稀土Ce对非调质钢中硫化物特征及微观组织的影响

通过稀土Ce微合金化手段,采用SEM、EDS和ASPEX等手段对不同Ce含量的非调质钢中的夹杂物形貌、数量和尺寸以及实验用钢的显微组织进行了表征,结合Thermo-Calc热力学软件对含Ce硫化物夹杂的形成过程进行了分析,并通过三维原子探针（3DAP）对晶界和相界面处的元素分布进行表征。结果表明,Ce在1800℃与S结合形成Ce₃S₄夹杂,1480℃转变为Ce₂S₃夹杂,1480℃以下形成Ce₂S₃为内核,Ti₄C₂S₂和Mn S包覆生长的复合夹杂物;添加Ce元素的实验用钢中90%以上的夹杂物的长径比小于2.5;Ce含量为0.019%（质量分数）时,实验用钢的组织最细,平均晶粒尺寸为4.17μm。3DAP的结果证明了Ce在晶界和相界处存在明显偏聚,阻碍了C扩散,抑制晶粒长大,另外,高温区形成的细小弥散含Ce夹杂物提供了形核质点,2者共同作用细化了非调质钢的组织。     

稀土Ce含量对4Cr5MoSiV1钢中夹杂物的变质作用

为探究Ce元素对热作模具钢中夹杂物的影响及其作用机理,用场发射扫描电镜(SEM/EDS)和附带的夹杂物自动分析系统对不同Ce含量的4Cr5MoSiV1钢中夹杂物的类型、形貌、数量、尺寸及其分布进行观察和统计分析。结果表明,不含Ce的试样中夹杂物不仅数量多、平均尺寸较大且形状不规则,主要类型为Mg-Al-O类、MnS和Mg-Al-O外覆盖MnS的夹杂物;随Ce含量的增加,试样中的夹杂物有数量和平均尺寸减小、并变质为球形稀土硫氧化物的趋势。当钢中Ce含量为0.0070%时,夹杂物的数量最少,平均尺寸最小;继续增加稀土Ce含量到0.0120%时,会形成更多的硫氧化物夹杂,且夹杂物有数量增多、平均尺寸增大的趋势。随着凝固过程的进行,Ce主要以稀土硫氧化物形式存在试验钢中,60%以上的夹杂物会被凝固前沿推动,且最终留在晶界附近。     

铈-硫易切削钢平衡析出相热力学计算与分析

采用Thermo-Calc热力学软件对铈-硫易切削钢300~1500 ℃范围内的析出相进行了热力学计算,并得到了平衡凝固相变路径图。此外,还讨论了Ce、S含量对Ce₂O₂S平衡相的影响和S、Mn含量对MnS平衡相的影响。结果表明,铈-硫易切削钢中平衡析出相主要有Ferrite、Ce₂O₂S、Corundum、Austenite、M₂(C,N)、Liquid、M₂₃C₆、MnS、Sigma、Spinel与M(C,N);随着Ce含量增加,Ce₂O₂S的析出量逐渐增加,但是S含量变化对Ce₂O₂S相的析出几乎没有影响;随着S含量增加,MnS平衡相的析出量逐渐增加,析出温度也逐渐增高,Mn含量变化对MnS相的析出量几乎没有影响,但Mn含量增加会使MnS析出温度升高;铈-硫易切削不锈钢铸坯中的硫化物呈球形、椭球形、纺锤形或短棒状并以簇状沿晶界分布,属于第Ⅱ类硫化物;通过添加稀土Ce,铈-硫易切削钢中球形稀土复合夹杂物所占比例较高,长宽比≤3的硫化物占比达到84.86%,硫化物的形态控制取得了较好的效果。     

稀土对A572.Gr65钢夹杂物及低温冲击性能的影响

为了研究不同含量混合稀土(Ce/La)对A572.Gr65钢低温冲击性能的影响,对A572.Gr65钢在-40 ℃和-60 ℃下进行低温冲击试验,并使用OM观测显微组织,利用SEM结合EDS观测夹杂物及断口形貌并检测其化学成分。结果表明,稀土可以明显变质A572.Gr65钢中夹杂物,将不规则的Al₂O₃和Al₂O₃-CaO夹杂物变质为球状稀土夹杂物;夹杂物尺寸由5 μm减小至不足2 μm。加入稀土后钢的低温冲击性能有明显提升,当稀土含量达到0.0057%时,-40 ℃冲击吸收能量由未添加稀土的317.4 J升至343.6 J,提升了8.2%;-60 ℃冲击吸收能量由未添加稀土的288.0 J升至328.1 J,提升了13.9%。     

稀土处理HRB400E钢洁净度研究

为了研究稀土对HRB400E螺纹钢中夹杂物成分和形貌的影响,对稀土处理后螺纹钢中可能存在的夹杂物进行热力学计算,并通过扫描电镜及能谱仪对稀土处理前后 HRB400E钢中夹杂物进行了表征和分析。结果表明,稀土可在现场冶炼时加入到螺纹钢中并且质量分数达到0.003 2%;稀土有净化钢液的作用,使钢中S质量分数从0.018%降低到0.004%,降低了77.78%;热力学计算表明,稀土质量分数为0.003 2%时,夹杂物生成的可能性由高到低为REAlO₃、RE₂O₂S、Al₂O₃。稀土对HRB400E钢中硫、氧化夹杂物有良好的改质效果,将夹杂物变质为RE₂O₂S和REAlO₃,稀土元素与S结合使钢中MnS夹杂的析出减少,有利于钢材综合性能的提升。     

稀土Ce对T91耐热钢组织及力学性能的影响

对不同稀土Ce加入量的T91耐热钢进行室温拉伸和冲击性能测试,采用SEM和EDS进行组织观察和断口研究。结果表明,加入稀土Ce能细化晶粒,改变钢中夹杂物的形貌和大小,从而有效改善T91钢的强度与韧性;韧窝中形成的细小球状稀土硫氧化物夹杂是力学性能转变的主要原因;稀土对改善室温冲击性能作用显著,稀土Ce含量在0.0020%时,试样室温冲击性能最佳。     

铈对S32750超级双相不锈钢低温冲击性能的影响

通过夏比冲击和示波冲击方法分析了两种Ce含量S32750超级双相不锈钢在20~－100 ℃范围内的冲击吸收能量及能量构成差异,利用Aspex自动扫描电镜分析仪、SEM、EDS研究了Ce对钢中夹杂物的改性行为及冲击断裂行为的影响。结果表明:高Ce试验钢的抗低温冲击断裂性能明显优于低Ce试验钢,前者韧脆转变温度相较后者下降16 ℃;Ce的添加使得试验钢－80 ℃冲击吸收能量提高45 J,其主要源于裂纹扩展能W_p的提升(76%)。冲击断口形貌观察和夹杂物分析结果显示,低Ce试验钢在－80 ℃冲击断口表现为完全解理断裂;相较于低Ce试验钢,高Ce试验钢中Al₂O₃夹杂显著减少,多为改性后的铈铝氧复合夹杂;硬脆Al₂O₃夹杂数量的减少有效改善了钢的冲击性能。     

Ce、Cu合金化高强高效无取向硅钢中的夹杂物和析出相分析

设计并制备了含Cu和Ce的高强高效无取向硅钢。通过热力学计算、FactSage和JmatPro相图计算以及扫描电镜(SEM)、透射电镜(TEM)和能谱仪(EDS)等研究了不同Cu含量的含Ce无取向硅钢中夹杂物和析出相粒子性质。结果表明：Ce的添加降低了试验钢中富Cu析出相的开始析出温度。Cu含量不仅影响富Cu析出相的尺寸、数量而且影响其形态，如1.24%Cu含量的钢中富Cu析出相尺寸细小、呈球状，2.24%Cu含量的钢中富Cu析出相尺寸较大且出现短棒状形态。Ce的添加改变了AlN、Al₂O₃等夹杂物的形态和尺寸，使夹杂物变性，降低了夹杂物对试验钢磁性能的有害影响。     

应用稀土氧化物冶金技术改善高强钢焊接性能

在高强钢中加入5×10~(-6)和23×10~(-6)稀土Ce,研究了Ce对焊接热影响区冲击韧性、微观组织、原奥氏体晶粒以及焊接接头断口形貌的影响与机理。钢中含Ce量为5×10~(-6)时,能在镁铝夹杂物外围生成少量CeAlO_3夹杂物,但不能完全改性镁铝夹杂物,当Ce添加量达到23×10~(-6)后,Ce能够完全改性MgO-Al_2O_3尖晶石,生成(CeCa)S+MgO-Al_2O_3+MnS稀土夹杂物。对含有Ce的高强钢板进行模拟焊接,结果表明,在4组不同焊接热输入条件下,钢中加入23×10~(-6)Ce后,比钢中加入5×10~(-6)Ce的钢焊接热影响区的Charpy冲击功有所提高。微观组织分析发现,23×10~(-6)Ce含量的高强钢试样焊接热影响区断口形貌呈现韧窝状,韧性更好;当热输入从25 kJ/cm逐步提高到100 kJ/cm时,含5×10~(-6)Ce的高强钢热影响区原奥氏体晶粒平均尺寸增加了75.6%;含23×10~(-6)Ce的高强钢的原奥氏体晶粒平均尺寸增加了52.4%,即钢中Ce含量的增加抑制了焊接热影响区原奥氏体晶粒的长大。通过微观组织分析对比,说明稀土Ce在高强钢中起到了延迟焊接热影响区上贝氏体组织形成的作用,同时抑制焊接过程中原奥氏体晶粒的长大。利用高温共聚焦显微镜观察到了稀土夹杂物钉扎于原奥氏体晶界,抑制焊接过程中晶粒的长大,验证了稀土Ce对高强钢焊接热影响区性能改善的机理。本工作表明应用稀土氧化物冶金可以改善稀土高强钢的焊接性能。     

稀土Ce对含Cu低温取向硅钢铸态析出物的影响

采用激光共聚焦显微镜和透射电镜探究了稀土元素Ce对含Cu取向硅钢铸态组织和析出物的影响。结果表明,稀土元素Ce对含Cu取向硅钢铸态的组织能起到细化晶粒的作用;未加Ce的铸锭中存在粗大的(Cu,Mn)S+AlN粗大复合析出物,以及少量MnS和Cu₂S单独析出物;稀土Ce的加入不改变析出物的类型,但使析出物数量明显减少、尺寸有所增大。     

Microstructure and properties of thermal-sprayed NiCrWRE coatings

The powders of NiCrW and NiCrWRE alloys were flame sprayed on a medium-carbon steel substrate by thermal spray welding. The micro- structure and tribological behavior of coatings were studied experimentally by means of scanning electron microscopy （SEM）, field emission gun scanning electron microscope （FEGSEM）, and wear tests. The addition of CeO2 modifies the coating morphology from a needle-like structure to a roughly cubic morphology; the refining and purifying effect of rare earth elements makes the microstmcture more compact and finer. Analysis of the worn surfaces reveals that the coatings with CeO2 addition show improved abrasive wear resistance over those without CeO2. By adding CeO2, the hardness of the coatings is significantly increased, and the wear resistance of the coatings is enhanced.     

Effect of rare earth on inclusion evolution and corrosion resistance of HRB400E steel

The effect of rare earth elements Ce and La on the evolution behavior of inclusions in HRB400E steel was studied through experimental observations and thermodynamic calculations. Neutral salt spray corrosion experiments were also conducted to investigate the effect of Ce–La on the corrosion resistance of steel. The results showed that the typical inclusions in steel without rare earth were MnS and MnO–SiO₂. A small amount of Mn–Si–O–S inclusions was also observed. After adding rare earth, the typical inclusions were transformed into isolated (Ce,La)₂O₂S, (Ce,La)₂O₃ + MnS, and (Ce,La)₂O₂S + MnS complex inclusions. The thermodynamic calculations indicated that the rare earth elements in molten steel preferentially reacted with MnO–SiO₂ inclusions and dissolved oxygen and sulfur to form (Ce,La)₂O₃ and (Ce,La)₂O₂S. Small amounts of [S] and [Mn] adhered to the surface of the nucleated rare earth inclusions to form complex inclusions. After Ce–La treatment, the corrosion rate of the steel decreased from 3.491 to 1.992 mm year⁻¹, and the corrosion resistance was improved. The change in corrosion behavior is due to the modification of the inclusions into rare earth inclusions with good compatibility with the steel matrix.     

Effects of rare earth elements on corrosion behaviors of low-carbon steels and weathering steels

The effects of rare earth elements on the corrosion properties of low-carbon steel and weathering steel were investigated. To elucidate the roles of rare earth elements (Ce and La) and the corrosion behavior of steels, salt spray tests, electrochemical techniques, X-ray diffractometer, scanning electron microscopy, Electron Probe Micro Analysis (EPMA), and Auger Electron Spectroscopy (AES) were conducted. The results showed that the addition of rare earth elements enhances the corrosion resistance of both low-carbon steels and weathering steels, indicated by lower corrosion current density and salt spray corrosion rate after rare earth alloying. On the one hand, rare earth elements modify the morphology of inclusions and thus slow down the micro-area electrochemical corrosion, which improves the electrochemical corrosion resistance of these two steels. On the other hand, rare earth atoms tend to segregate toward the interface between the rust layer and the matrix. Hence, salt spray corrosion resistance is improved due to the enhancement of adhesion and compactness of the rust by the addition of rare earth elements.     

铈在253MA耐热钢中赋存状态的热力学分析

基于多相多组元反应平衡原理及凝固过程固液相界面的溶质再分配理论,建立了稀土耐热钢凝固过程中夹杂物析出与溶质元素微观偏析的耦合热力学模型,并通过工业试验验证了该模型的准确性。利用该模型系统研究了在不同铈含量、氧含量、硫含量条件下253MA耐热钢中固溶的铈含量。在本模型计算条件下,为保证耐热钢中较高的固溶铈含量,铈添加量(质量分数)须在0.025%以上;钢中的氧硫的质量分数应满足[%O]+[%S]0.009([%O]0.0046)及2[%O]+[%S]0.014([%O]0.0046)。     

钇基稀土对高强船板钢夹杂物及低温冲击性能的影响

采用扫描电镜(SEM)和能谱仪(EDS)等分析方法,研究了钇基稀土含量对EH36高强船板钢夹杂物和低温冲击性能的影响。结果表明,EH36钢中添加适量稀土能够显著提高钢材的低温冲击性能。钢中稀土含量为0.018%(质量分数)时,-40 ℃横向冲击性能提高了59.4%,-60 ℃横向冲击性能提高了65.7%。低温冲击断口形貌由无稀土钢样的解理断面转变为韧窝断口,韧窝底部的细小球状稀土复合夹杂物对裂纹扩展起到缓冲作用,阻碍了裂纹的扩展。同时,稀土可以将EH36钢中长条状Al₂O₃-CaO-MnS夹杂物变质为细小的类球状稀土夹杂物,夹杂物粒径从约5 μm细化到3 μm以内。     

Modification Mechanism of Cerium on the Inclusions in Drill SteelEI北大核心CSCD

Fatigue fracture is the main failure forms of drill steel, and the hard oxide with large size is one of the main reasons for the fatigue fracture of drill steel. Therefore, the miniaturization and softening of inclusion can effectively improve the anti-fatigue performance of drill steel and prolong its service life. Rare earth elements have very good affinity with oxygen and sulfur in molten steel, and the hardness of resulting rare earth compounds is very low. In this work, the rare earth element cerium was added into drill steel to investigate the effect of Ce on the MgAl2O4 and sulfides. The composition, morphology, number, and size of inclusions in drill steel were analyzed by using SEM and EDS. The evolution process and modification mechanism of Ce on MgAl2O4 and sulfides were clarified by experimental results and calculated by thermodynamic software. The type of inclusions in drill steel without Ce addition is MgAl2O4 and (Ca, Mn) S. As the Ce content in drill steel reaches to 0.0078% (mass fraction), the type of inclusions changes to Ce-O and Ce-S. In addition, a few complex inclusions, mixture of Ce-O and MgO, were also found. The size of inclusions in drill steel decreases significantly as the oxides and sulfides were modified into Ce-O and Ce-S. The calculated results show that MgAl2O4 and (Ca, Mn) S in drill steel can be effectively modified into Ce-O and Ce-S as the Ce added into molten steel, and the modification sequence of Ce on the MgAl2O4 is as follows: MgAl2O4 -> CeAlO3+ MgO -> Ce2O3+ MgO -> Ce2O3. The content of Ce in drill steel has great influence on the type of inclusions. The modification mechanism of Ce on MgAl2O4 calculated by Factsage 6.3 agrees well with the experimental observations.     

添加不同稀土元素对固体包埋法在 304 不锈钢表面制备 Ti / Cr-RE 双层涂层电化学性能的影响

目的选择合适的稀土制备Ti/Cr-RE双层涂层,提高不锈钢的耐腐蚀性能。方法采用两步粉末包埋法,先在304不锈钢表面渗Ti,再制备稀土改性Cr涂层,获得Ti/Cr-RE双层涂层。通过添加不同的稀土氧化物Y2O3和Ce O2,获得两种双层涂层,对比分析涂层的表面形貌、断面形貌及物相组成,利用电化学测试方法测定304不锈钢基体及两种Ti/Cr-RE双层涂层在3.5%(质量分数)Na Cl溶液中的电化学腐蚀性能。结果添加不同稀土元素钇、铈,都能在渗Ti不锈钢表面形成一层致密、连续的稀土改性渗铬层。在两种稀土元素改性的Cr涂层中,稀土元素分别与Cr,Fe,Ni,Ti形成了金属间化合物。304不锈钢基体的自腐蚀电位为-0.324 V,腐蚀电流密度为0.1363μA/cm2;钇改性铬涂层的自腐蚀电位为-0.341 V,腐蚀电流密度为0.2058μA/cm2;铈改性铬涂层则具有更高的自腐蚀电位(-0.263 V)及更低的腐蚀电流密度(0.030 86μA/cm2)。结论钇改性铬涂层不能提高304不锈钢基体的耐腐蚀性能,铈改性铬涂层可以明显提高基体的耐腐蚀性能。