底吹钢包三相流的数值模拟

采用多相流体积法对某钢厂的LF炉底吹钢包建立了氩气/钢液/钢渣三相瞬态数学模型. 描述了钢包内多相流动的基本形貌,并与稳态计算的结果进行了对比;研究了不同吹气流量对渣滴卷入深度和渣眼直径的影响. 计算结果表明,渣滴卷入深度和渣眼直径随吹气流量的增加而增加,且在吹气流量为600 L/min时发生骤增,该流量为临界卷渣吹气流量;在保持吹气流量为300 L/min的条件下,当渣层厚度从150 mm增加到300 mm时,渣眼直径由455 mm减小至110 mm,且此时更容易发生卷渣现象.     

水口结瘤对结晶器流场影响的物理模拟

以某厂板坯结晶器为原型建立1：1的物理模型,通过监测液面波动,研究浸入式水口结瘤物对结晶器流场造成的影响。实验结果表明：水口结瘤物的存在会导致结晶器水口两侧流场的明显不对称,水口堵塞侧钢液更多集中于结晶器上部,下回流占据区域较小;未堵塞一侧漩涡卷渣出现的频率较高;较大拉速下,随着水口倾角的增大,液面平均波动逐渐减弱;拉速提高会造成水口两侧平均波高的差距变大,结瘤物脱离水口后液面恢复稳定的时间延长;结瘤物脱离瞬间会导致流场迅速恶化,影响铸坯质量。     

电磁制动对连铸器内钢水流场的影响及表面检测

采用数值模拟与钢水表面插钉法,对电磁制动条件下薄板坯连铸结晶器内钢水流动进行研究,分析了不同磁场强度对结晶器内钢水流动及弯月面波动的影响.模拟结果表明,电磁制动能够明显抑制高速流动的钢水,减小对结晶器窄面的冲击及钢水表面卷渣的影响,磁场电流强度由180A增加到284A时,钢水表面速度最大值由无电磁制动的0.85m/s分别降低至0.5,0.16m/s.插钉法可作为一种经济有效的方法检测钢水表面速度,且测量值与模拟结果比较吻合.通过合理控制磁场电流强度约260A可以优化结晶器内钢水流动,进而改善铸坯质量.     

Three-phase Fluid Numerical Simulation and Water Modeling Experiment of Supersonic Oxygen Jet Impingement on Molten Bath in EAF

By means of the computational fluid dynamics software Fluent 6.3, a mathematical model of three-dimensional three-phase fluid flow field in the molten bath of electric arc furnace （EAF） with side accessorial oxygen lances was developed to study the transient phenomena of oxygen jet impingement on the molten steel and the molten slag. The water modeling experiment was carried out to verify the simulation results. The impingement of the supersonic oxygen jet caused impact dent on the molten steel surface accordingly. The area of impact dent changed almost in linear relationship to flow rate of oxygen jet, which can be expressed by a deduced mathematical equation. And the relationship between the impact force of oxygen iet and the correspondingly formed apparent static pressure on molten bath was obtained, which was in linear relationship and a direct proportion, and can also be expressed by a deduced mathematical equation.     

QD08钢中Ds类夹杂物形成原因及控制

 QD08钢因其特殊的工作环境,要求具有较高的抗疲劳特性,而Ds类夹杂物是削弱QD08钢抗疲劳性能的主要原因。为了探究Ds类夹杂物的形成原因及调控方法,解决Ds类夹杂物超标问题,对该钢种炼钢-精炼-连铸全流程进行取样分析。分析结果表明,影响QD08钢疲劳性能的Ds类夹杂物主要成分为CaS-Al₂O₃-MgO-CaO,其尺寸在15~30 μm范围内波动,主要在LF精炼钙处理操作后开始出现。QD08钢中Ds类夹杂物是以钙镁铝酸盐为核心骨架,外围包裹CaS而形成的。结合夹杂物的成分分布,确定了钢中钙含量高不利于QD08钢中Ds类夹杂物的控制,被改性后的夹杂物熔点低,与钢液润湿性强而难以穿过钢渣界面进入到渣中,且夹杂物在钢液中易聚合长大,造成夹杂物尺寸的增加,为Ds类夹杂物的形成提供了条件。提出在精炼环节采用高氧化钙溶解度精炼渣和微钙处理工艺优化方案,并进行了工业验证试验。通过微钙处理保证了必要的夹杂物改性,可防止水口结瘤,配合减小中间包液面的波动,控制合适的拉坯速度,可避免钢包下渣和卷渣现象的发生。控制更多的夹杂物成分分布在非液相区,抑制了夹杂物的碰撞长大,使得Ds类夹杂物等级降低。试验结果表明,QD08钢中影响其疲劳性能的Ds类夹杂物得到了控制,初检合格率由93.6%提高至98.0%,为企业带来了直接的经济利益。     

Effect of vanadium on modification of inclusions in Mn- and Si-deoxidized steel during heat treatment at 1473 K

The effect of vanadium (V) on the modification of oxide inclusions in steels with different concentra-tions of Mn, Si, and V was determined before and after heat treatment at 1473 K.Changes in the morphology, size, and composition of these inclusions were analyzed.Equilibrium relations between the inclusions and steels at 1873 K and 1473 K were calculated using available thermodynamic data to roughly approximate the stable oxide inclusions in the steels.The results revealed that the concentra-tions of V and Si in the steel are critical for controlling the modification of the inclusions during heat treatment at 1473 K.MnO-SiO2-type oxide inclusions gradually transformed into MnO-V2O3-type or Mn-SiO2- and MnO-V2 O3-type inclusions in low-Si high-V steels heat-treated for 60 min.In addi-tion, the morphology of the inclusions changed from spherical to irregular.A Si-accumulated zone and a V-depleted zone formed close to the interface in the steel matrix.The experimental and calcula-tion results indicated that, during the heat treatment, an interface chemical reaction occurred be-tween the Fe-Mn-Si-V steel and the MnO-SiO2-type oxide inclusion.     

CO2矿物碳酸化的研究进展

CO₂的温室气体效应已为全世界环保工作者所重视。CO₂ 的矿物固定即碳酸化是减少其温室气体效应的有效方法之一。本文从矿物碳酸化的热力学、动力学方面分析了这种方法的可行性以及反应机理、速率影响因素等;总结了其工艺路线、生产成本以及产品的性能、用途等。指出用钢铁工业的废弃物-钢渣固定CO₂具有大的应用前景。     

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The tuyere-damaged phenomenon of COREX-3000 was investigated, and the conclusion was found that the combined effect of both melting loss under high temperature and scouring abrasion by high speed air flow led to the damage of tuyeres. The methods from five aspects were proposed to reduce the dilapidation of turyere through analyzing thermal distribution of COREX tuyere combustion zone. Based on that above, the measures that small coke was chosen as substitutes for part of Shanxi coke and oxygen-nitrogen blending injection replaced the oxygen injection were taken by Baosteel, which effectively prolonged the working life of tuyere.Besides, the effects of the measures above on COREX were analyzed in detail, and the following results show:Using Baosteel small coke improved the burden permeability to avoid that heat is gathered in tuyere combustion zone; Oxygen-nitrogen blending injection reduces heat production in tuyere combustion zone, lowers the heat conduction ability of air flow, and forms one thin carbon-nitride protective layer on tuyere surface to prolong the working life of tuyere.     

Consteel-LF-VD-CC生产55SiMnMo钢种的洁净度研究

针对贵钢在使用55SiMnMo中空钢实心坯制造的钎杆出现因硬性夹杂导致断裂的问题,对55SiMnMo中空钢生产工艺Consteel-LF-VD-CC进行全流程取样,对钢中气体含量和夹杂物进行分析,找到钢水洁净度的限制性环节,并由此得出改进措施. 钎杆断裂面的夹杂物分析显示,主要为较大粒径的带棱角的纯Al2O3硬性夹杂以及不规则形状的MgO-CaO-SiO2复合夹杂. 分析钢样可发现以下工艺问题：LF精炼后期渣面裸露吸气,钙处理后夹杂物变性不完全,钢包开浇过程中存在明显吸气和卷渣现象. 铸坯中T[O]含量为9×10-6,显微夹杂物以MnS, Al-Mn的复合氧化物夹杂为主,大型夹杂物以SiO2-Al2O3-MnO-CaO复合夹杂为主.     

合金元素含量对C82DA钢铸坯微观组织的影响

中心疏松和偏析缺陷常导致帘线钢C82DA小方坯产品质量评级不达标。本研究结合现场试验和数值模拟,探讨钢水过热度和合金元素含量对铸坯凝固组织的影响规律。采用移动边界法得到小方坯帘线钢的铸坯坯壳厚度生长规律,并在此基础上采用CAFé法对帘线钢的微观组织进行数值模拟,模拟结果与试验铸坯得到的微观组织形貌基本一致。研究结果表明：低过热度有利于增加等轴晶的个数并且减小其尺寸;通过探讨C、Si、Mn和Cr等元素含量对铸坯微观组织形貌的影响,得到了优化帘线钢微观组织的方案以及对应的元素含量。