Induced Surface Austenitic-Martensitic Transition by Mechanical Deformation in Mn Steel.Effect of Surface Properties

For a lot of applications in the mechanical industry,both attractive and mechanical properties of materials and wear resistance are required.Usually such a combination is achieved only by performing surface treatments.The aim of this investigation is the consolidation of 12% Mn steel surface by treatment of impacts.We show by optical and scanning electron microscopy,X ray diffraction,X ray spectrometry analysis and also by the realization of micro hardness,the effect of this kind of treatment on the mechanical and structural stability of the surface zone.Among of many obtained results,we distinguish the clear surface consolidation induced by a modification of surface zone crystalline structure.The mechanical deformation causes the transformation from an austenitic structure to the martensitic structure.     

Constitutive Relationship of New Steel 33Mn2V and Its Application in Piercing Process by FEM Simulation

 Based on test data from the hot forge experiments on Gleeble 1500, a Kumar type constitutive equation for 33Mn2V steel is established. Applying this constitutive equation in commercial FEM software of MSC/SuperForm 2005, the piercing process of 33Mn2V steel in Mannesmann mill is then simulated. The modeling results visualized the dynamic evolution of equivalent stress, especially inside the workpiece. It is shown that the non-uniform distribution of stress on the internal and external surface of the workpiece is a distinct characteristic of processing tube piercing. The numerical model was verified by comparing the values of calculated force parameters of the piercing process with those measured in laboratory conditions. And it shows that the Kumar-type constitutive relationship meets the practical needs.     

Li-Ni-Mn-O锂离子电池正极材料研究进展

Li-Ni-Mn-O正极材料由于具有比容量高、资源丰富、价格便宜、污染少等优点,而被视为最具发展潜力的锂离子电池的正极材料之一,近年来受到广泛关注。综述锂离子电池正极材料Li-Ni-Mn-O的研究进展,阐述其结构特征、制备方法及电化学性能。指出这些材料目前存在的主要问题并介绍解决方法,最后指出Li-Ni-Mn-O正极材料的发展前景和今后的研究方向。     

生物还原法提氧化矿中钴的探索性试验研究

处理氧化矿中钴的提取一直是个难题,本文采用生物还原法,用锰做电子接受体,将不溶的四价锰还原成可溶的二价锰,使软锰矿的晶体结构解体,释放出包裹在其中的钴金属。原矿中钴的含量为0.1左右,在含有还原细菌菌株的培养液中,采用适当的条件,可使钴有较高的回收率。     

Remarkable improvement of the signal-to-noise ratio of Mn/Fe in-beam Mössbauer spectroscopy

In-beam Mössbauer spectroscopy utilizing unstable ⁵⁷Mn beams is a powerful method to extract physical and chemical properties at the atomic scale. A parallel plate avalanche counter (PPAC), optimized to detect conversion electrons generated by the Mössbauer effect, can be employed to suppress higher-energy background γ rays. However, β rays are emitted by the ⁵⁷Mn parent nuclei of ⁵⁷Fe, which can significantly degrade the spectrum quality. In the present work, we have developed a new anti-coincidence-detection system with a thin plastic scintillation counter (0.5 mmt), which can be used to detect β rays and reject them from the recorded PPAC events. To demonstrate the anti-coincidence system, we carried out Mössbauer spectroscopy utilizing ⁵⁷Mn nuclei that were implanted into a non-magnetic aluminum metal plate at room temperature. Using the anti-coincidence method, we obtained a typical Mössbauer spectrum of high quality, despite a very low number of implanted ⁵⁷Mn atoms, of ∼5 × 10⁹. The signal to noise ratio of the obtained spectrum was increased remarkably, and the relative peak height above the baseline increased from 10% to 220% using the anti-coincidence method. The developed detection system is applicable to investigation of in situ properties, and avoids the potentially problematic agglomeration of probes in a sample.     

30t EBT电弧炉-LF-CC流程生产80Mn14钢的工艺实践

通过采用电弧炉出钢前在钢包中加入40%的锰铁,LF精炼前期调整成分,精炼中期和末期控制精炼渣碱度≥2.5,软吹氩搅拌,控制中间包钢水过热度≤35℃,连铸全程进行保护浇铸等工艺措施,贵阳特钢—炼钢厂成功进行了80Mn14钢(%:0.75～0.96C、13.00～15.50Mn、≤0.80Si、≤0.070P、≤0.030S)的30 t EBT AF-35 t LF-260mm×300mm连铸机流程生产,产品各项性能均满足标准要求。     

37Mn5连铸圆坯中心等轴晶率预测

为控制油井管用连铸圆坯的质量,基于薄片移动法建立了连铸圆坯凝固传热数学模型,并应用Procast软件的CA—FE模块对37Mn5钢Ф150mm圆坯凝固组织进行了模拟。中心等轴晶率模拟结果与工业试验检测结果相一致,据此,建立了柱状晶-等轴晶转变判据。基于此判据的中心等轴晶率预测结果表明,降低过热度、提高拉速和降低二冷零段...     

60Si2Mn钢摩擦焊后热处理工艺的改进

对60Si2Mn钢摩擦焊焊接接头热处理后的组织和性能进行了研究,通过显微镜(OM)观察焊缝的界面层显微组织形貌特征,分析了热处理工艺对焊接接头性能的影响.结果表明:该钢摩擦焊焊接接头为珠光体+铁素体+马氏体组织,组织不均匀.经正火预处理后,焊接接头为细小粒状珠光体,再进行淬火加回火处理,组织均匀,为回火索氏体,焊缝下屈...     

前驱体热处理温度对LiNi1/3Co1/3Mn1/3O2材料的影响

以NaCO3为沉淀剂,NH3·H2O为缓冲溶液,将NiSO4、CoSO4和MnSO4混合溶液共沉淀制备（Ni1/3Co1/3Mn1/3）CO3前驱体,将其在400-900℃热处理5h制备得（Ni1/3Co1/3Mn1/3）Ox氧化物。EDTA络合滴定、BET、XRD及SEM研究表明,随着热处理温度的升高,（Ni1/3Co1/3Mn1/3）Ox中过渡金属含量及结晶度随着增加,而比表面积却减小。（Ni1/3Co1/3Mn1/3）Ox与LiOH混合后在850℃热处理24h制备出LiNi1/3Co1/3Mn1/3O2材料,其结构、形貌及电性能的测试结果表明,前驱体在600℃条件下热处理制备的正极材料电化学性能最佳,其首次放电比容量为189.7mAh·g^-1,不同倍率循环60周后,循环保持率为92.4%。     

U71Mn钢轨气压焊接头的损伤行为

采用硬度计、轮廓仪、光学显微镜、扫描电子显微镜等对服役后的U71Mn钢轨气压焊接头的硬度、裂纹形貌及显微组织进行测试与观察,分析接头不同区域的损伤行为。结果表明:焊接接头两侧距接头中心30~50 mm处存在低凹区域,其位置与软化区位置吻合;轮轨接触使接头硬度提高,但是软化区的硬度始终低于母材;根据珠光体形态,接头从中心向两侧热影响区可依次分为层片状珠光体区域、部分珠光体球化区Ⅰ、珠光体球化区、部分珠光体球化区Ⅱ;软化区位于珠光体球化区;珠光体球化区与部分珠光体球化区的裂纹深度和裂纹尖端扩展角都较大,这是由于粒状珠光体对裂纹扩展的阻力较小导致的。