Novel Brick Technology for Carbon Reduction Footprint in Steel Shop Linings

Clean steel encompasses a multitude of concepts that are based on fulfilling customer requirements and can be produced in many ways depending on the existing equipment and detailed customer demands.A common feature of all clean steel production is tight process control along with continuous monitoring.To meet an increasing demand for cold-rolled(CR)steel sheets of improved mechanical properties,and to cope with the change of the annealing process from a batch-type to a continuous process,it is necessary to establish a technique for making ultralow carbon(ULC)steel with a C-concentration lower than 20 ppm for the steelmaking process associated with a major challenge to guarantee the competitiveness with observance of environmental requirements.Steel ladle lining plays an important role on the energy consumption during the production and the refractory lining design contributes to minimize thermal bath loss,carbon pick up and shell temperature.A new generation of unfired zero carbon refractories was developed with two specific approaches:(1)replacement of firing bricks reducing CO_(2) footprint and(2)replacement of carbon containing with performance increasing.Bricks can be used in working and safety linings with a unique microstructure with better heat scattering and similar thermomechanical properties.This work presents customers’performance compared to traditional products highlighting energy savings.

Thermal Evolution of Al-containing Magnesia Refractories for RH Snorkels

Resin-bonded, Al-containing magnesia refractories have been an alternative of rebonded fused-grains magchrome bricks to be used as inner lining in the snorkels and lower vessel of RH degassers, having the advantages of being chrome-free and energy-saving(without burning), with a comparable performance. Microstructural investigations indicate that metal Al powder remains independent in the matrix after heating at 700 ℃ and 900 ℃, and Al_4C_3, Al_2OC and Al_4O_4C crystalline whiskers start forming from 1 100 ℃. The whiskers grow and connect into a network matrix with increasing temperatures,remaining up to 1 600 ℃. Comparison of used bricks from different snorkels indicates a strong whisker networks formation in the brick achieving long service life and superior performance, which is attributed to flexible network structure of stable and interwoven whiskers. On contrary, there is a strongly-oxidized layer on the hot face and almost no whisker found anywhere in the brick with the short service life. It is vital to form the bonding phase of whiskers at high temperatures,generating overall properties of high hot strength, high erosion resistance and thermal shock resistance, which are essential in the working conditions of RH snorkels.

Bonding Mechanisms of Basic Refractories for RH Snorkels

Magchrome bricks,as the inner lining of RH snorkels,have played a vital role in the operation of RH degassers for a long term.In chrome-free campaigns,resin-bonded,Al-containing magnesia bricks have been an alternative of magchrome bricks with a comparable performance in the last decade.It is important to have found whisker formation in the matrix of Alcontaining magnesia bricks above 1100°C and in the correlation to their high performance of RH snorkels.In this paper,the bonding mechanisms of both refractories are investigated to differentiate from other refractories.In magchrome bricks,the bonding modes of fused magchrome grains are characterized by the reactions between magnesia and chrome ore at different burning temperatures.At 1500°C,liquid forms around chromite grains.It is sucked into surrounding magnesia and a gap forms around chromite grains at 1600°C.Plenty of Fe2O3,Cr2O3 and Al2O3 have diffused from chrome ore into magnesia at 1670°C.A complete dissolution of the chrome ore takes place at 1750°C,with chromite precipitating entirely.In unburnt,Al-containing magnesia bricks,a dense network of whiskers is formed during heating,which is a prevailing bonding feature,instead of traditional particle growing and merging.It is believed that the whiskers are formed by vapoursolid mechanism since there is no liquid droplet observed at the tip of whiskers.In most stringent working conditions of RH snorkels,the bonding mechanisms are emphasized for their application,instead of chromia component.

Novel Flexibilizer for Cement Rotary Kiln Bricks

A new type of magnesia spinel brick containing a novel flexibilizer was developed.The publication presents an investigation on its chemical composition,physical properties and cement clinker resistance.Compared to conventional magnesia spinel bricks,the new brick type shows reduced amounts of alumina,significantly improved hot properties and resistance against cement clinker attack whilst keeping its textural flexibility on the same level.Field trials revealed satisfactory results and confirmed the novel flexibilizer concept.

Influence of the Trends Robotics and Digitalisation on Ladle Slide Gate Development

The article focuses on the influence of operator and process safety and the trends of robotics and digitalisation on a ladle slide gate that was introduced to the market 6 years ago[1].After more than 50 installations,customer experience was gathered and new features were added to a system upgrade.These upgrades are related to safety,ease of operation,and low operational costs.Especially a newly introduced“open check”feature increases the confidence level of the operators and can boost performance.With growing requirements to increase safety for people and processes in the ladle preparation area and on the continuous casting floor,automation has become increasingly important in steel plants.A slide gate prototype is currently underway to launch an innovative new gate design striving for full automation.Several critical process steps are already available and successfully used in the steel plants,such as cylinder connection,slag detection integration,and ladle gate preparation area automation.Fully automated operation will be followed by digitalisation,allowing for tracking of performance,safety,and quality.This paper summarises new features available for slide gates and outlines individual initiatives towards fully automated operation and data acquisition examples of digitalisation.

An Innovative Submerged Entry Nozzle Design for Billet and Bloom Casting

Fluid flow in the mold has a significant impact on the quality of continuously cast steel products.Since it is strongly influenced by the SEN design,attention has to be paid on its geometry.In this paper the main principles of a novel SEN type will be described.Water modeling and Computational Fluid Dynamics(CFD)are applied to characterize the flow pattern under different conditions.Furthermore,the interaction with electromagnetic stirring(M-EMS)is analyzed by means of a liquid melt model.Finally,actual steel plant performance data and observations are discussed.

New Argon Stopper Technology for Slab Casting

Argon addition into the casting channel reduces the amount of clogging on the refractory wall to allow long sequence casting of aluminium-killed steel grades.The key to minimum surface defects on the final product is to establish the optimum quantity by optimising the gas distribution below the stopper nose.This is achieved by new argon stopper technology which supports low gas quantities with homogeneous gas and bubble distributions to float non-metallic inclusions(NMI)in the continuous casting mould.

Full-scale Water Modeling on Flow Field of Continuous Casting Mold

In the continuous casting process of aluminum killed steel grades,nozzle clogging is a common problem.Argon is usually injected into the casting channel through stoppers or nozzles to minimize clogs;however,complex two-phase flow regimes appear,and the flow in the mold might deteriorate.This could result in a higher defect rate in the cast product and should be avoided as much as possible.Therefore,it is important to understand the interaction between process conditions and the refractory products used and their impact on the flow pattern in the mold.In this study,a full-scale water model was established to simulate the slab casting process.Three nozzle shapes and three immersion depths were applied to investigate the flow behavior and liquid level fluctuations by the full-scale water model.The relationship between the flow behavior and continuous casting parameters was evaluated.The results provide guidance for the design and production of the refractory nozzle and the operation of the continuous casting plant.

High Quality Doloma Refractories-Essential for Stainless Steel Production

Since early 2020 RHI Magnesita has been running a fully integrated dolomite plant in Chizhou,Anhui Province,P.R.China.The current operation consists of a world-class dolomite mine including a state-of-the art sinter plant equipped with rotary kiln plus a plant where shaped and unshaped doloma products are being manufactured.As raw dolomite has been a technically usable carbonate rock for decades the article describes the way from raw dolomite stone to doloma production.

Corrosion-resistant Refractory Linings for Hazardous Waste Treatment inRotary Kilns

Mega trends like urbanization,industrialization and growing population drive the demand of daily necessaries and therefore result in increased refractory consumption for waste treatment carried out at elevated temperatures.It is estimated that for burning 1 t of waste about 5.5 kg of refractory materials need to be consumed.In the present study,the corrosion resistance of refractory bricks based on alumina-chromia and alumina-silica was tested by exposing them to slag from hazardous waste incineration.Samples from the cup test were investigated macroscopically and mineralogically.They showed that alumina-chromia bricks had high corrosion resistance when in contact with the tested slags,while alumina-silica bricks containing silicon carbide showed an overall good performance.

Typical Refractory Wear Phenomena in Copper Vessels and Novel Monitoring Technologies

Copper smelting furnaces are typically lined with magnesia-chromite refractories,which are exposed to multiple and complex stresses.The selection of the processing route,furnace type,and slag system is dictated by the specific ore type available;which will determine the individual refractory wear.This paper evaluates the common refractory wear mechanisms as observed in the copper Peirce-Smith converter and in the copper anode furnace.The chemical factors include corrosion caused by fayalite type slag and sulphur supply,as well as by Cu-oxide attack.Changes in the temperature during the furnace operation(thermal shock)create stresses in the brick lining which can only be absorbed to a limited extent.Mechanical factors include erosion,caused primarily by the movement of the metal bath,slag and charging material,as well as stresses in the brickwork due to punching.Finally,improper lining procedures can also affect the service life.All these wear parameters lead to severe degeneration of the brick microstructure and a decreased lining life,and in the worst case overheated furnace structures and possibly dangerous hot spots or even breakouts.Therefore,a detailed investigation and understanding of the wear mechanisms through“post-mortem studies”together with thermochemical calculations by FactSageTM software is an important prerequisite for the refractory producer.Based on these research results,combined with specific process knowledge,appropriate brick lining solutions for copper processing furnaces can be recommended.In addition to the described efforts to investigate refractory wear and optimise lining qualities,it is also essential to monitor the process and the effect on the refractories to further improve both safety and process.For this purpose,technologies using sensors and novel digital solutions can be applied.

Refractory Tubes with Innovative Liner Technology for Flow Control and Clean Steel Applications

Ladle shrouds(LS)and submerged entry nozzles(SEN)are flow control products used in continuous casting which transfer the liquid steel from the ladle to the tundish and further to the mould.Due to the strongly different and quickly changing temperature conditions before and during steel casting,highly thermal shock resistant refractory materials are required which simultaneously save steel process energy.A new technology embeds a special liner into the refractory body inner surface to reduce the heat transfer through the LS/SEN wall.To better understand the function of this insulation layer a mathematical model was applied.Temperature measurements carried out in the steel plant were compared with the simulation results.The research results indicate potential heat loss reduction and performance improvements in the steelmaking process.

Innovation of Regenerator Checkerwork for Glass Melting Furnaces

Regenerator checkerwork for glass melting furnaces should have high resistance against thermal stress and chemical attack,high mechanical stability,high efficiency to recover the heat from waste gas and low tendency for clogging.This article reviews the innovation of the regenerator checkerwork from the past decades.The state of the art for optimised material choice and optimised checker shapes will be reported.

Sintering Complexity of Magnesia-chrome Refractories

Magnesia-chrome refractories are appropriate to work under cyclic temperatures or atmospheric conditions because some oxides of chrome ore readily release oxygen(are reduced)upon heating and pick up oxygen(are oxidized)upon cooling or upon changing the atmosphere.They have been ideal lining materials for RH degassers for many years,despite challenging of Cr^(6+) disposal issue after using.The varieties of magnesia-chrome refractories depend on their raw materials and burning temperatures,which could be well demonstrated by their microstructures.But Indian chrome concentrate cannot be directly used in the production of magnesia-chrome bricks because of reducing sintering density.Silicate bonded magnesia-chrome bricks are produced with low purity magnesia after burning at relatively lower temperatures,resulting in liquid film forming as silicate bond around chrome ore particles.Direct bonded and rebonded fused-grains magnesia-chrome refractories are made of high purity magnesia or fused magnesia-chrome grains,forming euhedral and intergranular secondary chromite spinels as the main feature.The amount of secondary spinel increases with the rising burning temperature,leading to increasing hot modulus of rupture and overall hot properties as well.It is important to burn magnesia-chrome bricks under weakly reducing atmosphere.The oxygen content of burning atmosphere from 800℃ to 1650℃ would better controlled below 0.5%to increase the burnt strength and to avoid inner cracks and loose bonding of magnesia-chrome bricks,while the atmosphere contains 3%-6%O_(2) under most economical firing condition.

Norton-Hoff model for deformation of growing solid shell of thin slab casting in funnel-shape mold

A funnel-type mold is commonly used to provide necessary clearance for the submerged entry nozzle in the thin slab casting(TSC).The partially solidified shell is subjected to the mechanical deformations,which can lead to the defects formation and,as a results,to a breakout.Traditionally,the results of the flow simulation,performed by the finite volume method(FVM),are fed to the external package for the finite element analysis of stress and strain.A coupled model was assembled using“creeping solid”approach by blending the Norton-Hoff viscoplastic stress for the solidifying shell with the Newtonian viscous stress of the liquid melt.The FVM was used to combine both liquid and solid stress models within a single solver.The iterative procedure based on the improved both side diffusion method was introduced to treat the nonlinear relation between the viscoplastic stress and the strain rate.The modeled shell thickness was verified by previously published breakout measurements and the simulation results.Temperature distribution,obtained during the TSC simulation,dominantly corresponds to the viscoplastic range.Developed numerical approach is robust and has direct industrial application.

Correction to: Norton-Hoff model for deformation of growing solid shell of thin slab casting in funnel-shape mold

Correction to:J.Iron Steel Res.Int.(2022)29:88-102 https://doi.Org/10.1007/s42243-021-00734-8The original version of this article unfortunately contained mistakes.The assignment of the affiliations was incorrect,and the corrected table is given below.The original article has been corrected.