Effect Of Ce On The Microstructure And Properties Of 2101 Duplex Stainless Steel

Compared with traditional duplex stainless steel,2101 duplex stainless steel has low production cost and high cost performance.The Ni element in traditional duplex stainless steel is replaced by the cheaper N and Mn elements,and the structure is composed of a phase and γ phase.The advantages are applied in the marine and petrochemical fields.However,in practical applications,unreasonable heat treatment systems,prolonged high-temperature service,and improper handling of the welding heat-affected zone will cause the formation of precipitated phases and reduce the overall performance of 2101 duplex stainless steel.Brittle inclusions in the steel will cause the stress concentration of the steel during the stress process and develop into a crack source,and sulfide inclusions will become the nucleation core of pitting corrosion,reducing the corrosion resistance of the steel.In this experiment,rare earth Ce was used to treat 2101 duplex stainless steel,and the effects of Ce on the microstructure,mechanical properties and corrosion resistance of duplex stainless steel were investigated.In this experiment,a 25kg pressure induction furnace was used for smelting,and 2101 duplex stainless steel with different Ce mass fractions in the three furnaces was smelted.Inclusion and microstructure analysis experiments show that as the Ce mass fraction increases,the overall particle size of the inclusions decreases,and the number of inclusions per unit area decreases.Ce has the role of metamorphic inclusions.In steels without the addition of Ce,the types of inclusions are mainly Al2O3,MnS,and composite inclusions of both.When the mass fraction of Ce is 0.005%,the main inclusions in the steel is CeAlO3,when the mass fraction of Ce increases to 0.020%,the types of inclusions in the steel are mainly Ce2O2S,CeS,and a very small amount of Ce2O3.The thermodynamic software Thermo-Calc calculates and experimentally verifies that the optimal solution system is 1050 ℃+30min.The dual-phase steel has better microstructure stability and no precipitated phase after solution.Adding Ce to the steel increases the proportion of austenite phase,and when the amount is 0.005%,the two phases are closest to 1:1.With the increase of Ce content,the segregation of two-phase elements is improved,the grains are refined,and the grain size level is increased.The addition of Ce inhibits the enrichment of Cr and N elements at the phase boundary,and the precipitated phase after aging heat treatment is reduced.The related experimental results of mechanical properties show that with the increase of Ce mass fraction,the tensile properties and impact properties of steel are improved to a certain extent,and the hardness of steel shows a trend of first decline and then increase.In terms of tensile properties,as the Ce mass fraction increases,the yield strength and tensile strength of the steel increase,and the fracture morphology changes from ductile-brittle fracture to ductile fracture.In terms of impact performance,the impact energy in the solid solution state is relatively large.After aging,the impact energy of the steel decreases significantly.As the mass fraction of Ce increases,the impact energy shows an upward trend.The solid solution impact fractures are all ductile fractures,but with the increase of Ce mass fraction,the number of dimples increases and the distribution is more uniform,while the morphology of the impact fracture in the aging state changes from brittle cleavage fracture to ductile fracture.The outside is sharper.The addition of Ce increases the softer austenite ratio,reduces the overall hardness of the steel,and produces a hard precipitated phase after aging,which increases the hardness of the steel.The relevant experimental results of corrosion resistance show that with the increase of Ce mass fraction,the corrosion resistance of steel improves.In the ferric chloride immersion experiment,adding Ce reduced the average weight loss rate,the maximum pit diameter and the maximum pit depth of the pitting pits were both reduced,and the corrosion resistance was enhanced.The research methods of electrochemical experiments are kinetic potential polarization curves and electrochemical impedance spectroscopy.The experiments show that in neutral and acidic solutions,as Ce mass fraction increases,the pitting potential increases,and the capacitive impedance arc radius of the electrochemical impedance spectroscopy is increased,the corrosion resistance of steel reinforcement.