(1. 北京科技大学 材料先进制备技术教育部重点实验室，北京 100083； 2. 北京科技大学 现代交通金属材料与加工技术北京实验室，北京 100083)
摘 要: 研究热冷组合铸型(HCCM)水平连铸H62 (UNS C27400)黄铜管坯外表面点状缺陷的特点和形成机理，提出消除点状缺陷的措施。结果表明：管坯外表面点状缺陷主要为富锌低熔点物质，其锌含量达80%(质量分数)；点状缺陷的出现沿连铸方向呈周期性特征，管坯上部的点状缺陷数量明显多于下部的；连铸过程中，挥发的锌在冷型内表面形成的锌液滴与管坯外表面接触后发生熔蚀反应，使管坯外表面形成富锌的点状缺陷；通过快速降低冷型段内管坯温度，减少锌元素挥发及石墨铸型内表面锌液滴的形成，可有效消除点状缺陷。
关键字: HCCM水平连铸；黄铜管坯；富锌物质；表面缺陷；形成机理
（1. Key Laboratory for Advanced Materials Processing, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China; 2. Beijing Laboratory of Metallic Materials and Processing for Modern Transportation, University of Science and Technology Beijing, Beijing 100083, China）
Abstract:The characteristic and formation mechanism of spot defect on the outer surface of H62 (UNS C27400) brass tube fabricated by HCCM horizontal continuous casting were studied, and an effective method for eliminating the defect was proposed. The results show that the spot defect on the tube outer surface is main zinc-rich low-melting-point substance, whose zinc content (mass fraction) reaches 80%. The spot defects are periodically formed along the casting direction and the number of the defects on the upper part of the tube is much more than that on the lower part. During casting, the volatilized zinc attaches to the graphite mold inner surface and forms zinc droplets which causes an erosion effect on the tube surface when the zinc droplets contact with the tube, leading to the formation of the zinc-rich spot defect on the tube surface. A method of rapidly lowering the temperature of the solidified tube in the cold mold, which can reduce the zinc volatilization and the number of the zinc droplets on the inner surface of the mold, is proposed to eliminate the spot defects effectively.
Key words: HCCM horizontal continuous casting; brass tube; zinc-rich substance; surface defect; formation mechanism
