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By Karl Berger

As the hot rolling of steel moves into new more compact and effective processes, and as steel producers look for new ways to reduce their costs and increase their margins in ever tightening markets and tolerances, the evolution in Steckel mill technology, layouts, and new innovations may well keep the Steckel mill as a viable option, especially in areas of the world where minimized capital investments are required. In this paper we examine the evolution of the Steckel mills over the last two decades, with emphasis on new innovations and practical results, and provide a summary of hands on experience with some of these innovations. Also a focus on the South American Installations is given (from Siderperu to Gerdau’s newest Combination- Plate-Steckel-Mill). In addition, we aim to show the viability of the Steckel mill as an option for many existing or prospective steel producers, as the quality of the products rolled with Steckel mills reaches new quality parameters and as new innovations permit the rolling of thinner and wider materials, reaching new applications and wider share in markets, while maintaining a strong foothold in the traditional uses of Steckel mill products such as stainless steel, structural, and line pipe materials. As the ability to handle heavier, thicker, and wider coiled plate products increases, the coiled plate Steckel mills option is as strong an option as ever.

Aug 17, 2017

By Konrad Krimpelstätter

The need for more effective and flexible roll-gap lubrication technologies in hot and cold rolling mills is steadily increasing due to ever-greater requirements placed on the rolling process and the final products. In particular, the rolling of high-strength steels poses enormous demands for both the rolling mill and the coolant/lubricant to be used. The presented paper focuses on two innovative technologies for highly efficient roll-gap lubrication for hot and cold rolling, which were developed utilizing extensive knowledge and expertise about the tribological interactions in the roll-gap. The advanced work-roll lubrication package (A-WRL) for hot rolling and ESP mills is using specially designed mixer-nozzle units to mix the water/oil emulsion very close to the nozzles to minimize the risk for contamination and clogging. The nozzles are quickly exchangeable and are optimized to ensure uniform lubricant distribution, high plateout efficiency and minimum oil consumption. This eco-friendly solution does not require any chemical additives or cleaning agents and significantly reduces electrical energy consumption and work-roll wear. The roll cooling system on mill entry and exit side remains switched-on, which is of vital importance especially for highperformance hot strip mills. Minimum Quantity Lubrication MQL® represents a new generation of roll-gap lubrication technologies for cold rolling, which applies minimum amounts of pure rolling oil finely atomized with pressurized air directly onto the work roll surface. This allows controlling the oil film thickness depending on actual process and product parameters, providing increased lubrication flexibility, significant improvement of strip surface cleanliness through reduction of strip wear. MQL® was successfully installed and tested on two industrial tandem cold rolling mills in Europe. Advanced WRL and MQL® represent Primetals’ latest technologies that feature a robust and reliable system comprising standardized interfaces and flexible communication options. Both packages can easily be integrated into existing or new hot strip mills, ESP lines or cold mills.

Aug 17, 2017

By Felipe Beluche Lima, Caio Augusto Silva Santos

Brazil is the largest producer of crude steel in the Americas by BOF process and many challenges come along with the increasing market demand. In the BOF, a tubular wall hood structure has been showing premature failures related to the overlay welded tube technology placed in the hood wall. The main root causes were: thermal fatigue at 1800°C, hot spot formation, high heat-affected zone (HAZ) leading to susceptibility of stress cracking, carburizing corrosion and superficial wearing. Based on that, co-extruded tube technology (named composite tube by Sandvik) was the alternative chosen to enhance hood performance without compromising BOF process. In order to rises safety and productivity, composite tube has 100% metallurgical bond assuring stable expansion, high heat exchange efficiency, better corrosion resistance and less rough surface finishing. It was highly suggested to many others mills due to similar and already existing reported cases.

Oct 1, 2019

By Wen Xuan

Oolitic iron ores have significant economical importance because of their extensive resources in the world. However, their utilisation is often quite limited due to the high content of phosphorus inside. The phosphorus is often finely disseminated in the oolite structure and generally not liberated in the form of free particles. The iron ore used in this work is a typical oolitic goethitic iron ore with high phosphorus. The process of phosphorus removal from this ore is difficult because the phosphorus is not present as distinct minerals. As a result, no physical beneficiation process is able to separate the phosphorus from the iron bearing phases. The current concentrate contains low iron grade (Fe ~49%) and high phosphorus content (P 0.7~0.8%). The acid leaching is a potential way to dissolve phosphorus. Previous studies have shown that the thermal treatment makes the phosphorus more accessible for the acids and enables more efficient phosphorus dissolution. Some chemical additives are reported to enhance this phenomenon. A series of tests have been carried out using roasting - grinding - magnetic separation - leaching technologies to remove the phosphorus from this current concentrate. In the first stage, several tests were performed at pilot scale under the same conditions as described in some publications. The achieved results were similar to those from previous tests at laboratory scale. In the second stage, new test conditions were investigated in laboratory scale in order to achieve better result and to reduce the operational cost.

Aug 1, 2018

By Daniel Carvalho, Marcos Viana, Leonardo Demuner, Herbert Castro

Intensive process and technology improvements related to the BOF converter — the key process to increase steel plant productivity and stability — have been performed at Ternium Brazil. This paper details the road map for process developments and investments in equipment technology, as well as the results achieved. The main topics of this development are the process control and optimization systems, slag forming model, oxygen blowing pattern, end-of-blow point control and slag carryover control. The outcomes of this development are improvements in the reblow rate, end-of-blow oxidation, direct tapping, slag carryover, slopping ratio, metallic yield and lining life.

Oct 1, 2019

By Maurizio Massimo

Danieli developed the “3Q” suite of process control technologies to address three critical principles: delivering the highest product Quality, in the required Quantity, with Quickness of response required for today’s casting machines. Ever increasing market demands for productivity and slab quality necessitate the latest advances/improvements in equipment design, process technology, and control software for all types of slab casters, and Danieli boasts a unique experience that extends from ultra high-speed thin slab casters to extra high-thickness conventional slab casters. The “3Q” system is monitored and controlled by a unique, intelligent HMI incorporating. Touch screen technology and Operator Assistant tablets. Operator Assistant is a tablet based system that guides the operator through the plant process, so that in the event of a process change or an alarm the operator is automatically presented with the choice of possible solutions / actions. The comprehensive range of technological packages cover all aspects of caster design and automation control, from feeding of liquid steel into the tundish to the final slab leaving the caster.

Aug 17, 2017

By Anand Kumar Agrawal, Kinzel Klaus Peter, Lorenzo Micheletti, Cristiano Castagnola, Horst Kappes, Andre Oliveira, Björn Rösner, Philippe Bermes

Blast furnaces are widely employed today for iron production all around the world, with a total production of around 1.2 billion tons per year. Its operating principle, which relies on usage of coke to reduce the ore, to ensure the permeability in the reaction vessel, to maintain its flexibility of operation and acceptability for varying qualities of iron ores. The blast furnace route is widely considered as the most economic and efficient route of iron production, however it is based on fossil energy carriers. The blast furnace route has undergone significant developments in terms of energy efficiency in the last decades, which led to a substantial reduction in the use of fossil reduction materials. Being an energy intensive process, competitiveness and cost saving in the blast furnace plant was always strongly related to the saving of energy and hence reduction of CO2 emissions. In addition to this, EU emissions trading system (EU ETS) as a cornerstone of the EU's policy in response to climate change has set new “challenges” for iron production in Europe. Paul Wurth has always been deeply involved in the development of energy saving technologies for blast furnaces. In the following a review of energy saving achievements developed in the last decades will be presented and the potential of available CO2 saving technologies will be summarized. Additionally, an outlook about the potential of future technologies, concepts and their impact on the blast furnace and the steel plant’s energy balance will be discussed. Finally, the replacement of carbon by hydrogen as reduction agent in the steel plant will be reviewed, with special focus on a comparison of costs and incentives.

Oct 1, 2019

By Ron Webber

With the difficult economic challenges currently facing the steel industry, it is essential to perform a complete analysis when determining which rolls to purchase. A properly designed “Total Cost of Ownership” model can result in significant savings. This paper will review the costs associated with rolls in both Hot Strip and Cold Strip Mills. The multitude of factors that must be considered in performing a complete analysis for the roll purchasing process will be discussed. Models for both Hot Strip and Cold Mills will be presented. Examples where traditional analysis can lead to expensive, incorrect decisions will be presented.

Oct 30, 2017

By Fernando Henrique Gomes de Souza

Techniques which use a spring to supply the bias force to actuator are well adopted since they are inexpensive and simple to construct. In this work it was design an actuator concept using bias-type device technique, which comprises two coils that mutually push against each other to supply the stroke. For the coils springs, it was used a wire of NiTi shape memory alloys (SMA) and a wire of 400 grade maraging steel as construction materials.

Aug 8, 2018

By Priscilla Pessin Coppo

The prevention of dental enamel wear has particular relevance for preventive and restorative purposes in dentistry. The wear damage can increase due to salivary disorders and/or parafunction (bruxism); antagonists incisal surfaces become flat and coincident. This study aims to investigate the wear behavior and the related mechanisms in sliding pairs of conformal incisal enamel, with similar values of hardness and fracture toughness, with different applied normal loads and lubricated conditions. Bovine incisors, under pin on flat configuration, were tested in two lubrication condition (dry or with natural saliva) and two applied normal loads (8 and 16 N). The worn surfaces were investigated by 3D profilometry and SEM. The analysis of worn surfaces indicated mechanisms of brittle fracture, but with different severities. Under a normal load of 16 N and dry condition, wear is controlled by a brittle process: microcracking with flake-like wear particles, which results in high friction coefficient (> 0.85), wear rate and wear volume. On the other hand, under a normal load of 8 N and natural saliva, wear took place in the interprismatic region, with consequent exposure of prisms and fracture in localized regions. In this case, the friction coefficient was 16% lower and the wear volume was one order of magnitude lower. Under 8 N and natural saliva, the wear was greater than in the dry condition, probably due to tribochemical reactions.

Jul 31, 2018

By Nelson SOUTO, Nicolas LEGRAND, Christian COUNHAYE, Don EARLEY

The work is motivated by the automotive customer requirements for a roughness with high peak density (RPc > 75 peaks/cm) on steel sheet surfaces to maintain a good strip surface finish after painting. For that purpose, a new approach is utilized to compute roughness transfer and predict final roughness on uncoated steel sheets (average roughness, skewness, peak density) as a function of temper rolling conditions. The approach is based on the Monte Carlo method combined with the Abott curves and an auto-correlation function to numerically generate roughness profiles for roll and strip respectively. To compute the roughness transfer due to the interaction between roll and strip surfaces during rolling, a composite Abott curve that combines roll and strip Abott curves is used with an asperity crushing model integrated with a rolling model. This enables simulating two roughness transfer mechanisms in the roll bite: the strip asperity crushing mechanism by roll roughness and the strip asperity ploughing mechanism due to roll-strip interfacial sliding speed. The model shows the importance of considering the two mechanisms to predict roughness transfer correctly when strip elongation is high, typically a few percent, and roll bite friction is low. In these conditions, the forward slip at the exit of the roll bite tends to erode strip roughness significantly and decrease considerably the peak density on the strip. For lower elongation levels (~1%) and high roll bite friction, the ploughing mechanism becomes negligible and roughness transfer is controlled by the crushing mechanism only. With these two mechanisms, the model reasonably predicts the evolution of average roughness and peak density over a wide range of temper rolling conditions (new/worn work rolls, hard/soft grades, various elongations), but skewness is more difficult to predict for some trials.

Oct 1, 2019

In today’s competitive steelmaking environment, the optimization and continuous supervision of the blast furnace process is of major importance. Modern probes and process measurement systems can assess the specific operation of the blast furnace. They provide a better and detailed process understanding and control. The benefits are even more important when they are combined with process models and expert systems. Everyday operation, productivity and even the lifetime of a blast furnace can be significantly improved by collecting, interpreting and acting upon such process data correctly. Only a comprehensive knowledge of the various process phenomena together with measurement of process variables inside the blast furnace enables the operators to optimize coke and fuel rates, to run the blast furnace smooth, reliable, and safe, and to make best use of the available raw materials. While the improvement of the blast furnace process with respect to productivity remains the main task, also, the timely identification of abnormalities and the assessment of process variations is an objective. This paper describes the blast furnace measurement systems that are available for everyday automatic use and provides an understanding for the possibilities of modern probes. The different applications are daily blast furnace supervision, charging process optimization, and observation of the internal state. Finally, the paper gives recommendations on probe configurations for different blast furnaces sizes, considering both a technical and an economical point of view.

Aug 2, 2018

By Sander Mul, Michael Brandner, Armin Paar

Graphitic HSS roll grades such as ESW’s brand VANIMO can be considered as the latest developments for the last finishing stands in hot strip mills. These roll grades are developed on the basis of the alloying concept of (Carbide Enhanced) Indefinite Chill work roll materials. During the development of VANIMO, the amounts and types of carbide forming elements were increased and adjusted into the direction of cast HSS roll grades. The microstructure of graphitic HSS roll grades therefore consists of tempered martensite, cementite and several different carbide types as well as a well-defined amount of free graphite. The main purpose of graphitic HSS roll grades is to combine the high surface quality of Indefinite Chill alloys as well as the high wear resistance of HSS roll grades. Several systematic steps were taken to increase the wear performance from Carbide-Enhanced Indefinite Chill grades to the more advanced VANIC grade and further on to the highest alloyed roll grade VANIMO. In every development step, the surface quality of the roll grades was carefully monitored. The decision to invest in new testing equipment at ESW’s plant was driven by the wish to see microstructural effects of different alloys in a macroscopic dimension. Usually samples are taken from cast rolls and investigation is done in comparably small areas compared to the total surface of a roll. Rolling of strip is done with the entire barrel, so effects of alloy and microstructure can appear anywhere on the barrel surface. To ensure better understanding and deeper knowledge about influences of alloying trials we decided to install the last version of LRI (Lismar Roll Inspection). LRI includes the latest technology of Eddy Current with an enormous resolution. Depending on the formation of carbide precipitations, carbide network as well as matrix and free graphite, the EC test can detect smallest differences. The possibility to analyze the different results of EC and UT surface wave inspection will be discussed. A few examples of surface effects in the mill application will be discussed and improvement strategies explained.

Oct 1, 2019

By Alessandra Spaghetti

Rolling small-diameter hot wire rods at high speeds with conventional laying head pipes can wear the pipe out frequently and affect quality and consistency in the final product. Laying head upgrades using Sandvik SAF2507LHP™ (UNS S32750) tubes make possible to achieve optimal metallurgical properties, smooth coil formation and easier coil handling. Operators can also avoid unwelcome shutdowns due to frequent worn pipe changes and turndowns. Sandvik have been developing different customers and understand their process needs. The suitable selection materials that are able to withstand high levels of wear better than low alloy and carbon steel grades that are commonly used in industry is very important to improve the quality and increase productivity. UNS S32750 tubes were demonstrably superior to low alloy and carbon steels when used in Laying Head Pipe system regarding tubes lifetime, reducing replacement, production interruptions and increasing reliability.

Aug 17, 2017

By Giuseppe Pintaude

This study aims to evaluate the effect of specimen preparation on the dry sliding wear behavior of CA-6 NM stainless steel. Two different surface finishing manufacturing processes were applied: lapping and metallographic polishing. The wear tests were conducted in reciprocating ball-on-flat system, performed for two loads: 5 or 8 N. For all test conditions, hardmetal ball was employed as counterbody. The surfaces were evaluated using 3D interferometry technique to determine their surface roughness, including texture analysis regarding isotropy. Surface characterization results indicated the presence of texturing and preferential orientation, since the parameter Str was smaller than 0.5 for samples of both the studied conditions. Two distinct levels of isotropy evaluated through Str parameter were achieved: 0.13 for lapping and 0.3 for metallographic polishing process. It is clear from wear tests that the variation of average surface roughness is the key point for tribological behavior of CA-6 NM stainless steel.

Jul 31, 2018

By Daniel Suarez

Over the last few years the mining industry has continuously been facing increases in capital and operating costs for new projects; plant expansions and also significant increases in the operating costs of existing plants. To counteract such trend the industry is seeking technologies such as the Vertimill as an option to lower the operating costs of grinding circuits. The benefits the Vertimill offers in terms of lower energy consumption and lower media consumption are well established and documented; such benefits can significantly improve the viability of a new project, plant expansions or upgrading grinding mills that need to be replaced. The paper briefly describes the operation of the Vertimill, recent regrind applications in processing Iron ores where the impact of lower energy and grinding media consumption is very significant because of the large tonnages involved, and also applications as a tertiary and secondary grinding stages of grinding circuits. The paper also highlight the expected role the Vertimill can play in secondary applications and the expected impact on the overall economics of the project.

Aug 1, 2018

By Washington Martins da Silva Júnior

In stamping process, sliding between metal sheet and forming tool leads to wear of tool surface. Maintenance of stamping tools involves polishing the tool edge, or, in case of severe damage, replacement of the tool. Hard coatings have been applied on the stamping tool surfaces in order to reduce the maintenance cost causing a great economic impact in metal work industry. In this work, CrAlSiN coatings were applied by PVD onto SRV2W tool steel. The coating toughness was avaliated by the critical load in scratch tests. The following coating parameters were analyzed: 1- substrate surface finishing process; 2- coating architecture (multilayer or gradient); 3- chemical composition of the coating. AlSi concentration varied from the substrate/coating interface to the surface. Coatings were 3 µm thick. Scratch tests were carried out using a Vickers indenter. The applied normal load was varied from 0 to 13 N for a scratch length of 5 mm. In order to study the effect in the toughness, the substrate roughness was controlled by the finishing process before PVD coating. Samples subjected to polishing presented highest critical loads. Gradient coatings presented higher critical loads than those with a multilayer architecture. Coatings with higher concentration of AlSi near the surface supported higher loads before failure.

Jul 31, 2018

By Jeremy Fletcher

In today’s world, the requirement of Steel Producers to revamp and modernize their blast furnaces on-time, safely and with the latest technology is paramount. In addition they must meet the detailed design, construction and safety legislation and regulations, which can be different for the various countries around the world. Siemens MT is renowned for its ability to perform Blast Furnace rebuilds, relines and modernisations within extremely tight time frames and in a safe manner. Modular Blast Furnace construction concepts have been perfected to minimise project duration and plant downtime for furnace rebuilds. Safety and certainty are the keys for success. Siemens MT are constantly introducing new technologies into the market place including cyclone gas cleaning and triple external cone gas scrubber, along with step changes in technology such as dry gas cleaning and dry slag granulation. The economic environment and the continuing requirement for improved environmental performance, drive many of these innovations. This paper describes some of the latest rebuild reference projects of Siemens MT, along with the latest technical innovations installed on these furnaces, and some of the construction methodology used for a safe and secure rebuild.

Aug 1, 2018

By Alberto Pesamosca

The paper presents the results obtained by the AC EAF supplied by Danieli at Kroman Çelik (Gebze-Turkey) after the planned upgrade to 150 ton. The EAF – 7,4 m diameter, based on the full platform standard design - is able to handle a maximum power of 114 MW and is equipped with the most advanced and reliable technology, including module injection system and the Hireg electrodes regulation system. Excellent results were already obtained with 120 heat size in terms of fast start-up and excellent performance figures. After the upgrade, productivity was increased up to 212 t/h, maintaining high process efficiency (365 kWh/t with 32,1 Nm3/t O2).

Jul 30, 2018

By Marcelo Rebellato, Leonardo Silvestre, Zhang Yongqing, Felipe Bastos, Zhang Weiqiang

This work reviews the new version of GB1499.2-2018 Chinese national standard and specification, which governs the production of high-strength reinforcing hot rolled ribbed bars in China. In addition, it discusses the main concerns from Chinese rebar makers that might affect production and application of Nb-bearing rebars, like reheating temperature required to dissolve given niobium additions, the promotion of bainite microstructure and continuous yielding, as well as Nb strengthening effects. Through extensive investigation involving both thermomechanical laboratory simulations and industrial trial, the existing state and effects of Niobium along the reheating, rolling and cooling are illustrated. At the end, optimum processing conditions have been established to produce high strength rebars for the specified requirements. The adoption of new process conditions reflected in an amount of about 20.0 million tons of Nb-bearing rebar being produced in China in 2018 with required tensile properties and microstructure, and helped rebar makers to reduce production costs considerably. Based on production data, Niobium demonstrated positive strengthening effect for high strength rebars, in particular for small diameter rebars with earthquake resistant performance. What is more, the results of the research enrich the knowledge of the application of Niobium in steels when TMCP rolling is not used.

Oct 1, 2019