Microalloying and modification of steel with natural materials and industrial waste

The use of natural materials and industrial waste in the microalloying and modification of steel is studied. The metallurgical properties of a natural barium–strontium modifier are investigated, and its influence on the melting point of reducing slag is assessed. The results show that its industrial use is very promising. Terra software is used to assess the reduction of barium and strontium from their oxides by silicon and aluminum. The action of barium and strontium on the metal quality is analyzed. The potential of vanadium converter slag in microalloying steel with vanadium is established. The effectiveness of carbon from molten steel in the reduction of vanadium is assessed. Industrial tests are in good agreement with the theoretical findings. Recommendations are made for the optimization of microalloying and modification. The use of the materials here investigated improves the economics of steel production and considerably enhances the quality of the steel produced. The prospects for expanded of use of natural materials and industrial waste are discussed.     

Reduction of metals from vanadium converter slag by means of carbon and silicon

A method of alloying steel with vanadium by means of vanadium converter slag is considered. Thermodynamic analysis of the reduction of the oxides in vanadium slag during ladle treatment of the steel permits determination of the process parameters. The reduction of elements from oxides present in vanadium slag-in particular, vanadium, iron, and manganese-is evaluated in terms of the residual content of the corresponding oxides. It follows from thermodynamic calculations and experiments that, with optimal proportions of the reducing agents, relatively complete reduction of vanadium (98–99%) and iron from vanadium converter slag by carbon and silicon is possible, with limited reduction of titanium and manganese.     

Modification of steel with barium and strontium

The modification of steel by natural materials containing barium and strontium is considered. Thermodynamic modeling of the reduction of barium and strontium by silicon and aluminum is undertaken. The influence of modification by barium and strontium on the structure and mechanical properties of the steel is studied. The results are employed in the production of 25Γ2C and Γ13 steel in arc furnaces at the casting shop of OAO EVRAZ ZSMK and also in the production of 35XΓCЛ, 30XΓCЛ, and 12HЛ2ΦX steel at OAO Yurginskii Mashinostroitel’nyi Zavod by two-slag technology. The results of industrial tests indicate that modification with barium and strontium affects the microstructure and nonmetallic inclusions; and increases the margin of structural strength of the steel, estimated in terms of the yield point, strength, and impact strength at positive and negative temperatures. To identify the presence of barium and strontium in the steel, its structure is analyzed by means of extraction replicas on a transmission electron-diffraction microscope. The presence of barium and strontium within the grains indicates their reaction with the metallic melt, which affects the structure of the metallic matrix.     

氮化钒合金在400MPa级钢筋中的应用

介绍了攀钢采用氮化钒合金化与钒铁合金化生产400MPa级含钒钢筋(20MnSiVⅢ级钢筋)的对比试验结果,研究了钒、氮微合金化对钢筋的性能和组织的影响,探讨了氮化钒的强化机理,比较了使用两种合金的生产成本。     

提高炉渣中MnO向钢中传递的试验

 为了提高锰矿直接合金化锰的收得率,根据热力学分析结果确定了降低渣钢间锰分配比的影响因素。分析结果表明,提高温度和碳的活度是降低渣钢间锰分配比的必要条件。由此设计了感应炉试验方案,并进行了试验研究。结果表明,精炼渣在配加还原剂的情况下锰矿直接合金化锰平均收得率为90.8%,碳化硅作为还原剂在配碳量为1.2～1.4时,锰分配比最低;高温、高碳质量分数可以有效降低渣钢间锰分配比,底吹强度、锰矿加入量等工艺参数对锰矿直接合金化的效果有影响,应控制工艺避免锰矿石和还原剂的加入对钢中磷、硫产生的不利影响。     

W4Mo2Cr4VNb钢的组织和力学性能

 由于钨、钼、钒合金元素价格昂贵,因而导致含较多这类合金元素的钢的成本较高。合理运用高速钢的合金化理论,研究出了一种低合金高速钢——W4Mo2Cr4VNb。此钢的(W+Mo+V)含量比通用高速钢W9低很多,而且通过调整碳含量及加入价格较便宜的微合金元素铌,使该钢具有较好的综合力学性能和较低的成本。文章研究了W4Mo2Cr4VNb钢的组织和力学性能。     

Direct chromium alloying by smelting reduction of mill scale and low grade chromite ore

Direct alloying is the process in which all of the elements needed for alloying can be reduced from their oxides in a furnace or a ladle. This process is one way of reducing the amounts of energy and materials, reducing the loss of alloying elements, and improving working condition. Mill scale produced in rolling mills is considered a rich iron source (> 67% Fe) with minimum impurities. In this paper, iron high-Cr alloy was produced by a direct alloying with chromium in carbo- thermal reduction using fine of low grade chromites ore and mill scale. The smelting experimental heats were carried out in a 5?kg pilot plant submerged electric arc furnace. The charging materials and reduction parameters were varied and the optimum conditions for obtaining alloy with the highest metallic yield and the highest iron and chromium recovery were determined. When using coke as the reducing agent in stoichiometric amounts, for a mixture of mill scale (55%) and chromite ore (45%), 89.1% of the iron and 72.5% of the chromium were recovered, producing iron high-Cr alloy containing 17.9%Cr, 3.73%C, 0.46%Mn and 1.47%Si. The maximum iron and chromium recoveries obtained were 99.3% and 72.5%, respectively when using excess carbon. The present study clarifies the possibility of using a mixture of chromite ore , mill scale and coke as the precursor for direct chromium alloying. This method offers an alternative process route with cheaper raw materials and fewer process steps (by avoiding the step of ferrochrome production) for producing high chromium iron or steel alloys.     

Effect of the presence of alloying elements in interstitial-free and low-carbon steels on their surface composition after annealing in reducing atmospheres (dew point=−30 °C)

The X-ray photoelectron spectroscopy (XPS) method is used to study the outer surfaces of interstitial-free (IF) and low-carbon (LC) steels with different alloying element contents (P, Ti, Nb, and Mn) after annealing at temperatures of 805 °C and 705 °C, respectively, for 40 seconds in reducing atmospheres (dew point=−30 °C). The work discussed seeks to establish possible relationships between the bulk composition of the IF and LC steels and the contents of segregated alloying element observed by XPS on the surface of the annealed steels, as well as to establish the influence of the presence of a thin iron oxide film on the steel surface on the segregation and oxidation of the alloying elements. Despite the low Mn and Si bulk steel contents and the shortness of the annealing cycle, considerable enrichment of these elements on the surface is seen, mainly as manganese and silicon oxides. The formation of a MnO layer on the annealed steel surface seems to be related to the reduction of iron oxides and the increase in the metallic Fe content. Despite its low content in LC steels, carbon also seems to diffuse towards the annealed steel surface to reduce iron oxides.     

Effect of Microalloying Additions on the Microstructure and Mechanical Properties of Low Carbon Steel

Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing the strength by increasing the carbon content and alloying elements deteriorates the other properties.In this study,the microalloying technique was used to examine the possibility of attaining low carbon steels with good combination of strength,ductility and impact properties.A low carbon steel microalloyed with single addition of vanadium and another one microalloyed with combined addition of vanadium and titanium were used in this investigation and their properties were compared with non-microalloyed low carbon steel having the same base composition.Furthermore,other two nonmicroalloyed and V-microalloyed steels with higher carbon,silicon and manganese contents were also investigated to reveal the effect of base composition.Tensile,hardness,room and zero temperature Charpy V-notch impact tests were conducted to evaluate the variations in the mechanical properties of low carbon hot forged steel containing vanadium and combinations of vanadium and titanium.In addition,the microstructures of the different investigated steels were observed using both optical microscope and scanning electron microscope.Furthermore,the hardness of the ferrite phase was also determined using micro-hardness technique.The results showed improvement of the mechanical properties of the investigated steels by both single V-and combined V + Ti-microadditions.Tensile,hardness and impact tests results indicated that good combinations of strength,ductility and impact properties can be achieved by V-microalloying addition.Steel with combination of V and Ti microaddition has much higher hardness,yield strength,ultimate tensile strength and impact energy at both room and zero temperatures compared with non-microalloyed and single Vmicroalloyed steels.Higher C,Si and Mn contents result in increasing the strength accompanied with decrea     

Distribution of boron between oxide slag and steel

The influence of silicon (0.1–0.8%), aluminum (0.005%), and carbon (0.1%) in steel on the reduction of boron from slag (basicity 5) at 1400–1700°C is studied by thermodynamic analysis on the basis of HSC 6.1 Chemistry software (Outokumpu). Experiments on the boron distribution between CaO–SiO₂–MgO–Al₂O₃–B₂O₃ slag and steel are conducted in a high-temperature Tamman resistance furnace. Low-carbon steel with different silicon content is employed. According to the thermodynamic modeling and the experiments, direct microalloying of steel with boron is possible on the basis of its reduction by the silicon present in the steel. The reduction of boron from slag by silicon is theoretically analyzed and experimentally confirmed. The results of thermodynamic modeling indicate that boron may be reduced from CaO–SiO₂–MgO–Al₂O₃–B₂O₃ slag by silicon despite its low content in the steel (0.1–0.8%). With increase in the initial Si content in the steel, the boron concentration in the steel also increases. The influence of the Si content and the steel temperature on the final boron content is studied. When steel is held under slag containing 4.3% B₂O₃, the boron is reduced, mainly by silicon, whose content in the steel is 15–22% lower after the experiment. More boron is present in the steel sample with an elevated Si content. The degree of assimilation of boron is 5.8–6.9%; this is consistent with the thermodynamic modeling. The boron content in the metal may be regulated by adjusting the temperature and the silicon content of the steel. On the basis of the results, a technology for the direct microalloying of steel with boron may be developed.     

碳,硅和铝对奥氏体不锈钢粉末烧结时表面反应的影响

研究了碳、硅和铝合金元素对水雾化奥氏体不锈钢粉末烧结时的表面反应的影响。经实验发现,表面反应产物的形态及分布取决于合金元素的还原行为,这直接影响烧结材料的力学性能。     

近似核壳型微球对钢渣的熔融还原行为分析

以钢渣的纤维化应用为最终目标,将高分子材料科学中的核壳结构应用技术引入到钢铁冶金领域,用于高效还原重构熔融钢渣,并采用超高温激光共聚焦显微镜,对核壳微球在液渣中的熔融还原行为进行微观研究,分析温度和钢渣酸度系数对微球还原基层熔速的影响。研究结果表明,将核壳微球设计成悬浮于熔渣中间部位,其熔融还原反应要早于常规粉剂还原6 min到达平衡状态,渣中金属氧化物的还原回收时效性得到明显提高。不同还原基层核壳微球对比显示,铝基微球表现出极好的还原时效性,反应3 min内还原率达到了95.17%。高温、高酸度系数熔渣能够促进核壳微球还原基层的快速熔融,有效改善还原反应的热力学条件,提升还原渣中金属氧化物的时效性,达到渣金迅速分离的效果。通过微球还原基层-渣界面的熔融动力学模型,计算出微球还原基层介质在不同条件下的有效二元扩散系数范围为3.86×10^-11～4.92×10^-11 m²/s。对于工业应用还原基材重构改性钢渣而言,可以碳为主要还原基材配加适量的铝或硅来制备成核壳微球用于钢渣的还原重构,可显著提升钢渣还原重构的时效性,并取得...     

Influence of microalloying on the corrosion resistance of steel in saturated calcium hydroxide

The influence of microalloying vanadium or titanium on improving the corrosion resistance of mild steel in saturated calcium hydroxide solution was investigated. Potential-time, potentiodynamic polarization, and impedance measurement techniques were employed. The corrosion products have been examined by infrared and X-ray diffraction analysis and by scanning electron microscopy. It has been shown that the grain refining, due to microalloying, plays an important role in enhancing the corrosion resistance of steel. Scales of calcite and iron oxides on top of a protective oxide are formed on the investigated steels.     

Hardness of tempered martensite in carbon and low-alloy steels

This paper presents the results of a systematic study of the effect of carbon, manganese, phosphorus, silicon, nickel, chromium, molybdenum, and vanadium on the hardness of martensite in low to medium carbon steels tempered for one hour at 100°F (56°C) intervals in the range 400 to 1300°F (204 to 704°C). Results show that the as-quenched hardness depends solely on carbon content. On tempering, the effect of carbon on hardness decreases markedly with increasing tempering temperature. Studies of carbon-0.5 manganese steels showed that the incremental increase in hardness from 0.5 pct manganese after a given tempering treatment was independent of carbon content. Based on this result, studies of the effects of the other alloying elements were made using a 0.2 or 0.3 pct carbon, 0.3 to 0.5 pct manganese steel base composition. The hardness of the resulting tempered martensite was assumed to be due to a given alloy addition, and when two or more alloying elements were added, their effects were assumed to be additive. Each of the seven alloying elements increased the hardness of tempered martensite by varying amounts, the increase being greater as more of each element was present. Nickel and phosphorus have substantially the same effect at all tempering temperatures. Manganese has essentially the same hardening effect at any temperature in the range 700 (371°C) to 1300°F; silicon is most effective at 600°F (316°C), chromium at 800°F (427°C), molybdenum at 1000 to 1100°F (538 to 592°C), and vanadium at 1200°F (649°C). Using the data obtained, a procedure is established for calculating the hardness of tempered martensite for carbon and alloy steel compositions in the range studied and for any combination of tempering time and temperature. R. A. GRANGE was formerly with U. S. Steel Corporation (retired)     

氮在非调质钢中的作用

了氮在非调质钢中所起的有益作用。在Ｎｂ,Ｖ,Ｔｉ三咱微合金化元素中,钒有较高的溶解度,钒有较高的溶解度,是非调质钢最常用也是最有效的强化元素。钒在钢中通过形成细小析出相起细化晶粒和沉淀强化作用。与碳相比,氮与钒有更强的亲和力,且氮化物更稳定,因此,氮对控制钒的析出起更重要的作用。大量研究结果表明,非调质钢中增氮改变了钒在相间的分布,促进Ｖ（Ｃ,Ｎ）析出,使析出相的颗粒尺寸明显减小。因而氮增强了非调     

低碳微合金化非调质高强度螺栓用钢14MnVNTi的试验研究

研究了低碳微合金化非调质高强度螺栓用新钢种１４ＭｎＶＮＴｉ的强韧化机理，并对微合金化元素的作用机理及强化机制进行了论述。结果证明，新钢种１４ＭｎＶＮＴｉ用于制造８．８级高强度螺栓，完全可以取代传统的ＭＬ３５中碳调质钢。     

含钒铁水中钒元素高效利用的研究

基于承钢钒钛资源优势,提出一种低成本高效利用含钒铁水中钒元素的合金化方法.该方法改变了传统出钢过程中加入铁合金的合金化方式,直接利用铁水中的钒元素进行合金化,显著降低了生产成本.该技术应用于含钒钢筋、中高碳钢和低合金高强度结构钢中,产品的力学性能均达到标准要求,取得了初步成果.     

Reactions of metal oxides with carbon

The reaction of metal oxides with carbon is investigated. Baikov’s hypothesis regarding the role of atomic oxygen in the reduction of metals and the oxidation of carbon is confirmed theoretically and experimentally. The initial stages in the process include conjugate chemical reactions: dissociation of the oxide with the liberation of atomic and molecular oxygen; and the oxidation of carbon. The reaction of thermodynamically stable metal oxides with carbon is slowed by the accumulation of carbon monoxide in the system and the blocking of the reducing agent’s surface by metal carbides and oxycarbides. The production of silicon ferroalloys from briquetted batch is shown to be promising.     

Production of high-manganese steel in arc furnaces. Part 2

Metallographic data are presented for manganese steel before and after ladle treatment—specifically, treatment with calcium–strontium carbonate or argon injection in the ladle or both. Quantitative analysis of the nonmetallic inclusions is undertaken. The position of the inclusions relative to the grain boundaries is determined. Electron microscopy permits detailed study of the composition and form of the inclusions that appear during ladle treatment and without such treatment. The influence of various types of ladle treatment on the impact strength of manganese steel is discussed. Alloying of the manganese steel with vanadium is considered. Practical data regarding the influence of alloying with vanadium on the impact strength of the manganese steel are presented.