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摘要: 研究微波加熱液態金屬的升溫特征，在MobileLab-W-R型微波工作站中進行了微波直接加熱銅液和鐵液的實驗研究，實現了微波直接加熱銅液和鐵液實驗，對比研究了微波直接加熱和間接加熱銅液與鐵液的加熱效果，并研究了微波功率、金屬液質量、溫度等對微波直接加熱效果的影響，探討了微波直接加熱金屬液體的機理。結果表明，微波可以以較快的升溫速度直接加熱銅液和鐵液，且升溫速率與微波加熱功率呈近似線性遞增關系；在相同微波直接加熱條件下，同等質量的銅液和鐵液的升溫速度相近，但不同質量鐵液加熱時，由于其表面積、微波場強分布等因素的影響，鐵液質量對微波加熱效果的影響沒有明顯的線性關系。理論分析認為，銅和鐵在熔化后電阻率增大，磁導率明顯下降，導致微波在銅液和鐵液內部的趨膚深度顯著大于固態銅和鐵；電導損耗是實現微波直接加熱液態金屬的主要機制，液態金屬可通過電子與原子核碰撞、表面快速更新、內部缺陷阻礙電子運動、原子運動及碰撞等形式吸收微波，將微波能量轉化為自身熱量。Abstract: Characteristics of molten metal heated with microwaves were the focus of this study. A series of experiments on the direct microwave heating of molten copper and molten iron were conducted in a MobileLab-W-R microwave workstation; both metals were effectively heated by direct microwaves. Effects of indirect versus direct heating were comparatively analyzed using different types of heating chambers. The direct heating method was then further investigated, taking microwave power, mass of molten metal, and temperature into consideration. The mechanism of direct microwave heating of molten metal was discussed. The results show that microwave can directly heat molten iron and molten copper at high rates that increase linearly with increasing microwave power. Heating rates of molten iron are similar to those of molten copper at constant mass and microwave power. However, the mass of molten iron has no clear linear relationship with heating rates due to the involvement of other factors, such as surface area of the molten iron and distribution of the microwaves. According to the theoretical analysis, when the states of copper and iron are transferred from solid to liquid, their resistivities increase, but their permeabilities drop significantly. As a result, the skin effect depths of microwave in molten copper and iron are clearly larger than those in the solid metals. Conductivity loss is the main mechanism of achieving direct microwave heating of molten metal. Microwave energy can be absorbed in four ways: collisions between electrons and nucleus, rapid liquid surface renewal, hindering of internal defects of electron movement, and atom movement and collision. Absorbed microwave energy can be transferred into the internal energy of the molten metal.
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Key words:
- liquid metal /
- microwave heating /
- skin depth /
- conductivity loss /
- collision
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圖 1 微波加熱站示意圖
1—爐門；2—諧振腔；3—箱體；4—加熱腔；5—坩堝；6—磁控管；7—波導；8—物料；9—剛玉套管；10—熱電偶；11—溫度顯示器
Figure 1. Diagram of the experimental microwave workstation
圖 2 微波加熱腔. (a) 直接加熱用加熱腔；(b) 涂有吸波涂層的間接加熱用加熱腔
Figure 2. Microwave heating cavity: (a) heating cavity for direct heating; (b) heating cavity for indirect heating with absorbing coating
圖 3 不同質量鐵塊間接加熱實驗結果
Figure 3. Experimental results of iron heated with indirect heating pattern
圖 5 微波直接加熱不同質量鐵液的升溫曲線.（a）500 g；（b）1000 g；（c）1500 g；（d）>1450 ℃階段，不同質量鐵液升溫曲線
Figure 5. Heating curves of different quality molten irons with microwave power of 4 kW: (a) 500 g; (b) 1000 g; (c) 1500 g; (d) heating curve of molten iron of different quality above 1450 ℃
圖 6 不同微波功率下1000 g鐵液的升溫曲線
Figure 6. Temperature rise curves of 1000 g iron melt under different microwave powers
圖 8 微波直接加熱銅液和鐵液結果
Figure 8. Heating curves of molten copper and iron by microwave heating
表 1 實驗用鐵成分（質量分數）
Table 1. Composition of the iron for experiments
% C Si Mn S Ti P Fe 4.03 1.09 0.12 0.064 0.19 0.11 余量 
下載: 導出CSV
表 2 微波直接加熱金屬液實驗方案
Table 2. Experimental scheme of microwave direct heating of liquid metal
金屬 質量/g 間接加熱功率/kW 間接加熱終點溫度/℃ 直接加熱功率/kW 直接加熱保溫溫度/℃ 直接加熱終點溫度/℃ 鐵 500 4 1500 4 1450 1550 1000 4 1500 4 1450 1550 1000 4 1500 3 1450 1550 1000 4 1500 2 1450 1550 1000 4 1500 1 1450 1550 1500 4 1500 4 1450 1550 銅 1000 4 1400 4 1350 1450
下載: 導出CSV
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