The high-strength boron steel 22MnB5 steel is widely used for automotive lightweight constructions. A novel approach is promising to tailor strength and ductility in the hardened condition using locally pre-tempered sheets for the hot stamping process. It results in the formation of locally soft spots where mechanical joining is subsequently intended. A slow pre-cooling of the later joining zones with cooling rates below a certain critical cooling rate for obtaining a decreased strength in these regions is required. A tubular air cooling system suited for this task is presented and tested in a process where the subsequent quenching of the overall sheet is realized by rapid cooling in a water bath. Varying the air pressure and cooling duration allows controlling the size of the softened local spot in a wide range and still obtaining a bainitic microstructure. Using two-stage cooling with point jet nozzles and a subsequent hot stamping process with water-cooled dies resulted in a main sheet hardness of about 470 HV5 and of 260 HV5 in the pre-cooled spots, respectively.

高强度硼钢22MnB5钢广泛用于汽车轻量化结构。一种新颖的方法有望在硬化条件下使用局部预回火的板材进行热冲压过程，以调整强度和延展性。结果导致局部软斑的形成，随后需要进行机械连接。为了在这些区域中获得降低的强度，需要随后的接合区域的缓慢的预冷却，其冷却速率低于某个临界冷却速率。在此过程中介绍并测试了适用于此任务的管状空气冷却系统，该过程通过在水浴中快速冷却来实现整个板材的后续淬火。改变气压和冷却持续时间可以在较宽的范围内控制软化局部点的大小，并且仍然获得贝氏体微观结构。使用点喷射喷嘴进行两阶段冷却，然后使用水冷模具进行热冲压，分别在预冷点产生的主板硬度分别约为470 HV5和260 HV5。