Abstract: The effect of microstructure evolution on thermal conductivity of alloy 690 electrode was studied according to the working conditions of electrode materials in Joule furnace. Typical compositions of alloy 690 were smelted using pure metal and samples of 690 in different states were obtained by forging， hot rolling and cold rolling. The grain size， grain boundary type， grain boundary distribution， dislocation density， and precipitated phase species of the 690 samples in different states were tested by means of scanning electron microscope （SEM）， energy dispersive spectrometer （EDS）， electron back scatter diffraction （EBSD）， X-ray diffraction （XRD）， and the measurement of thermal conductivity by flash method. The microstructure evolution of alloy 690 materials for joule furnace electrodes in different processing states and its influence on thermal conductivity were clarified. The results show that， alloy 690 in the hot rolled state has the highest thermal conductivity， followed by the wrought state， while alloy 690 in the cold rolled state has the lowest thermal conductivity. The reasons for this are： （1） The grain size and total grain boundary area of 690 alloy change significantly under different deformation processes， and the cold-rolled state alloy has the smallest grain size and the highest total grain boundary area； （2） The grain boundaries of the forged and cold rolled state 690 alloys are dominated by small-angle grain boundaries， The low ΣCSL grain boundaries of the three states of alloy 690 are dominated by Σ3 grain boundaries；（3）The cold-rolled state 690 alloy has the highest dislocation density.（4）The main reason for the large decrease in thermal conductivity of alloy 690 in the cold rolled state is the high grain boundary total area ratio and the high dislocation density after cold rolling.

Key words: Alloy 690, Joule furnace, Microstructure, Thermal Conductivity

摘要：   根据焦耳炉电极材料使用工况，开展了690合金电极组织演变对其导热性能的影响。使用纯金属冶炼了典型成分的690合金，并通过锻造、热轧、冷轧获得不同状态的690样品。通过SEM、EBSD、XRD和闪光法测量导热系数等手段，测试了不同状态690样品的晶粒尺寸、晶界类型、晶界分布、位错密度、析出相种类，明确了焦耳炉电极用690合金材料在不同加工状态下的显微组织演变及其对导热性能的影响规律。结果表明：热轧态690合金的热导率最高，锻态次之，而冷轧态690合金的热导率最低。其原因为：（1）不同变形工艺下的690合金晶粒尺寸和晶界总面积有显著变化，冷轧态合金具有最小的晶粒尺寸和最高的晶界总面积；（2）锻态、冷轧态690合金晶界以小角度晶界为主，690合金低ΣCSL晶界均以Σ3晶界为主；（3）冷轧态690合金具有最高的位错密度；（4）冷轧态690合金热导率大幅下降的主要原因在于高的晶界总面积比例和冷轧后的高位错密度。

关键词: 690合金, 焦耳炉, 显微组织, 热导率