Cast to Perfection – Slab Casters- Primetals

As a pioneer in slab casting technology, Primetals Technologies offers a comprehensive range of integrated equipment and system solutions to ensure high productivity, fast start-ups, short ramp-up times to full production and maximum casting flexibility. Compact and modularly designed slab casters from Primetals Technologies, with more than 550 references worldwide, are distinguished by advanced technological packages and quality casting equipment and components. Individual solutions can be developed to meet specific customer requirements – from minor component upgrades to full turnkey slab caster projects. The capability to cast a wide range of steel grades, slab thicknesses and slab widths on the same casting machine allows producers to quickly adapt to changing market demands. Andreas JungbauerGeneral Product Manager for Continuous Casting, Primetals Technologies, Austria, speaks to Steel 360 about the technological suites offered by Primetals and their potential in increasing product quality and yield. Below are excerpts from an exclusive interview:

Andreas Jungbauer, General Product Manager for Continuous Casting, Primetals Technologies, Austria,
Andreas Jungbauer, General Product Manager for Continuous Casting, Primetals Technologies, Austria,

What is the role of automation in continuous casting in modern steel mills?

Advanced automation packages are decisive for casting products that meet the highest standards of quality at maximum levels of productivity and yield. New challenges that arise from ever-increasing market requirements and the need to enhance the continuous casting process to enable the production of new and special steel grades can be met with proven and exciting automation solutions.

Ensuring optimum steel quality requires the right equipment and process control combined with experience, metallurgical know-how and precision. On the basis of the knowledge acquired from hundreds of slab, billet and bloom caster references that Primetals Technologies has successfully implemented since the introduction of slab casting technology at voestalpine in Linz in 1968, steel producers have at their side a partner with vast automation know-how to enhance and optimize their existing casting operations.

What are the new technological packages offered by Primetals Technologies that help steelmakers enhance operational efficiency and product quality in continuous slab casting?

Primetals Technologies offers a suite of technological packages comprising an advanced secondary cooling and soft-reduction model that consists of DynaPhase, Dynacs 3D and DynaGap Soft Reduction 3D, which work in conjunction with Nozzle Expert and Speed Expert. The model suite takes cooling precision and control possibilities to an altogether new level of excellence. With its modular setup, the package can be installed on existing caster equipment and even integrated with basic automation systems from other suppliers. All process models can then be ideally adapted to the specific customer requirements in the Maintenance and Setup System (MSS) tool of Primetals Technologies.

When setting up an advanced secondary cooling system for a caster, it is of utmost importance that all parameters are taken into consideration that can have an impact on the calculation of the 3D temperature profile of the cast strand. This includes the evaluation results when testing the spray-water distribution of different nozzle types at the nozzle testing stand. The derived information, including the exact position of the nozzles in the cooling zones of a caster, is entered into the MSS of the Dynacs 3D model for the online calculation of the 3D thermal profile of the strand. The MSS allows all cooling-relevant settings to be configured in such a way that the spray-water distribution in the various cooling zones and the application of defined cooling strategies can be optimized for slab, bloom and billet casting machines.

With the DynaPhase software model, thermodynamic properties of each individual steel grade analysis can be calculated online on the basis of the relative proportions of coexisting steel phases at a particular temperature. This information is also entered into the Dynacs 3D system for calculating a 3D strand-temperature profile. The number of references worldwide currently stands at 42 since the introduction of this process model in 2013.

The DynaGap Soft Reduction 3D features the dynamic adjustment of the casting gap for strand-thickness changes. It also minimizes or eliminates centerline segregation for improved internal strand quality. This is made possible with the use of specially designed strand-guide segments where the casting gap is remotely adjusted. On the basis of the online information provided by the Dynacs 3D thermal tracking model, the required casting gap set points are dynamically calculated by the DynaGap Soft Reduction model.

Likewise, the Nozzle Expert detects clogged nozzles and broken hoses in continuous casting machines and ensures that the strand is uniformly cooled for high-quality steel production. The model automatically monitors the condition of the nozzles during the casting process, and it can also be used to check nozzle status following maintenance work or segment changes. This allows nozzles to be immediately repaired before re-starting the casting process. Nozzle Expert takes into consideration parameters such as nozzle type, water pressure, pipe lengths, pipe diameters and nozzle positions. It is based on statistical models and indicates the clogging ratio of all nozzles in each cooling zone. Since its introduction, the number of references worldwide stands at 44.

The two twin-strand continuous slab caster at the Shandong Iron Steel Group Rizhao Co., Ltd., China was designed by Primetals Technologies
The two twin-strand continuous slab caster at the Shandong Iron Steel Group Rizhao Co., Ltd., China was designed by Primetals Technologies

What is the role of sensors and pre-detection devices in a modern smart steel factory like the Mold Expert breakout detection system offered by Primetals Technologies? 

The role of intelligent sensors is increasing by the day in the age of ‘Industry 4.0’. The Mold Expert breakout pre-detection system increases plant availability and decreases maintenance time by prompt alarming. Thanks to its superior performance, the Mold Expert system has become the world’s leading system for mold monitoring, with close to 200 installations worldwide. In addition to breakout prevention, it provides an ever-increasing number of expert packages that are used to detect possible surface defects and inform operators about challenging casting conditions.

The well proven LevCon mold-level control package adapts reliably and extremely quickly to mold-level fluctuations and changing casting conditions. This is made possible by advanced model-based control algorithms that can actually look into the near future to avoid disturbances in the control loop. Unsteady bulging is actively suppressed by a powerful algorithm based on modern control theory. The intelligent interaction between the advanced software and highly robust mechanical components improves safety and brings plant operators one step closer to fully automatic casting operation.

Slab caster designed by Concast India
Slab caster designed by Concast India

The two-strand slab caster that Primetals Technologies provided to theAngang Iron & Steel Group in China in December 2018 is equipped with the DynaGap Soft Reduction package. What are the main benefits of this package?

 The DynaGap Soft Reduction model is a sophisticated process model that allows for dynamic roll-gap changes in slab and bloom casters. Working in conjunction with remote adjustable segment types such as the Smart Segment or the Smart Single Roll DynaGap (SRD), roller gaps can be adjusted to perform strand thickness changes, eliminate centerline segment, as already highlighted, and reduce porosity for substantially improved internal strand quality. The DynaGap Soft Reduction package has been installed in more than72 casters worldwide since 2011. As many as 24 additional projects are being implemented in 2019 and 2020.

In fact, the newest development is the SRD segment which has been specially developed for use in final solidification. It enables the upper rolls to be pressed down individually onto the solidifying strand. This enables the final solidification point to be followed precisely. SRD segments can be used together with or replace conventional types of segments. The first installation was carried out at one strand of a slab caster in the Ternium integrated steel works in Santa Cruz, Brazil. Tests proved a superior internal slab quality as compared to the second strand using conventional segments. The second strand of the caster will also receive SRD segments.

Precise knowledge of the final solidification point and the associated soft reduction is vital to reliably produce slabs for steel grades that require high internal quality. The new SRD segments can be precisely applied to the final solidification. This enables each individual roll gap to be adjusted dynamically as a function of the steel grade, overheating, cooling or casting speed. Each roll transmits an individual force, which makes even higher thickness reduction rates possible, and reduces the segregation and porosity in the centre of the strand.

SRD segments are designed for long operating cycles and easy maintenance. For example, each roll has its own overload protection, which prevents damage to the bearings and surfaces of the rolls. The rolls are embedded in a function unit so that they can be quickly replaced either in a maintenance workshop or directly on the caster during a break in production. The individual roll units can also be tested and calibrated before installation in the segments.

DynaGap Soft Reduction adjusts the roll gap at the point of solidification
DynaGap Soft Reduction adjusts the roll gap at the point of solidification

How does the DynaJet Flex modulated spray cooling system help boost the overall product quality in continuous strand casting?

 The first industrial application of DynaJet Flex technology happened in November 2018 with the spray cooling system starting up at the two-strand continuous slab casting machine, CC2, in the Dangjin, Korea plant of Hyundai Steel. DynaJet Flex allows for pulse width modulated cooling, thus enabling highest discretization of cooling zones in width direction and widening the operation window with higher turndown ratios compared to cooling systems currently in use. This minimizes the appearance of corner cracks especially for advanced high-strength steels. The order for the new system for the first strand was placed in late November 2017. After a successful test, the application of the system on the second strand was ordered immediately.

The caster has a rated capacity of 2.8 MnT of slabs per year. It has a machine radius of 9.5 meters and a metallurgical length of 43.5 meters. Slabs are cast in a width range of 800 to 1,650 mm and a thickness of 250 mm. Hyundai Steel is producing special steels for the automotive industry, e.g. Hyundai Motors, such as advanced high-strength steels of the second and third generation. Such crack sensitive steel grades require a width- adjustable secondary cooling to avoid overcooling of the slab corners.

The two-strand continuous slab caster offered by Primetals Technologies to Chinese steel producer HBIS Laoting Steel Co. Ltd., China

From India, Concast India Limited has expanded to South and South East Asia, the Middle East and entire Africa. How is it contributing to expand Primetals Technologies’ global presence in long steel casting?

Since the 1970s, Concast India Limited has specialized in long casting solutions and is a market leader in India. Concast India ideally supports Primetals’ competitiveness in long casting while the product spectrum in long casting has been increased by this cooperation. On the one hand, Concast India profits from Primetals’ sales network, on the other it contributes to our expansion in the subcontinent and beyond.

Concast India pioneered continuous casting technology in India, at a time when the steel industry in India was still in its early stages. The productive capacity of the Indian steel industry has grown significantly and Concast India has a leading position in catering to the continuous casting needs of the rapidly growing industry. It produces the highest quality of steel efficiently and in an environment friendly manner, earning the trust of its customers along the way. It has continuously innovated and supplied continuous casting machines of increasing complexities and sophistication that are keeping pace with the changing needs of customers. After establishing a leadership position in India, Concast India spread its footprint in the global arena and today has a presence in over 30 countries.

From the Tata Iron & Steel Co. Ltd., Jamshedpur, Kalyani Steels Limited, Pune, and SAIL’s Durgapur Steel Plant to Jindal Strips Ltd., Hissar, Bhushan Steel & Strips Ltd., Dhenkanal, as well as Adhunik Metaliks and Visa Steel Limited, Bhubaneswar, Concast India has supplied machines and equipment to numerous leading manufacturers in India.