Effects of Alloying Elements on Microstructure,Hardness, Wear Resistance,and Surface Roughness of Centrifugally Cast High-Speed Steel Rolls

A study was made of the effects of carbon, tungsten, molybdenum, and vanadium on the wear resistance and surface roughness of five high-speed steel (HSS) rolls manufactured by the centrifugal casting method. High-temperature wear tests were conducted on these rolls to experimentally simulate the wear process during hot rolling. The HSS rolls contained a large amount (up to 25 vol pct) of carbides, such as MC, M₂C, and M₇C₃ carbides formed in the tempered martensite matrix. The matrix consisted mainly of tempered lath martensite when the carbon content in the matrix was small, and contained a considerable amount of tempered plate martensite when the carbon content increased. The high-temperature wear test results indicated that the wear resistance and surface roughness of the rolls were enhanced when the amount of hard MC carbides formed inside solidification cells increased and their distribution was homogeneous. The best wear resistance and surface roughness were obtained from a roll in which a large amount of MC carbides were homogeneously distributed in the tempered lath martensite matrix. The appropriate contents of the carbon equivalent, tungsten equivalent, and vanadium were 2.0 to 2.3, 9 to 10, and 5 to 6 pct, respectively.     

柱式吸附法从钨酸钠溶液中分离钼的研究

进行了从钨酸钠溶液中分离钼的试验研究，结果表明，预先将溶液中的钼转化为硫代钼酸根后，用粒状活性炭柱式吸附法分离钼能获得较好的效果，钨损失小。     

过氧化钠熔融-硫氰酸铵差示光度法测定钼精矿和钼焙砂中钼

研究了用过氧化钠在高铝坩埚中700 ℃熔融样品5～10 min,用硫氰酸铵差示光度法测定了钼精矿和钼焙砂中钼含量的方法。对样品的熔融条件、样品溶液的制备条件和测定条件进行了优化。通过加入无水乙醇消除了MnO^2-₄的干扰,采用三氯化铁溶液沉淀吸附和酒石酸钠掩蔽的方式消除了钨(Ⅵ)、铬(Ⅵ)和钒(Ⅴ)等其它共存离子的影响。结果表明,于吸收波长λ=480 nm处,钼质量浓度在14.0～26.0 μg/mL范围内符合比尔定律,检出限为4.2×10^-2 μg/mL。将本法用于钼精矿管理样品GLY-01、钼精矿和钼焙砂生产样品中钼的测定,测定值与参考值或重量法测得结果一致,相对标准偏差(RSD,n=11)为0.10%～0.14%。     

Advanced technology in tungsten and moly PM

Worldwide consumption of tungsten and molybdenum was 44 000 tonne and 97 000 tonne, respectively, in 1988. But only a small percentage of this volume is processed to pure or alloyed semifinished or finished products. Some 6% of all molybdenum consumed (5000 to 5500 tonne) is in the form of molybdenum and molybdenum alloys. For tungsten this percentage is higher, 10% of tungsten consumed was pure tungsten or tungsten alloy products. The same amount was produced as heavy metal every year, totalling 8000–9000 tonnes of tungsten content in tungsten and tungsten based alloys including heavy metal, says Ralf Eck of Metallwerk Plansee.     

Measurement of the abrasive capacity of powders of carbides and borides of refractory metals

Summary The abrasive capacity of carbides and borides of titanium, zirconium, hafnium, vanadium, chromium, tantalum, molybdenum, and tungsten was investigated.     

Electrochemical synthesis of intermetallic compounds and complex carbides based on molybdenum (tungsten) and cobalt (nickel)

Systems for the joint electrodeposition of molybdenum (tungsten) and nickel(cobalt) from ionic melts have been identified. Conditions for depositing the intermetallics molybdenum(tungsten)-nickel(cobalt) and double carbides based on these were ascertained. It is shown that the process of electrochemical synthesis is determined, on the whole, by the ratio of partial currents of reacting components, energies of interaction between them, and the occurrence of parallel reactions between components.Institute of General and Inorganic Chemistry, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(384), pp. 1–6, March–April. 1996. Original article submitted June 20, 1994.     

人工神经网络解析分光光度法同时测定钨和钼

用单纯形法优化了钨、钼－二溴羟基苯基荧光酮－ＣＴＭＡＢ显色体系的实验条件。应用三层ＡＮＮ－ＢＰ网络解析钨和钼的吸收光谱,分光光度法同时测定了钨和钼并与偏最小二乘法、因子分析、Ｐ－矩阵法、卡尔曼滤波、主成分回归等化学计量学方法的解析结果进行了比较,表明神经网络方法优于其它方法。使用改进的ＢＰ算法,避免了神经网络学习过程中可能产生的麻痹现象。提出了目标向量的简单变换方法及便于网络参数选择的收敛评价函数。     

氧化钨纳米粉的制备与表征

用盐酸酸化钨酸钠溶液得到了钨酸沉淀,然后通过水热法制备了氧化钨异形纳米粉;在制备过程中,考察了硫酸盐添加量、水热反应时间及仲钼酸铵对氧化钨异形纳米粉形态的影响。用场发射扫描电镜(FE-SEM)和X光能谱仪(EDX)等测试手段对产物进行了表征,并研究了其形成机理。     

Effect the tungsten(VI) and molybdenum(VI) ions on the electrical conductivity of ammonium hydroxide solutions

The effect of the W(VI) and Mo(VI) ions on the electrical conductivity of ammonium hydroxide solutions (7 mol/L) is studied in the tungsten or molybdenum concentration range 0.1–0.5 mol/L and the temperature range 20–60°C. The electrical conductivities of the solutions are shown to depend linearly on the solution temperature and the metal concentration, and the coefficients of linear regression equations are calculated. The temperature coefficients of the electrical conductivities of the solutions are determined.     

陈化除钼渣处理工艺试验研究

针对某地APT厂堆存的除钼渣的特点,提出采取碱性浸出-硫化沉钼-人造白钨的工艺,提取其中的铜、钼、钨。系统地考察了碱浸工序的工艺参数,确定碱性浸出的最佳条件。结果如下：碱用量为除钼渣的50％,添加剂A用量为除钼渣的5％,液固比L／S=3／1,温度为70℃,时间为3h,钨钼浸出分别为99．12％和98．42％,铜保留率～100％。对浸出液采用硫化沉钼,钼的沉淀率达到98．03％,钨的沉淀率为4．19％。沉钼后液采用人造白钨,钨的沉淀率达98．29％,产品WO,品位达50．10％。     

Stability of refractory compounds in fused basalt

Summary A study was made of the reaction of titanium, zirconium, niobium, molybdenum, and tungsten carbides, aluminum, zirconium, and silicon nitrides, titanium, zirconium, chromium, and molybdenum borides, molybdenum disilicide, chromic oxide, and refractories based on silicon nitride and carbide with molten basalt at a temperature of 1400°C. It has been established that molybdenum disilicide exhibits the highest stability in molten basalt.Translated from Poroshkovaya Metallurgiya, No. 2 (50), pp. 47–49, February, 1967.     

The resistivity of refractory compounds at high temperatures

Summary The authors measured the temperature dependence of the electrical resistance of carbides of titanium, zirconium, hafnium, niobium, molybdenum and tungsten and borides of titanium and zirconium. The thermal coefficients of the electrical resistance were calculated for the measured carbides and borides. Attempts were made to correlate the values of the electrical resistances with the electron structure of the compounds.     

Processing mineral raw materials in Siberia: ores of molybdenum,tungsten, lead and gold

Problems related to the processing of mineral raw materials from Siberia (i.e. molybdenum-, tungsten-, lead- and gold-containing ores and concentrates) are reviewed. It is shown that hydrometallurgical methods for processing such raw materials are more advantageous than pyrometallurgical ones. For example, hydrometallurgical treatment of molybdenum and tungsten concentrates can be used industrially. Studies have shown that the recovery and concentration of molybdenum and tungsten from leach solutions can be effectively carried out using macroporous anion exchangers. Other studies show that nitric acid/iron(III) solutions are most efficient for leaching lead from lead sulfide concentrates. Metallic lead as well as lead-containing compounds can be produced by electrolysis of lead nitrate leach solutions. These solutions also provide a hydrometallurgical method for the oxidation of pyrite and arsenopyrite in gold-containing raw materials prior to the recovery of gold by complex-forming reactants. Salt decomposition of sulfides and dissolution of gold by non-cyanide complex-forming reagents can be used also for the recovery of gold from refractory arsenopyrite concentrates. Hydrometallurgical technologies recover about 93–98% of metals. Moreover, it is quite easy to improve production efficiency by modifying the design of the industrial equipment and by preventing the formation of environmentally harmful products.     

Activity of carbon in nickel-rich Ni-Mo and Ni-W alloys

Effects of molybdenum and tungsten on carbon activity in nickel have been experimentally determined at 1000, 1100, and 1200 °C. Seventeen nickel-molybdenum and thirteen nickel-tungsten binary alloys were carburized in a flow of purified methane and hydrogen mixed gas. A sealed capsule technique was also employed for carburization of a few series of nickel-molybdenum alloys. The carbon concentration was determined either by hot extraction techniques (LECO and Coulomatic) or by weight gains of these specimens. The carbon concentration at a constant carbon activity decreases with increasing either molybdenum or tungsten concentration in nickel. The effect of tungsten on the carbon solubility in nickel is slightly larger than that of molybdenum. The experimental data were analyzed in terms of the regular solution model with two sublattices due to Hillert and Staffansson. Temperature dependence of the interaction coefficients between carbon and molybdenum or tungsten was expressed as DG_Mo/RT = −4.45 + 11650/T andDG _W /R = 1.21 + 9010/. Formerly Graduate Student, Department of Metallurgical Engineering, Tokyo Institute of Technology Formerly Professor, Department of Metallurgical Engineering, Tokyo Institute of Technology     

Thermodynamic Assessment of the Reduction of WO<Subscript>3</Subscript> by Carbon and Silicon

An interesting process in terms of resource conservation is the arc surfacing of worn components by means of powder wire in which the filler contains tungsten oxide WO₃ and a reducing agent (carbon and silicon). Thermodynamic assessment of the probability of 21 reactions in standard conditions is based on tabular data for the reagents in the range 1500–3500 K. This range includes the temperatures at the periphery of the arc and in the upper layers of the surfacing bath. The reactions assessed include direct reduction of WO₃ by carbon and silicon, indirect reduction of WO₃ by carbon, and reaction of tungsten compounds with carbon and silicon to form tungsten carbides and silicides. The possible reaction products considered are W, WC, W₂C, WSi₂, W₅Si₃, CO, CO₂, SiO, and SiO₂. The reduction of the oxide is written for 1 mole of O₂, while the reactions of tungsten compounds with carbon and silicon compounds are written for 2/3 mole of tungsten W. The probability of the reactions is estimated in terms of the standard Gibbs energy. In the range 1500–3500 K, the standard states of the reagents are assumed to be as follows: W(so); WO₃(so, li), with phase transition at 1745 K; WC(so); W₂C(so); C(so); CO(g); CO₂(g); WSi₂(so, li), with phase transition at 2433 K; W₅Si₃(so, li), with phase transition at 2623 K; Si(so,li), with phase transition at 1690 K; SiO(g) and SiO₂(so, li), with phase transition at 1996 K. To assess the influence of the possible evaporation of tungsten oxide WO₃ in the arc (T_b = 1943 K) on the thermodynamic properties, the thermodynamic characteristics of two reactions are considered; the standard state in this temperature range is assumed to be WO₃(g). Thermodynamic analysis of the reduction of tungsten oxide WO₃ shows that the temperature of the melt and the composition of the powder wire may affect the composition and properties of the layer applied. At high melt temperatures (>2500 K), the formation of tungsten and also tungsten carbides and silicides is likely. These reactions significantly change the composition of the gas phase, but not that of the slag phase in the surfacing bath. Below 1500 K, the most likely processes are the formation of tungsten silicides and tungsten on account of the reduction of WO₃ by silicon. In that case, the slag phase becomes more acidic on account of the silicon dioxide SiO₂ formed. However, this temperature range is below the melting point of WO₃ (1745 K). In the range 1500–2500, numerous competing reduction processes result in the formation of tungsten and also tungsten carbides and silicides in the melt. The reaction of tungsten compounds with carbon and silicon to form carbides and silicides is less likely than reduction processes. Evaporation of tungsten oxide WO₃ in the arc increases the thermodynamic probability of reduction; this effect is greatest at low temperatures.     

Effect of molybdenum on the fracture characteristic of high-speed steel quenched matrix

The fractures of three model alloys, imitating by their chemical composition the matrixes of the quenched high-speed steels of various Mo: W relations were analyzed. According to the measurements of the stress intensity factor K_Ic and the differences in the precipitation processes of carbides it was found out that the higher fracture toughness of the matrix of the molybdenum high-speed steels than on the tungsten ones is the results of the differences in the kinetics of precipitation from the martensite matrix of these steels during tempering. After tempering at 250 and 650°C the percentage of the intergranular fracture increases with the increase of the relation of Mo to W in the model alloys of the high-speed steel matrix. This is probably the result of higher precipitation rate of the M₃C carbide (at 250°C) and the MC and M₆C carbides (at 650°C) in the privileged regions along the grain boundaries. The change of the character of the model alloy fractures after tempering at 450°C from the completely transgranular one in the tungsten alloy to the nearly completely intergranular one in the molybdenum alloy indicates that the coherent precipitation processes responsible for the secondary hardness effect in the tungsten matrix begin at a lower temperature than in the molybdenum matrix. After tempering for the maximum secondary hardness the matrix fractures of the high-speed steels reveal a transgranular character regardless the relation of Mo to W. The higher fracture toughness of the Mo matrix can be the result of the start of the coherent precipitation processes at a higher temperature and their intensity which can, respectively, influence the size of these precipitations, their shape and the degree of dispersion. The transgranular character of the fractures of the S 6-5-2 type high-speed steel in the whole range tempering temperatures results from the presence of the undissolved carbides which while cracking in the region of stress concentration can constitute flaws of critical size which form the path of easy cracking through the grains. The transgranular cracking of the matrix of the real high-speed steels does not change the adventageous influence of molybdenum upon their fracture toughness. On the other hand, the carbides, undissolved during austenitizing, whose size distribution in the molybdenum steels from the point of view of cracking mechanics seems to be unsatisfactory, influence significantly the fracture toughness of these steels.     

不同方法制备的球形铸造碳化钨粉末的性能研究

球形铸造碳化钨粉末是一种新型的超耐磨陶瓷颗粒材料,对比研究了不同方法制备的球形铸造碳化钨粉末的化学成分、显微形貌、微观组织、相结构、显微硬度、流动性以及松装密度等特性。结果表明:相对等离子重熔球化法和感应重熔球化法而言,等离子旋转电极雾化法制备的球形铸造碳化钨的总碳含量与共晶碳含量理论值的偏差最小、游离碳和杂质含量最低;粉末颗粒内部更致密、共晶组织更细密、显微硬度最高。感应重熔球化方法制得的粉末流动性最好、松装密度最大。     

Formation of nitrides of the Group VI transition metals

Conclusions An analysis is carried out of the thermodynamic probability of nitrides of the Group VI metals being formed by various reactions. A study was made of the kinetics of formation of molybdenum and tungsten nitrides from the metals in powder form and their oxides in an ammonia stream. It was established that the kinetics of formation of molybdenum and tungsten nitrides is described by pseudo-topokinetic equations, the nitride formation being controlled by topochemical processes with surface activation. As a result of kinetic, chemical, and x-ray diffraction studies suitable processing parameters have been determined for the synthesis of pure molybdenum and tungsten nitrides.DeceasedTranslated from Poroshkovaya Metallurgiya, No. 3(195), pp. 60–66, March, 1979.     

用高钼白钨精矿制取高纯三氧化钨工艺实践

介绍了采用苏打压煮、NaHS除钼、叔胺萃取、蒸发结晶处理柿竹园高钼白钨精矿 ,生产高纯三氧化钨的工艺。并对加入添加剂以提高三氧化钨回收率、净化钨酸钠溶液等问题进行了探讨。     

Electrodeposition of coatings of double carbides of tungsten and molybdenum from tungstate–molybdate–carbonate solutions

The electrochemical deposition of coatings of double tungsten and molybdenum carbides from tungstate–molybdate–carbonate melts is investigated. The composition of formed coatings is investigated by X-ray fluorescent and X-ray phase analyses. The crystal size and coating thickness are determined using scanning electron microscopy. Optimal deposition parameters of W₂C · Mo₂C coatings are as follows: the melt composition is Na₂WO₄–(1.0–4.0 mol %) Li₂WO₄–(1.0–4.0 mol %) Li₂MO₄–(1.0–5.0 mol %) Li₂CO₃, the cathode current density is 750–1500 A/m², the process temperature is 1123–1173 K, and the electrolysis duration is 4 h.