Physical and numerical simulation of the coalescence of liquid inclusion particles in molten steel
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摘要: 基于相似原理，采用水模擬鋼液，用有機試劑模擬鋼液中液態非金屬夾雜物，同時采用數值仿真方法共同研究了夾雜物種類、兩相間界面張力及黏度對于液滴聚并過程的影響規律.結果表明，夾雜物液滴間的聚合趨勢與其自身的物理性質有緊密聯系，其中液滴相與連續相之間的界面張力會促進其相互聚并，而液滴相的黏度則正相反，在液滴聚并過程中起抑制作用.因此，通過改變液態夾雜物與高溫鋼液之間的界面參數以及黏度參數，有望達到聚合或分散的控制目標，進而實現夾雜物尺寸的靈活控制.Abstract: In steelmaking process, nonmetallic inclusions are often considered to be detrimental to the mechanical properties and product quality of steel as they influence the microstructure of the steel matrix to a large extent, and thus, much industrial efforts are being made to promote inclusion removal by upward flotation. From this point of view, inclusions with large size are favorable; however, quality problems or mechanical defects are more likely to happen if some of them remain in the steel. In addition, fine nonmetallic inclusions can be utilized as nucleation sites of acicular ferrite during phase transformation to improve the steel strength by promoting the formation of a fine-grained structure; this procedure is known as oxide metallurgy. In both cases, the key issue is to control the size of inclusion particles. The main factor affecting inclusion size is the collision, agglomeration, and coalescence behavior of inclusions in the molten steel. Interfacial characteristics between inclusions and steel melts are known to have a significant influence on this coalescence behavior. To analyze this influence mechanism in depth, physical and numerical simulation methods were applied to investigate the effects of inclusion type, interfacial tension, and viscosity on droplet coalescence. Based on the similarity principle, water and organic reagents were chosen to simulate molten steel and liquid nonmetallic inclusions, respectively, in the physical modeling part. The results indicate that the coalescence tendency of inclusion droplets is closely related to the physical properties of the droplets. The interfacial tension between the droplet phase and the continuous phase promotes the mutual aggregation of droplets, while the viscosity of droplets plays an inhibitory role during the aggregation process. Therefore, it is feasible to achieve aggregation or dispersion of inclusions in liquid steel by changing interfacial or viscosity parameters, thereby realizing flexible control of the inclusions particle size.
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圖 1 鄰苯二甲酸二辛酯液滴的初始形貌(a)、輪廓擬合(b)、粒徑分布(c)和所對應的實際液態夾雜粒徑分布(d)
Figure 1. Initial morphology (a), fitted contour (b), size distribution of DOP particles (c), and the corresponding size distribution of actual liquid inclusions in molten steel(d)
圖 2 物理模擬實驗裝置示意圖
1―鋼包模型; 2―底吹攪拌; 3―頂面環形吹氣; 4―滴定管; 5―頂部注水; 6―錐形瓶收集; 7―靜置分層
Figure 2. Schematic diagram of experimental apparatus
圖 4 三種模擬夾雜物上浮去除率隨時間的變化
Figure 4. Variation curves of the removal rates of different model inclusions over time
圖 5 液滴對聚并過程體積分數、壓力云圖與速度場分布
Figure 5. Volume fraction, total pressure, and velocity field during coalescence process
圖 7 不同界面張力條件下液滴聚并現象形貌(μ=0.05 Pa ·s)
Figure 7. Coalescence phenomena of different interfacial tensions (μ=0.05 Pa ·s)
圖 8 聚并時間與界面張力關系
Figure 8. Relationship between coalescence time and interfacial tension
圖 9 不同黏度條件下液滴聚并過程(γ=50 mN ·m-1)
Figure 9. Coalescence phenomena under different viscosities (γ=50 mN ·m-1)
圖 10 聚并時間與液滴黏度的關系
Figure 10. Relationship between coalescence time and droplet viscosity
表 1 原型和模型及其介質的主要參數
Table 1. Main parameters of prototype ladle, model, and the medium
項目 鋼包上口直徑/mm 鋼包下口直徑/mm 熔池深度/mm 噴嘴直徑/mm 密度/(kg·m-3) 吹氣量/(L·min-1) 液體 夾雜物 氣體1) 原型 3660 3364 4095 100 7.1×103 3.9×103 1.784(Ar) 800 模型 245 215 273 2.62) 1×103 0.98×103(二辛酯) 1.977(CO2) 0.5 注：1)溫度T=273 K，壓強p=1.013×105 Pa. 2)實際吹氣孔為狹縫型，長5.3 mm，寬1 mm，按同等面積折合成圓形噴嘴直徑為2.6 mm. 
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表 2 液態夾雜模擬試劑部分物理性質
Table 2. Partial physical properties of reagents chosen to simulate liquid inclusion
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中文字幕在线观看表 3 數值模擬計算條件設置
Table 3. Parameter setting for numerical calculation
序號 密度/(kg·m-3) 黏度/(Pa·s) 界面張力/(mN·m-1) 液滴 水 液滴 水 液滴與水 1 950 998.2 0.05 0.001003 10 2 950 998.2 0.05 0.001003 20 3 950 998.2 0.05 0.001003 50 4 950 998.2 0.05 0.001003 70 5 950 998.2 0.05 0.001003 90 6 950 998.2 0.01 0.001003 50 7 950 998.2 0.10 0.001003 50 8 950 998.2 0.15 0.001003 50 9 950 998.2 0.20 0.001003 50 10 950 998.2 0.25 0.001003 50 11 950 998.2 0.30 0.001003 50
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