稀土对重轨钢铸、轧态组织与力学性能的影响

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1、东北大学硕士学位论文摘要稀土对重轨钢铸、轧态组织与力学性能的影响摘要本文对稀土在钢中应用的国内外状况进行了简要评述，对稀土元素的性质、在钢中作用的机理进行了较为全面的总结。采用对比实验的方法，研究了稀土对铸态和轧态重轨钢组织和力学性能的影响。采用硬度测定的手段，研究了重轨钢连铸坯由表及里的组织分布特点。通过金相观察、扫描电镜观察及能谱分析对钢中的异常组织进行了确认。实验结果表明：(1)BNbRE、U71Mn钢连铸坯表面至心部的硬度都可分为三个区间，由此可推断连铸坯由表面至心部的组织由细等轴晶区(约20ram)、柱状晶区(约60mm)及中心等轴晶区(约40mm)组成。(2)稀土加入钢中后，

2、可减轻磷的偏析，进而使磷共晶组织得到明显改善。(3)稀土有促使连铸坯表层铁素体析出的作用。(4)在BNbRE钢轨的轨顶、轨腰和轨底位置均观察到了稀土对硫化物夹杂的改性作用。(5)在轧态和铸态重轨钢中，稀土都可以起到减小珠光体片层间距的作用。本实验说明，稀土加入连铸重轨钢中，对改善钢的组织，提高钢的力学性能是有益的，特别是与铌共同加入时效果更为明显。因此，稀土在重轨钢中的应用有非常广阔的前景。关键词：稀土处理，连铸，重轨钢，力学性能，夹杂物改性，东北大学硕士学位论文AbstractEf．fectofRareEarthonCastandHotRolledMicrostructureandPr

3、opertiesofHeavyRailSteelsABSTRACTTheapplicationstatusofrareearthinsteelhasbeenbrieflydiscussedinthispaper．AttheSalTletime，thepropertiesofrareearth，theactionmechanismofrareearthinsteelhasbeensummarizedindetail．Theextensivestudieshasbeenmadeontheactionmechanismofrareearthinthecontinuouslycastslabsa

4、ndhotrolledrailsteelbyusingcontrastexperimentsinthispaper．Themicrostructuredistributionfromsurfacetocenteroftheslabshasbeenstudiedbydetermininghardness．TheabnormalmicrostructurehasbeenconfirmedbyOPandSEManalysis．Theresultsshowthat：1．Thehardnessofcastslabsfromsurfacetocenterwasdividedintothreesect

5、ions．Thereforeitisknownthattherearethreedifferentmicrostmctures．Ontheoutsideoftheslabsthegrainisfme，inthemiddlethegrainiscylindricandthelargeinthecenter．2．Therareearthaddedintheheavyrailsteelcandecreasethesegregationofphosphorus，andimprovethestructureofeutecticofphosphorl／$．3．Thequantityofferrite

6、inthesurfacelayerisconsiderblyincreasedfortheadditionofrareearth．4．Theshapeandpropertiesoftheinclusionsintherailsteelcarlbechangedandthedetrimentaleffectsofinclusionscanbeoffsetintermsoftheeliminationofaluminastringersandelongatedmanganesesulfidephase5．Thelamellarspacingofpearlitecanbedecreasedno

7、tonlyinthecominuouslycastslabsbutaisointherolledsteel．IthasbeenshownthatthemechanicalpropertiesofBNbREismuchbetterthanU71Mn．Itshowsthattherareearthadditionisgoodforthemechanicalproperties．Ithasbeenmademoreclearinthispa