优碳钢带脆断原因分析与控制措施

Analysis and Control of Brittle Fracture of Fine Carbon Steel Strip

针对以65Mn热轧钢带为基料冷轧制造高硬度锯片过程中,钢带分剪、重卷时发生的突发脆断现象,经合理取样,采用光谱成分分析、金相显微镜微观组织观察、布氏硬度检测等分析手段对失效原因进行全面分析。结果表明,失效钢带的成分、晶粒度及拉伸性能符合标准要求,晶粒偏粗,晶粒度约6级,以珠光体组织为主,但珠光体周围被网状铁素体包裹,晶界弱化,恶化局部力学性能,在大载荷拉矫时,极易诱发断带,是其失效脆断的主要原因。对未出库或再生产热轧钢带,卷取后经充足待温缓冷后发货,可显著改善该类现象;对已出库未完全缓冷钢带,可采用回炉退火,改善组织性能,避免断带。热轧钢带在冷轧前先进行预退火,促使基料硬度明显下降,再进行冷轧,减小钢带变形抗力,有效提升轧制速度,显著提高生产效率及性能稳定性。

In the process of making high hardness saw blades with 65Mn hot-rolled steel strip as the base material,the sudden brittle fracture occurred during the shearing and rewinding of the steel strip.After reasonable sampling,spectral composition analysis,microstructure observation and Brinell hardness detection were used to analyze the failure causes.The results show that the composition,grain size and tensile properties of the failed steel strip meet the standard requirements.The grain size is coarse,the grain size is about grade 6,and the pearlite structure is the main microstructure but the pearlite is surrounded by mesh ferrite,the grain boundary is weakened,and the local mechanical properties are deteriorated.This kind of phenomenon can be significantly improved by taking hot rolled steel strip which is not out of storage or reproduced,and then delivering it after sufficient cooling.For the steel strip that has not been completely slow cooled out of the warehouse,the annealing can be used to improve the microstructure and avoid the broken strip.Hot-rolled steel strip is pre-annealed before cold rolling to reduce the hardness of the base material,and then cold rolling is carried out to reduce the deformation resistance of the steel strip,effectively improve the rolling speed,and significantly improve the production efficiency and performance stability.