Preparation Of 21Cr Lean Duplex Stainless Steel By Strip Casting And Research On Its Microstructures And Properties

The raw materials’ price of stainless steel,especially the price of Ni and Mo,has a severe impact on the cost of stainless steel product.Driven by the need of high cost performance and saving Ni resource,economical stainless steels have been developed a lot in recent years.Lean duplex stainless steel(LDSS)is a kind of resource-saving stainless steels containing nitrogen,low nickel and low molybdenum.2101 is a kind of typical LDSS with high strength,excellent plasticity,toughness and good corrosion resistance,especially pitting corrosion resistance.Under analyzing the researches and application of LDSS,this paper designed two kinds of LDSS containing low nickel or none,the following researches were carried out on this basis.(1)By using twin-roll strip casting technique,two kinds of lean duplex stainless steels containing low nickel or none,2101-1 and 2101-2,were prepared successfully with good quality both on surface and sides.And the length of 2101-2 can reach more than 1 Om without apparent cracking.(2)The as-cast strip was subjected to hot rolling and cold rolling,followed by annealing treatment at different temperatures.The microstructures and evolutions were studied by means of OM,SEM and XRD,including the analysis of phase,the calculation of the phase ratio and the grain size.The effect of different annealing temperature on the mechanical properties of the two experimental steels were studied by the tensile test at room temperature.The appropriate temperature for the experimental steels were obtained,which is 1050℃ for 2101-1 and 1000℃ for 2101-2 respectively.(3)Based on the tensile test experiment and the relationship between the work hardening rate,exponent and the true strain,and the microstructure evolution after deformation in experimental steel was investigated accurately through the observation of deformed specimen in different strain by TEM.It is found that the strengthening effect of 2101-1 is dominated by the TWIP effect,while the 2101-2 has both TRIP and TWIP effects.In the observation of 2101-2 deformed structure,the orientation relationship between ε-martensite,α’-martensite and austenite was determined,and the amount of stain induced martensite during 2101-2 deformation was calculated by XRD.(4)With the potentiodynamic scanning technique,polarization curve of the two kinds of lean duplex stainless steels are obtained to evaluate the corrosion property.It has been found that both of the 2101-1 and 2101-2’s pitting potentials reach maximum in 1000℃.Also,the results showed that there is a close negative correlation between the self-corrosion potential and self-corrosion current.The PRE value of each phase were calculated from the chemical composite detected by electron probe EDS,and it is found that the pitting potential tends to be higher when the PRE value difference of the ferrite and austenite phase is smaller.Also,the pitting potential is found to have closely positive correlation with the austenite content,which means more austenite content indicates a higher pitting potential.