电磁搅拌电流对连铸紫铜管组织和性能的影响

Effect of Electromagnetic Stirring Current on Structure and Properties of Continuously Cast Copper Tube

水平连铸管材常产生晶粒粗大、壁厚不均匀、表面裂纹、气孔等缺陷。为改善连铸铜管的质量,在水平连铸装置中配置了电磁搅拌器,并在连铸外径80 mm、壁厚12 mm的紫铜管的过程中向电磁搅拌器通入80~190 A工频电流对熔体进行电磁搅拌。检验了铜管的组织、表面质量、壁厚均匀性和电导率,并与未施加电磁搅拌连铸的紫铜管进行了比较。结果表明:由于施加了电磁搅拌,紫铜管中的气孔等缺陷明显减少从而致密度提高,表面裂纹消除,壁厚差不超过±0.5 mm。随着电磁搅拌电流的提高,紫铜管组织由粗大的柱状晶转变为细小的等轴晶。未施加电磁搅拌连铸的紫铜管氧含量为0.0291‰,而施加由190 A电流产生的电磁搅拌连铸的管坯氧含量下降到了0.0060‰,电导率则从98.214%IACS提高到了100.72%IACS。

Deficiencies,such as coarse grains,uneven wall thickness,surface crack,and gas hole,often occurred in the horizontally continuously cast tube.The horizontal continuous caster was provided with an electromagnetic stirrer,and line-frequency current of 80 to 190 A was fed into the electromagnetic stirrer in continuously casting copper tube 80 mm OD by 12 mm wall thickness to make the melt to undergo electromagnetic stirring,for the purpose of improving quality of the copper tube.The copper tube was tested for microstructure,appearance,wall thickness uniformity and conductivity,and compared with one continuously cast without the application of electromagnetic stirring.The results indicated that the copper tube exhibited much less defects such as gas hole and thereby higher density,crack-free surface,and difference in wall thickness not more than±0.5 mm because of the application of electromagnetic stirring.With the increase of electromagnetic stirring current,microstructure of the copper tube converted from coarse columnar crystals to fine equiaxed crystal.Oxygen contents were 0.0291‰in the copper tube continuously cast without the application of electromagnetic stirring and 0.0060‰in one continuously cast with the application of electromagnetic stirring caused by current of 190 A,and electrical conductivities were 98.214%IACS for the former and 100.72%IACS for the latter.