稀土Ce对20MnTiB冷镦钢中夹杂物演变的影响

Effect of Rare Earth Ce on the Evolution of Inclusions in 20MnTiB Cold Heading Steel

工业化实验生产不同稀土(Ce)含量的20MnTiB冷镦钢,通过实验观察和热力学计算,研究了在Ca处理的基础上,Ce对20MnTiB冷镦钢生产过程中夹杂物演变的影响。结果表明,经Ce处理后,大尺寸类球状Al_(2)O_(3)·MgO·CaO·CaS夹杂物被变质分解为1μm左右类球状的CeAlO_(3)·MgO·CaO·CaS夹杂物,2μm左右不规则状的该类型夹杂物被变质球化。热轧后,0Ce试样盘条中夹杂物沿轧制方向拉长,夹杂物尺寸更大,形状愈发不规则,此外,还发现长条状MnS夹杂物。而在27Ce试样中,经Ce处理后w[S]降低40%,抑制了凝固过程中MnS夹杂物的形成,且经轧制后,盘条中夹杂物小尺寸、类球状的特性并未发生改变。热力学计算结果与实验结果相吻合。Ce处理后,大尺寸、不规则夹杂物的变质分解、小尺寸、不规则状夹杂物的变质球化以及MnS夹杂物的消失,避免了在冷镦过程中由于夹杂物不规则形貌引起的应力集中,从而有利于实验钢冷镦性能的提升。研究结果可为进一步开发新型稀土微合金化冷镦钢提供技术和理论支撑。

Industrialized tests were carried out to produce 20MnTiB cold heading steel with different rare earth(Ce)contents,the effect of Ce on the evolution of inclusions during the production of 20MnTiB cold heading steel based on Ca treatment was investigated through experimental observations and thermodynamic calculations.The results show that after Ce treatment,the large-size spheroidal Al_(2)O_(3)-MgO-CaO-CaS inclusions were metamorphosed and decomposed into about 1μm spheroidal CeAlO_(3)-MgO-CaO-CaS inclusions,and irregular inclusions of this type around 2μm were metamorphosed and sphericalized.After hot rolling,the inclusions in the 0Ce specimen wire rod elongated along the rolling direction,the inclusions were larger in size and more irregular in shape,in addition,long strips of MnS inclusions were found.However,in the 27Ce specimen,the S element content was reduced by 40%after Ce treatment,which inhibited the formation of MnS inclusions during the solidification process,and the small-sized,spherical-like characteristics of the inclusions in the wire rods did not change after rolling.The thermodynamic calculations are in agreement with the experimental results.After Ce treatment,the metamorphic decomposition of large-sized and irregular inclusions,the metamorphic spheroidization of small-sized and irregular inclusions,and the disappearance of MnS inclusions avoided the stress concentration caused by the irregular morphology of inclusions in the process of cold heading,which is conducive to the enhancement of the cold heading performance of the test steel and the reduction of the possibility of cold heading cracking.The results can provide technical and theoretical support for the further development of new rare earth microalloyed cold heading steels.