Cold Sheet Rolling, Processing, Coating & Finishing
This paper presents the project of Nucor Steel–Arkansas’ new cold mill complex (high-performance push pickling line with in-line skinpass mill, S6-high cold rolling mill, 4-high temper mill and a continuous galvanizing line), which produces the latest generation of advanced high-strength steels (AHSS) for the car body. The project includes the complete equipment delivery with electrics and automation and the start-up of the lines. Combining ANDRITZ’s know-how in processing state-of-the-art steel grades (including third-generation AHSS) with the production expertise of Nucor is setting new milestones in the U.S. steel market for automotive applications.
Solid-state lasers (SSLs) are increasingly becoming acknowledged as state of the art for welding of flat-rolled sheet. This trend has developed because of its reduced service requirements and operating costs associated. The current coil joining process has to be more flexible, robust and reliable to meet the industry’s demands. Flexibility in joining of different grades, thicknesses and varying coatings is mandatory. This presentation deals with the differences in joining results and boundary conditions of the competing laser technologies of traditional CO2 vs. the SSL. A comparison of the critical factors related to the different associated wavelengths will be reviewed.
In cold rolling mills, vibrations of mechanical parts and/or strip can interfere with several quality parameters. Since vibrations occur at higher speeds, rolling speed has to be limited quite often. Besides conventional vibration countermeasures, this paper introduces a promising new approach. An active vibration damping system using piezoelectric elements as actuators has recently been developed by SMS group. A pilot installation in a tandem cold mill using the new active damping technology was started in 2017. The system provided an increase of the chatter limit speed, which increases the mill’s production significantly.
The main quality issue within a reversing cold mill has been strongly related to emulsion carryover and the high process temperature, which are the mechanisms to create a point oxidation randomly located on the strip surface, named “thermal stain.” Galvanizing lines do not accept these stains. This paper shows how — after making significant process temperature improvements, and implementing better emulsion control and pinch roll (PR) functionality changes, new PR materials and new air nozzle header design — the occurrence of stains decreased by 40% year over year. Furthermore, due to the quality improvements and the new air nozzle design, the noise level decreased by 10 decibels and there was 20% less air consumption.
In continuous galvanizing line operations, the thickness and the uniformity of the zinc coating are governed by the gas jet wiping process; a complex multi-phase, multi-scale phenomenon. To advance the fundamental understanding of such an intricate process, an efficient and accurate numerical model would be highly valuable. This work is a sequel on the development of a three-dimensional numerical model, aiming to consider the moving strip, the unsteady turbulent jet, and their mutual interactions with the falling excess liquid zinc. The present work examines the challenge of coupling unsteady compressible gas dynamics to liquid zinc free surface flow to better describe what happens during gas jet wiping.