Effects of Different Cutting Processes on Characteristics of Cut Damage for the Third-Generation Automobile Medium-Mn Steel

2017 ◽  
Vol 89 (9) ◽  
pp. 1700375 ◽  
Author(s):  
Ying Chang ◽  
Shuo Han ◽  
Xiaodong Li ◽  
Cunyu Wang ◽  
Guojun Zheng ◽  
...  
2018 ◽  
Vol 27 (2) ◽  
pp. 530-540 ◽  
Author(s):  
Guojun Zheng ◽  
Xiaodong Li ◽  
Ying Chang ◽  
Cunyu Wang ◽  
Han Dong

Author(s):  
Xiaodong Li ◽  
Ying Chang ◽  
Cunyu Wang ◽  
Shuo Han ◽  
Daxin Ren ◽  
...  

With the development of the automotive industry, the application of the high-strength steel (HSS) becomes an effective way to improve the lightweight and safety. In this paper, the third-generation automotive medium-Mn steel (TAMM steel) is studied. The warm-stamped TAMM steel holds the complete and fine-grained martensitic microstructure without decarbonization layer, which contributes to high and well-balanced mechanical properties. Furthermore, the martensitic transformation mechanism of the TAMM steel is investigated by the dilatation tests. The results indicate that the effects of the loading method on the Ms temperature under different loads are different. The Ms temperature is hardly influenced under the tensile loads and low compressive load. However, it is slightly decreased under the high compressive load. Moreover, the effects of the strain and strain rate on the Ms temperature are insignificant and can be neglected. As a result, this research proves that the martensitic transformation of the TAMM steel is rarely influenced by the process parameters, such as stamping temperature, loading method, load, strain, and strain rate. The actual stamping process can be designed and controlled accurately referring to the continuous cooling transformation (CCT) curves to realize the required properties and improve the formability of the automotive part.


Author(s):  
Ying Chang ◽  
Cunyu Wang ◽  
Kunmin Zhao ◽  
Han Dong ◽  
Jianwen Yan

The medium-Mn steel is a promising third-generation automobile steel. Its chemical composition, microstructure, and thermal and mechanical properties are introduced and a warm-stamping process for the medium-Mn steel is proposed. The optimal process parameters are identified through the design of experiments (DOE) and range analysis. The evaluated experimental indexes include tensile strength, elongation, and hardness. The optimal forming process consists of an austenitization temperature of 840 °C, a soaking time of 4 min, and an initial stamping temperature of 500 °C. The proposed process was applied to the warm stamping of an automotive B-pillar. The microstructure of ultrafine, uniform, and complete martensite laths was obtained. The formed part exhibits approximately 1420 MPa tensile strength, over 11% elongation and 460 HV hardness. The optimal warm-stamping process has proved effective and applicable for forming medium-Mn steel parts. It will help promote the application of the third-generation automotive steels.


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