Scielo RSS <![CDATA[Latin American applied research]]> vol. 32 num. 3 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Supermartensitic 13 %Cr large diameter seamless pipes: Mechanical corrosion and weldability properties]]> The demand for weldable 13%Cr pipes with outside diameter such as 18", 20" and 24" has increased greatly. Considering such a requirement, Dalmine and NKK have developed a new production route for OD 20" pipes. Girth welded joints (GTAW) were produced. The mechanical properties of both base material and welded joints meet the target requirements. Corrosion qualification was aimed to determine the Sulfide Stress Cracking (SSC) resistance in slightly sour oil wells. Influence of chloride content (NaCl 5÷25%), H2S partial pressure (1÷10 kPa) and pH (3.5÷5), was assessed. CO2 corrosion resistance was verified with static exposure tests at medium/high pressure of CO2, high chloride (25% NaCl) and temperature up to 150°C. <![CDATA[On microstructure development and inclusion generation in a continuously cast resulphurised steel]]> An experimental study on solidification structure development and on endogenous inclusion precipitation in a continuously cast resulphurised steel is presented. Results were obtained by investigating two heats of a free cutting C-Mn steel cast in billets with a diameter of 145 mm. The as cast structure was evaluated by macro- and microscopic analyses. Primary and secondary dendrite arm spacing measurement allowed to estimate the solidification time experienced by the steel in different region of the billet section. Modification of the pearlite vs. ferrite fraction was also studied as a function of distance from billet surface and thus with reference to solidification conditions. Endogenous inclusions of the type MnS and CaO-Al2O3 were analysed. Their formation was discussed as a function of the composition of the heats. Also for the inclusions resulting after steel solidification, the data suggested that the effects of local solidification condition and of segregation played a role of primary importance. <![CDATA[Advanced high chromium ferritic steels for boiler components operating at high temperature]]> In the last 15 years Dalmine and Centro Sviluppo Materiali (CSM) have worked together to develop the high Chromium ferritic steels for tubes and pipes to manufacture high temperature boiler components used in new high efficiency power plants. The activities started in 1985 with the development of P/T91 process and metallurgy, in the frame of ECSC project, followed, in 1994, by the evolution of P/T91 with the addition of 1% W. This new European steel called E911 was introduced during the COST 501 European Programme to improve the high temperature mechanical properties. This paper describes the process routes and compares the mechanical and creep behaviour of the two grades as well as the evolution of microstructure and precipitates after aging. <![CDATA[Analysis of slag foaming during the operation of an industrial converter]]> In the converter operation, a proper control of the slag-metal reactions that take place along the process is required to guarantee successful results. During the decarburization reaction a high gas flow rate is generated which increases the slag volume and can, eventually, promote its spill out of the converter. In this work, samples of slag and metal were taken out of an industrial converter at different stages of the process using a special device. The evolution of slag weight and composition was determined. Furthermore, calculations were performed in order to estimate the foaming capacity of the slags at the different stages of the process. It was found that the foam height reaches a maximum in the first half of the process, mainly due to the higher slag viscosity. <![CDATA[Joining steels by means of an amorphous welding porcess]]> The Laboratorio de Sólidos Amorfos started research on amorphous bonding processes in 1998. Since the beginning of 2000 a three year project devoted to this subject "Joining metals by amorphous metals diffusion" has been subsidized by the ANPCyT(1) and Siderca. In this work the antecedents of the project are summarized, the welding method is described and the results obtained up to now are reported. <![CDATA[Rheological effects in roll coating of paints]]> the aim of this work is the study of the problems that arise during roll coating application of paints on steel sheets. We put in evidence the particular effects due to the non-Newtonian properties of these fluids. At speeds above a certain critical value, the flow of paint through the applicator suffers a hydrodynamical instability called ribbing, which generates a patterned interface on the film applied. Threshold of instability as well as waveform of the pattern is function of rheological properties of paints as well as surface tension. Thixotropy of paints as well as shear-thinning behaviour has been determined for several industrial paints used in the steel industry, and correlated with levelling performance after application. <![CDATA[Modelling the microstructural evolution during hot rolling]]> A metallurgical model that describes the microstructural evolution of C-Mn steels in the hot strip mill, and that predicts the yield strength and the ultimate tensile strength based on the steel chemistry and the processing conditions is presented. The model comprises the microstructural evolution during hot deformation in the austenitic range (taking into account the effects recrystallization and grain growth), and the austenite decomposition during cooling (formation of ferrite, perlite and/or bainite). A comparison between calculated and measured yield strength and ultimate tensile strength values for several steels and processing conditions is also included. <![CDATA[Numerical model of steel slab reheating in pusher furnaces]]> The difficulty in measuring load temperatures inside reheating gas furnaces may be circumvented by appropriate use of on-line numerical models. In this article we describe a model of pusher furnaces, used to reheat steel slabs. The model uses thermocouple measurements at fixed positions inside the furnace to calculate the temperature of the combustion products, and takes into account radiative exchanges among those gases, the furnace refractories and the load. A good correlation is found between a temperature profile measured after the slab leaves the roughing stands and the results of the numerical calculations. We conclude that the model is a powerful tool to monitor the thermal state of the load inside the furnace and is suitable, together with an appropriate control algorithm, to automatically calculate the furnace settings required ensuring the objectives of the heating process. <![CDATA[Laser instrument for determination of the degree of cleanliness in cold-rolled steel plate manufacturing]]> Cold-rolled steel plate emerges from the manufacturing process with a thin layer of residual dirt that has to be kept under control for two main reasons: it may be indicative of deviations from normal functioning in previous manufacturing stages and it may impair the effectiveness of downstream operations such as painting, galvani-zing, etc. Standard measurements of this residual dirt are based on not trustworthy laboratory sample measurements, outside the production line. We developed a method that allows on-line determina-tions of the cleanliness degree for the whole manu-factured steel plate bobbin. Based on this method, we designed the first industrial instrument (ELMES I), which is now in operation at the final inspection line of the Siderar's plant at Ensenada (Buenos Aires) <![CDATA[On the modelling of liquid steel processes]]> An iterative (k-L)-predictor / (e )- corrector algorithm that models turbulent flow was developed in previous publications. In this paper, the 3D finite element turbulent model was used to analyze the liquid steel movement produced by gravity force, inert gas stirring or electromagnetic force stirring.