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通过拉伸和冲击等力学性能实验以及扫描电镜和能谱分析等检测手段,研究了Cu-P耐候钢中稀土含量和稀土固溶量对钢综合力学性能的影响及其作用规律。研究结果表明,对于氧含量为0.004%~0.007%(质量分数,下同),硫含量为0.008%的稀土耐候钢,稀土含量在0.005%~0.025%的范围内,固溶稀土量为5×10-6~16×10-6。适量稀土使得钢中带状硫化锰夹杂物逐渐变质为尺寸小于2μm的球状弥散分布的稀土夹杂,钢的组织得到细化,并且在固溶稀土的作用下,耐候钢的综合机械性能得到提高,即改善材料的塑韧性的同时也提高了强度。耐候钢中加入稀土提高了钢的横向冲击韧性,尤其对低温冲击值提高明显,促使钢从解理断裂向韧窝断裂转变。韧窝中的细小球状稀土氧硫化物夹杂是其转变的主要原因。当耐候钢中稀土含量小于0.012%时,随着稀土含量和稀土固溶量的增加,钢的综合机械性能改善明显。
Through tensile and impact mechanical properties experiments and scanning electron microscopy and energy spectrum analysis and other detection methods, the study of the Cu-P weathering steel rare earth content and the amount of rare earth solid solution on the mechanical properties of steel and its role in law. The results show that for rare earth weathering steels with 0.004% -0.007% oxygen content and 0.008% sulfur content, the content of rare earth is in the range of 0.005% -0.025%, and the amount of rare earth solution is 5 × 10-6 ~ 16 × 10-6. Appropriate amount of rare earth makes the banded manganese sulfide inclusions gradually degenerate into rare earth inclusions of spherical diffuse distribution whose size is less than 2μm, the microstructure of the steel is refined, and the comprehensive mechanical properties of weathering steels are improved under the action of solid solution rare earths, That is to improve the plasticity of the material while also increasing the strength. The addition of rare earth to the weathering steels increases the transverse impact toughness of the steels, especially the low temperature impact value, which promotes the transformation of steel from cleavage fracture to dimple fracture. Dimples in the small spherical rare earth oxysulfide inclusions is the main reason for the change. When the content of rare earth in weathering steel is less than 0.012%, with the increase of rare earth content and the amount of solid solution of rare earth, the comprehensive mechanical properties of steel improve obviously.