The effects of molybdenum and aluminum on the hot corrosion (sulfidation) behavior of experimental nickel-base superalloys

The hot corrosion behavior of a series of wrought nickel-base superalloys containing approximately 13 wt pct Cr was studied as a function of molybdenum content from 0 to 8 wt pct Mo in each of four Al + Ti levels (3 pct Al, 41/2 pet Al, 6 pct Al, and 1 pct Al-31/2 pct Ti). Specimens were tested in a burner rig with a 5 ppm sea salt concentration in a 1 pct sulfur diesel fuel burned at a 30:1 air-to-fuel ratio and were cycled between 1600°F (870°C) or 1800°F (980°C) and room temperature every 50 h during a 1000-h test. It was found that molybdenum significantly reduced the amount of hot corrosion attack at 1600°F (870°C) for the three aluminum-containing series of alloys. For the titanium-containing series of alloys tested at 1600°F (870°C) and all alloys exposed at 1800°F (980°C), molybdenum exerted little influence on hot corrosion behavior. Aluminum was found to markedly increase sulfidation rates at both 1600°F (870°C) and 1800°F (980°C) for all molybdenum levels. Titanium appeared to be beneficial to the hot corrosion resistance of these alloys at 1600°F (870°C) and detrimental at 1800°F (980°C). It was further noted that 1600°F (870°C) represented a more severe sulfidation condition than 1800°F (980°C) under these test conditions.     

Effect of enriching the blast with oxygen on the production cost of pig iron

Conclusion By mathematically modeling the blast-furnace smelting of conversion pig iron with a change in the oxygen content of the blast from 21 to 30% and a change in blast temperature from 800 to 1400°C, it was possible to determine how blast temperature affects the increases that occur in furnace productivity, coke rate, and pig-iron cost when blast oxygen content is increased by 1% within the ranges from 21 to 25% and from 25 to 30%. Under the furnace operating conditions that were examined, the savings in coke realized when the blast is enriched with oxygen decrease as blast temperature increases. In fact, coke rate increases at blast temperatures above 1100°C when the blast is enriched with oxygen in the range 25–30%. The effect of oxygen enrichment on pig-iron cost within this concentration range is negative throughout the range of blast temperatures examined. Adding more oxygen to the blast reduces the production cost of the pig iron only when blast oxygen content is within the range 21–25% and blast temperature is no greater than 1000–1100°C. At higher temperatures, adding more oxygen to the blast is economically inexpedient even within the lower ranges of oxygen content. Moscow State Institute of Steel and Alloys. Translated from Metallurg, No. 5, pp. 43–44, May, 1999.     

炭化工艺参数对铁焦冶金性能的影响

复合铁焦被认为是实现低碳高炉炼铁的革新技术之一。为了获得高质量的铁焦,需要采用适宜的炭化工艺条件。研究了炭化工艺参数对铁焦机械强度、反应性和反应后强度等冶金性能的影响,并对炭化后铁焦的金属化率、微观结构和碳微晶结构进行了解析。结果表明,炭化温度的升高可以提高铁焦的抗压强度和反应性。当温度为900～1 000℃时,铁焦的抗压强度和反应性较优。炭化时间的延长可以使铁焦的抗压强度提高,反应性降低。当炭化时间为3～4 h时,铁焦抗压强度和反应性较优。升温速度越快,铁焦的机械强度越低。适宜的升温速度为:Ⅰ段(室温至550℃)小于7℃/min,Ⅱ段(550℃至1 000℃)小于5℃/min。为防止铁焦冶金性能因碳气化溶损反应而劣化,在CO和CO₂混合炭化气氛中,CO₂与CO体积比(V(CO₂)/V(CO))应控制在0.11以下。在优化的炭化工艺条件下,制备的铁焦抗压强度大于3 500 N,反应性大于60%,反应后强度在16%左右。     

Effect of parameters on reduction behaviour of preheated converter sludge pellets in grate-rotary kiln process

Effects of parameters including temperature, time and coal ratio on the reduction behaviour of preheated iron-bearing converter sludge pellets in a simulated rotary kiln are studied through orthogonal tests. ANOVA analyses show that reduction time and temperature have remarkable influence on the metallisation degree, occupying 55.02 and 30.08% of the total contribution, while temperature is the most significant factor affecting the compressive strength, with 90.98% contribution. The metallisation degree increases with the increasing time from 1.5 to 2.5 h, and first increases and then decreases with the increasing temperature from 1000 to 1100°C. The compressive strength increases with the increasing temperature. Under the optimal condition of temperature 1050°C, time 2.5 h, coal ratio 1.3, the metallisation degree is 72.92%, and the compressive strength is 1310 N/p, which satisfies the requirement of iron burden for blast furnace.     

Numerical simulation on novel blast furnace operation of combining coke oven gas injection with hot burden charging

A novel blast furnace operation of coke oven gas (COG) injection simultaneously with hot burden charging has been proposed to solve the problem of insufficient heat in the BF shaft zone under the condition of COG injection and make full use of the abundant sensible heat of high temperature burden. In this paper, the novel process has been simulated with a multifluid blast furnace model. The results show that, in comparison with the operation of COG injection only, under the operation of COG injection together with hot burden charging, the temperature in the upper zone of the shaft increases while that in lower zone decreases. Furthermore, the reduction of iron bearing material is improved in the top zone, and the cohesive zone tends to descend and narrow. The coke ratio, fuel ratio and CO₂ emissions of the operation of charging hot pellet and coke with the temperature of 800°C are decreased by 4.0, 4.7 and 5.3% respectively, while the hot metal productivity is increased by 7.14%. Therefore, COG injection combined with hot burden charging operation not only increases temperature in the upper part of the blast furnace but also decreases energy consumption per tonne hot metal.     

高炉块状带焦炭强度模拟研究

 重点研究焦炭在高炉块状带内的抗压强度与温度和反应程度的关系。使用1台热模型对高炉块状带进行了模拟研究,1台可调气氛高温抗压试验机对所获焦炭试样进行了抗压强度检验,得到了焦炭在实际温度下的反应后抗压强度分布。在高炉间接还原区内,焦炭抗压强度随温度的升高而直线下降,在高温区内强度下将更为严重。焦炭失碳率是影响其强度的主要因素,在高煤比条件下应采用高反应性煤种并保留适量未燃煤,以保护焦炭强度。     

Mechanical properties of Ir-Nb alloys containing Ni and Al

Two alloys made by adding 5 or 10 at. pct, respectively, of Ni-18.9 at. pct Al to an Ir-15 at. pct Nb alloy were investigated. The microstructure and compressive strength at temperatures between room temperature and 1800 °C were investigated to evaluate the potential of these alloys for ultra-high-temperature use. Their microstructural evolution indicated that the two alloys formed fcc and L1₂-Ir₃Nb two-phase structures. The fcc and L1₂ two-phase structures were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The 0.2 pct flow stresses were above 1000 MPa at temperatures up to 1200 °C, about 150 MPa at 1500 °C, and over 100 MPa at 1800 °C. The strength of the quaternary Ir-base alloys at 1200 °C was even higher than that of Ir-base binary and ternary alloys. And the strength of quaternary Ir-Nb-Ni-Al was equivalent to that of the Ir-15 at. pct Nb binary alloy at 1800 °C. The compressive ductility of quaternary (around 20 pct) was improved drastically compared with that of the Ir-base binary alloy (lower than 10 pct) and the ternary Ir-base alloys (about 11 pct). An excellent balance of high-temperature strength and ductility was obtained in the alloy with 10 at. pct Ni-18.9 at. pct Al. The effect of Ni and Al on the strength of the Ir-Nb binary alloy is discussed.     

Fundamental research on iron coke hot briquette – A new type burden used in blast furnace

In order to improve blast furnace efficiency, reduce CO₂ emission and accelerate energy utilisation, a new preparation process of iron coke hot briquette (ICHB) based on the raw materials conditions in China, a new type blast furnace ironmaking burden, was experimentally investigated in this paper. The new preparation process was researched and optimised through single factor experiment and orthogonal experiment. Meanwhile, the reactivity and the post-reaction strength of ICHB prepared under the optimised conditions were tested and the effect of ICHB on the thermal performance of conventional coke was researched. In addition, softening and dripping properties of mixed burden with optimised ICHB charging was simultaneously investigated. The results showed that the optimised preparation parameters of ICHB include 15% iron ore, 65% bituminous coal, 350°C hot briquetting temperature, 1100°C carbonisation temperature and 4 hours carbonisation time. The reactivity and the post-reaction strength of ICHB prepared under the optimisation conditions are 62.4 and 10.6%, respectively. ICHB has protective effect on conventional coke and the protective effect is more obvious with 10% ICHB adding. With the increase of ICHB charging ratio, softening interval T₄₀–T₄ of mixed burden is widened while melting interval T_D–T_S (namely cohesive zone) is narrowed. Additionally, the permeability of mixed burden becomes better and dripping ratio is first increased then decreased. The suitable charging ratio of ICHB in mixed burden is about 30%.     

Analysis on the stamping coke dissolution of hot metal in the blast furnace hearth

By utilising the carburiser-cover methods, this article mainly focuses on the impacts of different carbon sources on hot metal carburising in the blast furnace hearth. The carburising rate, an indicator of the evaluation of coke including stamping coke and graphite, is compared at 1450–1550°C. Additionally, the apparent activation energy of carburisation of coke 1, coke 2 and graphite are 236.9, 178.8 and 46.0?kJ?mol^?1, respectively. The difference in activation energy for the three carbon sources in question is attributed to the mineral matters in coke, because it is capable of influencing the effective contact interface area between the liquid iron and carbon. As to the overall viscosity of the interface layer between the hot metal and carbon, it is mainly affected by the temperature and ash content and its composition. When the temperature increases from 1450 to 1550°C, the viscosity of the minerals on the interface layer will decrease correspondingly. The defined surface area of mineral reduces from 86.7 to 70.7% in coke 1 and from 82.5 to 69.3% in coke 2. Finally, to improve the carburising rate the basicity of the oxide contents in the coke should be increased by adding CaO or MgO.     

捣固焦炭内在质量及等反应后强度指标

 为了研究捣固焦炭对大高炉的适应性,在1050～1200℃使用焦炭连续热反应装置对A类顶装焦、B类捣固焦、C类捣固焦3类焦炭进行等温等反应的溶损反应。当焦炭的失重率分别达到30%,35%,40%时,停止反应,通过I型转鼓检测焦炭的反应后强度。结果表明：捣固处理在一定程度上可以改善焦炭的热态性质;在1100～1150℃时焦炭强度破坏程度最严重;等反应后强度与国家标准CSR存在差异性。     

Effect of Purity Levels on the High-Temperature Deformation Characteristics of Severely Deformed Titanium

In the present investigation, high-temperature compression tests were conducted at strain rates of 0.001 to 0.1 s^?1 and at temperatures of 873 K to 1173 K (600 °C to 900 °C) in order to study the hot deformation characteristics and dynamic softening mechanisms of two different grades of commercial purity titanium after severe plastic deformation. It was observed that the effects of deformation rate and temperature are significant on obtained flow stress curves of both grades. Higher compressive strength exhibited by grade 2 titanium at relatively lower deformation temperatures was attributed to the grain boundary characteristics in relation with its lower processing temperature. However, severely deformed grade 4 titanium demonstrated higher compressive strength at relatively higher deformation temperatures (above 800 °C) due to suppressed grain growth via oxygen segregation limiting grain boundary motion. Constitutive equations were established to model the flow behavior, and the validity of the predictions was demonstrated with decent agreement accompanied by average error levels less than 5 pct for all the deformation conditions.     

Raw Material Strength in a Blast Furnace at Operating Temperature

This paper presents simulative tests in a continuous hot model of the lumpish zone in a blast furnace. Samples after reaction were analysed in compression tests and a relationship between reaction degree and temperature in a blast furnace was derived. Compression strengths of coke, pellets and sinter with different reaction degrees were measured at relevant temperatures using a high temperature compression testing machine with adjustable atmosphere. Based on the results, the regulation of strength variability and the mechanism of breakage of raw materials in blast furnaces were researched. As an effect of the increases of temperature and carbon loss rate, the strength of coke had a negative linear relationship with the temperature in the indirect reduction zone in a blast furnace. The carbon loss rate of coke in the stock column of a blast furnace is about 36% and the strength can be decreased by more than 90%. A practical way to save coke strength is to reduce the carbon loss rate. The strength of pellets was decreased by about 60% to 70% in the lumpish zone. If the original strength of pellets was higher than 2000 N, the high temperature strength roughly kept at a coordinative level over 1000 N and was sufficient to avoid damage in the blast furnace. Due to the reduction of hematite and disappearance of calcium ferrite, the strength of sinter showed a strong decline when the reduction degree reached 10%. The value at the top of the cohesive zone was only about 15% of that on the charging bank. Powder from sinter was easily produced at these two places.     

Flow of molten slag and iron at 1500 °C to 1600 °C through packed coke beds

The blast furnace dripping zone is of great importance to the mass transfer of elements such as sulfur, carbon, and silicon, to and from the liquid metal phase. To understand mass transfer in the dripping zone, not only mass-transfer reactions and kinetics should be known, but the flow phenomena and process dynamics should be understood as well. The flow of hot metal and slag in the dripping zone was studied in experiments, in which liquid slag and metal trickled through a packed coke bed at 1500 °C to 1600 °C. The results indicate that slag and iron flow concurrently in a funicular type of flow. The iron flows through the core of the voids in the bed and is enveloped by slag, which flows filmwise in between the coke and the iron. This mode of flow allows for a large contact area between slag and iron, through which mass can be transferred. While flowing, the liquid can only pass and access a void, if and when the fluid capillary pressure at the void neck can be overcome. As a result, liquid droplets collect into rivulets. These rivulets flow down, along the accessible voids, using only a part of the available volume. The residence times of the fluids in the bed depend partly on the length of the pathway and are a function of the bed structure, the void neck distribution, and the stochastics of the flow. During flow, slag may react with coke, thus changing the distribution of the slag composition, and its sulfur capacity. In addition, the residence time distribution of the slag and the liquid holdup change as a result of these reactions. Holdup and residence time distribution of the liquids as measured in the experimental setup could not be modeled quantitatively, most likely due to the doubly distributed nature (in space and in time) of the model parameters, induced by reactions between slag, coke, and liquid metal.     

焦炭强度变化及喷煤的影响

对焦炭在高炉内的强度变化规律及喷煤的影响进行了研究。应用连续高炉块状带热模型得到失碳率和温度在块状带的分布;使用可调气氛高温抗压实验机测量了在高温下焦炭的抗压强度与失碳率的关系。推导出了不同的焦炭在高炉内实际抗压强度的计算公式,分析了喷煤和煤粉燃烧率对焦炭失碳率的影响,根据喷煤对焦炭强度的影响,给出了计算最佳煤粉燃烧率的方法。     

Optimization of hot workability in stainless

The hot working behavior of 304L stainless steel is characterized using processing maps developed on the basis of the Dynamic Materials Model and hot compression data in the tem- perature range of 700 °C to 1200 °C and strain-rate range of 0.001 to 100 s♪-1. The material exhibits a dynamic recrystallization (DRX) domain in the temperature range of 1000 °C to 1200 °C and strain-rate range of 0.01 to 5 s_-1. Optimum hot workability occurs at 1150 °C and 0.1 s_-1, which corresponds to a peak efficiency of 33 pct in the DRX domain. Finer grain sizes are obtained at the lower end of the DRX domain (1000 °C and 0.1 s^-1). The material exhibits a dynamic recovery domain in the temperature range of 750 °C to 950 °C and at 0.001 s"1. Flow instabilities occur in the entire region above the dynamic recovery and recrystallization domains. Flow localization occurs in the regions of instability at temperatures lower than 1000 °C, and ferrite formation is responsible for the instability at higher temperatures.     

包钢入炉焦和风口焦的研究

通过对入炉焦和风口焦的工业分析、热反应性实验以及显微组分进行数据对比分析,认为包钢高炉循环碱含量较高,加快了焦炭的反应性,降低了焦炭反应后强度,在配煤炼焦中适当配入一定比例的低变质程度的煤,有利于提高焦炭的热反应强度.     

焦炭热性能对高炉操作影响的研究进展

通过调研国内外焦炭热性能对高炉操作影响的研究进展,发现日本炼铁界对焦炭反应性关注度较高,且观点较一致:在确保焦炭冷、热态强度的前提下,较高反应性的焦炭有利于抑制风口部位焦炭的粉化和改善高炉炉内矿石还原速度,利于低成本冶炼;国内对焦炭反应性对高炉操作影响机理方面的探讨较日本少,观点与日本不同,认为焦炭具有较低的反应性和高强度利于高炉操作。建议更为全面深入研究热性能对高炉操作的影响,并在生产实践中进行探索,以求在领域内达成共识。     

The influence of substructure on the elevated and room temperature strength of a 26 Cr-1 Mo ferritic stainless steel

The high temperature flow stress behavior of an electron beam melted 26 Cr-1 Mo ferritic stainless steel was determined for large torsion strains (e ~ 15) over a temperature range from 400 °C (750 °F) to 1000 °C (1830 °F) and a strain rate range from 6 × 10^-3 to 6.3 s^-1. The room temperature compressive yield strength measured after torsional warm working was also investigated. It was found that the high temperature flow strength and the room temperature compressive yield strength were strong functions of the subgrain size. Strain softening was observed during warm working while the room temperature compressive yield strength was found to increase with prior torsional strain. The increase in the subgrain misorientation angle and, to a lesser extent, the subgrain shape change that occurs with increased warm working strain appear to be responsible for the strain dependence of the flow stress at both elevated and low temperatures. At the time this investigation was performed, all authors were affiliated with the Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305.     

兰炭替代部分焦炭对焦炭层透液性的影响

为探究高反应性兰炭替代部分焦炭加入高炉的可行性,文章通过对气化后的焦炭和兰炭进行冷、热态透液性试验,获得液体在焦床中的流动速度、滴落量及滞留量.结果表明,在高炉上部气化阶段,高反应性兰炭对焦炭有一定的保护作用.在冷态滴落实验中,小粒径燃料条件下,随着兰炭比例的增加,液体滴落速度变缓,滴落量降低16.8％.当兰炭粒度增加...