微波场中高碳锰铁粉及固相脱碳物料的电磁性能

 碳酸钙粉热分解产生的CO2对高碳锰铁粉固相脱碳具有很好的脱碳作用,但脱碳过程中物料电磁性能的变化对微波加热的影响很大。 将高碳锰铁粉与碳酸钙粉按质量比1∶1均匀混合,在微波场中加热进行固相脱碳反应,脱碳温度分别为900、1000、1100、1200℃,且各保温脱碳60min。用矢量网络分析法测试试样的电磁性能。结果表明,高碳锰铁粉脱碳前后的电磁性能变化很大。脱碳物料的εr′在7.00~10.00范围内,εr″≈0.05。脱碳物料的μr′≈1.00,μr″≈0.00。温度为900和1200℃时,脱碳物料的电磁性能相近。高碳锰铁粉加热到1000和1100℃时,脱碳物料的tanδε和tanδμ最大,微波加热效果良好。     

微波加热高碳铬铁粉固相脱碳动力学

采用微波加热对高碳铬铁粉固相脱碳进行了动力学研究.以碳酸钙粉为固体脱碳剂,按高碳铬铁粉中碳与碳酸钙粉完全分解后产生的CO₂的摩尔比为1︰1和1︰1.4混合,在微波场中对内配碳酸钙高碳铬铁粉加热到不同温度并保温脱碳一定时间,测定其碳含量并计算固相脱碳反应的表观活化能.实验表明:提高内配碳酸钙的比例,物料的脱碳率会相应提高,但混合物料的微波加热升温速率会变小;对于脱碳摩尔比相同的物料,随着脱碳温度的提高和保温时间的延长,物料的脱碳率随之提高.当1200℃保温脱碳60 min时,两种脱碳摩尔比下物料脱碳效果最好,脱碳率分别为65.56%和82.96%.微波场能促进高碳铬铁粉中碳的活化扩散和CO₂的吸附扩散.微波加热内配碳酸钙高碳铬铁粉固相脱碳反应近似为一级反应,脱碳反应的表观活化能为68.43 kJ·mol-1.      

二氧化碳气氛中高碳锰铁固态脱碳的工艺研究

热力学计算表明了在二氧化碳气氛下高碳锰铁固态脱碳的可行性。实验采用正交试验法来分析各因素影响程度的大小。高碳锰铁颗粒表面与CO_2发生固-气反应,颗粒内部锰的氧化物与其碳化物发生固-固反应进行脱碳。结果表明:固体颗粒度是脱碳的主要影响因素,增大目数,升高温度,减小换气间隔能促进脱碳反应进行。试验中最低含碳量可达0.025%。     

Solid-Phase Decarburization of High-Carbon Ferromanganese Powders by Microwave Heating

The solid-phase decarburization of high-carbon ferromanganese powders (HCFPs) was investigated using calcium carbonate as the decarburizer by microwave heating and conventional heating methods to explore the differences of microwave heating and conventional heating. Experimental results show that HCFPs containing calcium carbonate were heated up to 900, 1000, 1100, and 1200 °C and held for 60 min for decarburization by microwave heating at decarburization ratios of 76. 69%, 82.90%, 84.11%, and 85.75%, respectively. These ratios arc higher than the decarburization ratios used for conventional heating under the same experimental conditions. The microwave heating can significantly improve decarburization ratio. This indicates the microwave heating field features a non-thermal effect, which in turn, visibly enhances the carbon diffusion ability of HCFPs. It also improves the kinetic conditions of solid-phase decarburization.     

真空下高碳锰铁固态脱碳规律的研究

通过热力学计算表明,在常压下难以进行的高碳锰铁固态脱碳,真空下可以实现。将高碳氧化锰与高碳锰铁混合,置于管式炉内高温处理,并抽真空,通过温度调节,一定时间后取出产物测定碳含量,并分析影响脱碳反应的因素。试验结果表明:延长反应时间及提高团块紧实度能够显著促进反应的进行,反应物中高碳氧化锰的比例及其反应温度与脱碳反应有一定关系。     

Decarbonization and chromium conservation thermodynamics of partial CO2 instead of Ar or O2 in AOD furnace

Decarbonization and chromium conservation technology is mainly achieved by blowing O2 and Ar during the traditional AOD furnace smelting process. The CO2 emissions per ton of steel production in the steel industry are about 1. 57t. If the CO2 emissions can be collected and recycled in the steel production process, it can not only save energy and reduce emissions, but also reduce the cost of smelting. The feasibility of using CO2 instead of Ar or O2 to be injected for smelting stainless steels was verified by thermodynamic calculations. The reaction limits of the different carbon content, the rising and falling temperature of elemental oxidation, the reaction rate under different ratios of CO2 injection, the depth of decarburization, and the result of chromium retention were also calculated. The thermodynamic mechanism of blowing CO2 to replace O2 decarburizing and protecting chromium was analyzed. The results show that blowing CO2- O2 mixed gas in high carbon zone is conducive to decarbonization and chromium conservation in the AOD smelting process. With the increase of CO2 ratio, the effect of chromium retention is enhanced whereas the decarburization rate is reduced. When the CO2 injection amount is increased, the decarburization reaction rate in the molten pool is too slow, causing the molten pool temperature to be low, and the CO2 injection ratio should be controlled between 20 vol.% and 40 vol.%.     

Modelling Decarburization in Electrical Steels

A model is presented to predict the decarburization rate of electrical steels during reactive annealing. In a first step, the warm annealing atmosphere composition is calculated as function of the composition of the cold gas containing N₂‐H₂‐H₂O‐CO‐CO₂‐CH₄‐O₂. In a second step, the decarburization kinetics, which is controlled both by the surface reaction and by the diffusion of carbon towards the surface, is calculated. The model is then used to study the balance between surface reaction and the diffusion control of the decarburization process. We could conclude that for low sheet thickness and/or low H₂O/H₂ ratio in the annealing atmosphere, the decarburization is surface reaction controlled, while for commercial thicknesses and industrially applied dew points, the process is diffusion controlled. Furthermore, we looked at the difference in decarburization between complex N₂‐H₂‐H₂O‐CO‐CO₂ atmospheres used in industrial application, and N₂‐H₂‐H₂O atmospheres typically used in lab annealing. We could conclude that the decarburization rate is influenced by the addition of CO and CO₂ and that the final carbon level is increased if CO and CO₂ are added to the gas.     

H2/H2O气氛下Fe?C合金薄带气固脱碳反应动力学

为对H₂/H₂O气氛下Fe?C合金薄带的气固反应脱碳进行动力学研究,在保证快速脱碳而铁不氧化的前提下,利用可控气氛高温管式脱碳炉,研究了不同的脱碳温度、薄带厚度、脱碳时间对Fe?C合金薄带脱碳效果的影响。结果表明延长脱碳时间、提高脱碳温度、减少薄带厚度均可提高脱碳效果。当脱碳温度为1353 K,在脱碳过程中,薄带可以分成明显的3层,由表面到内部依次是完全脱碳层、部分脱碳层和未脱碳层。完全脱碳层的组织为铁素体,此部分碳含量最低;部分脱碳层由铁素体、渗碳体和少量石墨相组成,未脱碳层由珠光体和大量石墨相组成,此部分碳含量最高。脱碳层的厚度随着脱碳时间的延长而增加,脱碳层的厚度y与时间t平方根满足良好的线性关系,可用函数y =kt0.5描述,碳原子扩散所需扩散激活能为122.36 kJ?mol?1,脱碳反应为表观一级反应,表观活化能为153.79 kJ?mol?1。      

Improved manganese extraction in the production of manganese ferroalloys

In the production of manganese ferroalloys from ore, about 50% of the manganese in the ore is lost. The manganese lost with the enrichment-slag tailings may be returned to the production of manganese ferroalloys by dithionate method of enrichment of the slurries. A technology is developed for the production of high-carbon ferromanganese from concentrate obtained by the chemical enrichment of tailings slurries. Low-phosphorus Mn slag is used in the production of ferrosilicomanganese and refined manganese ferroalloys. A method is described for alloying hot metal with manganese from slag during the production of lowand medium-carbon ferromanganese. Processes are developed for the production of medium-carbon ferromanganese by mixing ore–limestone melt with high-carbon ferromanganese and removing the phosphorus from Mn-bearing melts by bubbling with CO. The degree of phosphorus removal (70–90%) depends on the bubbling time. By means of improved production of manganese ferroalloys and extraction of manganese from slag and slurries, the manganese extraction may be significantly increased.     

关于我国高炉锰铁发展前景的思考

分析了高炉锰铁产量变化及近期下滑的主要原因,预测了高碳锰铁市场需求,通过对高炉与电炉两种冶炼高碳锰铁方法的对比,认为在我国条件下高炉锰铁发展前景看好．但必须进一步落实资源供应,搞好环境保护,提高技术装备水平,强化冶炼进程,提高我国锰铁高炉的竞争力。     

RH碳酸盐分解CO2脱碳工艺

 提出RH碳酸盐分解CO2脱碳工艺。通过从RH上升管喷吹碳酸钙粉剂实现钢水脱碳和净化钢液的目的。分析RH碳酸盐分解CO2的脱碳机理,并进行工业试验,考察RH碳酸盐分解CO2脱碳工艺对钢水洁净度的影响。结果表明,采用RH碳酸盐分解CO2脱碳工艺缩短RH精炼处理时间3 min,吨钢成本降低3～5元。铸坯的平均[w(T[O])]可达0.001 0%以下,显著提高钢水的洁净度。     

微波加热内配碳酸钙高碳铬铁粉固相脱碳

高碳铬铁无渣脱碳法可避免有毒铬渣的排放,利用微波场可快速加热粉状物料的特性,在高碳铬铁粉中配加一定比例的碳酸钙粉,可实现高碳铬铁粉快速固相脱碳.实验结果表明:配加一定比例的碳酸钙粉,不会影响内配碳酸钙高碳铬铁粉混合物料的微波加热特性;提高混合物料的脱碳摩尔比、微波加热温度和保温时间,有利于高碳铬铁粉的深度脱碳,但相应加剧脱碳铬铁粉的氧化程度.合适的固相脱碳条件为:脱碳摩尔比1∶1.0~1∶1.4,微波加热温度1100℃,保温脱碳时间60 min.在上述条件下可使碳质量分数为8.16%的高碳铬铁粉脱碳至3.91%~1.71%,脱碳率为52.08%~79.04%.      

Oxide Inclusions in Ferromanganese and Its Influence on the Quality of Clean Steels

Low and medium carbon ferromanganese produced by oxygen decarburization process and electric silicothermic process was briefly introduced, and the quality of products by these two processes was analyzed. Results showed that the total oxygen content in medium carbon ferromanganese by electric silicothermic process in China, which ranged from 0.039% to 0.171%, was between those of the common and refined products by oxygen decarburization process outside of China. The increments of total oxygen content in liquid steel were estimated when ferromanganese was added for the purpose of Mn element adjustment at the end of smelting. Refined low and medium carbon ferromanganese, which had low total oxygen content, was recommended for composition adjustment of clean steels during final stage of a heat. It is possible that the inclusions in the ferromanganese alloy greatly influenced the quality of clean steel indirectly by affecting the amount, size and composition of inclusions in steel.     

Theoretical interpretation of the decarburization mechanism in convective oxygen steelmaking

The theory of gas absorption is introduced in order to understand the decarburization mechanism theoritically. When the existing decarburization kinetic data are applied to instantaneous reaction regimes of the theory, it can be clearly explained. The decarburization mechanism in convective oxygen steelmaking can be described sufficiently by the overall reaction l/2O₂ +C → CO whether decarburization follows a direct or indirect path. The reason for this phenomenon is that the feature of instantaneous reaction remains unchanged by the intensive convection in the liquid phase. The decarburization mechanism depends only on the two stages of carbon concentration. The criterion for transition from a high-carbon to a low-carbon regime is estimated to be C < (k_a/k_L) ·P _{O 2}. In the high-carbon regime, which shows zeroth-order kinetics with respect to carbon concentration, oxygen absorption into a liquid phase is always considered to be the controlling step, and the controlling parameters area, k_G, andP _{O 2}, among which the most important parameter is the gas/liquid interfacial area,a, in the case of high-speed injection of pure oxygen. In the low-carbon regime, the controlling step is the transport of carbon in molten steel, and first-order kinetics in terms of (k_L·a) · C can be approximated. It indicates that if the outer controlling parameter (k_L · a) is conserved, the intrinsic change in carbon concentration is more important than the kinetics itself. Formerly Graduate Student at Seoul National University. This paper is a part of the dissertation of Dr. Zong in partial fulfillment of his Ph.D. degree.     

Thermodynamics of carbon in liquid manganese and ferromanganese alloys

The thermodynamics of carbon in manganese and ferromanganese melts were studied to predict the refining limit of carbon during the decarburization of molten ferromanganese. The equilibrium carbon content in a Mn-C melt was determined by the C-CO equilibrium in the presence of pure solid MnO at 1673 to 1773 K. The activities of manganese and carbon in the Mn-C melt were then calculated from the experimental results, the equilibrium constant for the reaction, and the Gibbs-Duhem equation integrated by the Belton-Fruehan treatment. The standard free-energy change of carbon dissolution in the manganese melt was determined to be 41,700 — 59.6 T J/g · atom, with the standard state taken as 1 wt pct carbon in solution. The effect of iron on the activity coefficient of carbon in ferromanganese was determined by measuring the carbon solubility in Mn-Fe melts. The first- and second-order interaction parameters between carbon and iron in ferromanganese melts were determined. The activity coefficient of carbon in the ferromanganese alloy melt can be expressed as

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An experiment simulating the heating environment of CSP furnace was performed to study the effects of heating temperature, holding time and heating atmosphere on the decarburization of 50CrV4 spring steel. The results show that the decarburization layer depth of 50CrV4 steel increases with increasing the holding time. With holding time of 30 and 60min, the decarburization layer depth increases with increasing the heating temperature below 1050?? and decreases when the temperature is over 1050??. The decarburization layer depth reaches the peak at 1050??. The mixed atmosphere of O2+CO2+H2O+N2 can effectively reduce the decarburization layer depth more than that of O2+CO2+N2 and H2O+N2. Combined with the oxidation model and Fick??s Second Law, the decarburization calculation model is established and corrected with experimental data.     

炼钢过程底吹气体的冶炼效果对比

 基于炼钢过程底吹气体热力学及动力学进行分析,研究了底吹氧气、二氧化碳、氩气、氮气的冶炼效果。研究结果发现,氩气或氮气不与熔池元素反应,底吹时熔池温度基本不变,钢中氮质量分数较高;底吹氧气或二氧化碳时,脱碳速率和钢中氮、氢质量分数基本相同,熔池温度升高了162和45 ℃。同时发现,与底吹氧气相比,二氧化碳可减少炼钢烟尘量,炉渣中[w((TFe))]降低2.50%,[w((O))]降低90.2%。     

微波烧结YG12硬质合金脱碳的控制

通过在混合料中增加炭黑和在填料中添加炭黑两种方法,来抑制微波烧结YG12硬质合金在微波烧结过程中出现的脱碳现象,从而提高微波烧结硬质合金的性能.结果表明:在混合料中添加炭黑可以抑制合金的脱碳行为,当炭黑添加量为0.4％(质量分数)时,合金的抗弯强度较理想,合金抗弯强度可达2 250 MPa;而通过在填料中添加炭黑有效抑...     

Pt涂层蜂窝金属和Ce改性Fe2O3催化CO的性能对比

铁矿石烧结烟气中含有较高浓度的CO（体积分数0.5%～2%）,因此对其进行CO脱除意义重大。为了探究不同类型催化剂的催化效果,采用浸渍法制备了Pt涂层蜂窝金属催化剂和铁铈氧化物催化剂,并通过X射线荧光光谱分析（XRF）对其组分含量进行了分析。二者在模拟烧结烟气中进行CO脱除性能的对比实验,活性测试表明,不同CO初始体积分数、烟气温度以及水汽含量对CO催化氧化的脱除效率影响较大。当模拟烟气中不含水汽的时候,二者在180 ℃及更高温度下对CO的脱除效率均能达到60%以上。反应温度为180 ℃,水汽体积分数为11.7%时,Pt负载型催化剂中的CO转化率为63.9%,而该条件下Ce改性Fe₂O₃催化剂的CO转化率仅为34.9%。当温度在180～300 ℃范围内,Pt负载型催化剂具有较好的抗水性,且继续升高温度,水汽体积分数增加对催化剂效率的负面影响更显著。如水汽体积分数从0增加到27.1%时,与180 ℃时的催化效率相比,Pt负载型催化剂在240 ℃时的催化效率由73.9%降至62.3%,降幅远远增大。另外,对这两种催化剂进行了抗硫性测试。当水汽体积分数为0时,Ce改性Fe₂O₃催化剂抗硫性更佳,但当SO₂和水汽同时存在的情况下,Pt负载型催化剂具有更好的抗硫性。因此,在实际烧结中建议采取高效的脱硫措施并布置脱水层以减少其对于催化剂的负面影响。