高炉钛矿护炉的机理研究

从热力学和热模拟试验两方面研究了碳饱和铁浴内Ti(C,N)的生成机理.利用CONFOCAL激光高温显微镜的试验数据重新确定了Ti在碳饱和铁浴内的溶解度和Ti(C,N)形成所需的最低Ti含量.结果表明在碳饱和铁浴内生成碳化钛和氮化钛的最低Ti含量较采用现行热力学数据的计算值要低.采用长坩埚法研究了不同温度梯度条件下Ti(C,N)的形成,发现Ti(C,N)在温度梯度较大的耐火材料和铁水界面有团聚行为.     

碳热还原法制备Ti(C,N)粉末

研究了用淀粉作为碳源还原氢化钛制备碳氮化钛纳米粉的工艺及利用热力学计算分析了反应机理。结果表明 :在实验范围内 ,降低合成温度、缩短保温时间或提高氮气流量有利于形成氮含量高的碳氮化钛粉末。通过控制合成温度和保温时间 ,可以控制Ti(C1 -xNx)中的碳氮比 ,得到不同x值的碳氮化钛粉末。实验结果与理论计算相一致     

高炉钛矿护炉的机理研究

用钛矿进行护炉操作已是高炉操作者常用的护炉方法。遗憾的是 ,使用钛矿护矿的机理直到现在还不是很清楚。现有的对一代退役炉缸进行的剖析研究结果表明 :当使用钛矿护炉时 ,Ｔｉ(Ｃ ,Ｎ)将在炉缸铁浴内形成并沉积于炉缸受侵蚀部位的工作面或砖缝之中 ,并认为Ｔｉ(Ｃ ,Ｎ)的沉积和团聚物起到了保护炉缸的作用。但现有的研究对Ｔｉ(Ｃ ,Ｎ)究竟在什么样的条件下形成和析出、Ｔｉ(Ｃ ,Ｎ)为什么会在侵蚀热点部位团聚的行为不太清楚。本研究从热力学和热模拟试验两方面研究了碳饱和铁浴内Ｔｉ(Ｃ ,Ｎ)的生成机理。利用ＣＯＮＦＯＣＡＬ激光高温…     

用磁选的方法从含钛高炉渣中回收碳氮化钛

采用冶炼钒钛磁铁矿产生的含TiO2 20%～26%的高炉渣为原料,通过对渣中的钛氧化物进行还原碳化和氮化处理生成碳氮化钛后,利用铁作为载体,用磁选的方法实现碳氮化钛和脉石矿物的分离.磁选后获得Ti(C,N)品位大于36.46%,回收率达到43.77%的碳氮化钛精矿.     

高炉中析出Ti(C,N)的热力学探讨

由热力学计算结果分析了高炉冶炼含TiO_2铁矿时钛的物理化学行为,指出:有固体碳存在的,渣—铁界面不可能有纯TiN生成,析出的固体应该是Ti(C,N),其中TiN含量随着渣—铁界面处氮分压值的增加而增加。当高炉渣含TiO_2为13—28％时,生铁含钛量主要受形成碳氮化钛的反应所控制,与渣中TiO_2含量无关,温度低,有利于限制Ti(C,N)的析出。“低硅钛”操作是合理的。     

从0.8米~3高炉解剖看钒钛烧结矿在高炉内还原过程及其渣铁形成特点

作者对钒钛烧结矿小高炉冶炼解剖试样,进行了工艺岩石学初探,提出了钒钛烧结矿在炉内还原相变历程图,研究了碳氮化钛生成机理和存在状态以及渣铁形成相变特点。指出了碳氮化钛主要在风口区渣焦接触反应生成,渣铁反应生成碳氮化钛是很次要的。渣中大量碳氮化钛固体微粒和铁珠吸附碳氮化钛包壳导致炉渣性能恶化、渣铁难分。因此,强化喷吹,改革炉型,提高炉缸氧住,消除碳氮化钛影响对强化钒钛矿高炉冶炼是很有意义的。     

钛微合金钢中碳氮化钛固溶量及化学组成的计算与分析

根据相关热力学理论,提出了钛微合金钢中钛、碳、氮元素在奥氏体中的平衡固溶量及平衡沉淀析出的碳氮化钛的化学式系数的理论计算方法,对典型化学成分的钛微合金钢进行了理论计算并对计算结果进行了分析.结果表明,通常情况下在较高温度析出或未溶的碳氮化钛相当接近于TiN.     

通过添加钛细化S45C钢铸态奥氏体显微组织

本文研究了添加钛对铸态奥氏体（γ）结构的影响,不添加钛的铸态γ结构由粗大柱状晶粒组成。添加钛可促使等轴γ-晶粒的形成,也能细化γ结构晶粒。仅当钛加入量介于0．13％-0．17％狭小范围时,方可形成全部等轴晶和非常细小γ-晶粒结构。相图热力学计算结果表明：在此组成范围内,碳氮化钛作为初晶相结晶,通过初始碳氮化钛微粒诱导在δ-枝晶凝固过程中,从柱状晶到等轴晶转变（CET）时形成非常细小的等轴γ-晶粒结构,这些微粒是等轴δ-枝晶形核场所。试验结果表明,细小碳氮化钛的存在可以阻止包晶转变后γ-相的晶粒长大,其可导致铸态γ-结构的细化。     

高钛渣提取碳氮化钛的研究

在热力学分析基础上,以攀钢高钛渣为基准配制的TiO2-CaO-SiO2-Sl2O3-MgO五元合成高钛渣为主要原料,采用碳热还原法制取碳氮化钛.确定了碳化处理过程中不同气氛(氩气,氮气)下的产物,采用X-射线衍射仪和扫描电镜研究了产物的相组成和显微结构,证实了在氩气气氛下,产物主要为TiC;在氮气气氛下,产物主要为Ti(C,N);氩气气氛下碳化钛的粒度比同一实验条件氮气气氛下碳氮化钛的粒度要小2～4μm.     

钛精矿碳热还原制备碳氮化钛的研究

以钛精矿和石墨为原料,在氮气气氛下通过碳热还原法制备出碳氮化钛(Ti CN)粉体。结合XRD、SEM、化学成分分析和TG-DSG综合热分析研究了配碳量及反应温度对钛精矿碳热还原进程的影响。研究结果表明,配碳量的增加影响逐级还原反应温度以及反应总失重,当配碳量达到23%时碳氮化钛产物中出现游离碳。钛精矿碳热还原过程中铁氧化物优先还原,钛氧化物经逐级还原形成Ti CN,还原顺序为Ti O2→Ti4O7→Ti3O5→Ti N→Ti(C,N,O)→Ti CN。得到的碳氮化钛粉体呈微米级不规则形状。     

碳饱和熔铁中Ti化合物析出规律的研究

利用过饱和析出法,研究了碳饱和熔铁中Ti与TiC、Ti(C,N)的平衡.结果表明,在铁液中与Ti(C,N)平衡的Ti含量远小于与TiC平衡的Ti含量;Ti的溶解度值与温度近似成线性正比关系,与N2分压成反比关系.对实验铁样进行电镜分析发现,Ti沉积物在坩埚底部和侧面较多,而铁液表层和中心部位较少,表明Ti化合物是以非均质形核晶体析出,相比较石墨质耐火材料更有利于Ti化合物的非均质形核.     

Analysis of titanium distribution behaviour in vanadium-containing titanomagnetite smelting blast furnace

The operating data of a commercial vanadium-containing titanomagnetite smelting blast furnace (BF) have been examined over a period of one year. The liquidus temperatures and viscosities of a large number of slags were calculated by using the software Multi-Phase Equilibrium. The results show that both the slag liquidus temperature and hot metal temperature of the BF were 60 K lower than that of conventional BF operation, while both slags had similar viscosity. The correlations between the Ti distribution of hot metal and slag and the operating temperature, and hot metal and slag chemistry were analysed. Ti distribution ratio increases with increasing temperature and carbon content in hot metal. The Ti distribution calculated based on a slag/hot metal equilibrium model gave reasonably good agreement with plant measurements. This suggests that the slag and hot metal phases were close to equilibrium in the furnace hearth. A sensitivity analysis showed that temperature and C content has a significant influence on the Ti distribution ratio. The effect of slag chemistry on the Ti distribution is insignificant. Lowering of the operating temperature and carbon in hot metal can help reducing the Ti distribution into the hot metal, hence reducing the formation of Ti(C,N).     

含钛高炉渣铁侵蚀炉衬的显微结构分析

对含钛高炉渣，铁显微结构的研究表明，攀钢高炉随冶炼强度的提高，炉渣组成发生变化，渣中TiC,TiN,Ti(C,N)含量减少，影响护炉效果，含钒钛的铁水中含有TiC,TiN,Ti(C,N),对护炉起着很大作用，因此钒钛矿护炉不单是含钛渣完成的，也有含钒钛铁水的作用。     

高炉炉缸富钛保护层的解剖分析

通过对长期加钛护炉高炉的炉缸进行解剖获得了富钛保护层的样品,并推测了富钛保护层在高炉中的形成过程。研究发现Ti(C, N)晶粒最初从铁水中析出,然后通过晶界迁移在炉渣中长大,最后Ti(C, N)晶粒与熔渣和铁水一起凝结形成保护层。此外,采用酸蚀法观察了Ti(C, N)晶粒的微观形貌,发现Ti(C, N)晶粒表面相对平整且具有大量环形层状结构,另外还有少量立方体式堆砌形式存在,Ti(C, N)晶粒内部并不致密。     

模拟复吹转炉脱钛预处理的理论和试验

 采用具备顶底复吹功能的500 kg感应炉模拟了转炉预脱钛工艺,分析了钛的氧化反应机理。试验结果表明：终点铁水钛质量分数平均为0.008 2%,脱钛率平均为71.3%。脱钛率随铁水温度升高而降低,随熔池供氧量增加而增加。铁水的终点钛质量分数与终点硅、锰质量分数存在平衡关系,与过程中碳的氧化没有相关性。渣铁间钛分配比为0.6～1.6,随渣中氧化亚铁质量分数的提高而提高,随铁水温度的升高而降低。试验结果和低温下有利于脱钛的理论分析一致。     

Precipitates in Steels With Ti Additive Produced by CSP Process

 Hot strips of low carbon steels with Ti additive [contain C 004%-007%, Si≤06%, Mn≤06%, Ti 006%-014% (mass percent)] produced by EAF CSP (Electric Arc Furnaces Compact Strip Production) process were examined by TEM, HREM and XRD. Carbonitrides with different N/C ratio were found in the samples. The varying composition of the Ti carbonitrides resulted from the supersaturation of Ti and temperature at which the compound was formed. In the tested steel, total mass fraction of the precipitates including cementite, carbonitride and a small quantity of Fe3O4, Al2O3, Ti2CS and AlN was about 0305%. XRD results showed that about a quarter of the powder extracted by electrolysis was titanium nitrides, carbonitrides and carbides. Particle arrays formed by interphase precipitation could be observed either in slabs or in hot strips. The dominant reaction mechanisms were discussed. Compared with the conventional cold charge process, small amount of Ti addition would be more effective for precipitation of fine precipitates in the steels produced by CSP process.     

Study on the interface of direct hot rolling titanium-clad steel plates

In this study,the interface characteristics of a direct hot rolling titanium-clad steel plate were analyzed,and the mechanism of interface cracking was explored.The detrimental effect from the formation of TiFe,TiC,and a Si-enriched layer on the bonding strength was clarified,and an industrial-scaled titanium-clad steel plate with shear strength over 200 MPa was produced with a carefully set schedule accordingly.It was found that hot rolling titanium-clad steel plates had a flat interface without obvious cracks.In the rolling process,both Ti and Fe atoms interdiffused,but Fe diffused much faster than Ti.The Fe-diffused area consisted of three regions.After a high temperature heat treatment,the diffusion depth of Fe and Ti elements increased significantly and evident Si segregation and TiFe layers were identified.Thermal cracking initiated in the Si segregation layer and then propagated along the TiFe layer and Fe-diffused layer on the titanium side.     

Relation between microstructure, composition, and hot cracking in Ti-stabilized austenitic stainless steel weldments

A stabilized, fully austenitic alloy D9, a 15Cr-15Ni-2Mo stainless steel with a titanium addition corresponding to UNS 38660, is a candidate material for the fuel-clad and wrapper applications of the Prototype Fast Breeder Reactor (PFBR). The fully austenitic microstructure and the presence of titanium in this alloy lead to high susceptibility to hot cracking during welding. The fusion-zone and the heat-affected zone (HAZ) cracking susceptibility of alloy D9 was studied at three titanium levels, 0.22, 0.32, and 0.42 pct, all other elements remaining constant. The longitudinal and transverse Varestraint (Transvarestraint) hot-cracking tests were used to evaluate fusion-zone and HAZ cracking. The results showed that titanium increases cracking in the fusion zone by 15 to 20 pct in the range of Ti levels studied. The microanalysis of fusion-zone hot cracks using electron probe microanalysis (EPMA) showed an enrichment of Ti, C, N, and S along cracks and in the interdendritic regions. The corresponding phases were identified as TiC, TiC_0.3N_0.7, and the carbosulfides Ti₂CS and Ti₄C₂S₂, which are believed to form eutectics with austenite to produce cracking. The amounts of these phases increased with increasing Ti content. In the HAZ, a similar relation between titanium level and cracking was found. The comparison of the weldability of the D9 with an FA mode type 321 revealed that Ti-bearing eutectics were responsible for a high degree of cracking irrespective of the solidification mode. The results show that in the D9, the ratio of Ti to C and N must be controlled to minimize cracking.     

氯化钠-硫氰酸钾-正丙醇体系析相萃取分离和富集钛

研究了正丙醇-硫氰酸钾-水体系析相萃取分离和富集Ti的行为及与一些金属离子分离的条件。结果表明, 氯化钠能使正丙醇的水溶液分成两相,在分相过程中, Ti和硫氢化钾生成的Ti(SCN)₆^2-与质子化正丙醇C₃H₇OH₂⁺ 形成的缔合物［Ti(SCN)₆^2-］［C₃H₇OH₂⁺］₂能被正丙醇相完全萃取。当正丙醇、硫氰酸钾和氯化钠的浓度分别为30%（V/V)、8.0×10^-2 mol/L和0.17 g/mL时, Ti的萃取率达到98.9%以上,V、Ce、Mg、Mn、Cd、Cr、Al、Fe、Zn、Ni、Ag 和 W不被萃取,实现了Ti与上述金属离子的分离。对合成水样中的钛进行分离和测定, 结果满意。