Study Of Properties And Microstructure Of Dip Aluminized Layer Of Carbon Steel Surfaces

In order to study microstructure and properties of dip aluminized layer of Carbon Steel surfaces, through quadratic orthogonal regression experiment, this paper researched the relation among hot dip aluminizing time of Q235 steel, dip aluminizing temperature and aluminium deposition thickness, as well as the relation among thermal diffusion time and diffusion temperature and thickness of diffusion layer, therefore mathematical models were built and the optimal technological parameters for hot dip aluminizing were determined. And the experiment of hot dip aluminium and thermal diffusing permeation on the Q235 steel surface was performed. By adopting the contrast method, the principle, organizaton of dip aluminized layer, high temperature oxidation resistance and wear resistance of hot dip aluminizing of dip aluminized layer and thermal diffusing permeation of dip aluminized layer were studied, the curves of high temperature oxidation kinetics and wear kinetics were drawed. With the application of metallurgical microscope, SEM ,XRD and other research methods, the composition and structure of hot-dip aluminizings samples are areanalyzed.This experiment establishes that the optimal technological parameters of Q235 steel of the hot dip aluminium is temperature of 770℃and the time of dipping is 13min, and the optimal technological parameters of Q235 steel of the thermal diffusing permeation is temperature of 950℃and the time of diffusion is 6h.The results of the experiment show that the high temperature oxidation resistance and the corrosion resistance of thermal diffusing permeation steel are the best, about 1.5 times better than hot dip aluminizing steel, 6 times better than non-dip aluminizing steel.The wear resistance of thermal diffusing permeation steel is the best, 4 times better than hot dip aluminium and 7 times better than non-dip aluminizing steel.The analyzation of results indicates that dip-aluminized steel has two layers:aluminized layer and transition layer Al2O3.The steel after diffusion treatment also has two obvious layers:the inner diffusion layer and the outer diffusion layer.The inner diffused layer is maily composed of Fe3A1 and a few FeAl and the outer diffused layer is mostly composed of FeAl and a few Fe3A1. In the process of diffusion, the continuous ,compact Fe2Al5 phase and FeAl3 phase, which are formed on the surface of the steel, have stable chemical property and their compactness is more excellent than A12O3, so the high temperature oxidation resistance and wear resistance of thermal diffusing permeation steel are better than hot dip aluminizing steel..