Tube hydroforming is a well-established process in industry for producing complex shaped parts with closed cross section geometry and high geometrical accuracy. Hot-metal gas forming (HMGF) extends the conventional tube hydroforming process by a complex thermo-mechanical approach and thus potentially enables the complex processing of tubes from the relatively new class of quenching & partitioning-steels (Q&P steels). To prove the feasibility of an integrated Q&P treatment in the HMGF process, a simple demonstrator geometry is considered in the present study. The applied forming pressure is limited to 70 MPa, resulting in incomplete forming of the parts in the corner areas. The resulting, locally varying contact situation between workpiece and die allows the investigation of different cooling rates and their influence on local microstructural changes and on the corresponding mechanical properties. A numerical finite element simulation is used to estimate local cooling rates in three different areas of the tube (maximum cooling rates between 60 and 280 K/s), which are then correlated with hardness measurements and typical microstructural features. The hardness distribution is inhomogeneous over the cross section of the part (varies about 150 HV), with a minimum in the areas without die contact during quenching. Ferritic areas are observed in these regions due to the significantly lower cooling rates. Tensile tests show that the stress-strain behavior after the shortest partitioning time of 10 min is not only better from an energy efficiency point of view, but also provides both high strength (R_m =2050 MPa) and high ultimate strain (19.7 %), while longer partitioning times result in inferior properties. Thus, the present study shows that the Q&P treatment can be integrated into the HMGF process, but the local cooling rates must be taken into account as they strongly influence the final mechanical properties of the workpiece.

管液压成型是工业上成熟的工艺，用于生产具有封闭横截面几何形状和高几何精度的复杂形状的零件。热金属气体成形（HMGF）通过复杂的热机械方法扩展了常规的管液压成形工艺，因此有可能实现对来自较新类型的淬火和分隔钢（Q＆P钢）的管的复杂处理。为了证明在HMGF工艺中进行综合Q＆P处理的可行性，在本研究中考虑了一个简单的演示器几何形状。施加的成型压力限制为70 MPa，导致角区域中零件的成型不完全。所结果的，工件和模具之间局部变化的接触情况允许研究不同的冷却速度及其对局部微观结构变化和相应机械性能的影响。数值有限元模拟用于估算管子三个不同区域的局部冷却速度（最大冷却速度在60至280 K / s之间），然后与硬度测量值和典型的微观结构特征相关联。零件横截面的硬度分布不均匀（变化约150 HV），淬火过程中没有模具接触的区域的硬度分布最小。由于冷却速度明显降低，在这些区域中观察到铁素体区域。_m = 2050 MPa）和高极限应变（19.7％），而更长的分配时间导致性能变差。因此，本研究表明，Q＆P处理可以集成到HMGF工艺中，但是必须考虑局部冷却速率，因为它们会严重影响工件的最终机械性能。