This paper investigates the root cause of an unexpected brittle transverse cracking in a carbon steel slab. The observed failure in the form of a deep and relatively straight transverse crack appeared in the middle of the slab during storage before hot rolling. The microstructure of the failed slab, and more specifically that in the vicinity of the crack were studied using electron and optical microscopy. Energy-dispersive X-ray spectroscopy (EDS) was used to study the chemical composition of different phases, observed in the microstructure. Analysis of the chemical composition of the alloy showed that chromium and nitrogen contents of the failed slab were out of standard range. Results of fractography showed that grain boundary de-cohesion and trans-granular fracture were dominant features in the fracture surface. Correlations between microstructure, processing parameters, and observed abnormal brittle fracture were discussed.

本文研究了碳钢平板中意外的脆性横向裂纹的根本原因。在热轧之前的储存过程中，观察到的以深且相对笔直的横向裂纹形式出现的破坏出现在板坯中间。使用电子和光学显微镜研究了失效平板的微观结构，更具体地说是裂纹附近的微观结构。能量分散X射线光谱（EDS）用于研究在微观结构中观察到的不同相的化学组成。合金化学成分分析表明，失效板坯的铬和氮含量超出标准范围。断口扫描结果表明，晶界去内聚和跨晶断裂是断裂表面的主要特征。