以共晶铸铁 (eutectic cast iron, ECI) 作为C源, 通过熔铸时渗碳体的原位生成及渗碳体石墨化工艺制备石墨黄铜. 利用SEM和EDS分析石墨黄铜的显微组织, 探讨了显微组织与力学性能和切削性能的关系. 结果表明: 铸造过程中原位生成的渗碳体通过石墨化退火后分解成石墨颗粒均匀弥散地分布于黄铜基体上, 颗粒尺寸为3~6 μm, 铸铁添加量为7%时石墨颗粒出现偏聚. 随着铸铁添加量的增加, 基体组织不断细化, 抗拉强度和显微硬度增加, 伸长率降低; 随着石墨体积分数的增大, 石墨黄铜的切屑形貌得到不断改善. 当铸铁添加量为5%时黄铜的切屑形貌最好, 为短片状和C型, 其切削性能与铅黄铜HPb59-1相当。

Graphite is believed to be an attractive candidate substituting for lead to produce free-cutting brasses, because of its lubricating property and the role in chip breaking. The major hindrances of developing graphite-brass are the large density difference and nonwetting characteristic between graphite and copper. In this work, eutectic cast iron (ECI) was added into brasses instead of other form of carbon source. Cementite particles were in situ formed during casting, then annealing treatment was conducted to facilitate the graphitization of cementite particles, and finally uniformly dispersed graphite particles with the size of 3~6 mm were obtained in brass alloys. SEM and EDS observation indicate that the microstructures of the graphite-brass are refined with the cast iron content increased from 1% to 7%. The tensile strength and microhardness are increased, and the chip morphologies are improved gradually with the cast iron content increased from 1% to 7%. However, the graphite brass with 7% addition shows suboptimal chip morphologies because of the segregation of graphite particles. The chips of graphite brasses with 5% addition are desired, which are short and discontinuous. Its tensile strength, elongation and Vickers hardness are 502.00 MPa, 22.6% and 148.9 HV, respectively. The graphite brass shows comparable machinability to conventional lead brass HPb59-1。