Considering the development of 56" line pipes, the barrel length ofthe work rolls of the DH finishing stand had been extended up to4.8 m in 1981. This made it possible to roll plates with a maximumwidth of 4,700 mm. The 5.5 m roughing stand had been commissionedin 1985. With a view to further improve the rolling process, DHrecently decided to revamp and modernize the existing finishingstand instead of ordering and commissioning a new stand. One anda half year experience with the revamped finishing mill confirm thatthis option is quite satisfactory and affords high productivity andavailability.

The most significant developments the electric furnace has benefitedfrom over the last decade are presented. The new technologies havemade it possible to improve productivity and to reduce productioncosts. The advantages offered by the electric furnace in the EU pertainto four main issues: costs, organisation, customer service and environmentalregulations. The evolution of electric steel production in the EUand in the world is discussed.

Gas-stirred treatment makes the ladle vibrate. Monitoring of thevibration has been studied in details: it is an industrial non-intrusivetechnique to control the process efficiency. Optimum gas stirringconditions can be defined, in terms of global kinetics of inclusionremoval at low vibration level.

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.

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

A new technique for automatic assessment of centre line segregationbased on image analysis is presented. This innovative tool candetect both centre line segregation and centre line cracks from digitalizedsulphur prints giving an objective result. A data base containingprocess data from the caster and the new index for segregationmeasurement have been created. First analyses of this data base bydata mining tools have been performed showing very promisingresults.

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.

Cementite decomposition leading to the formation of the whiteetching layer (WEL) on the surface of rail tracks was investigated byelectron energy loss spectroscopy (EELS) in the TEM and by threedimensionalatom probe (3D-AP). It is shown that the carbonconcentration inside cementite laths undergoing severe plasticdeformation in the transition zone between the pearlitic substrateand the WEL remains stoechiometric. However there exists a boundarylayer at the ferrite/cementite interface where the carbon compositiondecreases, indicating that decomposition is an interfacialphenomenon. Carbon atoms diffuse into the ferrite and segregatealong structural defects leading to a heterogeneous supersaturatedcomposition in the white etching layer.

The tools of the hot strip mill are reviewed in details: furnace, roughingmill, descalings, finishing mill and coolings involved in themodification of the transverse thermal profile. Industrial databases,numerical simulations and experiences are used to identify the mainparameters and their influence. From this analysis actions are definedthat 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 resultingfrom intergranular ferrite that forms at the beginning of the γ-α transformation. Sumitomo has developed a hot tensile machine and aunique slab surface microstructure control process to improve hotductility. The process based on controlled accelerated secondarycooling has been successfully implemented on Kashima n°2 caster.

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 experimentalmethod for measurement of heat transfer coefficient are presented.Heat transfer in the sprayed area is dependent on a large number offactors, such as surface temperature, roll velocity, local pressure,coolant jets inclination and interference of multiple sprays. The experimentalapproach is the only reliable method to get a precise descriptionof the cooling of industrial working rolls.

The application software “Integrated Solution for Sinter Plant andBlast Furnace Charging” is presented. This is a decision-makingsupport system that includes a mathematical model for the automaticand optimized generation of charging solutions for the sinter plantand blast furnace processes.
This model assures the quality specifications of the products, environmentallimits as well as availability of materials, with particularfocus on the operational stability. Furthermore, it allows managerialanalysis including the acquisition strategies of new consumablesand fuels.

The control of temperature distribution across the strip is essential forthe hot strip flatness improvement. Hot strips of Arcelor in Avilès maydisplay wavy edge defects that are generated after the finisher and areattributed to residual stresses introduced by the accelerated coolingon the run-out-table. A first approach has established that the thermaldrop on the run-out-table has a significant effect on flatness, at theedges in particular. Among several systems that may control temperatureat the edges, the edge masking technology has been selected,considering the previous implementation on CSP mills. Wavy edgesare 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 foron-line control of the effectiveness of the flow of the stirring gas inthe ladle in secondary metallurgy. A new method, based on the useof conoscopic holography, has been developed by Arcelor-Aceralia.It measures on line the vibrations in the walls of the ladle and relatesthem to the argon flow rate. This method is useful for determiningthe real state of the stirring process, obtaining an accurate index ofthe process of melt agitation that influences the composition homogeneityand cleanliness.

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

More stringent customer requirements and productivity give steelmakers an incentive to deliver higher surface quality strips. To controland to improve the surface properties, CRM has developed a sensorgrabbing highly magnified images of a moving product. The chosenmethod 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 linedeformation. The result is an on-line 3D analysis sensor for assessing topography.

A new mold flux has been developed to favour cuspidine crystallisationat the upper level of the mold. This reduces the local heat fluxand allows an even solidification of the slab shell, thus preventingany occurrence of longitudinal cracks. Pilot tests have establishedthat the new flux make it possible to cast hypoperitectic steel slabsat casting speeds up to 5 m/min.

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

Medium-slab casting combines all of the benefits of conventionalthick-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.

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.