机械轴承钢的热处理和摩擦学性能研究

对机械轴承用高硫钢进行了淬火与回火处理,研究了热处理过程中硫化物的存在形式及转变特征,并分析了热处理工艺对高硫轴承钢的摩擦学性能的影响。结果表明,860℃淬火+200℃回火后的高硫钢种的硫化物分布最为均匀弥散,且硫化物形态主要以类球状和纺锤状为主,尺寸也相对均匀;经过860℃淬火+200℃回火后的高硫钢的摩擦学性能最好。     

真空碳脱氧对非金属夹杂物的影响

非金属夹杂物对电站转子锻件的质量产生重大的影响。多年来,它是不允许用碱性平炉冶炼这一类高级优质合金钢的主要原因。本文在真空碳脱氧碱性平炉转子钢的试验中,就非金属夹杂物的特性,分析了真空碳脱氧这一新的工艺对转子锻件中非金属夹杂物的影响。分析结果表明,经真空碳脱氧处理后,非金属夹杂物含量下降56％,同通常作为生产电站转子锻件的主要冶炼设备——酸性平炉冶炼、大气浇注的转子钢相比,平均低77％,比真空浇注的低27％。夹杂物的颗粒更加细小,颗粒度更均匀。尤其是经过真空碳脱氧处理后,转子锻件中的硫化物,由酸性平炉的条状、线状,改变为球状或纺锤形。分析了硫化物形态变化的原因,揭示了真空碳脱氧以改善转子锻件质量(尤其是横向冲击韧性)的实质。     

无取向硅钢中硫化物的析出机理

结合无取向硅钢中硫化物的析出热力学、动力学计算和扫描电镜(SEM)、透射电镜(TEM)检测,系统研究了硫化物在无取向硅钢中的析出机理,并讨论了硫化物对退火过程中晶粒长大的影响.结果表明,无取向硅钢中硫化物以(Mn,Cu)S复合析出相为主.在凝固过程中,MnS和Cu2 S均不具备析出热力学条件.MnS先于Cu2 S在晶界形核,随着温度的降低将以位错形核为主.在均热过程中,w(Si+Al)≥2.5％的无取向硅钢中的MnS和w(Si+Al)≤1.6％的无取向电工钢中的Cu2 S主要在晶界形核.同时,均热过程中MnS在晶界的析出量远大于Cu2 S,Cu2 S主要在后续的热处理过程中析出.MnS和Cu2 S的Ostwald熟化研究表明,w(Si+Al)≥2.5％无取向硅钢中的MnS和Cu2 S对晶粒长大的影响明显大于w(Si+Al)≤1.6％无取向电工钢.     

Ti-Mg-Al复合脱氧X70级抗酸海底管线钢氢捕获效率及HIC敏感性

采用NACE TM 0284-2016标准评估了一系列不同Al含量的Ti-Mg-Al复合脱氧X70级别抗酸海底管线试验钢的氢致开裂(HIC)敏感性,并通过测量氢扩散通量(J∞L)和有效氢扩散系数(Deff)研究了其氢捕获及扩散动力学行为.结果表明:Al的添加因能促进针状铁素体形成而显著提高试验钢的抗拉强度;随着Al含量增加,试验钢中的夹杂物不仅数量增加,成分也发生变化,由以均匀分布的单一Mn-S和Al-Ti-Mg-O-Mn-S复合夹杂物为主转向以带状分布的单一Al-O夹杂和Al-Ti-O-Mn-S型复合夹杂为主;当Al含量增加至0.03％时,试验钢的屈服强度降低,且[H]容易在脆性Al2 O3夹杂物周围引发内部微裂纹,并产生表面氢鼓泡.Al的添加主要是通过影响钢中非金属夹杂物的特性,从而改变氢在钢中的捕获和扩散动力学行为,进而影响钢的HIC敏感性.在本实验范围内,Al的添加量不宜超过0.03％.     

纯Al及Al-Mn合金中球状稀土相的形成

本文测定了含稀土纯 Al 及 Al-Mn 合金中球状稀土相的形貌,组成及分布。结果表明,适量稀土可使 Al 中多角形块状化合物球化,在轧制过程中球状稀土相不变形,不聚集,均匀分布在晶内。稀土改变了 Al 基体中杂质元素的微区分布规律,导致 Fe,Si 等元素由晶界向球状相迁移,晶界获得净化。分析了球状稀土相形成及晶界净化的原因。     

重力对镍基单晶高温合金枝晶生长和微观偏析的影响

使用长50 m的落管研究Ni-Cr-Al-W-Ta镍基单晶高温合金在重力(1g)和微重力(μg)条件下的凝固行为。用金相显微镜(OM)观察合金的凝固组织并用图像分析软件测量和统计一次和二次枝晶间距,使用扫描电镜能谱(SEM-EDS)测定不同位置枝晶干与枝晶间的化学成分并计算微观偏析系数。结果表明,在重力和微重力条件下这种合金的枝晶特征和合金元素的微观偏析明显不同。重力样品一次和二次枝晶间距比微重力样品的大,随着凝固距离的增大一次枝晶间距的差异变大,而二次枝晶间距的差距变化不大。随着凝固的进行,微重力样品枝晶间Ta、Cr和Al元素的含量呈现先明显升高后略微降低的趋势,W元素含量呈现逐渐下降的趋势,枝晶间液相的密度呈现略微降低的趋势。重力样品枝晶间Ta、Cr和Al元素含量的分布趋势与微重力样品基本相似,W元素含量的分布则与微重力样品明显不同,大部分凝固阶段呈上升趋势,使枝晶间液相的密度沿逆重力方向提高。上述结果表明,在重力条件下凝固前沿溶质密度差导致的对流作用微弱,不是造成枝晶间距增加的主要原因,主要原因应该与凝固前沿热对流造成的温度梯度的降低有关。     

DSC中样品皿技术问题

以快速凝固Al—Mn合金样品为例,说明了DSC中样品用皿的一些技术问题;尤其是常被人们忽略的样品与铜皿间的反应问题,并介绍了一种简便易行且行之有效的解决方法。     

Ti对金红石型药芯焊丝熔敷金属组织性能影响

以金红石型药芯焊丝为基础,通过在焊丝中加入不同含量的钛铁,研究了Ti对熔敷金属组织及力学性能的影响。结果表明,随焊丝钛含量的增加,脱氧方式从Ti、Si、Mn联合脱氧逐渐转为以Ti脱氧为主,且熔敷金属中夹杂物的Ti含量逐渐增大,同时熔敷金属中合金元素含量增加,屈服强度逐渐趋近抗拉强度,塑性变差。组织分析发现,以复合氧化物形式存在的化合钛对针状铁素体的形成有促进作用,以合金元素形式存在的固溶钛对针状铁素体的形成有抑制作用。     

Al含量对Zn-xAl-4Sb合金平衡凝固组织的影响

利用SEM、EDS、XRD研究了不同Al含量的Zn-xAl-4Sb(x=0、0.5、1.0、2.0、4.0、6.0)合金在炉冷条件下(冷却速度0.04℃/s)的凝固组织,探讨了Al和Sb以Zn-Al-Sb三元中间合金加入锌液的可能性.结果表明:合金中的Al优先与Sb生成AlSb相;当Al含量小于1.0%时,随着Al含量的增加,合金中AlSb相的量增加,β-Sb3Zn4相逐渐减少;当Al含量为1.0%时,β-Sb3Zn4相消失,合金组织为Zn基体上分布AlSb相;当Al含量大于1.0%时,合金中出现Zn-Al共晶,且共晶的量随Al含量的增加而增多;用Zn-Al-Sb室温下等温截面的富锌角表示了Zn-xAl-4Sb体系的室温相组成.因Al和Sb形成高熔点AlSb相,很难在锌液中溶解,故Al和Sb不宜以Zn-Al-Sb三元中间合金的方式加入.     

原位生成Al(OH)_3凝固天然橡胶的性能研究

将AlCl3与氨水溶液添加到天然胶乳中原位生成Al(OH)3凝固天然橡胶,通过扫描电镜观察Al(OH)3在橡胶中的分布情况并研究了不同Al(OH)3含量对天然橡胶硫化性能、物理力学性能及热稳定性的影响。结果表明,Al(OH)3对天然橡胶的硫化性能影响较大,且能提高天然橡胶的成炭率,反应生成量为15份Al(OH)3时其分散均匀且所得的胶料的性能优异。     

Microstructural evolution and solidification cracking susceptibility of Fe–18Mn–0.6C–xAl steel welds

In this work, the solidification behavior and solidification cracking of Fe–18Mn–0.6C–xAl (x = 1.49, 2.37, 4.79, 6.04 wt%) alloys were investigated. A longitudinal Varestraint test was applied to evaluate the solidification cracking tendency of Al-added high-Mn steel welds. In terms of total crack length and maximum crack length at 4 % applied strain, the solidification cracking susceptibility of high-Mn steel decreased with increasing Al content. Addition of Al suppressed the formation of low melting point eutectics (γ + (Fe,Mn)₃C) along the grain boundaries during the final stage of solidification, which resulted in the decrease of solidification cracking tendency. The Al segregated extensively to the dendrite core opposite to Mn and C during solidification, which promoted the formation of δ ferrite. Further, the transition of the solidification sequence from the primary austenitic to primary ferritic mode provided a noticeable improvement in solidification cracking resistance in high-Mn steel welds similar to austenitic stainless steel welds.     

Interfacial structure of steel–aluminum bonding plate under non–equilibrium rapid solidification

A steel–aluminum solid–liquid bonding plate is prepared using a non–equilibrium rapid solidification method (including four kinds of processes such as roughening the steel plate surface, immersing influx at the steel plate surface, short–time bonding and rapid solidification). The interfacial structure of the bonding plate is investigated by means of electron probe microanalysis and X–ray diffraction. The results show that the interfacial structure of the bondingplate under non–equilibrium rapid solidiication is quite different from that of the bonding plate in conventional steel–aluminum solid–liquid bonding, i.e. the interface of the bonding plate under non-equilibrium rapid solidification ismade up of an aluminum-rich region (in the form of a group of Fe₄Al₁₃ teeth that grow from the contact surface to the steel side) at the bulge of steel plate surface and an aluminum–poor region (in the form of Fe–Al solid solution of which the Al content is less than 3.5 wt%) at the concave surface of the steel plate alternately.     

Interfacial structure of steel–aluminum bonding plate under non-equilibrium rapid solidification

A steel–aluminum solid–liquid bonding plate is prepared using a non-equilibrium rapid solidification method (including four kinds of processes such as roughening the steel plate surface, immersing in flux at the steel plate surface, short-time bonding and rapid solidification). The interfacial structure of the bonding plate is investigated by means of electron probe microanalysis and X-ray diffraction. The results show that the interfacial structure of the bonding plate under non-equilibrium rapid solidification is quite different from that of the bonding plate in conventional steel–aluminum solid–liquid bonding, i.e. the interface of the bonding plate under non-equilibrium rapid solidification is made up of an aluminum-rich region (in the form of a group of Fe₄Al₁₃ teeth that grow from the contact surface to the steel side) at the bulge of steel plate surface and an aluminum-poor region (in the form of Fe–Al solid solution of which the Al content is less than 3.5 wt%) at the concave surface of the steel plate alternately.     

Thermal analysis and solidification pathways of Mg–Al–Ca system alloys

Mg–Al–Ca alloys are creep resistant magnesium alloys with high application potentials. The solidification pathways and microstructure formation in this alloy system are still under discussion. In this paper, the solidification behavior of AZ91 and AM50 with Ca addition (AZC91x and AMC50x alloys) was investigated by a computer-aided cooling curve analysis (CA-CCA) system. Microstructure and phase identification were carried out by SEM and EDX analysis. The results show that the Ca-containing phase formation mainly depends on Ca content and Ca/Al ratio. With increasing the Ca/Al ratio these phases transform from Al₂Ca to (Mg, Al)₂Ca and Mg₂Ca. Moreover, Ca addition decreases the liquidus temperature of Mg–Al alloys, but influences the solidus temperature in a more complex way. Increasing the Ca content also decreases the solid fraction at which dendrite coherency occurs. The relationship between solidification interval, dendrite coherency point, formation of Ca-containing phases and hot tearing is also discussed.     

Inclusion Modification with Mg Treatment for 35CrNi3MoV Steel

The effects of Mg on the inclusion characteristics of 35CrNi3MoV steel have been studied. The results show that Mg treatment reduces obviously the amount of inclusion in the steel.Magnesiurn and oxygen in liquid steel form dispersed fine particles of MgO, to which other oxides or sulphides nucleated at heterogeneity and grown during solidification. In this way the inclusions are modified. The small spherical inclusions containing MgO have been observed in the Mg treated steel in contrast to the large angular inclusions with Al2O3 in the conventional steel. Especially the elongated MnS inclusion is replaced by small MgS·MgO or MgS. MnS·MgO complex inclusion. The formation of inclusions have been discussed.     

Mechanisms of inclusion formation in low alloy steels deoxidised with titanium

Abstract

In the present investigation, the conditions for inclusion formation in two Ti deoxidised steels and one Al–Ca deoxidised steel have been examined by means of optical and electron microscopy, in combination with a thermo dynamic analysis of the phase relations involved. It is concluded that the Ti containing inclusions form as a result of a series of reactions occurring in the ladle, during solidification and in the solid state. The important solid state reaction products are MnS, TiN, and MnOTiO₂ . The presence of Mn rich compounds at the surface of the inclusions is consistent with the observation of a Mn depleted zone in the surrounding steel matrix. In contrast, the primary inclusions in the Al–Ca deoxidised steel are complex oxysulphides, which are thermodynamically more stable and can therefore form in the liquid state.     

Solidification Studies of 3003 Aluminium Alloys with Cu and Zr Additions

The effects of Cu and Zr additions, on the microstructure formation, precipitation and ingot cracking, in commercial 3003 Al alloys have been studied. The investigation was carried out by characterizing the grain structure in DC-cast rolling ingots, and studying the solidification microstructure of Bridgman directionally solidified samples. To better understand the influence of the different Cu and Zr contents on the phase precipitations, differential thermal analysis (DTA) experiments were performed. Results from the ingot microstructure analysis show that in commercial alloys with relatively high contents of Cu and Zr, no significant differences in measured grain sizes compared to conventional 3003 Al alloys could be found. However, only Zr containing alloys exhibited significantly larger grain sizes. Increased grain refiner and/or titanium additions could compensate for the negative effects on nucleation normally following Zr alloying. Different types of precipitates were observed. Based on DTA experiments, increased Cu and Zr contents resulted in the formation of Al2Cu phase, and increased solidification range. It was also found that increased Mn content favors an early precipitation of Al6(Mn,Fe) giving relatively coarse precipitates. It was concluded that the Cu alloying has a detrimental effect on hot tearing.     

Al对M2高速钢凝固过程的作用

研究了Ａｌ在Ｍ２高速钢凝固过程中的行为及其对凝固组织的影响。结果表明，Ａｌ具有扩大δ铁素体区，促进以柱状树权晶方式结晶的作用；在Ａｌ在Ｍ２钢中呈负偏析分布，并参与形成Ｍ２Ｃ共晶耐碳化物。     

CSP生产低碳钢的组织演变和析出物研究

为了阐明EAF-LF-CSP工艺生产的低碳钢组织细化机理,在薄板坯和不同道次变形后的同一轧件上取样,利用金相、SEM、TEM、XEDS等技术研究了连轧过程中显微组织演变和钢中第二相析出物.结果表明:与普通连铸板坯相比薄板坯的凝固组织更加细小;随轧制道次增加,薄板坯表面和心部的组织差异逐渐减小,轧后室温组织细化;CSP生产的低碳钢中存在大量纳米尺寸的氧化物和硫化物,起到细化晶粒的作用.CSP生产中采用快速冷却和凝固工艺、单道次大压下连轧工艺和层流冷却工艺,是成品组织细化的主要原因.     

Removal of malodorous organic sulfides with molecular oxygen and visible light over metal phthalocyanine

Organic sulfides are malodorous compounds in environment. In this work, deodorization of model substrates, methyl phenyl sulfide, 2-mercaptobenzoic acid and benzyl 2-propenyl sulfide, have been studied in an aerated methanolic aqueous solution under visible light irradiation (lambda>450nm), using metal phthalocyanine sulfonate (MPcS, M=Al, Pd) as a photocatalyst. The result shows that all the representative sulfides could be efficiently oxidized, with concomitant formation of sulfoxide and sulfone as the main products. Kinetic study using sodium azide and benzoquinone as reactive species scavenger reveals that the sulfide oxidation is mainly initiated by singlet oxygen. It is also observed that the rate of sulfide oxidation increases with increasing the water content in the mixed solvent. Recycle experiments with immobilized PdPcS on organoclay or immobilized AlPcS on anionic resin demonstrates that the sensitizer could be repeatedly used, without significant loss in the photosensitization activity.