模铸大圆坯纵裂原因分析

Longitudinal Crack Analysis of Rounded Ingot

采用化学分析、扫描电镜等手段对中碳钢、模铸大圆坯?"纵裂"的化学成分、金相组织、显微硬度、脱碳层深度等进行检验分析,结果表明,纵裂的主要原因是铸态组织中晶粒和网状铁素体非常粗大,晶界的高温塑韧性差,且由于钢锭的冷速较快,使钢在凝固过程中产生较大的热应力和组织应力,导致钢锭浇注冷却后,钢锭发生"纵裂"。

The chemical composition, metallographic structure, microhardness and depth of decarburization about the longitudinal crack in the medium carbon steel and molded rounds were tested and analyzed by chemical analysis and SEM etc.The results shows that the main reason of the longitudinal crack formation is due to the coarse grain and coarse network ferrite in the cast structure which leads to bad plasticity and toughness of the grain boundary at the high tempreture. The faster cooling speed of steel ingot creates thermal stress and structural stress during the solidification process, which leads to longitudinal crack when the ingot is cooled.