Combined with XRD, XPS, SEM-EDS and ICP-OES characterizations, the phase composition and morphology of acid ammonium salt precipitation vanadium products under different pH values were studied; also the migration and transformation behavior of V, Fe and Mn were analyzed when the pH value of vanadium precipitation was 2.20. The results show that the pH value of vanadium precipitation significantly affects the composition and morphology of the product. The filter cake of vanadium precipitation is amorphous at low pH value, and the crystal form is gradually determined with the increase of pH value. V exists in the form of CaV2O6 in vanadium extraction tailings, polyvanadate in filter cake, and V2O5 in the final product. The main forms of Fe in tailings are Fe2O3 and Fe2TiO5, which are less abundant in vanadium filter cake and final product. Mn exists in the form of MnSO4 in the tailings, and mainly enters the supernatant during vanadium precipitation, while MnV2O6·4H2O exists in the filter cake and with 0.210% in the final product.
The bimetallic structure composed of IN625 nickel-based high-temperature alloy with excellent high-temperature properties and lightweight and high-strength TC4 titanium alloy has broad application prospects in the aerospace field. However, due to the large differences in physical and chemical properties of the two metals, the direct fabrication of IN625/TC4 bimetallic structure inevitably results in the formation of metallurgical defects such as cracks in the transition region, so the effective connection of IN625/TC4 bimetallic structure has been a hot spot and a difficult area of research in the industry. In this work, laser melting deposition technology was used to prepare IN625/TC4 bimetallic structure without cracks and other metallurgical defects by adding Cu interlayer, and studied the microstructure and mechanical properties of the transition region. The results show that the phase composition inside the transition region of the IN625/TC4 bimetallic structure deposited by laser melting with Cu interlayer is mainly γ-Ni, γ-Cu, (Cr, Mo), Ti2Cu, TiCu, TiNi3, α-Ti and β-Ti. Tensile results at room temperature indicate that the tensile strength of the IN625/TC4 bimetallic structure with Cu interlayer is about 228.9 MPa. The fracture location is near the Cu/IN625 transition region, and the fracture morphology shows quasi-dissociative fracture characteristics.
In order to solve the problems of land resources waste and environmental pollution caused by accumulation of vanadium extraction tailings, two kinds of vanadium extraction tailings were studied in this paper. Biomass was used as reducing agent for high temperature reduction experiment, and the component analysis and phase analysis of reduction products were carried out to explore the influences of oxygen absorption ratio, time and temperature on metallization rate of reduction products. The results show that the iron metallization rate can reach 58.67% when the oxygen absorption ratio is 4, the reduction temperature is 1450 ℃ and the reduction time is 2 h. The chromium metallization rate of vanadium-precipitated waste slag can reach 99.19% when the oxygen absorption ratio is 1.75, the reduction temperature is 1550 ℃ and the reduction time is 4 h. Two kinds of vanadium extracting tailings were mixed to prepare ferrochromium alloy by high temperature reduction of biomass. The preliminary experiment proved that the reduction product was melted under the condition of oxygen absorption ratio of 4, reduction time of 3 hours and reaction temperature of 1550 ℃. The content of chromium in the alloy was 61.51%, the content of iron was 31.05%, and the content of elements met the national standard requirements of FeCr65C4.0 alloy.
In view of the problems of low yield, poor strength and high energy consumption in the sintering process of vanadium titanomagnetite, a new sintering technology of preformed calcium ferrite is proposed in this paper, and its feasibility and theoretical basis are revealed through the tablet sintering and thermal analysis test. The results show that with the increase of substitution ratio (preformed calcium ferrite to partially substitute CaO), the microstructure of roasted products changes from granular structure to melting corrosion structure, the content of SFCA increases, while perovskite content decreases. In addition, the quantity of melts increases, the coalesce of sintering bubbles is promoted, the average porosity decreases from 42.9% to 36.2%, and the densification of the matrix is promoted. The formation of calcium ferrite melts in the heating process can be divided into three reactions, according to the formation temperature from low to high, it is the eutectic reaction of CF+CF2 → L, the melting of SFCA-I and SFCA, respectively; the addition of preformed calcium ferrite can reduce the generation temperature of initial melts, and increase the total sintering melts by about 9 %; promote the melting of iron oxides into the initial melts, increase the content of calcium ferrite, and promote solid-liquid assimilation reaction.
从2020年我国钛工业钛精矿、海绵钛、钛锭、钛材等品种的产能、产量、应用和进出口等数据分析了我国钛工业的整体情况,并对目前行业存在的问题提出了建议。
总结回顾了中国钛白粉工业2019、2020年的各项行业数据和表现,分析了当前面临的形势及发展趋势,认为高质量发展成为钛白粉行业未来发展的主旋律,钛白粉产能集中度虽有提高,但洗牌效应短期内难以呈现,这也是行业发展的一个难题,另外行业监管、氯化法钛原料问题、环保及清洁生产问题仍不容忽视。
为了探究Mg处理对易切削钢中夹杂物的影响,以1144高硫易切削钢为试验钢种,采用金相和能谱仪等手段研究了Mg处理对1144易切削钢中夹杂物的形态、尺寸分布和夹杂物成分的影响。结果表明:在易切削钢铸坯中,Mg处理使得易切削钢铸坯硫化物夹杂由Ⅱ类向Ⅲ类、Ⅰ类转变,分布更为均匀,同时使得复合硫化锰夹杂物比例提升。在轧材中,使得钢中夹杂物球化,并且钢中硫化锰夹杂物的尺寸和分布也得到了较好的改善,同时,Mg处理能够有效提高易切削钢的切削加工性能。
某低品位钒钛磁铁矿,TiO2品位为6.15%,矿物组成复杂,为充分回收其中的钛铁矿,针对钛的赋存状态及粒级分布特点,制定了强磁磁选预抛尾、重选提质、细磨弱磁选除铁、反浮选脱硫与一粗一扫两精浮钛组合工艺流程,研究了磁感应强度、磁介质大小、脉动冲程、磨矿浓度、磨矿时间、浮选调整剂及捕收剂用量等的影响,在获得最优工艺条件的基础上,按“一段强磁抛尾—两段重选抛尾—磨矿—除铁—浮选”的工艺流程进行了闭路试验。试验获得了TiO2品位48.22%,回收率为35.19%的钛精矿。矿石中主要有用的矿物钛铁矿得到了有效的回收。
在弹簧钢55SiCr成分基础上进行钒微合金化处理,获得了55SiCrV,通过淬火+回火正交试验、显微组织观察、力学性能测试和X射线衍射等手段,研究并分析了淬火+回火工艺对弹簧钢55SiCrV微观组织和力学性能的影响,结果表明:0.20%V的添加可使55SiCrV组织中存在大量弥散均匀分布的10~35 nm含钒析出相,强化效果最佳。淬火+回火处理可以改变55SiCrV的显微组织比例,其中的残余奥氏体可以降低强度和增加塑性,55SiCrV获得最佳力学性能匹配(Rm=1 815 MPa、Z=28%)的热处理工艺为900 ℃淬火+430 ℃回火,对应其残余奥氏体含量为2.3%。
从2020年全球钒资源概况,五氧化二钒、偏钒酸铵、钒铁和钒氮合金等品种的产能、产量、需求、进出口贸易和市场价格等方面阐述和分析了钒工业的整体情况,并介绍了2020年全球钒电池领域发生的主要大事件。依据目前国内外钒行业运行态势对后市进行了展望,认为全球钒扩能态势短期内不会大改,钒产品供过于求的状态将促使价格呈现盘整回归态势。“双碳”背景下的中国市场依旧是全球钒需求的主场,钒氮合金亦将成为钒产品近中期的发展趋势,钒企间的协同创新将促进钒产业逐步呈现良性“竞合”局面。
主要介绍先进热成形技术、脉冲电流辅助成形技术和电磁辅助成形技术的特点,及其在钛合金薄壁板材成形中应用的研究进展。热成形是钛合金塑性加工应用最为普遍的成形工艺,利用高温下钛合金塑性变形软化的特征,能够实现复杂钛合金零件的成形。脉冲电流和电磁辅助成形技术目前尚未开展大规模的产业应用,其在高强度难成形材料的成形加工方面具有潜在应用前景。
电渣重熔对于提高钢的纯净度有明显的效果,但对于低氧含量钢种存在增氧现象。通过采用GCr15轴承钢作为自耗电极,研究在大气环境下和Ar保护下使用不同渣系对轴承钢中氧含量及夹杂物的变化规律。研究发现,采用CaF2-Al2O3-CaO三元渣系在氩气保护下电渣重熔GCr15轴承钢时,电渣锭中的氧含量随渣系中的Al2O3含量下降而降低,而使用不含Al2O3渣系重熔的电渣锭中氧含量最低;氩气保护下重熔的电渣锭中的夹杂物直径均比使用同种渣系在空气中重熔的电渣锭要小。氧含量增加主要是因为电渣重熔过程渣池温度过高,导致渣中Al2O3稳定性变差所致。
利用透射电镜(TEM)对纳米二氧化钛的形貌和粒度进行分析后,将纳米二氧化钛制成乳胶漆、汽车漆、家具漆和防腐漆,对其进行耐候性、随角异色等性能分析。结果表明,金红石纳米二氧化钛可大幅度提高乳胶漆的耐候性、耐水性、耐碱性和耐洗刷性能,可提高家具漆和防腐漆的耐候性;纳米二氧化钛和铝粉配合制成的汽车漆具有随角异色效果,二氧化钛的粒度对其随角异色性能有很大影响,平均粒径为280 nm的普通颜料钛白改性铝粉漆无随角异色效果,平均粒径为35 nm的纳米二氧化钛改性铝粉漆有显著的随角异色效果,并且随纳米二氧化钛加量的增加,其不同角度的颜色差异增大。
利用真空感应悬浮熔炼炉制备了(TiC+TiB)/Ti-6Al-4Sn-8Zr-0.8Mo-1.5Nb-1W-0.25Si复合材料,增强体占比分别为0%、2%、4%(体积比)。利用金相显微镜、SEM、XRD、TEM和高温拉伸试验机研究了其显微组织和高温拉伸性能。结果表明:钛合金主要由α-Ti相和Ti2ZrAl相组成,Ti2ZrAl相分布在α-Ti片层交界位置。同时,复合材料中还存在多边形块状TiC和TiB长晶须。钛合金组织为典型的魏氏组织,在β-Ti晶粒内α-Ti相长成近平行排列的长针状。钛基复合材料中随着增强体数量增加,α-Ti长径比显著减小,β-Ti晶粒细化。在650~700 ℃范围钛基复合材料强度显著提高,2%增强体复合材料在650 ℃强化效果最优,4%增强体复合材料在700 ℃强化效果最优。温度超过700 ℃后,增强体强化效果减弱。复合材料塑性总体较低。钛基复合材料强化方式为细晶强化、固溶强化和载荷传递强化。高温拉伸时钛基复合材料的断裂方式为脆性断裂。