Simon Seuren

Homogenization Strategy and Material Characterization of High-Manganese TRIP and TWIP Steels

In this work a hot forming strategy, consisting of forging and hot rolling, to homogenize casted blocks of high-manganese steels with 0.3 % carbon and 22 % manganese is introduced. The resulting distribution of carbon and manganese is evaluated by microprobe scans. The micro-segregation of manganese could be reduced from 7 weight percent to 2. To create the obtained hot forming strategy hot compression tests have been carried out. The deformation behavior has been characterized for two steels with 22 % manganese and between 0.3 and 0.7 % carbon content in the temperature range between 700 and 1200°C and strain rates between 0.1 and 10 s-1.

Accounting for shear deformation in fast models for plate rolling

For on-line prediction of roll force and torque, fast models have been available for a long time, which are mainly based on the slab method or other solution methods that allow for computing times in the range of seconds. Such fast models typically treat the rolling process as a plane strain problem and neglect shear deformation, which is always present in real processes. The shear deformation results in inhomogeneous strain profiles and thus might lead to inhomogeneity in microstructure over plate thickness. In this paper, a novel method is presented that allows for superposition of shear strain onto the strain state obtained from the slab method. The shear strains are interpolated from an extensive finite element (FE) parameter study of rolling processes that covers the entire parameter range of today’s plate rolling. For the regimes of very thick and thin plates different interpolation functions are introduced. It is shown that when the proposed shear strain model is combined with the slab method, similar results are obtained as with a full-scale FE calculation of the rolling problem but with a calculation time in the range of seconds.

A New Compression-Torsion-Tribometer with Scalable Contact Pressure for Characterization of Tool Wear during Plastic Deformation

A contact pressure which reaches up to ten times the yield stress of the workpiece material is characteristic for cold extrusion processes. Common tests for friction and wear are limited to rather low contact pressures. Thus, the aim of this paper is to present a new compression-torsion-tribometer which is able to scale the contact pressure to a multiple of the yield stress of the workpiece. In order to enable a contact pressure that greatly exceeds the yield stress of the workpiece material, the workpiece specimen is encapsulated laterally. As main parameters, contact pressure, glide length, and relative velocity can be adjusted independently, thus allowing for multiple load cycles. The resulting torque is measured continuously as an indicator for wear. Afterwards wear can be also quantified by examination of surfaces. Hence, the developed setup enables a comparison of tool surfaces and coatings and a characterization of wear behaviour under high contact pressure.

Recent developments in modeling of hot rolling processes: Part I - Fundamentals

The numerical simulation of industrial rolling processes has gained substantial relevance over the past decades. A large variety of models have been put forward to simulate single and multiple rolling passes taking various interactions between the process, the microstructure evolution and the rolling mill into account. On the one hand, these include sophisticated approaches which couple models on all scales from the products microstructure level up to the elastic behavior of the roll stand. On the other hand, simplified but fast models are used for on-line process control and automatic pass schedule optimization. This publication gives a short overview of the fundamental equations used in modeling of hot rolling of metals. Part II of this paper will present selected applications of hot rolling simulations.

Recent developments in modeling of hot rolling processes: Part II - Applications

This publication gives a short overview of current developments in modeling and simulation of hot rolling processes of metals at the Institute of Metal Forming of RWTH Aachen University. It is based on the fundamentals treated in Part I also contained in this conference issue. It features applications in the field of fast on-line models, where a fast multi-stage rolling model and an analytical approach for predicting the through-thickness shear distribution are presented. In addition, a new concept for sensitivity analysis by automatic differentiation is introduced and discussed. Finally, applications of rolling simulations in the field of integrated computational materials engineering are presented with a focus on TWIP and linepipe steels as well as aluminum.