Primetals Technologies (a Mitsubishi Heavy Industries company) has been refining the roll geometry of continuous casting machines for decades, resulting in an increasingly stable mold level during the casting process. Its most recent development is a model for establishing the ideal caster roll geometry already at the design stage.

This solution allows for a preview of how the caster will perform during operation, as it simulates both the unsteady bulging effect and mold level fluctuations caused by the phenomenon of bulging. The model enables steel producers to implement new or revamped casters that are designed to minimize mold level fluctuations during production. Therefore, they will be able to cast at higher speeds while producing slabs of high metallurgical quality.

A stable process during continuous casting is essential to produce high-quality products. Bulging is common and occurs as liquid steel at the core of the hot strand pushes against the shell of the slab as the strand moves between two rolls. During this process, heavy fluctuations in the mold level can build up, which might cause surface defects, or, in a worst-case scenario, a breakout, in which liquid steel pours out of the shell. Intensified bulging often results in operators having to reduce the casting speed.

Unsteady bulging is a complex problem involving, among other factors, mold-level deviations, solidification in the mold, and shell growth in the secondary cooling zone. The newly developed model is designed to consider all these parameters.

Utilizing Fourier transform, Primetals Technologies’ innovative software tool is capable of including a wide spectrum of parameters such as targeted steel grade, section size, and casting speed in its calculations. In this way, it identifies just the right frequency spectrum needed to set the optimal roll geometry.

With these simulations, it is possible to optimize the distance and diameter of the rolls before installing the equipment. Roll pitches are one of the main factors causing unsteady bulging, and by optimizing roll geometry, unsteady bulging is reduced by about 50%. Over the last months, this achievement was accomplished repeatedly at several steel plants where this solution is already implemented.

There are more benefits to be had with the new software model. Minimizing the occurrence of unstable bulging increases the caster’s range to include peritectic and ferritic steel grades, as no reduction in casting speed is necessary. Moreover, smoother strand shells and increased slab-surface quality are ensured.

The optimization of the rolls can be executed also for existing casters implemented by other plant builders.

Primetals Technologies was founded in January 2015 by Siemens VAI, Mitsubishi Heavy Industries, and partners. The company’s predecessors—Mitsubishi-Hitachi Metals Machinery and Siemens VAI—contributed significantly to the company’s portfolio. In early 2023, Mitsubishi Heavy Industries obtained full ownership of Primetals Technologies.

voestalpine EAF order. Earlier this month, voestalpine placed an order with Primetals Technologies for a 180-ton EAF (Electric Arc Furnace) Ultimate to be implemented at the Austrian steel producer’s site in Linz, Austria. Startup is scheduled for 2027. The EAF Ultimate will be playing a key role in voestalpine’s green transition program “greentec steel.” As a first step in this decarbonization program, one electric arc furnace will be built at each of voestalpine’s sites, in Linz and Donawitz.

Primetals Technologies will supply the complete EAF Ultimate equipment, a dedusting system, a waste-heat recovery system, electrical grid stabilization, and material handling for alloying materials and additives. The order also includes full Level 1 and 2 automation, a power supply system including a static synchronous compensator (STATCOM) for optimized grid stabilization, and the LiquiRob robotic system, which increases efficiency and occupational safety at the plant.

EAF Ultimate

The EAF Ultimate will be designed to incorporate solutions for environmentally friendly steel production. For example, the heat recovery system will convert much of the waste heat into steam, which is then fed back and used in other production units.

In August 2022, Primetals Technologies announced a significant contribution to Salzgitter’s SALCOS green steel transition project in Germany. This collaboration and other recent references as well as expertise in both the production of advanced steel grades and leading automation solutions were the most important factors influencing the decision to choose Primetals Technologies as the supplier for the new electric arc furnace and meltshop equipment.