【作者】 邓小和；

【导师】 杨吉春；

【作者基本信息】 内蒙古科技大学 ， 钢铁冶金， 2008， 硕士

【摘要】 本研究通过改变稀土、镁的加入量,进行了RE-Mg复合处理的SS400钢的试验研究,来确认稀土、镁在变质夹杂、去除夹杂、改善显微组织和动态再结晶中的作用。首先,通过金相显微镜、扫描电镜及能谱仪对4种不同稀土、镁含量的试样中夹杂物进行观察。试验表明:稀土、镁可以使钢中非金属夹杂物变性,有效控制夹杂物的大小、分布和形貌,使其平均颗粒直径减小并呈弥散分布。硫化物夹杂物尺寸由15.35μm减小到9.83μm,氧化物夹杂物尺寸由18.52μm减小到8.79μm。其次,将试样正火、淬火处理后,通过金相显微镜、扫描电镜对4种不同稀土、镁含量的试样组织进行观察。试验表明:稀土、镁的加入改善SS400钢显微组织,细化晶粒,使组织晶粒度提高,晶粒度等级由7~7.5提高到9~9.5;使SS400钢珠光体组织片间距明显减小,平均珠光体片层间距由334.6 nm减小到130.4 nm;使钢中珠光体数量减少,珠光体面积百分数由23.16%减小到16.61%;显微硬度提高,由148.2提高到了187;使淬火马氏体组织板条马氏体束细化。最后,在Gleeble-1500热模拟试验机上测定不同稀土、镁含量的真应变—真应力曲线,分析稀土、镁对SS400钢动态再结晶的影响。实验表明:稀土对动态再结晶有强的固溶拖曳作用,稀土、镁复合处理后SS400钢形变抗力大;动态再结晶开始时间Rs增大,提高了再结晶温度。本课题在低合金钢中加入微量稀土、镁,提高钢质增强国际竞争力,把稀土资源优势转化为钢的品种优势和经济优势,具有十分重大的意义。更多还原

【Abstract】 The samples are gained by appending RE-Mg compound to the steel. In this dissertation, the influences of RE-Mg on the inclusions, microstructure and dynamic recrystallization of SS400 are studied and analyzed.Firstly, the inclusions in different RE-Mg content sample are observed, through careful and directed attention by spectrum and scanning electronic microscope. It is found that RE-Mg compound modification can modify the inclusions in the steel very well and also control the size and distribution of the inclusions. Sulfide inclusions size decreased from 15.35μm to 9.83μm, oxide inclusions size decreased from 18.52μm to 8.79μm.Secondly, the normalizing and quenching microstructure in different RE-Mg content sample are observed, through careful and directed attention by spectrum and scanning electronic microscope. It is found that the addition of RE-Mg in steel can improve the microstructure, keep the grain smaller, increase the microhardness, decrease the inter lamellar spacing of the pearlite, reduce the amount of perlite and make the lath martensite smaller. The grain size increases from grade 7.5 to grade 9.5, the pearlite area percentage reduce from 23.16% to 16.61%. The microhardness increases from 148.2 to 187 HV.Lastly, on the heat simulation test machine, the true stress-true strain curves are mensurated to study the effect of RE-Mg in SS400 dynamic recrystallization. The resistance to deformation of SS400 steel augment, the Rs of dynamic recrystallization augment and the temperature of dynamic recrystallization increase.The addition of mini-elements (RE-Mg) can advance the quality of steel. By This approach,we can enhance the international competition ability and make the resource advantage change to variety advantage which has great meaning.更多还原