Abstract
In the present study, the effects of rare earth metal (REM) Ce on the number, size distribution and type of inclusions, as well as the grain size, tensile and impact properties of LDX2101 duplex stainless steel, were investigated using thermodynamic analysis, optical microscope, image software, scanning electron microscope, tensile and impact testing machines. The results indicate that when the Ce content in steel is 0%, the main inclusions are irregular and large size Al2O3 and Al2O3-MnS. When the Ce content in steel is 0.005% or 0.02%, the inclusions are mainly spherical and small size inclusions CeAlO3, Ce2O2S and Ce2O3. With the increase in Ce content, the proportion of small size inclusions gradually increases; the number of inclusions per unit area decreases from 122 to 58 and the average grain size reduces from 16 ± 0.7 μm to 12 ± 0.3 μm. Moreover, the mechanical properties of steels are improved, and the tensile strength, yield strength and elongation are elevated by 4.69%, 2.83% and 4.9%, respectively. The impact fracture mode of steel without Ce is cleavage fracture, however, the fracture mode is transformed into a mixed fracture of cleavage and dimple after adding 0.005% and 0.02% Ce.
Highlights
Duplex stainless steel is a kind of two-phase steel with approximately equal proportions of ferrite phase and austenite phase
Duplex stainless steel has outstanding resistance to pitting corrosion and chloride stress corrosion cracking, and high strength and excellent welding performance, and it has been extensively used in rigorous environments of chemical, marine, oil and natural gas [2,3]
LDX2101 stainless steel is a typical lean duplex stainless steel and its contents of Mn, N and Cr are increased with the decreased content of Ni compared with AISI 304 austenitic stainless steel [6,7,8]
Summary
Duplex stainless steel is a kind of two-phase steel with approximately equal proportions of ferrite phase and austenite phase. It covers the performance characteristics of ferritic stainless steel and austenitic stainless steel [1]. With the lightening of corrosion-resistant industrial equipment, higher requirements of the mechanical properties of lean duplex stainless steels are urgent. It is necessary to improve the mechanical properties of lean duplex stainless steels. Lv et al [9] and Wan et al [10] showed that the strength and plasticity of duplex stainless steels could be improved by reducing the grain size. Liu et al [11,12] demonstrated that the size, shape, distribution and composition of inclusions and grain size will obviously affect the impact toughness of duplex stainless steels
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