圓坯凝固末端電磁攪拌作用下的流動與傳熱行為

李少翔; 王璞; 蘭鵬; 劉華松; 劉麒麟; 李樹貴; 張家泉

doi:10.13374/j.issn2095-9389.2019.06.006

圓坯凝固末端電磁攪拌作用下的流動與傳熱行為

doi: 10.13374/j.issn2095-9389.2019.06.006

1.
北京科技大學冶金與生態工程學院, 北京 100083
2.
寶山鋼鐵股份有限公司, 上海 201900

基金項目:

國家自然科學基金資助項目 U1860111

北京科技大學本科教育教學改革項目 JG2017M11

詳細信息

通訊作者:
張家泉, E-mail: jqzhang@metall.ustb.edu.cn

中圖分類號: TF777.4
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- 被引次數: 0
出版歷程
- 收稿日期: 2018-11-30
- 刊出日期: 2019-06-01

Melt flow and heat transfer at the crater end of round billet continuous casting using final electromagnetic stirring

1.
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
2.
Baoshan Iron & Steel Co., Ltd., Shanghai 201900, China

More Information

Corresponding author: ZHANG Jia-quan, E-mail: jqzhang@metall.ustb.edu.cn

摘要

摘要: 以特殊鋼圓坯連鑄為研究對象, 建立了研究凝固末端電磁攪拌作用效果的三維耦合數值模型.利用分段計算模型獲得末端電磁攪拌區域鋼液流動與凝固的實際狀態, 并采用達西源項法處理凝固末端鋼液在糊狀區的流動, 研究了不同電磁攪拌工藝參數下的電磁場分布及鋼液的流動與傳熱特征.通過測量攪拌器中心線磁感應強度和鑄坯表面溫度驗證了模型的準確性.研究結果表明: 電流強度每增加100 A, 攪拌器中心磁感應強度增加19.05 mT, 電磁力隨著電流強度的增加顯著增大.在20~40 Hz范圍, 隨著電流頻率的提高, 中心磁感應強度略微下降, 但電磁力仍有所增加.在攪拌器區域, 液相穴內的鋼液在切向電磁力的作用下旋轉流動, 其切向速度隨著電流強度和頻率的增加而變大.末端電磁攪拌可促進鋼液在圓坯徑向的換熱, 隨著電流強度和頻率的提高, 鑄坯中心軸線上的鋼液溫度降低, 同時末端攪拌位置處的中心固相分率增加.
- 圓坯連鑄 /
- 凝固末端電磁攪拌 /
- 電磁場 /
- 糊狀區流動 /
- 傳熱
Abstract: Final electromagnetic stirring (F-EMS) is widely used in the billet and bloom continuous casting process because it effectively improves the as-cast quality. Numerous industrial trials on F-EMS have been conducted; however, the real melt flow and heat transfer characteristics at the crater end remain unclear. In this study, based on a round billet special steel continuous casting process, a coupled three-dimensional numerical model was developed to describe the F-EMS phenomenon. The flow and solidification behavior of the melt in the F-EMS region were obtained by a segmentation calculation model, and the Darcy source term method was employed to suppress the velocity within the mushy region. The effect of stirring current intensity and frequency on the electromagnetic field, melt flow, and heat transfer was investigated numerically. The model was validated using the measured data of magnetic flux density in the stirrer center and the strand surface temperature. According to the simulation results, with every 100 A increase in the current intensity, the maximal magnetic flux density increases by 19.05 mT. The electromagnetic force significantly increases with the increase in current intensity. With the increase in current frequency within 20-40 Hz, the magnetic flux density decreases slightly, whereas the electromagnetic force increases. Moreover, a swirling flow field in the stirrer region is observed under the rotary electromagnetic force, and the tangential velocity of melt increases with the increase in current intensity and frequency. Additionally, the swirling flow enhances the local melt heat transfer at the radial direction of the round strand. As the current intensity and frequency increase, the temperature of the melt in the liquid core decreases, and the center solid fraction at the F-EMS-implemented position increases accordingly.
- round billet continuous casting /
- F-EMS /
- electromagnetic field /
- melt flow in mushy zone /
- heat transfer

HTML全文

圖 1 末端電磁攪拌模型結構圖

Figure 1. Model of the F-EMS

下載: 全尺寸圖片幻燈片

圖 2 攪拌器中心軸線上的磁感應強度(a) 及鑄坯表面溫度(b) 的計算值與測量值

Figure 2. Comparison between calculated and measured values of the magnetic flux density (a) and billet surface temperature (b)

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圖 3 鑄坯表面的磁感應強度云圖(a) 及鑄坯橫截面上的電磁力矢量圖(b)

Figure 3. Contour plot of magnetic flux density on the strand surface (a) and electromagnetic force density on the transverse section (b)

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圖 4 不同電流強度下攪拌器中心軸線上(a) 及攪拌器中心點(b) 的磁感應強度分布

Figure 4. Distribution of magnetic flux density along the central axis of the strand (a) and in the stirrer center (b) under different current intensities

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圖 5 不同電流頻率下攪拌器中心軸線上(a) 及攪拌器中心點(b) 的磁感應強度分布

Figure 5. Distribution of magnetic flux density along the central axis of the strand (a) and in the stirrer center (b) under different current frequencies

下載: 全尺寸圖片幻燈片

圖 6 不同電流強度(a) 與頻率(b) 下攪拌器中心處鑄坯橫截面上的切向電磁力分布

Figure 6. Distribution of tangential electromagnetic force along the radial direction at mid-plane of the stirrer under different current intensities (a) and frequencies (b)

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圖 7 沿拉坯方向的鑄坯中心軸線溫度與坯殼生長情況

Figure 7. Distribution of temperature at the strand center and growth of shell thickness along the casting direction

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圖 8 攪拌器區域液芯處的鋼液流線圖

Figure 8. Streamline of melt in the liquid core in the stirrer region

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圖 9 鑄坯縱斷面上的液相分率分布(a) 及攪拌器中心處鑄坯橫截面上的液相分率和流線圖(b)

Figure 9. Liquid fraction contour on the longitudinal section of the strand (a) and cross section of the stirrer center (b)

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圖 10 不同電流強度(a) 與頻率(b) 下攪拌器中心處鑄坯橫截面上的鋼液切向速度沿徑向分布

Figure 10. Tangential velocity profile along the radial direction at center plane of the stirrer under different current intensities (a) and frequencies (b)

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圖 11 不同電流強度(a) 與頻率(b) 下鑄坯中心軸線上的溫度分布

Figure 11. Temperature variations at the strand center along the casting direction under different current intensities (a) and frequencies (b)

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表 1 材料熱物性參數

Table 1. Thermophysical properties of material employed in this study

參數	數值
真空磁導率/(H·m^-1)	1.257×10^-6
鋼液、線圈和空氣相對磁導率	1
鐵芯相對磁導率	1000
鋼液電導率/(S·m^-1)	7. 14×10^-5
鋼液密度/(kg·m^-3)	7020
鋼液比熱容/(J·kg^-1·K^-1)	680
鋼液導熱系數/(W·m^-1·K^-1)	29
鋼液黏度/(kg·m^-1·s^-1)	0.0055
凝固潛熱/(J·kg^-1)	270000
熱膨脹系數/K^-1	1x10^-4
固相線溫度/K	1738
液相線溫度/K	1784
糊狀區常數^[17]	1×10⁸

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表 2 連鑄工藝參數

Table 2. Main technical parameters of the continuous casting process

參數	數值
斷面直徑/mm	178
拉速/(m·min^-1)	2. 0
過熱度/K	34
二冷區比水量/(kg.L^-1)	0. 65
M—EMS工作電流/A	400
M-EMS工作頻率/Hz	6
F—EMS工作電流/A	400 ~ 800
F-EMS工作頻率/Hz	20 ~40
F—EMS中心位置（距彎月面距離）/m	10. 5

下載: 導出CSV

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