摘要
目的研究Sb微合金化对大断面球墨铸铁组织性能的影响,以提升大断面球墨铸铁件质量。方法向铁液中加入质量分数约为0.02%的合金元素Sb,随后浇注成180 mm×180 mm×200 mm的球墨铸铁立方体试块,并对其进行部分奥氏体化正火(880℃×2 h)和回火(500℃×2.5 h)处理。借助光学显微镜(OM)、扫描电子显微镜(SEM)、拉伸试验机和布氏硬度计等仪器研究未合金化试块、热处理前后的Sb合金化试块表层和中心位置的微观组织和力学性能,分析拉伸断口形貌,并探讨形成机理。结果未合金化铸态试块由铁素体和石墨组成,其表层石墨球数量较多、球径较细,中心部位出现了碎块状石墨等畸变组织,其综合力学性能较差;Sb合金化铸态试块由大部分珠光体、少部分牛眼状铁素体、细小球状石墨及少量的渗碳体组成,表层和中心位置的石墨球数量均得到增加,中心位置的增加较为明显,石墨球径细化明显,断口为脆性断裂,其强度和硬度偏高,塑性偏低;热处理后的试块强度和硬度得到适当降低,塑性得到明显改善,石墨球的数量、大小和分布变化不大,断裂模式为以解理断裂为主、伴有少量塑性变形的韧脆混合断裂模式。结论经部分奥氏体正火(880℃×2 h)和回火(500℃×2.5 h)的Sb微合金化试样强度和塑性较佳。
The paper aims to study the effect of Sb micro-alloyed on the properties of microstructure and heavy section ductile iron,to improve the quality of heavy section ductile iron.Heavy section ductile iron simulation cubic test block with the size of 180 mm×180 mm×200 mm were produced by adding 0.02%of trace elements Sb(mass fraction)into the molten iron,and the samples were treated with partial austenitizing normalizing(880℃×2 h)and tempering(500℃×2.5 h).The microstructure and mechanical properties of the surface and central position of heavy section ductile iron samples before and after micro-alloying and heat treatment were studied,and the tensile fracture morphology was analyzed by means of optical microscope(OM),scanning electron microscope(SEM),tensile testing machine and Brinell hardness tester,and the formation mechanism was discussed.The unalloyed as-cast sample is composed of ferrite and graphite,with more graphite balls of smaller diameter on the surface,while the graphite distortion structure such as fragmented graphite appears in the center,with poor comprehensive mechanical properties.The as-cast Sb micro-alloyed sample consists of most pearlite,a small amount of ferrite with bull's eye,fine round spherical graphite and a small amount of cementite.The number of graphite balls on the surface and in the center increases obviously,especially in the center.The diameter of the graphite balls is obviously refined and the fracture surface shows typical brittle fracture characteristics,and their strength and hardness are high and the plasticity and impact toughness are low.After heat treatment,the strength and hardness of the sample decrease,the plasticity and low temperature impact toughness are improved obviously,the number,size and distribution of the graphite balls change little,and the fracture surface shows a ductile brittle mixed fracture mode with cleavage fracture and a little plastic deformation.After partial austenite normalizing(880℃×2 h)and tempering(500℃×2.5 h),the strength,plasticity and low temperature toughness of Sb micro-alloyed heavy section ductile iron can be better.
作者
李仁强
潘昊亮
孟银娜
LI Ren-qiang;PAN Hao-liang;MENG Yin-na(School of Intelligent Engineering,Henan Mechanical and Electrical Vocational College,Zhengzhou 451191,China)
出处
《精密成形工程》
北大核心
2021年第5期147-154,共8页
Journal of Netshape Forming Engineering
基金
河南省科技攻关计划(162102210352)。
关键词
Sb微合金化
大断面球墨铸铁
部分奥氏体化正火
微观组织
力学性能
Sb micro-alloyed
heavy section ductile iron
partial austenitizing normalizing
microstructure
mechanical properties
