Ce-Mg复合处理对含硫齿轮钢SCr420H洁净度的影响

 为了探究不同的Ce、Mg含量对含硫齿轮钢SCr420H洁净度的影响,在真空感应熔炼条件下对含硫齿轮钢SCr420H进行Ce-Mg复合处理,分析了Ce、Mg的收得率、脱氧与脱氮效果及夹杂物的形貌、种类、数量、尺寸及形态。结果表明,Ce的收得率稳定在10%～15%,Mg的收得率在1%～1.5%之间;Ce-Mg处理能够在铝脱氧的基础上进一步将钢中氧质量分数降低至0.000 9%;Ce-Mg处理后形成的含Ce、Mg夹杂物呈现近球状形态,可在一定程度上改善含硫钢中夹杂物的形态。     

镁处理对低碳微合金钢中夹杂物和凝固组织的影响

以低碳微合金钢HR60为研究对象,探讨了镁处理对钢中夹杂物变性以及凝固组织的改善作用。研究得到如下结论:镁处理对车轮钢中Al_2O_3具有显著的变质作用,当钢中Mg质量分数为0.002 6%时,夹杂物变质充分,基准钢中Al_2O_3+Mn S夹杂物变质为Mg O·Al_2O_3+Mn S或Mg O·Al_2O_3+Mn S+(Ti,Nb)(C,N)夹杂物;镁处理后钢中夹杂物平均粒径减小,数量显著增多,尺寸小于2μm的夹杂物数量占60%以上,细小夹杂物在钢中呈弥散分布;试验钢经过镁处理后,铸态组织由"多边形铁素体+珠光体"演变为"多边形铁素体+珠光体+针状铁素体"混合组织,针状组织在一定程度上细化了凝固组织;理论计算表明,降低钢液与夹杂物之间的界面能,减小夹杂物与钢液之间的润湿角(θ),是镁处理钢中夹杂物细化的重要原因。     

耐蚀合金中TiN析出机制

摘要：TiN颗粒尺寸及其分布对耐蚀合金性能有明显的影响，因此有必要对TiN在铸坯中的分布及其析出行为进行研究。采用扫描电镜(SEM)、金相显微镜（OM）观察了TiN夹杂物在铸坯中的分布、尺寸及其形貌；基于热力学和动力学理论分析了耐蚀合金铸坯中TiN夹杂物的析出时机及其尺寸，结合试验结果和理论计算明确了TiN夹杂物在凝固后铸坯中的位置和尺寸与析出时机的关系，为控制TiN夹杂物提供理论指导。结果表明，冶炼过程中析出的TiN夹杂物尺寸较大，在凝固过程中被枝晶吞没，位于铸坯枝晶内和等轴晶内；微观偏析计算结果表明，在凝固分数为0.55时，TiN开始析出，最开始析出TiN夹杂物的逐渐长大，长大后的TiN易于被二次枝晶吞没，最终位于铸坯中的枝晶间和等轴晶内，后期析出的TiN则在枝晶间和等轴晶间。固相中析出的TiN夹杂物长大较慢，尺寸细小，最终位于奥氏体晶界。     

Mg对M2高速工具钢中碳化物的影响

摘要：在实验室条件下，向M2高速钢中加入Ni-Mg合金，对M2高速钢进行变质处理，研究其对高速钢一次碳化物的影响。采用电感耦合等离子体原子发射光谱法检测高速钢中的Mg含量，采取电解萃取的方法分析碳化物类型及相对含量的变化，在SEM-EDS扫描电镜下观察碳化物分布、尺寸、形貌的变化。结果表明，向M2高速钢中加入Mg能降低二次枝晶间距，细化碳化物的尺寸。Mg细化碳化物的效果随Mg含量的变化而变化。当Mg质量分数为8×10-6时效果最好，之后随着Mg含量的上升，效果变差。微量Mg细化碳化物的原因是Mg会向晶界偏聚，阻碍合金元素的扩散，从而抑制了碳化物的长大；同时Mg能对高速钢中的夹杂物改性，形成的大量细小、弥散的含Mg夹杂物可以诱导碳化物的析出，从而达到细化碳化物尺寸的效果。     

微量稀土元素对奥氏体不锈钢21-4N显微组织及碳化物的影响

通过对21-4N钢添加微量稀土Ce元素,分析不同Ce含量对21-4N钢铸态、锻态下的显微组织的影响。结果表明:适量稀土Ce元素的加入,可以显著细化铸态树枝晶间距、"类珠光体"团及一次碳化物M_7C_3,改善铸态"类珠光体"形貌,减少一次碳化物数量;显著细化锻态奥氏体晶粒尺寸。当Ce含量过高,铸态"类珠光体"团粗化、一次碳化物数量增加;锻态奥氏体粗化。Ce元素含量0.011%≤w(Ce)≤0.015%时,21-4N钢的铸态"类珠光体"团尺寸小、形状球化,一次碳化物细小且数量增加;锻态奥氏体晶粒细小。     

GCr15轴承钢凝固过程组分变化对夹杂物析出的热力学研究

基于Fact Sage热力学软件的最小吉布斯自由能原理,研究了不同[Ca]、[Mg]、[Al]、[O]含量条件下GCr15轴承钢凝固过程中夹杂物的析出行为。结果表明:随着[Ca]含量由0.000 5%增加至0.004 5%,轴承钢中析出的夹杂物类型由Ca O·2Mg O·8Al_2O_3、Ca O·2Al_2O_3向2Ca O·Si O_2、Ca S转变,钢中夹杂物总质量分数由约0.004 5%增加到约0.009 4%。随着[Mg]含量从0.000 1%增加到0.000 9%,钢中析出的夹杂物由Ca O·Al_2O_3、2Ca O·Si O_2向Mg O·Al_2O_3和Ca S转变,钢中夹杂物总质量分数由约0.003 2%增加到约0.004 1%;[Al]含量由0.005%增加至0.05%时,钢中析出的夹杂物类型由2Ca O·Si O_2向Ca O·Al_2O_3、Ca O·2Al_2O_3转变,夹杂物总量由0.002 8%增加至0.003 3%,变化相对不明显;随着[O]含量由0.000 3%增加至0.002 1%,钢中析出的夹杂物类型由Ca S向Ca O·Al_2O_3、Ca O·2Al_2O_3转变,夹杂物析出量由0.002 4%增加到约0.005 1%。     

T1铸造高速钢的变质研究

Ｔ１铸造高速钢的变质研究ＭｉｎＬａｏｊｕｎ等铸造钨高速工具钢的组织和性能可通过加入能形成弥散初生碳化物的添加合金元素来变质，弥散碳化物使钢的硬度提高，并且细化铸态组织中粗的枝晶，铌或追加机与所需要的定比碳一起产生这种细化效果，原因是凝固时产生高温晶核...     

CSP生产线生产Ti微合金化高强耐候钢铸态组织研究

对CSP生产的Ti微合金化高强耐候钢的铸坯组织、化学成分偏析、枝晶间距、夹杂物进行研究,结果表明,CSP生产的Ti微合金化高强耐候钢铸坯的低倍组织在结构上和传统板坯及CSP生产的普通集装箱铸坯相差不大,但高强耐候钢铸坯组织更为细密,一次枝晶间距、二次枝晶间距较普通集装箱铸坯稍小.铸坯中偏析较严重的元素是C、S、P,其它元素偏析较轻.铸坯中大颗粒夹杂物较少,主要是Al、Ti、Ca、S类夹杂物,由于Ti、Ca、S含量较少,夹杂物含量较低.而通过对Al类夹杂物进行分析,发现Al类夹杂物在连铸坯横截面上均匀分布,没有明显的偏聚,夹杂物含量在0.001 4%～0.002 2%波动,符合夹杂物存在特性,波动幅度在正常范围内,铸坯中Al夹杂物大部分粒度在2.5 μm以下.     

铸型温度对单晶高温合金叶片凝固组织的影响

在高温度梯度真空定向凝固炉中,采用螺旋选晶法通过3种不同铸型温度分别制备了[001]取向的DD6单晶高温合金叶片,利用光学显微镜和扫描电镜观察了不同工艺条件下合金的铸态组织,研究了铸型温度对单晶高温合金凝固组织的影响。结果表明,随着铸型温度的升高,合金的一次枝晶间距和二次枝晶间距变小,合金元素的偏析程度降低,枝晶干和枝晶间的铸态γ′相尺寸减小,共晶的尺寸和含量稍有减小,显微疏松的尺寸和体积分数稍有减小。     

55SiMnVB连铸坯的凝固组织与质量

分析了５５ＳｉＭｎＶＢ弹簧钢铸坯的凝固组织，测定了树枝晶二次枝晶臂间距，同时对铸坯中的非金属夹杂物了金相形貌的观察与复写，结果表明，５５ＳｉＭｎＶＢ弹簧钢铸坯的凝固组织较疏轻，二次枝晶臂间距较一般合金结构钢小（１００～２５０μｍ）；激冷层较薄（６～８ｍｍ）；中心等轴晶率低（２０％～２６％），铸坯夹杂物含量偏高（０．７１％～１．２８％），降低钢液过热度和提高凝固末端电磁搅拌强度，对减轻偏析，提高中心     

Ce/Mg处理对M50轴承钢洁净度的影响

采用真空感应熔炼工艺冶炼航空轴承钢M50,对比分析了Ce处理、Mg处理和Ce–Mg复合处理对氧、硫含量和夹杂物分布特征的影响,结合热力学计算,阐明了加入Ce、Mg元素对钢液洁净度的影响机理。研究发现,Ce具有很强的脱氧、脱硫能力,加入Ce会优先生成Ce₂O₂S夹杂物,随着钢液中氧含量的降低,Ce还会与As等有害杂质元素结合,起到净化钢液的效果。过量的Ce会加剧其与镁铝尖晶石材质耐火材料的反应,导致钢中夹杂物数量的增加,Ce的质量分数为0.018%时,钢中夹杂物的尺寸和数量最小;添加Mg不仅可以脱氧、脱硫,还可以抑制Ce与镁铝尖晶石耐材的反应,Ce–Mg复合处理可以显著降低钢中的夹杂物的尺寸和数量,将钢中的氧的质量分数降低至0.00075%。      

Microstructure, tensile and creep properties of as-cast Mg-3.8Zn-2.2Ca-xCe（x=0, 0.5,1 and 2 wt.%） magnesium alloys

The microstructure and mechanical properties of as-cast Mg-3.8Zn-2.2Ca alloy with different Ce contents were investigated by both optical and electron microscopy, X-ray diffraction, differential scanning calorimetry analysis, tensile and creep tests. The results indi-cated that adding 0.41 wt.%-1.83 wt.% Ce could refine the grains of the alloy, and the grain size gradually decreased as the Ce content in-creased. Furthermore, addition of either 0.41 wt.% or 0.89 wt.% Ce caused the morphology of the Ca2Mg6Zn3 phase to change partially from semi-continuous block to discrete fine particles. However, after adding 1.83 wt.% Ce, portions of the Ca2Mg6Zn3 and Mg12Ce phases were mixed and this Ca2Mg6Zn3+Mg12Ce eutectic changed to a different coarse semi-continuous morphology. In addition, addition of 0.41 wt.%-1.83 wt.% Ce improved the tensile and creep properties of the alloy. Amongst these Ce-containing alloys, the alloy with 0.89 wt.% Ce exhibited the best ultimate tensile strength and elongation while the alloy with 1.83 wt.% Ce had the best yield strength and creep properties.     

Effect of cerium on the cleanliness of spring steel used in fastener of high-speed railway

The effects of Ce addition on the quantity, size, distribution of inclusions and the content of oxygen, sulfur and other hazardous residual elements in spring steel used as fastener in high speed railway were investigated by metallographic examination, SEM-EDS and composition analysis. The results indicated that the contents of oxygen decreased with the addition of Ce([Ce]0.1%) and the content of sulfur continually decreased with increasing content of Ce([Ce]1.2%). However, with the further increase of Ce element addition, the content of [O] and T[O] began to increase. The content of Ce corresponding to the lowest [O] and T[O] lied in the range of 0.10%–0.13% and 0.045%–0.065%, respectively. The addition of Ce in spring steel resulted in the formation of rare earth oxides/oxysulfides and decreased the size of inclusions to less than 3 μm in globular or spheroid shape. Moreover, the residual harmful elements(As, P, Pb and Sn) were found to exist in the Ce-containing inclusions, which had proved that the Ce addition could capture the residual elements and suppress their precipitation behaviors in the grain boundary.     

Ce对440C不锈轴承钢夹杂物演变的影响

为探究稀土Ce对440C不锈轴承钢中夹杂物的改性作用,利用实验室MoSi₂电阻炉对440C不锈轴承钢进行稀土Ce处理,采用OM、SEM等系统分析了Ce的添加对440C不锈轴承钢脱氧及夹杂物演变的影响。结果表明,随着Ce加入量的增加,其收得率逐渐升高。Ce的加入使钢中TO质量分数由0.002 5%降低至0.001 2%。未加入Ce的钢中夹杂物主要为Al₂O₃、MnS以及镁铝尖晶石;加入质量分数为0.011 5%的Ce后,夹杂物被改性为以Ce-Al-O为主的夹杂物;当Ce的添加量达到0.036 4%时,夹杂物被完全改性为Ce-O-S夹杂物。适量的Ce可以降低夹杂物尺寸及面积比例,但过量加入会使夹杂物尺寸变大。在本试验条件下,当Ce质量分数为0.011 5%时,钢中夹杂物细小弥散效果最明显。以上结论可为Ce在高碳铬不锈轴承钢中的应用提供参考。     

Evolution of inclusions and change of as-cast microstructure with Mg addition in high carbon and high chromium die steel

The effects of Mg on the inclusions and the as-cast microstructure of high carbon and high chromium die steel, a grade of cold working die steel with high C content of 1.4–1.6% and high Cr content of 11.0–13.0%, were systematically investigated. It is found that inclusions vary with the route as Al₂O₃ (No Mg) to MgO·Al₂O₃ +?Al₂O₃ (5?ppm Mg), and then to MgO+MgO·Al₂O₃ (11 and 15?ppm Mg). The average diameter of the inclusions decreased from 1.91 μm (no Mg) to 1.29 μm (15?ppm Mg), while the number density increased from 2.69?×?10⁴ mm^??3 (no Mg) to ～5.62?×?10⁴ mm^??3 (15?ppm Mg). The changes in the size and the number density were discussed in terms of the effect of inclusions on the nucleation process and the wettability of them with steel melt. The as-cast microstructures were greatly refined with Mg addition that correlated with the evenly dispersed fine Mg containing inclusions.     

镁对低碳铝镇静钢SPHC中夹杂物变性的影响

运用热力学计算分析了镁对SPHC钢(0.065%C、0.025%Al)中夹杂物的作用,并结合80 t顶底复吹转炉流程工业试验,研究镁对SPHC钢中夹杂物的影响机理。热力学计算结果证明,当[Al]²/a_[Mg]³≤7.69×10¹⁰,钢中就会生成单独的MgO·Al₂O₃;对SPHC钢进行喂0.875 kg/t镁线的工业试验结果表明,镁处理可细化夹杂,使团簇状Al₂O₃变为细小的MgO·Al₂O₃夹杂,MnS夹杂也得到了变性,夹杂物数量减少,提高了钢液的纯净度。     

铈对S32550双相不锈钢微观组织及冲击性能的影响

 双相不锈钢兼具奥氏体和铁素体不锈钢的优良性能,多用于船舶、化工、核反应等领域。为了进一步提高S32550双相不锈钢的力学性能和抗腐蚀性能,采用真空感应炉成功冶炼了S32550双相不锈钢,并研究了有无添加稀土铈对其锻造、轧制后的微观组织、夹杂物形貌及冲击性能的影响。结果表明,添加稀土铈可以细化组织晶粒,使形状分布不均匀的铁素体组织与奥氏体组织均匀化;改善夹杂物形貌分布大小,对有害夹杂MnS进行改质,降低硫含量,使多余硫元素与铈反应形成Ce₂O₂S、Ce₂S₂夹杂弥散分布在钢中;另外,添加稀土铈可以提高S32550双相不锈钢在室温和低温(-40、-20 ℃)下的冲击韧性,在低温下可出现韧窝带,降低冷脆效应对钢材的危害。     

A Coupled Thermodynamic Model for Prediction of Inclusions Precipitation during Solidification of Heat-resistant Steel Containing Cerium

A coupled thermodynamic model of inclusions precipitation both in liquid and solid phase and microsegregation of solute elements during solidification of heat-resistant steel containing cerium was established.Then the model was validated by the SEM analysis of the industrial products.The type and amount of inclusions in solidification structure of 253 MA heat-resistant steel were predicted by the model,and the valuable results for the inclusions controlling in 253 MA steel were obtained.When the cerium addition increases,the types of inclusions transform from SiO2 and MnS to Ce2O3 and Ce2O2S in 253 MA steel and the precipitation temperature of SiO2 and MnS decreases.The inclusions CeS and CeN convert to Ce2O3 and Ce2O2S as the oxygen content increases and Ce2O3 and CeN convert to Ce2O2 S,Ce3S4,and MnS as the sulfur content increases.The formation temperature of SiO2 increases when the oxygen content increases and the MnS precipitation temperature increases when the sulfur content increases.There is only a small quantity of inclusions containing cerium in 253 MA steel with high cleanliness,i.e.,low oxygen and sulfur contents.By contrast,a mass of SiO2,MnS and Ce2O2 S are formed in steel when the oxygen and sulfur contents are high enough.The condition that MnS precipitates in 253 MA steel is 1.2 w[O]+w[S]0.01%and SiO2 precipitates when 2 w[O]+w[S]0.017%(w[S]0.005%)and w[O]0.006%(w[S]0.005%).