The main milestones of the development of the modern steel industry are recalled and the changes which have occurred during the last ten years of the 20th Century are examined in the light of the evolution of the economical context in that period (protection of the environment, energy management, development of electric arc steelmaking and of compact and efficient production units, etc.). Several trends for the future evolution of the steel industry are discussed : environment friendly technologies and operations, controlled recycling of scrap, deep modifications for the electric arc furnace, methods for reducing the emission of greenhouse gas, etc.

The reasons of the success or phaseout of an industrial process remain mysterious. The history of the Perrin process allows to analyze this problem. After having described the process and the physical- chemical mechanisms underlying it, the author presents the good results obtained for the dephosphorization and the deoxidation of liquid steel and the problems which had to be solved in the case of desulphurization. Different aspects of the application of the process are discussed and different views on its adoption by steel producers are compared.

The twin cathode technology by Danieli is the new generation of DC superpower EAF. This design concept allows the utilization of reduced diameter standard electrodes and low density currents compared to single electrode DC or standard AC EAF of the same power. The operative results of this technology are shown at Hylsa Aceros Planos Mexico.

Several innovations in the casting of steel into ingots have found their full application in continuous casting. Bessemer made significant contributions in this area, but the decisive developments were made by others between 1920 and 1950 in the USA, England, Germany, etc. After the casting of billets became a well established process, new developments allowed to apply the process to slab casting and a high degree of performance is reached now. The direct casting of thin products, first attempted by Bessemer, is just becoming industrial reality.

This paper describes the first industrial application of the new DYNAFLEX oscillator developed by VAI on the two billet casting machines at Lech-Stahlwerke (Germany). Its main features are : no servohydraulic components, a system of leaf-springs arranged in cascade, simplicity of adjustment of stroke, frequency and wave form during casting. These factors suppress the need for maintenance of the oscillator, prevent mechanical backlash and result in a significant increase in machine availability and product quality, as well as in reduced maintenance costs.

In September 1998, the Sollac Florange HSM started up its second reheating furnace, with nearly the same size and thermal power as the first furnace built in 1983. This equipment has introduced new techniques, such as pulse width modulation on lower zones in order to control thermal power, or gas characteristics fine tuning with the correctometer using a furnace with only one burner, etc. Using two furnaces instead of one and a higher reheating capacity means some significant changes for the other tools of the HSM.

The Mardyck hot-dip galvanizing line began operations on July 2, 1998. The line is devoted to supply the very demanding market of the automotive industry. The main products have pure zinc or zinc-iron coatings and correspond to steels with a wide range of mechanical properties. The first tons for unexposed parts were produced less than one month after the start-up of the line, and tons suitable for exposed parts as early as the beginning of October.

Galtec, the subsidiary of Hoogovens and Sidmar, started the commercial production in February 1998. The CGL, located in Sidmar's cold rolling mill, is designed for applications in the building and white goods sector. The start-up curve was very steep ; more than 370,000 tons were produced during the first year 1998.

An expert system model for a fume extraction system has been developed and installed at an electric arc furnace steelplant. Expert rules advise plant engineers of plant abnormalities that could result in fugitive emissions to atmosphere and/or result in excessive energy consumption. Neural network algorithms are incorporated into the model to mimic instrumentation and to analyse general trends. Since the installation of a prototype, significant financial savings have been made.

The E911 steel grade has been developed from grade P91 to increase the creep properties at 600 oC through the control of vanadium, nitrogen and the addition of tungsten. Grade 911 shows a better creep performance than grade 91. Microstructure stability of both steels was investigated by isothermal ageing tests for up to 10,000 hours at 600 and 650 oC and their mechanical behaviour is compared. Results on welded joints have also been compared with base material.