YL82B盘条经过20 d自然时效后进行拉伸试验，试样断口表现为黑心白点的平齐断口。通过化学成分分析、金相检验及断口宏微观分析等方法对出现该断口的原因进行了分析。结果表明：YL82B盘条黑心白点平齐断口形成的主要原因是试样中心存在网状渗碳体或马氏体，部分存在大颗粒状夹杂物。这些网状渗碳体、马氏体或大颗粒夹杂物是导致断面收缩率不合格的主要原因。

The YL82B wire rods were subjected to tensile test after 20 d natural aging, the fracture of the samples showed the flush fracture of black center and white spot. The causes of the fracture were analyzed by means of chemical composition analysis, metallographic examination and macro and micro analysis of the fracture. The results show that the main reason for the formation of the flush fracture with black center and white spot of YL82B wire rods was the existence of reticular cementite and martensite, or some large granular inclusions in the center of the samples. These reticular cementite, martensite or large particle inclusions were the main reasons for the unqualified reduction of area.