The main components of the Castrip facility at Nucor are presented and the specific features of the twin-roll casting are highlighted with reference to conventional and thin slab casting. Nucor expected in February 2005 a monthly production of 25,000 tons of strips with an average thickness of 1.4 mm and a minimum thickness of 0.84 mm. Most products are utilized in construction application as light gauge hot rolled low carbon steel grades.
Nucor is now in the planning stages for a second Castrip facility in the United States and is exploring opportunities for utilizing the technology internationally through joint ventures.

The most significant developments the electric furnace has benefited from over the last decade are presented. The new technologies have made it possible to improve productivity and to reduce production costs. The advantages offered by the electric furnace in the EU pertain to four main issues: costs, organisation, customer service and environmental regulations. The evolution of electric steel production in the EU and in the world is discussed.

A new method for controlling the BOF process is proposed that involves the use of an original in blow heterogeneous sampler and a dedicated laser analytical method. The aim is to deliver a fast and comprehensive analysis of steel and slag collected by the heterogeneous- samplings. Combined with a metallurgical model, the data obtained with the heterogeneous samples make it possible to dynamically assess the refining progress in order to allow a safe direct tapping practice.

Raw material yard management and the feeding of the blast furnaces are essential processes for an integrated steelwork, and for CST in particular as the Company plans to raise their annual output from 5 to 7.5 Mt. Accordingly, CST has developed a model of raw material supply that takes into account every step of the cycle. The model includes two complementary modules, one for supply and consumption of the raw materials and the other one for raw materials transport. The model has revealed the need for a significant increase of the conveyor capacity and has made it possible to define more appropriate priority rules.

Virtual sensors allow the measuring of variables for which no physical sensor is available using indirect measurements of related variables. In this work we describe the implementation of a virtual sensor for the zinc coating thickness in a hot dip galvanizing line from related process variables such as blowing pressure, knives-to-strip distance, knives-topot distance, etc., based on artificial neural networks that model nonlinear dynamical relationships. The virtual sensor is currently working on Avilés Galvanizing 2.

A new technique for automatic assessment of centre line segregation based on image analysis is presented. This innovative tool can detect both centre line segregation and centre line cracks from digitalized sulphur prints giving an objective result. A data base containing process data from the caster and the new index for segregation measurement have been created. First analyses of this data base by data mining tools have been performed showing very promising results.

High carbon and chromium martensitic stainless steels are used when hardness and corrosion resistance are essential. Their mechanical properties and cold workability are impaired by large Cr carbides formed during solidification. This can be overcome by a nitrogen addition as a substitute for high carbon. Results are reported about 0.080% N addition to a 1.4116 grade (C=0.47%, Cr=14.5%, Mo=0.5%). The new grade offers a better combination of hardness, toughness and corrosion resistance than the three higher carbon grades 1.4109, 1.4112 or 1.4125.

The tools of the hot strip mill are reviewed in details: furnace, roughing mill, descalings, finishing mill and coolings involved in the modification of the transverse thermal profile. Industrial databases, numerical simulations and experiences are used to identify the main parameters and their influence. From this analysis actions are defined that could be taken to improve or to preserve the thermal profile.

Transverse cracking may occur in high strength low alloy CC slabs. This phenomenon is associated to a hot ductility trough resulting from intergranular ferrite that forms at the beginning of the γ-α transformation. Sumitomo has developed a hot tensile machine and a unique slab surface microstructure control process to improve hot ductility. The process based on controlled accelerated secondary cooling has been successfully implemented on Kashima n°2 caster.

Cementite decomposition leading to the formation of the white etching layer (WEL) on the surface of rail tracks was investigated by electron energy loss spectroscopy (EELS) in the TEM and by threedimensional atom probe (3D-AP). It is shown that the carbon concentration inside cementite laths undergoing severe plastic deformation in the transition zone between the pearlitic substrate and the WEL remains stoechiometric. However there exists a boundary layer at the ferrite/cementite interface where the carbon composition decreases, indicating that decomposition is an interfacial phenomenon. Carbon atoms diffuse into the ferrite and segregate along structural defects leading to a heterogeneous supersaturated composition in the white etching layer.

The cooling of working rolls is a critical factor of the hot rolling process, to limit roll surface wear and to control roll thermal deformation. An inverse heat conduction approach and an experimental method for measurement of heat transfer coefficient are presented. Heat transfer in the sprayed area is dependent on a large number of factors, such as surface temperature, roll velocity, local pressure, coolant jets inclination and interference of multiple sprays. The experimental approach is the only reliable method to get a precise description of the cooling of industrial working rolls.

The application software “Integrated Solution for Sinter Plant and Blast Furnace Charging” is presented. This is a decision-making support system that includes a mathematical model for the automatic and optimized generation of charging solutions for the sinter plant and blast furnace processes.
This model assures the quality specifications of the products, environmental limits as well as availability of materials, with particular focus on the operational stability. Furthermore, it allows managerial analysis including the acquisition strategies of new consumables and fuels.

The control of temperature distribution across the strip is essential for the hot strip flatness improvement. Hot strips of Arcelor in Avilès may display wavy edge defects that are generated after the finisher and are attributed to residual stresses introduced by the accelerated cooling on the run-out-table. A first approach has established that the thermal drop on the run-out-table has a significant effect on flatness, at the edges in particular. Among several systems that may control temperature at the edges, the edge masking technology has been selected, considering the previous implementation on CSP mills. Wavy edges are considerably removed or even suppressed on the operator side, while they are reduced but not eliminated on the drive side.

Up to now, no model or contactless sensor has been available for on-line control of the effectiveness of the flow of the stirring gas in the ladle in secondary metallurgy. A new method, based on the use of conoscopic holography, has been developed by Arcelor-Aceralia. It measures on line the vibrations in the walls of the ladle and relates them to the argon flow rate. This method is useful for determining the real state of the stirring process, obtaining an accurate index of the process of melt agitation that influences the composition homogeneity and cleanliness.

The effects of the thermo-mechanical parameters, in a Hot Strip Mill equipped with a coilbox, on the mechanical and micro-structural behavior of a titanium stabilized interstitial free steel are reported. The coiling temperature has the most significant effect on the mechanical properties. Increasing the coiling temperature reduces yield stress, tensile strength and hardness while it increases the elongation at fracture and drawability. The mechanical properties have been interpreted, through metallographic studies, in terms of ferrite grain size and of occurrence, distribution and size of the titanium precipitates.

More stringent customer requirements and productivity give steel makers an incentive to deliver higher surface quality strips. To control and to improve the surface properties, CRM has developed a sensor grabbing highly magnified images of a moving product. The chosen method is based on the principle of triangulation: a very thin line is projected on the surface and the relief is calculated by the analysis of line deformation. The result is an on-line 3D analysis sensor for assessing topography.

Medium-slab casting combines all of the benefits of conventional thick-slab casting and some of the benefits from thin-slab casting. The medium-slab caster incorporates the proven equipment design, operational aspects and automation features from conventional casting.

A new mold flux has been developed to favour cuspidine crystallisation at the upper level of the mold. This reduces the local heat flux and allows an even solidification of the slab shell, thus preventing any occurrence of longitudinal cracks. Pilot tests have established that the new flux make it possible to cast hypoperitectic steel slabs at casting speeds up to 5 m/min.

New manufacturing technologies have been introduced by JFE Steel Chita Works to increase the availability of seamless pipes with lower as well as higher thicknesses. For rolling the thinner seamless pipes, new plug lubricants and cermet coatings have been developed and the roll gap control technology has been implemented. For rolling the thicker seamless pipes, a new plug has been designed that allows a new pass schedule through all mills. The quality assurance system has been improved with lower frequency ultrasonic waves.

Exhaust systems are submitted to ever more severe service conditions, high temperature thermomechanical fatigue in particular. A numerical method is proposed for the design and the lifetime prediction of stainless steel exhaust manifolds submitted to a thermal fatigue load that is deducted from motor bench tests. The method relies on behaviour and damage models and on finite element analysis design of stainless steel exhaust manifolds. A dedicated damage criterion is proposed on the basis of the peak temperature and plastic strain amplitude reached during a thermal cycle. A more general thermomechanical fatigue damage model is also discussed.