Tailoring Soft Local Zones in Quenched Blanks of the Steel 22MnB5 by Partial Pre-cooling with Compressed Air
Tailoring Soft Local Zones in Quenched Blanks of the Steel 22MnB5 by Partial Pre-cooling with Compressed Air
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DOI：
10.1007/s11665-020-04916-5
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发表时间：
2020-07
影响因子：
2.3
通讯作者：
O. Golovko;Max-Henry Stolte;K. Wölki;S. Hübner;B. Behrens;H. Maier;F. Nürnberger
中科院分区：
文献类型：
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作者：
O. Golovko;Max-Henry Stolte;K. Wölki;S. Hübner;B. Behrens;H. Maier;F. Nürnberger
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.
