氮在Fe-Cr-V液态高氮合金中的溶解行为

 采用MgO坩埚高频真空/加压感应炉在氮气压力04~10 MPa、温度1 570~1 640 ℃下,对加压感应熔炼Fe Cr V系高氮不锈钢进行了实验研究。结果表明,在30CaO 45Al2O3 25SiO2渣覆盖的情况下,氮在Fe 15Cr 10V、Fe 18Cr 10V、Fe 18Cr 15V和Fe 20Cr 20V液态合金中的溶解度分别为0595%、0736%、0776%和1020%,溶解度与氮分压的关系基本符合Sievert定律。渣对钢液吸氮和铝脱氧都起重要的作用,1 873 K、10 MPa氮气氛中,在30CaO 45Al2O3 25SiO2、40CaO 40Al2O3 20SiO2、40CaO 50Al2O3 10SiO2三种不同渣系作用下氮在液态Fe 18Cr 15V中的浓度分别是0776%、0849%和0884%。     

基于铝热还原制备FeV50渣中钒的赋存状态

通过渣金V-O平衡及VO-Al平衡理论研究,分析了铝热还原FeV50合金制备过程不同冶炼阶段对渣中钒赋存状态的影响,计算得到钒在渣中的热力学还原极限。通过不同物相分析手段,得到铝热还原FeV50合金制备过程实际渣中钒的稳定结构。研究结果表明:渣金共存时渣中钒的稳态为VO;出渣后VO与V_2O_3的稳定性与冶炼氧分压有关,其平衡氧分压为0.41 Pa,常压条件下,VO会进一步氧化。渣中钒含量随合金铝含量的增加而降低,当合金铝质量分数分别为8.0%和20.0%时,对应渣中理论钒质量分数分别为0.16%和0.10%。实际冶炼过程中,冷态刚玉渣中的钒除了已还原FeV_x初级合金之外,主要以类质同象的形式与镁、铝、铁等元素固溶形成Mg(Al,V)_2O_4和(Mn,Fe)V_2O_4复合尖晶石结构。     

提钒尾渣含碳球团电弧炉熔融还原热力学分析与试验

对提钒尾渣中钒、铬氧化物碳热还原热力学进行分析计算,结果表明,钒氧化物的还原顺序为:V2O5→VO2→V2O3→VO→VC→[V],铬氧化物的还原顺序为:Cr O3→Cr O2→Cr2O3→Cr4C→[Cr]。采用50 k VA电弧炉进行提钒尾渣含碳球团进行熔融还原,考察了配碳量和碱度对钒铬在渣铁间的分配比和铁、钒、铬回收率的影响。试验结果表明:随着配碳量的增加,钒、铬在渣铁间分配比增加,铁、钒、铬的回收率下降;随着碱度的增加,钒、铬在渣铁间分配比下降,铁、钒、铬回收率升高;提钒尾渣电弧炉熔融还原较适宜的配碳量为12%~14%,较适宜的碱度为1.0~1.1,在此条件下,铁、钒、铬的回收率可达90%以上。     

碱性钒铬溶液除杂工艺研究

以钒铬渣钠化焙烧工艺得到的碱性钒铬浸出液为原料,分析了主要元素V、Cr及杂质Si、P的含量,探讨了铝盐对碱性条件下Si和P的去除机制,研究了·18H_2O用量、pH值、反应温度、反应时间及陈化时间等因素对Si、P去除效果的影响。结果表明:在弱碱性条件下,铝盐沉淀法可有效去除钒铬溶液中的Si和P,除Si率达98%,除P率达92%,满足后续沉钒要求。最佳除杂工艺条件为:Al∶Si(mol)=1.2,pH值9.0,温度90℃,反应时间15 min,陈化时间1 h。除杂过程中V和Cr的损失均小于5%,且进入除杂渣中的V和Cr容易洗涤回收,净化后液经沉钒、煅烧,沉钒率大于98%,最终得到的粉状V2O5产品质量满足标准《YB/T 5304—2011》中99级要求。     

梯度式电铝热法冶炼钒铁中间合金研究

针对现有电铝热法冶炼钒铁出现的渣中钒(TV)含量高,还原剂Al利用率低的问题,本文从反应热力学、渣的物相组成以及渣系液相温度的角度进行了分析研究。热力学研究结果表明:相同加Al条件下,渣中TV含量随温度的升高而增加;相同温度条件下,随着合金中Al含量的增加,渣中TV含量逐渐降低。岩相分析显示渣中MgO主要分布于镁铝尖晶石相中,而V元素几乎全都固溶于镁铝尖晶石中,控制MgO含量有利于降低渣中TV。基于上述规律,本文提出一种梯度式电铝热冶炼钒铁方法,将整个加料过程分为3期,每期的氧化钒重量比例为5∶3∶2,每个阶段的加铝系数呈梯度式减少,分别为1.25,0.93和0.58,整体平均加铝系数为1.02,低于现有工艺的1.05。采用新方法冶炼钒铁的渣中TV含量约为0.64%,合金中铝含量约为0.4%,均优于现有电铝热法的水平。     

钒渣亚熔盐工艺中主要物相演变及钒、铬元素微区转浸率研究

基于亚熔盐反应可以在低温下高效高选择性将钒渣中的钒、铬元素转化为可溶性盐,对钒铬渣亚熔盐反应前后主要物相演变过程,钒、铬元素的赋存变化规律以及钒铬物相微区转化率进行分析研究。结果表明,表面晶格多缺陷比致密的钒铬尖晶石更有利于O~(2-)离子的晶格取代,加速钒铬尖晶石的分解过程;亚熔盐反应前后Cr元素的回收率为99.63%,而V元素的回收率为90.01%;主要含V物相微区转化率计算证明,亚熔盐反应后Fe_2O_3中V含量的增加是导致其回收率低的主要原因。     

坩埚材质及顶渣成分对帘线钢夹杂物成分的影响

 使用碳管炉熔炼帘线钢72A,研究不同材质坩埚及不同成分顶渣对钢中夹杂物的影响。结果表明,MgO坩埚冶炼的帘线钢中夹杂物变形率高于ZrO2、SiO2、Al2O3坩埚。采用SiO2坩埚冶炼时,钢中夹杂物几乎不变形,其SiO2含量大于90%(质量分数,下同)。采用Al2O3坩埚,个别夹杂物Al2O3的含量达到40%左右,不适合冶炼帘线钢。钢中夹杂物成分进入较低熔点区(即不大于1500℃的区域)的条件为：采用MgO坩埚,顶渣碱度为10时,wAl2O3≤3%,或顶渣碱度为09时,wAl2O3为9%;采用ZrO2坩埚时,顶渣碱度为11~12时,wAl2O3为3%。     

混合钒氧化物倾翻炉钒铁冶炼工艺研究

研究了适用于倾翻炉一步法和两步法钒铁冶炼过程混合钒氧化物铝热反应的冶炼特性。考察不同钒氧化物配比、不同配铝系数对渣中钒损及单炉冶炼效率的影响。结果表明:V2O3的增加能够有效降低平衡态渣中钒含量,但不利于提高单炉冶炼效率,原料配比(罐数比)从0∶8提高到6∶2时,渣中钒含量从2.23%降低至1.85%,单炉渣量减少19.7%,单炉冶炼时间从180 min增加到194 min;两步法冶炼过程中,随着配铝系数提高到1.20,贫渣钒含量从一步法钒铁冶炼的1.85%降低至0.44%,渣中平均钒含量降低至0.88%;贫渣时间从194 min减少至146 min,精炼时间则从0增加到94 min,单炉冶炼周期较一步法延长46 min;最优试验条件下,合金产品中钒含量提高到51.6%,铝含量降低到低于0.3%的水平,在提高合金品质的同时也提高了铝的利用率。     

基于梯度配铝的FeV50合金制备及其影响因素

分析了Al,Si,C热还原制备FeV50合金的热力学可行性及铝热还原过程渣金钒铝平衡,采用分期梯度配铝的方式,考察了原料配比、反应温度、加料制度和多期配铝系数对渣中TV含量及合金成分的影响。通过不同还原剂热还原的热力学分析表明:1500 K时,常压条件下碳热还原过程优先生成VC,只有当体系真空度高于76.8 Pa才能得到稳定钒基合金产品;硅热反应仅适用于高价钒氧化物的还原,配加CaO有利于反应的进行以及钒氧化物的还原效率;铝热还原V_2O_5和V_2O_3的单位反应热分别为368.4和221.0 k J·mol~(-1),基本能够满足密闭系统维持自发反应的热量需求。铝热还原渣金热力学平衡分析结果表明FeV50渣中TV含量随合金Al含量的升高而降低,当合金Al含量为2.0%时,渣中理论TV含量为0.27%;若要使渣中理论TV含量降低到0.15%,合金Al含量需达18.8%以上。基于此,采用"梯度配铝"工艺试验,在三期加料制度4-3-1,配铝系数1.30-1.00-0.30,原料配比3∶1,体系温度1850℃的条件下,渣中平均TV含量由均匀配铝的1.85%降低到0.69%,合金Al含量从1.6%降低到0.4%。     

FeV80合金碳含量控制研究

分析了碳在Fe V80合金中的赋存状态及脱碳热力学条件,考察了石灰碳含量、C/V比、通电时间及脱碳剂对合金碳含量及渣中钒含量的影响。理论分析结果表明:常压条件下,铝热还原过程中合金中碳的主要赋存状态为VC和Fe3C。V-C-O系及V-Fe-C-O系平衡CO分压分别为3.2 Pa和127.7 Pa;只有当体系PCO低于该值时,才能实现碳的完全氧化及钒的彻底还原。同时,作为碳氧反应的动力学热区,适度提高渣金界面自由氧活度有利于合金中碳的氧化脱除。试验结果表明:降低入炉石灰碳含量及减少入炉石灰量均能有效降低原料碳来源,有利于合金碳含量的降低;通电时间对合金碳含量的降低无明显效果,但缩短通电时间易导致熔融合金沉降受阻;脱碳剂Fe O的添加能够促进合金碳氧反应,但易引起钒的二次氧化。优选工艺条件下,合金平均碳含量降低到0.10%,渣中平均钒含量为1.32%。     

Research on Nitrogen Solubility of Fe–Cr–Mn–V–N System Alloys in Liquid and Solid Phases

In this paper, the thermodynamic model of nitrogen solubility in vanadium nitrogen microalloyed high strength weathering steels of Fe–Cr–Mn–V–N system, according to Hillert’s model for Gibbs energy of its various phases, was established and validated. In the model, the effect of the nitrogen partial pressure on the activity coefficient and the lattice structure characteristics of the vanadium nitrogen precipitated phase were considered. It would be of guiding significance for the design and smelting of Fe–Cr–Mn–V–N system alloys. Based on the established model, the nitrogen contents in \(\delta\), \(\gamma\), \(\alpha\) phase and liquid were calculated as a function of the temperature for Fe–Cr–Mn–V–N system alloys. The results show that: first, the maximum solubility of nitrogen in the solidification process is obviously affected by the phase transition when there is a sudden change in the solubility of nitrogen at the phase transition point. The maximum nitrogen solubility of the molten steel in the delta phase region determines whether nitrogen bubbles are formed during the solidification process. The nitrogen solubility is lowest in the solid–liquid region (about 1673 K). Secondly, the increase of Cr and Mn content is beneficial to improve nitrogen solubility in liquid and solid phases. However, the increase of V content mainly affects the nitrogen solubility in the solid phase because the nitrogen in this temperature range is precipitated in the form of vanadium nitride, as the second phase plays a role in strengthening. In addition, the alloying element Mn has a significant effect on nitrogen solubility since the Mn element is the promoting element of austenitic formation. During the solidification process, the delta ferrite region gradually reduces and may disappear with increasing Mn content. Therefore, increasing the Mn content of the alloy system in the design of alloy composition, can reduce the precipitation trend of the nitrogen during the solidification process, which can effectively avoid bubble formation in high nitrogen weathering steels. Lastly, with the increase in the nitrogen partial pressure, the solubility of nitrogen increases during the liquid and solid phases.     

Nitrogen solubility and nitride formation in FeCrNi alloys

A series of FeCrMnNi alloys was melted under high nitrogen gas pressure. The nitrogen concentration in the solidified metal was found to be experimentally related to the melt pressures that ranged from 0.1 to 200 MPa, to the alloy composition, and to alloy concentration. The nitrogen solubility followed Sievert's law. The activity coefficients determined at these higher pressures for the alloying elements Cr, Mn and Ni were similar to those previously obtained at lower pressures. At the higher nitrogen melt-pressures, the nitrogen concentration exceeded the interstitial nitrogen solubility resulting in the formation of metal-nitrides.     

Ti 465Al 25V 10Cr 03Ni合金高温变形动态再结晶行为

 采用热模拟实验研究了变形参数(应变量、变形温度、应变速率)对Ti 465Al 25V 10Cr 03Ni合金微观变形组织的影响。研究结果表明,在应变量逐渐增加的热压缩变形过程中,一定变形量后开始出现层片弯曲、折曲或破碎,随着应变量的增加,动态再结晶形成的等轴晶粒增多,残余层片团减少。变形温度对钛铝合金的变形组织有着显著影响,提高热变形温度,有利于合金中的动态再结晶以及变形组织的均匀化,降低残余层片团的体积分数。较低的应变速率能促进变形时的动态再结晶,有利于提高变形组织的均匀性。还对γ TiAl合金动态再结晶新晶粒形成过程进行了讨论。     

Effects of Ti,Zr, V,and Cr on the rate of nitrogen dissolution into molten iron

The rate of nitrogen dissolution into molten iron-M (M: Ti, Zr, V, and Cr) alloys at temperatures from 1873 to 2023 K has been measured using an isotope exchange reaction. The rate of nitrogen dissolution into molten iron is shown to increase by adding an element with a stronger affinity for nitrogen than Fe, such as Ti, Zr, V, and Cr. Of these, Ti increased the reaction rate most and the rate constant for the Fe-0.08 mass pct Ti alloy was 1.5 times larger as that for pure iron at 1873 K. The correlation of rate constant with thermodynamic interaction parameter with nitrogen was observed. This effect is discussed in terms of the change in the activity of the vacant site on the surface of the molten alloy.     

Effects of aluminum, silicon, and boron on the dissolution rate of nitrogen into molten iron

An isotope exchange technique is employed as a method for measuring the nitrogen dissolution rate into molten iron alloys, and the effects of Al, Si, and B addition have been studied at temperatures ranging from 1873 to 2023 K. The results are compared with those of other elements such as Ti, Zr, V, and Cr. The rate of nitrogen dissolution into molten iron is shown to decrease by the addition of Al, Si, and B due to a weaker affinity for nitrogen than Fe, which is contrary to the case of Ti, Zr, V, and Cr. Among them, B shows the largest effect when their contents are lower than 1 mass pct. A reasonable correlation of the rate constant with an interaction parameter between nitrogen and each element has been observed, which can be explained by the change in the activity of the vacant site on the surface of the molten alloy. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

钕对NiAl基共晶合金高温流变行为的影响

 研究了钕对NiAl 28Cr 55Mo 05Hf共晶合金显微组织及高温流变行为的影响。结果表明：NiAl 28Cr 55Mo 05Hf基体合金是由黑色的NiAl相和灰白色的Cr(Mo)相组成的共晶组织，在相界处聚集有白色的Ni2AlHf(Heusler)相，加入稀土钕可细化组织；NiAl 28Cr 55Mo 05Hf(wNd=005%)合金在较高的应变速率(=194×10-2 s-1和=194×10-3 s-1)下，含稀土合金的流变应力大于不含稀土合金的流变应力，而在低应变速率(=194×10-4 s-1)下，这种强化现象消失。幂指数规律和温度补偿的幂指数规律可以很好地描述各种合金的高温压缩流变行为。加入稀土可降低合金的应力指数和变形激活能，这是因为稀土偏聚在相界上，致使相界上的空位浓度发生变化。     

Effect of cerium content on microstructure and hydrogen storage performance of Ti24Cr17.5V50Fe8.5Cex（x=0-1.0） alloys

Effect of Ce addition on microstructure and hydrogen storage performance of Ti24Cr17.5V50Fe8.5Cex (x=0, 0.5at.%, 0.8at.% and 1.0at.%) alloys was studied by X-ray diffraction, scanning electron microscopy and P-C-isotherm measurements. The results indicated that Ce addition was a useful way to improve the flatness of the plateau and increase hydrogen storage capacity of Ti24Cr17.5V50Fe8.5 alloy. It was indicated that both homogenization of composition and increase of hydrogen diffusion coefficient were the main reasons for improving the hydrogen storage performance of Ti24Cr17.5V50Fe8.5Cex alloys.     

Nitrogen solubility in complex liquid Fe−Cr−Ni alloys

Measurements of nitrogen solubility were performed in a series of liquid iron-chromium-nickel alloys near the composition of the commercial superalloy INCOLOY^* 800 (I:21 pct Cr, 33 pct Ni, bal. Fe). This work was carried out at 1450 to 1600°C and up to one atmosphere of nitrogen gas pressure. Sieverts' law was obeyed by nitrogen in all the alloys. Changes were observed in the compositions of all the melts studied, mainly due to the chromium loss by volatilization. These changes necessitated nitrogen solubility measurements in a series of alloys immediately surrounding alloy I. The experimental results have been prepared as a regression polynomial equation for the logarithm of nitrogen solubility as a function of temperature and reported weight percentages of chromium and nickel in the alloys. The standard Gibbs free energy of nitrogen solution in a region around alloy I is given as ΓG ^o=−58,700+48.20T Joules/g atom N. At 1600°C, the temperature coefficient of nitrogen solubility in I is −2.65×10⁻⁴ pct N/K. The shape of a portion, of the nitrogen solubility surface for the Fe−Cr−Ni system near to alloy I at 1600°C is defined.     

铝质量分数对FeCrAl合金多孔材料性能的影响

铁铬铝（FeCrAl）合金是一种典型的耐热合金,由其开发而成的耐高温金属多孔材料已经在煤气净化、高温催化剂载体等方面获得了广泛的应用。在反应合成制备FeCrAl合金多孔材料过程中,铝质量分数在多孔材料孔结构、力学性能及抗氧化性能等方面具有重要影响。本文在Fe?20%Cr合金（质量分数）基础上添加不同质量分数的铝粉（0～20%）,以铁、铝、铬元素混合粉为原料,通过反应合成方法制备了一系列FeCrAl合金多孔材料（Fe?20Cr?xAl,x=0～20%,质量分数）,研究了铝质量分数对Fe?20Cr?xAl多孔材料物相、孔结构、力学性能以及抗氧化性能的影响。结果表明,添加5%铝（质量分数）的Fe?20Cr?xAl多孔材料具有较优的孔隙度和力学性能,同时在600～800 ℃高温氧化实验中表现出最优的抗氧化性能和力学性能稳定性。