Fabrication And Properties Of Powder Metallurgical Fe-17Cr-4Ni-4Cu-Nb Breathable Steel

Breathable steel is a new type of porous metal material with both structural and functional properties.Because of its excellent performance and unique structure,it is widely used in the aerospace,energy,construction,machinery and chemical industries.In particular,the use of breathable steel injection molds can solve the problem of trapped air and exhaust gas in the injection molding industry.Thus,it can improve the molding quality of injection molded parts.In this thesis,the powder metallurgy method is used to produce the breathable steel,and the influence of pressing pressure on the pore structure and properties of the breathable steel without the addition of pore forming agent is investigated to determine the optimum pressure required for sintering of the breathable steel.Then,the influence of sintering temperature on the pore structure and properties of breathable steel is investigated after the pressure has been determined.Finally,the influence of pore-forming agent content on the pore structure and properties of breathable steel samples was investigated in order to determine the process conditions and parameters for the preparation of the breathable steel test.The main research contents and results of the thesis are as follows:（1）By studying the pressing pressure,it is obtained that the pressure has little effect on the porosity of the sintered specimen,and when the pressure is 300 MPa,the gas permeability and corrosion resistance of the breathable steel are the best.Therefore,the final pressing pressure of this experiment was determined to be 300 MPa,and the effects of sintering temperature and pore forming agent content on the pore structure and properties of sintered specimens were explored.（2）The effect of the sintering temperature on the pore structure and the properties of the breathable steel has been studied.The results show that with the increase of sintering temperature,the porosity shows a trend of first increasing and then decreasing,and the air permeability is also the same.However,for the corrosion resistance of the breathable steel sample,the corrosion potential is the highest and the corrosion current density is the lowest at the sintering temperature of 1250°C.This indicates that the corrosion resistance of the breathable steel obtained at this sintering temperature is the best.As the sintering temperature is increased,the hardness of breathable steel gradually increases.（3）The effect of the amount of pore generator on the properties of the aerated steel at different sintering temperatures has been discussed.The results show that with the increase of the pore forming agent content,the porosity of the sintered gas permeable steel also increases,and the relative gas permeability coefficient increases with the increase of the porosity.In addition,by studying potentiodynamic polarization curve of gas permeable steel sample in 3.5 wt%Na Cl solution,it can be found that sintering temperature of 1300°C and pore-forming agent content of 10%have best corrosion resistance.When the sintering temperature is 1300°C,the hardness of the respirable steel increases with the increase of the pore-forming agent content.The optimum parameters of the preparation process are:pressing pressure 300 MPa,sintering temperature 1300°C,pore-forming agent content 10%.The gas-permeable steel produced by this process has excellent overall performance,and the relative gas permeability coefficient is 24.26 m³·（h·k Pa·m²）^-1,and the corrosion resistance is better than that of commercial gas-permeable steel.