50t顶底复吹转炉的水力学模型实验研究

通过50t顶底复吹转炉水力学模型实验,研究氧气顶底复吹转炉顶枪枪位、底吹气体流量对转炉熔炼过程中熔池搅拌和时间以及对冶炼过程的喷溅及熔池的冲击深度影响。结果表明,当模型枪位在120～210mm,实际枪位1．00～1．56m;模型底吹流量控制在0．38Nm^3／h,实际底吹流量控制在146～190Nm^3／h左右时,熔池混匀时间短,吹炼时喷溅量少。较浅的熔池冲击深度就可达到良好的搅拌效果,有利于避免冲击炉底。当冲击深度较大时,混匀时间反倒增加。     

插入浸渍圆筒钢包底吹气体优化研究

以150 t钢包为原型,采用水模型实验的方法研究插入浸渍圆筒底吹钢包内钢液的卷渣现象,研究了底吹气量、浸渍圆筒直径及插入深度对钢液卷渣及均混时间的影响。同时建立钢包底吹气体钢液流场数学模型,利用Mixture多相流模型对钢包吹氩过程进行数值模拟计算,分析不同底吹气量下插入浸渍圆筒钢液的流动状态和钢液表面的卷渣。通过水模拟和数值模拟比较,结果表明:插入浸渍圆筒后,增大了临界卷渣吹气量,加强了熔池搅拌,更有效地缩短了混匀时间。     

转炉预直炼法脱磷期亚音速顶吹的物理模拟

在1∶6物理模型上，通过水模型实验，对梅钢复吹转炉亚音速喷吹条件下的熔池搅拌情况进行了研究。结果表明，亚音速喷吹条件下的熔池均混时间明显长于超音速的。在亚音速喷吹条件下降低枪位、增加顶底吹气体流量可降低均混时间；A2底吹为本实验最佳布置方式，A6为适合预直炼的布置方式。     

鱼雷罐倒T形喷吹脱硫水模试验研究

通过水力模型试验,分析了鱼雷罐倒T形喷吹脱硫过程中熔池内的流动状态,研究了工艺参数对鱼雷罐倒T形喷吹脱硫混匀时间的影响规律.结果表明,鱼雷罐倒T形喷吹脱硫过程中2支上升流股相互影响,会消耗部分能量,不利于搅拌动能的充分发挥;试验条件下,随着喷吹气体流量的增加,熔池内液体的混匀时间显著降低,当喷吹气体流量增加至3 m3/h后,混匀时间随喷吹气体流量略有增加;随着喷枪插入深度的增大,熔池内液体的混匀时间逐渐降低.     

侧吹气流的旋转对侧顶复吹AOD转炉熔池内流体混合特性的影响

基于在保证足够高的运动相似性下对非旋转气体射流120 t侧顶复吹AOD转炉内流体混合特性的研究,利用水模拟研究了套管式螺旋板型喷枪的旋转气体射流下AOD熔池内流体的混合特性。考察了侧吹气体射流的旋转和吹气量(侧吹和顶吹)及相邻两侧枪间夹角的影响。结果表明,在相同的吹气量下,旋转气体射流可提供更强烈的搅拌,提高混合效率。枪间夹角对流体流动和混合有更大的影响。与非旋转侧吹气流下的情况相类似,相邻两侧枪间的夹角由18°增至22.5°有利于熔池内液体的混合。顶吹气体射流会明显降低熔池内液体的混合效果。     

转炉熔渣中底吹气体搅拌行为研究

采用数值模拟方法,研究了转炉溅渣护炉前向熔渣底吹气体过程喷嘴个数、底吹流量以及底吹位置对熔池中流场的影响规律。结果表明,采用四喷嘴,控制底吹流量1.14 m·s~(-1),能获得混匀时间短、成分较均匀的良好流场。在熔池尺寸较大时,偏心底吹流场影响较小。     

120t顶底复吹转炉水模型优化研究

以某厂120 t顶底复吹转炉为原型,依据相似原理,在保证模型与原型几何相似以及动力学相似的条件下,通过水力学模型试验研究了顶吹气体流量、底吹气体流量及氧枪位置对熔池混匀时间和冲击深度的影响。结果表明:当顶吹流量为104. 4 Nm~3/h、底吹流量为1. 41 Nm~3/h、氧枪位置为177 mm时,熔池的混匀时间最短,冲击深度约为熔池深度的1/2,处于合理范围之内。基于水模型试验结果进行了工业试验,结果表明:工艺参数优化后顶底复吹转炉冶炼的技术指标明显改善,120 t转炉的吹炼时间从13. 72 min缩短至12. 86 min,终渣(T. Fe)质量分数从16. 33%降低至12. 16%。     

底吹熔池氧枪排布对气体振荡射流强化搅拌效果的定量评价

为阐明底吹熔池气体射流振荡强化搅拌机制,提出了基于Betti数来定量表征底吹气体振荡射流强化搅拌效果的新途径,并以此为评价标准提出底吹炉氧枪排布的优化方案。首先,基于正交试验理论,设计了多水平因子水模型实验方案;其次,运用摄像设备捕捉了19组底吹水模型容器内气液流态演化过程的连续图片,通过图像处理技术得到连续流态图片的Betti数;最后,通过Betti数的分布规律来实现不同工况下气体射流振荡搅拌效果的差异化表征。结果表明:在单排氧枪排布方式下,在0°～14°范围枪倾角越大,射流产生气泡数量越多,分布更为均匀;在双排氧枪排布方式下,非对称喷吹的射流振荡搅拌效果明显更好,且采用0°与7°倾角的特征数值更为理想。     

侧吹气流方向对大功率CO2激光焊缝成形的影响

激光深熔焊过程中会在熔池上方产生等离子体云，若该等离子体云过密，将降低激光入射到工件表面能量密度。在工业应用中，常采用侧吹辅助气体来减弱等离子体云的影响。本文通过试验，研究了在不同气体流量下，侧吹气体方向不同对焊接过程稳定性和焊缝成形的影响。结果发现：使用大功率CO2激光焊接AH32时。侧吹气体方向对焊缝成形有着明显的影响。从熔池和等离子体两个方面，解释了侧吹气体方向的影响机制。     

不锈钢冶炼用AOD炉内的射流行为和流体流动

在分析氩一氧脱碳（AOD）炉内侧吹射流行为特征的基础上,建立了描述AOD炉内三维流动的数学模型,考察了喷吹气体流量和喷枪布置对AOD熔池内湍流场的影响规律．结果表明,供气强度对AOD炉内射流流股轨迹和钢液流动产生明显影响;多枪喷吹,使熔池中流场和湍动能分布变得更加合理．计算结果与物理模型的观测结果吻合．     

底吹电弧炉熔池混合过程的模拟研究

实验测量了电弧炉底部单喷嘴和多喷嘴喷吹的熔池水模型中混合时间和若干断面流场、混合时间随喷嘴直径、数量、位置及示踪剂投放点变化的函数关系。通过数值法求解了熔池流场及其混合过程。结果表明，仅靠增加喷嘴直径来改进熔池搅拌效果不显著。偏心、深熔池处布置的多喷嘴喷吹的流场混合能力较强，原因是这样布置使熔池流场具有较强烈的圆周方向对流并能获得更多的搅拌功率。     

高效喷气精炼过程中的机械搅拌

在喷气精炼过程中,气泡的分散和细化是提高精炼效率的必要条件。在水模型实验中应用了单向的偏心搅拌模式来寻找最佳的气泡微细化条件。影响气泡微细化的因素有：搅拌模式、偏心度、搅拌转速、喷嘴结构、喷嘴的浸入深度以及气体流量。气体的喷入方式包括两种,一是从搅拌桨下方的喷嘴中直接喷入,二是从一个位于搅拌桨下方的弯管中喷入。在偏心搅拌模式下,漩涡远离了搅拌桨的轴心,小气泡产生于搅拌桨附近的强湍流或高剪切应力场中,随着机械搅拌产生的宏观流向漩涡方向移动。因此,单向的偏心搅拌模式能促进气泡在溶池内的细化和分散。     

预焙铝电解槽阳极底部开排气沟对电解质流场的影响

对预焙铝电解槽阳极底部开排气沟时周围电解质流场进行计算,发现部分阳极气体可以通过排气沟向外排放,减少气泡在阳极底部停留时间和阳极底掌气泡覆盖率,从而有利于降低极间电阻压降和阳极效应系数,减少电解能耗;另一方面气体带动电解质进入排气沟,然后进入电解槽侧部通道,扩大了电解质循环通道,促进了阳极周围电解质流动和槽内的传质传热,有利于保持电解正常进行,相比之下排气沟为通沟时较非通沟更有利于保持电解质流动稳定;同时由于排气沟促进了阳极气体排放,使铝液与阳极气体发生“二次反应”(即电解还原的铝卷入电解质中被阳极气体重新氧化)的机会减少,有利于提高铝电解电流效率。     

工艺参数对连续碳纤维表面电磁搅拌化学镀镍的影响

目的解决连续碳纤维在镀覆过程中易出现黑心现象以及无法完全浸泡于镀液中的问题,制备镀层均匀的连续碳纤维镍镀层。方法引入外加电磁搅拌对连续碳纤维进行化学镀镍,研究了施镀时间、镀液温度、镀液pH值以及电磁搅拌转速对连续碳纤维表面微观形貌及镀层沉积速率的影响规律。结果当搅拌转速一定时,随着施镀时间、镀液温度、镀液pH值的不断增加,碳纤维表面镀层逐渐变得均匀完整,且镀层厚度逐渐增大。但当施镀时间超过20 min,镀液温度超过75℃,镀液pH值超过8时,镀层表面沉积了大量形状不一的胞状镍颗粒,形成粗糙的表面形貌。镀层的沉积速率随着镀液温度、镀液pH值的升高而增大。当搅拌转速由200 r/min增加到300 r/min时,镀层的沉积速率随着搅拌转速的增加而不断增大;当搅拌转速由300 r/min增加到400 r/min时,镀层的沉积速率随着搅拌转速的增加而不断减小。结论电磁搅拌辅助连续碳纤维化学镀镍的最佳施镀工艺参数为:施镀时间15~20 min,镀液温度75℃,镀液pH为8,搅拌转速200~250 r/min。采用此工艺参数能获得表面致密、均匀完整的镍镀层。     

Codeposition of micro- and nano-sized SiC particles in the nickel matrix composite coatings obtained by electroplating

Micro- and nano-sized SiC particles were codeposited with nickel by electrolytic plating from a nickel sulfamate bath and the effects of plating parameters such as pH of the plating bath, SiC content in the plating bath, and stirring speed on the deposition behaviors of Ni-SiC composite coating layers were studied. The result revealed that the micro-sized SiC particles are more negative than the nano-sized SiC particles in the Zeta potential. The codeposition of SiC can be increased by increasing the SiC content in the plating bath and the pH of the plating bath within the present experimental range. In case of micro-sized SiC particles, increasing stirring speed always lowered the codeposition of SiC. In case of nano-sized SiC particles, the codeposition of SiC showed a maximum at the stirring speed of 100 rpm. The nano-sized SiC particles are more difficult to codeposit than the micro-sized SiC particles and showed rougher plated surface compared with the micro-sized SiC particles, which may be attributable to the agglomeration of nano-sized SiC particles in the plating bath.     

Co-electrodeposition of Functionally Graded Ni-NCZ (Nickel Coated ZrO<Subscript>2</Subscript>) Composite Coating

In this study, functionally NCZ (electroless nickel plated ZrO₂) content graded Ni-NCZ composite coating has been successfully co-electrodeposited from a bath with gradually increasing of stirring rate. For this, different composite coatings were electroplated in the same bath with different stirring rates to find the optimum condition. SEM, XRD, EDX and electrochemical studies showed that co-electrodeposition in a bath with stirring rate of 250 rpm results in the maximum co-electrodeposited particle content and the best particle distribution and corrosion resistance. Also, this sample had the highest wear resistance with respect to the other samples. To produce NCZ content graded Ni-NCZ composite coating, the stirring rate was continuously increased from 0 to 250 rpm. The electroplated coating had a continuous gradient increasing of co-electrodeposited NCZ content from substrate toward the surface. This distribution of NCZ particles results in a gradient increasing of the microhardness in the cross section of the coating. Bend test revealed that the functionally graded composite coating shows better adhesion to the substrate compared with the uniformly distributed Ni-NCZ on the same substrate. This result has been attributed to lower mechanical mismatch between coating and substrate in the functionally graded composite coating with respect to the uniformly distributed one.     

Submerged Gas Jet Penetration: A Study of Bubbling Versus Jetting and Side Versus Bottom Blowing in Copper Bath Smelting

Although the bottom blowing ShuiKouShan process has now been widely implemented in China, in both lead and copper smelters, some doubts, questions, and concerns still seem to prevail in the metallurgical community outside China. In the author’s opinion, part of these doubts and concerns could be addressed by a better general understanding of key concepts of submerged gas injection, including gas jet trajectory and penetration, and the concept, application, and benefits of sonic injection in jetting regime. To provide some answers, this article first offers a discussion on the historical developments of the theory and mathematical characterization of submerged gas jet trajectory, including the proposed criteria for the transition from bubbling to jetting regime and the application of the Prandtl–Meyer theory to submerged gas jets. A second part is devoted to a quantitative study of submerged gas jet penetration in copper bath smelting, including a comparison between bubbling and jetting regimes, and side versus bottom blowing. In the specific cases studied, the calculated gas jet axis trajectory length in jetting regime is 159 cm for bottom blowing, whereas it varies between 129 and 168 cm for side blowing for inclination angles of +18° to ?30° to the horizontal. This means that side blowing in the jetting regime would provide a deeper penetration and longer gas jet trajectory than generally obtained by conventional bath smelting vessels such as the Noranda and Teniente reactors. The theoretical results of this study do corroborate the successful high-intensity practice of the slag make converting process at Glencore Nickel in Canada that operates under high oxygen shrouded injection in the jetting regime, and this would then suggest that retrofitting conventional low-pressure, side-blowing tuyeres of bath smelting and converting reactors with sonic injectors in jetting regime certainly appears as a valuable option for process intensification with higher oxygen enrichment, without major process changes or large capital expenditure, i.e., no need for full reactor replacement.     

制备玻璃/铝基废弃物复合材料搅拌槽的结构优化

运用流体软件FLUENT对采用机械搅拌法制备玻璃/铝基废弃物复合材料的搅拌流场进行模拟,采用MRF动参考系模型和标准k-ε模型,在稳态条件下模拟了正交组合轴流搅拌桨在不同离底高度、不同层间距和不同直径产生的流场.分析各种参数条件下搅拌槽宏观速度场、轴向速度和径向速度的分布.结果表明,搅拌桨离底高度h=50 mm,搅拌桨层间距l=65mm,搅拌桨直径d=10 mm,搅拌槽流场有利于流体的搅拌混合.     

3D numerical simulation of electrical arc furnaces for the MgO production

Targeted at the 3000 kVA and 1500 kVA electric arc furnaces for MgO production, 3D models are developed to characterize the thermal behavior in the furnaces. The electromagnetic stirring effect of the molten bath is studied respectively with a rated current, and its influence on the temperature field is predicted by the model in FLUENT. Some calculated results are proved reliable by comparison with the measurements. It can be seen that a stronger stirring effect leads to a higher average flow velocity in the 3000 kVA furnace, and the size of its molten bath is much larger than that in the 1500 kVA furnace. The appropriate location of the three electrodes can help to maintain a homogenous bath temperature distribution. The comparison between the calculated results and the measurements proves that the dimensional designs of the two furnaces are acceptable for the prevention of the local overheating or overcooling. Large-capacity electric arc furnaces are qualified with significant advantages in energy conserving and increase of productivity.     

Electrolytic deposition behaviors of Ni−SiC composite coatings containing submicron-sized SiC particles

Submicron-sized SiC particles (130 nm mean diameter) were codeposited with nickel by electrolytic plating in a nickel sulfamate bath to from Ni−SiC composite coatings. The effects of plating parameters, such as pH of the plating bath, SiC content in the plating bath, stirring rate, and current density on the deposition behaviors of Ni−SiC composite coatings were investigated. Results revealed that zeta potential decreased with increasing pH; the iso-electric point was measured to be }7.0 in pH. The codeposition of SiC increased with increasing pH, and the deposition rate increased with increasing SiC content in the plating bath. This may be due to the increased flux of approaching SiC particle towards the cathode due to enhanced SiC content in the plating bath. The codeposition of SiC exhibited a maximum at the stirring rate of 100 rpm. This can be explained by hydrodynamic effects and particle characteristics. The deposition rate increased with increasing current density. The codeposition of SiC increased up to a maximum of 15 A/dm² and then decreased This can be explained by electrophoretic movement of the SiC particles due to the adsorption of nickel ions and protons in the plating bath on the SiC particle surface. Submicron-sized SiC particles provided for a rough plating surface. This effect may be attributable to the strong tendency of submicron-sized SiC particles to agglomerate in the plating bath.