The use of artificial intelligence technique for the optimisation of process parameters used in the continuous casting of steel

The productivity and quality of a continuous caster depend mainly on process parameters, i.e. casting speed, casting temperature, steel composition and cleanliness of the melt, water flow rates in the different cooling zones, etc. This work presents the development of an algorithm, which incorporates heuristic search techniques for direct application in metallurgical industries, particularly those using continuous casting process for the production of steel billets and slabs. This is done to determine the casting objectives of maximum casting rate as a function of casting constraints. These constraints are evaluated with the aid of a heat transfer and solidification model based on the finite difference technique, which has been developed and integrated with a genetic algorithm. The essential parts of continuous casting equipment, which must be subjected to monitoring, as well as a methodology of mathematical model and physical settlements in each cooling region, are presented. The efficiency of the intelligent system is assured by the optimisation of the continuous casting operation by maximum casting rate and defect-free products. This approach is applied to the real dimension of a steel continuous caster, in real conditions of operation, demonstrating that good results can be attained by using heuristic search, such as: smaller temperature gradients between sprays zones, reduction in water consumption and an increase in casting speed. (C) 2002 Elsevier Science Inc. All rights reserved.26111077109

Structural aspects and mechanical properties induced by laser surface remelting of a tool steel

A tool steel was surface remelted by a 1.8 kW continuous CO2 laser under conditions of different scanning speeds. Microstructural examination of longitudinal and cross sections of the melted tracks permitted the determination of simple expressions correlating the width and depth of melted pool with the beam scanning speed. Microstructural analysis has indicated a strong modification in the laser remelted zone with secondary dendrite arm spacings of about 1 mu m. This is indicative of a high cooling rate of the order of 10(6) K/s, determined by comparison with the dendrite arm spacing of 80-100 mu m typically observed in a similar material conventionally solidified at a cooling rate of about 0.5 K/s. Vickers hardness measurements were carried out along the treated zone cross sections, and it was found that values of about 800 HV can be attained, which is high compared to a value of 300 HV for the original substrate. A slight variation of treated zone hardness with beam scanning speed was observed.91475

Laser cladding of a martensitic stainless steel on a tool steel substrate

The improvement of surface quality of a tool steel by laser cladding has been investigated by using a stainless steel as the coating material. Microstructural analysis indicated a significant modification in the laser remelted zone with secondary dendrite arm spacings of about 2 mu m and corresponding cooling rates of the order of 10(3) K/s. The microhardness achieved in the coating (800 HV) is about four times the hardness of the substrate, which is high compared to a value of 530 HV normally attained in conventional treatments of the same tool steel. The processing conditions used yield a 700 mu m coating depth with a uniform chromium distribution and without porosity.9322923

The use of artificial intelligence for the optimization of a laser transformation hardening process

This work proposes an interaction between a heat transfer model and an artificial intelligence (AI) heuristic search method which is linked to a Knowledge Basis for the optimization of a Laser Transformation Hardening (LTH) process. The developed computational program selects the best combinations of laser operational variables for the highest martensitic production acid for laser energy saving. The mathematical model consists on an analytical part to describe the workpiece laser heating and a numerical part for the cooling process. The Knowledge Basis is a rule-based system constituted of heat treatment constraints. The use of the developed search method for determining optimized laser operational variables can be considered a very effective tool in the improvement of the LTH process performance.10427529

Laser welding of low carbon steel blanks

A pulsed Nd:YAG laser was used in this investigation to produce welded blanks of low carbon steel sheets. The selected welding parameters have assured a complete joint penetration for the entire length of the joint with sound weld quality. The shielding gas device used in experiments has provided plasma suppression and protection of the melted zone from oxidation. Microhardness was measured across the weld zones indicating a fusion zone/base metal hardness ratio of 1.3. The ball punch deformation test was used for a better understanding of formability and has indicated a reduction of 9.4% in average cup height at failure by the presence of the laser weld.10318319

Microstructure of reaction zone in WCp/duplex stainless steels matrix composites processing by laser melt injection

The laser melt injection (LMI) process has been used to create a metal matrix composite consisting of 80gm sized multi-grain WC particles embedded in three cast duplex stainless steels. The microstruture was investigated by scanning electron microscopy with integrated EDS and electron back-scatter diffraction/orientation imaging microscopy. In particular the search of the processing parameters, e.g. laser power density, laser beam scanning speed and powder flow rate, to obtain crack free and WCp containing surface layer, has been examined. Before the injection of ceramic particles into remelted surface layer, the influence of processing parameters of laser surface remelting on the microstructure and properties of selected duplex steels was also investigated. Although after simple laser surface remelting the austenitic phase is almost not present inside remelted layer, in the case of LMI the austenite was observed in vicinity of WC particles, due to increase of carbon content acting as austenite stabilizer. The diffusion of carbon in the reaction zone results also in a formation Of W2C phase in the neighborhood of WC particles with a strong orientation relationship between them. The maximum volume fraction of the particles achieved in the metal matrix composite layer was about 10% and a substantial increase in hardness was observed, i.e. 575 HV0.2 for the matrix with embedded particles in comparison to 290 HV0.2 for untreated cast duplex stainless steels. (c) 2007 Elsevier B.V. All rights reserved.202102113212