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采用光学显微镜、扫描电镜(SEM)、热膨胀仪和显微硬度计,对比研究碳含量为70级和80级的帘线钢在相同冷却速率下的组织构成、珠光体片间距、晶界渗碳体(GBC)、相变点和显微硬度。结果表明:70级帘线钢易出现先共析铁素体;80级帘线钢由于碳含量高,冷却速率较慢时,易出现晶界渗碳体,随着冷却速率的增大,相变点降低,先共析铁素体、晶界渗碳体析出减少,珠光体片间距减小,硬度增高。“,”By using optical microscope, scanning electron microscopy(SEM), thermal dilatom- eter and micro-hardness tester the structure , the imerlamellar spacing of pearlite, the grain boundary cementite(GBC), the phase transformation point and micro-hardness of the 70 and 80-grade tire cord steels are studied under the similar cooling rate. The results show that the proeutectoid ferrite is apt to appear in the 80-grade tire cord steel and on the contrary for the 80-grade tire cord steel the grain boundary cementite(GBC) tends to occur when the cooling rate is relatively slow because it contains higher carbon. The hardness of the steel grade rises with increase of the cooling rate, fall of the phase transformation point, decrease of proeutec- toid ferrite and GBC and the reduction of the interlamellar spacing of pearlite.