高供氧压力下高马赫数氧枪数值模拟

  以北方某钢厂100 t转炉为原型，建立顶吹转炉炉内流场的三维数学模型，采用Fluent软件研究了不同高马赫数氧气射流与熔池钢液速度流场分布之间的依赖关系。研究发现，高马赫数氧枪在Ma（马赫数）为2.0～2.3时，曲线平稳，为最佳供氧压力。在提高供氧压力的同时，氧气射流的最大速度、熔池钢液面的冲击直径及冲击深度也随之增加。模拟结果显示，氧气射流在设计工况氧压小于1.0 MPa时，射流之间相互干扰作用最弱；氧气射流在设计工况氧压力大于1.0 MPa后，冲击直径与冲击深度增幅较小。基于上述研究，在实际生产中应用了高马赫数氧枪后，并结合变枪变压操作工艺，可以改善熔池底部钢液流动状况、稳定转炉吹炼过程、控制炉渣喷溅。     

电炉氧化期高压高强度供氧

氧化期提高氧压和供氧强度试验是在0.5t电弧炉内进行。冶炼钢种为ZG35、ZG45和阀门钢,熔毕碳适当配高,料熔化80％吹氧助熔,助熔压力控制在20～30 kg/cm~(2),氧化期吹氧压力50～70kg/cm~(2),最高达100 kg/cm~(2),供氧强度3～4m~(3)/t·min。     

氧枪喷头参数优化与应用

为缩短转炉冶炼周期,通过改进氧枪喷头参数实现提高供氧流量而氧压不升高,达到缩短供氧时间、提高一倒出钢率的目的。因设计喷头喉口直径增加,氧射流冲击深度略深,实际操作过程中枪位适当提高加以应对。     

100t转炉氧枪的优化设计

以水钢100t转炉氧枪为研究对象,利用氧枪设计经典理论,结合水钢生产工艺,通过设计计算研究得,水钢氧枪在提高转炉冶炼节奏,缩短供氧时间,提高供氧强度方面已不能满足生产的需要。为此,研究以氧枪设计经典理论为基础,紧密结合水钢生产实际,以氧枪设备参数设计为研究切入点,进行新氧枪的设计。并利用Fluent软件对氧枪射流流场及射流与熔池的作用情况进行了模拟验证。研究表明,氧枪参数即当喉口直径为36．8mm,出口直径为46．7mm时,满足生产的要求。     

超音速氧枪射流特性的数值模拟

利用GAMBIT建立了轴向计算长度2 200 mm和径向计算长度800 mm的超音速氧枪的数学模型,并采用FLUENT软件对氧枪射流特性进行数值仿真研究。分析了单孔氧枪超音速射流特性,以及操作压力(0.6~1.0 MPa)和环境温度(298~1 873 K)对流动特性的影响。结果表明,入口滞止压力在设计压力±25%内对射流轴向衰减及径向扩展影响不大,其与射流的超音速区长度呈二次曲线关系变化,随环境温度升高,射流轴向衰减变缓慢,核心区长度增加,超音速区长度和环境温度呈线性关系,环境温度对射流径向影响很小。     

120 t转炉氧枪喷吹射流特性及其冶金效果

运用数值模拟的手段研究了天钢联合特钢有限公司120 t转炉氧枪优化前后两种氧枪顶吹射流特性,并分析射流与熔池相互作用特性。研究结果表明,新枪可有效提高氧射流对熔池的作用效果,提高氧气利用率。分析冶炼数据发现,相较于原枪,优化后供氧时间缩短2.12 min,吨钢氧耗下降5 Nm3/t,渣中Fe O含量下降1.75%。     

变角氧枪对熔池弱搅拌区影响的数值模拟研究

针对唐钢50 t转炉冶炼条件,采用Fluent软件对氧气射流—钢液两相间相互作用进行了数值模拟研究,分析了变角氧枪作用下熔池内钢液流场、枪位及喷孔倾角对弱搅拌区比率的影响规律,为变角氧枪结构优化提供了理论依据。结果表明:与非变角氧枪相比,变角氧枪作用下钢液流场更均匀;熔池底部存在弱搅拌区,随着枪位的提升,熔池弱搅拌区比率有所增加;除喷头F外,研究的变角氧枪作用下熔池的弱搅拌区比率普遍低于非变角氧枪;在同一枪位下,与对角喷孔倾角相差0.5°相比,对角喷孔倾角相差1°时,熔池内弱搅拌区比率更低;在研究的9个喷头中,喷头D(11°/12°)作用下熔池内弱搅拌区比率最小。     

转炉炼钢氧气压力的选择

 转炉的工作氧压由喷头马赫数决定,使氧射流对熔池的穿透深度[(L)]与熔池深度[(L0)]有一个合适的比例[(L/L0)]。据实际调查,国内有1/3转炉钢厂的工作氧压不合理。根据理论分析和生产实践经验,转炉的工作氧压应比氧气喷头马赫数所对应的滞止压力高5%～15%,可以减少射流在超音速范围内的激波损失,使氧射流对熔池有较大的冲击深度,也可防止因喷孔出口处的负压而使喷孔快速熔损。在氧气喷头设计和制定供氧制度中还需了解氧气管道压力损失[Δp],用实测法所得到的[Δp]值较为可靠。     

转炉供氧参数对喷溅的影响

 通过水模实验测量了氧枪喷头参数及供氧条件对喷溅率的影响。试验结果加深了对氧射流与熔池作用的认识,为氧枪喷头设计及制定供氧制度提供了依据。多孔喷头射流对熔池的作用是各单孔喷头叠加的结果。为获得良好的冶金效果,要把氧枪喷头参数和供氧制度都控制在合理范围。     

顶吹工艺中氧枪喷嘴射流的液流分析

在炼钢过程中，为了控制转炉吹炼和喷溅现象，了解顶吹氧枪的射流特性是很重要的。然而，目前几乎没有关于氧枪喷嘴射流特征的理论研究。为此，国外某公司以流体动力学为基础，通过液流分析，研究了单孔和多孔氧枪的射流特征。单孔喷嘴射流计算的核心长度与高精度的测量结果是一致的。液流分析说明，较高的环境温度将导致较低密度和较高速度的射流，但对动压力几乎没有影响。     

大罐顶渣向钢液增氧因素分析

 依据实验数据计算结果,对钢液增氧的因素及其采取的相应措施进行了分析与探讨。研究结果表明：在氧化性顶渣条件下,钢液中w（［Als］）的变化率≥20％,而在还原性顶渣条件下,钢液中w（［Als］）的变化率≤10％;氧化性顶渣对钢液供氧的贡献率大于钢包与中间包衔接的水口处吸气对钢液供氧的贡献率;减少转炉下渣量及对顶渣进行改质可减轻炉渣向钢液供氧程度;大罐下渣量不会使中间包成为新的增氧源。     

Numerical Simulation of Fluid Flow in Bath during Combined Top and Bottom Blowing VOD Refining Process of Stainless Steel

The fluid flow in a bath in combined top and bottom blowing vacuum‐oxygen decarburization (VOD) refining process of stainless steel has numerically been simulated. The three‐dimensional mathematical model used is essentially based on that proposed in our previous work for the flow in combined side and top blowing argon‐oxygen decarburization (AOD) process, but considering the influence of reduced ambient pressure. Applying it to the flow in the bath of a 120 t VOD vessel under the refining conditions, the results present that the model can fairly well simulate and estimate the flow phenomena. The flow pattern of molten steel in the bath with the combined blowing is a composite result under the common action of the jets from a three‐hole Laval top lance and gas bottom blowing streams. The jets have a leading role on it; the molten steel in the whole bath is in vigorous stirring and circulatory motion during the blowing process. The streams do not alter the basic features of the gas agitation and liquid flow, but can evidently change the local flow pattern of the liquid and increase its turbulent kinetic energy to a certain extent. The flow field and turbulent kinetic energy distribution in the combined blowing with three tuyeres are more uniform than those in the blowing with double tuyeres. Increasing properly the tuyere eccentricities is of advantage for improving the velocity and turbulent kinetic energy distributions, the stirring and mixing result in the practical VOD refining process.     

15-5PH不锈钢大型锻件冶炼脱氧工艺研究

摘要：以实际工艺流程50t EBT-VOD-LF-VC冶炼15-5PH不锈钢为背景,通过FactSage 8.0和经典Wagner模型研究冶炼硅铝复合脱氧过程中钢液中的铝含量、炉渣组成以及冶炼温度等因素对钢液中氧含量的影响进行了热力学研究。结果表明：Al-Si复合脱氧为15-5PH不锈钢冶炼过程中的最佳脱氧工艺,为了保证脱氧的冶炼效果,应控制钢液中的酸溶铝的质量分数在0.015%左右;降低冶炼温度有利于降低钢液平衡氧含量;考虑炉渣的物理性能和钢渣界面平衡反应得出脱氧工艺的最优炉渣成分,碱度为2.5~3.0,w（(Cr2O3)）=0.5%,w（(Al2O3)）=20%,w（(MgO)）=5%,w（(CaF2)）=5%;经过工艺优化后生产的15.5PH不锈钢中氧含量明显降低,均满足产品要求,炉渣碱度对平衡氧含量和实际生产全氧含量的影响规律基本相同。     

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.     

大型转炉多孔喷头射流与熔池作用的水模研究

利用1／10有机玻璃模型,根据相似原理,研究了宝钢300t转炉多孔喷头射流与熔池的作用。测定了不同吹炼条件(氧气流量、枪位高度、喷头孔数、炉容比)下的熔池混匀时间、喷溅量、穿透深度与渣钢之间的乳化率。测定结果表明,氧气流量、炉容比对喷溅量影响较大;氧气流量、枪位高度对穿透深度有重要影响。渣钢间的乳化要求有适当的枪位高度。6孔交错布置喷头有较好的吹炼性能。     

Numerical Simulation of Jet Behavior and Impingement Characteristics of Preheating Shrouded Supersonic Jets

As a novel supersonic j et technology,preheating shrouded supersonic j et was developed to deliver oxygen into molten bath efficiently and affordably.However,there has been limited research on the jet behavior and im-pingement characteristics of preheating shrouded supersonic j ets.Computational fluid dynamics (CFD)models were established to investigate the effects of main and shrouding gas temperatures on the characteristics of flow field and impingement of shrouded supersonic j et.The preheating shrouded supersonic j et behavior was simulated and meas-ured by numerical simulation and j et measurement experiment respectively.The influence of preheating shrouded su-personic j et on gas j et penetration and fluid flow in liquid bath was calculated by the CFD model which was validated against water model experiments.The results show that the uptrend of the potential core length of shrouded super-sonic j et would be accelerated with increasing the main and shrouding gas temperatures.Also,preheating supersonic j ets demonstrated significant advantages in penetrating and stirring the liquid bath.     

Transferring Characteristics of Momentum/Energy during Oxygen Jetting into the Molten Bath in BOFs: A Computational Exploration

This paper presents a numerical study of transferring characteristics of momentum/energy during oxygen jetting into the slag–metal molten bath in basic oxygen furnaces by a multi‐fluid volume of fluid model. The evolution of the momentum/energy and turbulence of jets along their axial travel were studied. The results were quantitatively compared within a wide range of oxygen supply pressures, at which the jets may be at under‐ or over‐expanding state. The efficiency of the momentum/energy transfer from the jets to the molten bath was also assessed with respect to lance height and operation pressure. The numerical results show that the momentum and kinetic energy for the jets suffering from shock waves likely cause more intensive damping compared to the jets with expansion waves. The turbulence kinetic energy and turbulence dissipation rate are observed to firstly increase and then decrease. This effect is more pronounced at a lower operation pressure. Based on these results, the optimum lance height was identified for a rapid slagging operation. It is also shown that the efficiency of the energy transfer from the jets to the molten bath is very low. Decreasing lance height or increasing operation pressure promotes the efficiency of the momentum transfer from the jets to the molten bath but lowers the efficiency of the kinetic energy transfer.     

Effect of oxygen flow rate and temperature on supersonic jet characteristics and fluid flow in an EAF molten bath

A new operation method for the oxygen lance of an electric arc furnace (EAF) was proposed, meeting the simultaneous demand for low oxygen flow rate and high stirring power in a particular smelting stage. When the oxygen flow rate needs to be reduced, the stirring power of the jet can be improved by increasing oxygen temperature properly. Free supersonic jet characteristics at different flow rates and stagnation temperatures were studied by numerical simulation and validated by a jet measurement experiment. The results showed that the designed Mach number can be maintained by coupling adjustment of flow rate and stagnation temperature. Meanwhile, a three-phase, full-scaled numerical model for a commercial 75t EAF with three oxygen lances on the side-wall was established to study the fluid flow in the molten bath. The velocity distribution, cavity profile and total kinetic energy of the EAF bath induced by the impingement of supersonic jets onto the liquid bath were discussed and compared. It was found that the fluid flow characteristics of the EAF molten bath can be improved even if the oxygen flow rate was reduced as long as the oxygen temperature could be increased reasonably.     

炼钢温度下复吹转炉流场的数值模拟研究

以某钢厂的110 t复吹转炉为原型, 建立三维全尺寸几何模型, 通过数值模拟的方法研究了环境温度对多流股超音速氧气射流特性的影响, 并对比分析了常温和炼钢温度下氧气射流对转炉熔池的冲击搅拌效果.研究结果表明:随着环境温度的升高, 氧气射流的速度衰减减慢, 射流流股半径增大, 与此同时, 射流本身的温度升高、密度降低, 导致射流动压的增加幅度低于射流速度的增加幅度;而且, 高温环境中射流的聚合现象被抑制.在多相流研究中发现, 当环境温度由300 K提高至1723K时, 氧气射流的冲击深度由0.11035 m升高至0.14807 m, 冲击深度增大了34.18%, 熔池平均速度有一定提高, 说明在多相流研究中环境温度的影响不容忽略.