Ce对75Cr1钢洁净度、组织与耐点蚀性能的影响

Effect of Ce on Cleanliness,Microstructure,and Pitting Corrosion Resistance of 75Cr1 Steel

通过对不同Ce含量的75Cr1钢中夹杂物的特征分析,以及对显微组织演变的原位观察和电化学极化实验,研究了Ce处理对75Cr1钢的洁净度、组织与耐蚀性能的影响。结果表明:Ce能有效去除钢中的O、S等杂质元素,随着Ce含量的增加,75Cr1钢中典型夹杂物从初始的Ca-Mg-Al-O+MnS+CaS+TiN转变为Ce_(2)O_(2)S和Ce_(2)O_(2)S-CeAlO_(3)夹杂,而后转变为稀土硫化物夹杂;O、S含量降低到一定程度后,Ce与P和As等残余元素结合形成稀土磷化物和稀土砷化物夹杂;夹杂物的尺寸、数量呈现先减小后增加的趋势,形状从不规则形状转变为球状,当Ce过量时又转变为不规则形状。适量的Ce处理可以明显细化奥氏体晶粒并抑制其长大,还可以提高钢的耐蚀性能。添加质量分数为0.0195%Ce时,75Cr1钢的洁净度、组织细化和耐点蚀性能最佳。

Saw blades are always running under a high resonance,large lateral pressure,large tensile stress,and corrosive environment.Nonmetallic inclusions in steel break the continuity of the matrix and easily cause stress concentration and crack formation.Furthermore,the inclusions,especially MnS/CaS,cause the initiation of pitting corrosion.Rare-earth elements in steel can play the role in liquid steel purification,inclusion modification,and solid solution alloying.Rare-earth inclusions can act as the nucleation sites for the formation of theδ-Fe/γ-Fe phase during the solidification of molten steel,thus refining the solidification structure,and have relatively lower pitting sensitivity.In this study,the effect of Ce treatment on the cleanliness,microstructure,and corrosion resistance of 75Cr1 steel was investigated via inclusion characterization and in situ observation of the microstructure evolution as well as electrochemical polarization experiments.Results showed that Ce can effectively remove O,S,and other impurity elements in steel.With the increase in Ce content,the typical inclusions in 75Cr1 steel changed from the initial Ca-Mg-Al-O+MnS+CaS+TiN inclusions to Ce_(2)O_(2)S and Ce_(2)O_(2)S-CeAlO_(3)inclusions and then to rare-earth sulfide inclusions.After the oxygen and sulfur contents were reduced to a certain extent,Ce started to combine with residual elements such as P and As to form rare-earth phosphide and arsenide inclusions.The size and number of inclusions firstly decreased and then increased.Meanwhile,the morphology of the inclusions firstly changed from irregular to spherical and then changed to irregular again when excessive Ce was added.The addition of appropriate Ce can refine the austenite grains and inhibit their growth;moreover,the corrosion potential and pitting corrosion resistance of steel are improved and the self-corrosion currents decrease.The 0.0195%Ce-containing 75Cr1 steel showed the highest cleanliness,a refined microstructure,and enhanced pitting corrosion resistance.