Energy-efficiency increase through hybridization of solid forward extrusion with electrical resistance heating - Modeling the contact between electrodes and workpiece

重点考察了WZL开发的复合温固态正挤压工艺。在该工艺中，工件在成形期间通过电阻加热而被加热。由工艺的性质决定，局部加热发生在易受内部V形裂纹影响的区域。与传统的热固体正挤压工艺相比，这导致了更高的能量效率。到目前为止，在混杂的温固体正向挤压中引起能量效率增加的效果不能在工业上使用。原因有二。首先，由于在工件和冲头以及工件和反冲头之间的接触区域中的复杂的电-热-机械叠加现象，会出现高度波动的加热时间。这些大于典型的冷固体正向挤压工艺时间。其次，对于接触区域的工具侧，观察到以变化的表面粗糙度和边际质量损失的形式的烧蚀。烧蚀降低了工具寿命。高波动的加热时间以及烧除导致工艺稳定性降低。本研究旨在广泛地解释凸模、反凸模与工件接触系统中的电-热-力相互作用。这些知识使得能够全面推导出具有更短加热时间和减少烧蚀的接触系统。

Focus of examination is the hybridized warm solid forward extrusion process developed at WZL. In this process the workpiece is heated during forming through resistance heating. Determined by the nature of the process local heating takes place in the area susceptible to inner chevron cracks. This results in a higher energy-efficiency compared to the conventional warm solid forward extrusion processes. As of now the effects within the hybridized warm solid forward extrusion causing increased energy-efficiency cannot be used industrially. There are two reasons for this. Firstly, due to complex superimposed electro-thermal-mechanical phenomena in the contact area between workpiece and punch as well as workpiece and counterpunch highly fluctuating heating-up times occur. These are greater than typical cold solid forward extrusion process times. Secondly, as for the tool-side of the contact area a burn-off is observed in the form of a changing surface roughness and a marginal mass loss. The burn-off reduces the tool lifetime. The high, fluctuating heating-up times as well as the burn-off result in a reduced process stability. This research aims at extensively explaining the electro-thermal-mechanical interactions within the contact system of punch, counter punch and workpiece. This knowledge enables the comprehensive derivation of a contact system with shorter heating-up times and reduced burn-off.