热冲压高强钢不同充氢时间下的氢浓度计算及其与氢脆层关系研究

Research on hydrogen diffusion in hot stamping steel and its relationship with hydrogen embrittlement layer

分别通过理论公式及有限元模拟,计算了热冲压高强钢B1500HS在不同充氢时间下的氢浓度分布,并通过微观形貌观测,分析了同一条件下的氢脆层特征。计算结果显示:随着充氢时间的增加,热冲压钢中氢的扩散距离和高氢浓度分布区面积增大;同时,热冲压钢力学性能显著下降,拉伸断口呈现明显的脆韧分区现象,且充氢时间越长,脆性区深度越大。对比分析氢浓度分布和拉伸断口的脆韧分区结果发现:只有氢浓度达到某临界值,才会出现光滑的脆性区,低氢浓度区域依旧保持韧性断裂的特征。

The hydrogen concentration of hot stamping steel B1500 HS under different charging times was calculated by both classic theoretical method and finite element simulation method.Moreover,the morphology of the hydrogen embrittlement layer under the same experimental conditions was analyzed as well.The calculated result indicates that the diffusion distance of hydrogen and area containing high hydrogen concentration increase with charging time.In the meantime,the reduction of mechanical property is significant,and the fracture surfaces consist of two regions,e.g.,the central dimple fracture layer and the peripheral hydrogen embrittlement layer,the brittle layer depth increases with longer permeated time.By comparison between the distributions of hydrogen and brittle-ductile layers,it can be concluded that the brittle layer is only generated when the hydrogen concentration approaches a critical value,while at the low hydrogen concentration area it still remains ductile fracture characteristics.