Abstract: A circular bead produced by a laser beam (CLW) is a method of joining superposed sheets by scanning circularly a laser beam. Among the various applications, it could be highlighted the welding of austenitic stainless steel AISI 304 sheets for heat exchangers. This work aims to report the effect of fiber laser CLW in tensile shear strength of superposed sheets as well as the corrosion behavior in relation to the process parameters. It was carried out circular beads using stainless steel AISI 304 sheets varying the laser power and speed. The samples were then submitted to optical and electronic microscopy, tensile-shear tests and electrochemical experiments. Among the experimental conditions, the weld sample with 800 W power and 50 mm/s speed presented an ultimate tensile strength of 159 MPa, 17% higher than the sample with the lowest result. The corrosion rate, corrosion and pitting potentials did not change significantly in the welded joint with different conditions compared to the base metal.

Electric arc furnace (EAF) slag has a range of functions, including improving energy efficiency through the "slag foaming" phenomenon. As such, the study of slag is important in EAFs. One of the factors that determine foaming quality and efficiency is the presence of solid particles. MgO saturation is highly significant since, in addition to ensuring the presence of solid particles, it also ensures chemical compatibility to minimize refractory consumption. The present study aims to examine MgO saturation, using the software FactSage v.6.4 for all calculations, in the CaO-SiO2-FeO-MgO-Al2O3 slag system and the influence of binary basicity, FeO and Al2O3 content on this system. Ternary diagrams revealed the influence of Al2O3 content on the liquid field and other phases present. Isothermal saturation diagrams (ISDs) were constructed, showing the same dual saturation points found in the ternary diagrams. The ISDs were validated by comparing the results of different heats in terms of the electrical energy consumption. The closer the heat is to the MgO saturation line, the less energy is consumed.

Slag foaming is part of steelmaking process and could bring several benefits: it helps to save energy, improves productivity, enhances the refractory service life, decreases noise pollution and protects the bath from nitrogen incorporation. Unfortunately, slag foaming is a highly dynamic process that is difficult to control. There are factors that limit the quality of the foam generated on the slag, such as: basicity, FeO content, surface tension, viscosity, carbon and oxygen injection. This paper aims to discuss the main factor that induces foaming, mathematical models proposed by different authors and the use of isothermal solubility diagram (ISD) to predict the foam quality.

In steel mills that operate with electric arc furnaces (EAF), it is interesting to ensure greater stability to the electric arc to aim at less distortion in the electrical system, with consequent reduction in electric power consumption. The slag foaming increases electric arc stability by reducing the total harmonic distortion (THD) between EAF phases. In this study, information about the chemical composition of the slag and electrical parameters of an EAF were collected. With the composition data, it was possible to determine the FeO and MgO content and basicity of the foamy slag which caused a reduction in THD and in electric power consumption. The effective viscosity of foaming slag was calculated and an increase in the effective viscosity provided a decrease in THD. A reduction of THD showed a decrease in the consumption of electric power in the EAF refining stage.