Minitab software analyzes cleaning effect of molten salt cleaning incrustation and corrosion by changing the formulation and temperature, and compared with dilute hydrochloric acid cleaning corrosion. The test shows that with temperature and the mass fraction of sodium hydroxide increasing, the ability of cleaning the incrustation enhancement, but with increasing of the mass fraction of sodium hydroxide the amount of corrosion is not obvious change. after an hour molten salt cleaning, corrosion on the surface of the specimen is not obvious removed, but after molten salt treatment, the corrosion is easy removed by dilute hydrochloric acid, the time is almost 1/15 of the dilute hydrochloric acid cleaning time alone. Through the test of molten salt cleaning incrustation and corrosion process recommendation are given:when cleaning incrustation, control the NaOH mass fraction between 30% and 50%, the temperature between 330℃ and 360℃, the cleaning time between 30 and 60 minutes, When cleaning corrosion, first using molten salt treatment after a period of time then using dilute hydrochloric acid cleaning, can greatly reduce the pickling time.At the end of the paper, hardness and tensile strength of different metal substrate were measured. and the influence of different metal substrate by molten salt cleaning are analyzed, the test shows the molten salt cleaning is suitable for carbon steel and cast iron pieces.