Ana Socalici

This article presents a study on the influence of the intensity of the welding current on the properties of the mechanical strain strength of welded joints made by using submerged arc welding technology. The influence of the welding current on the microstructure of the welded joints was also observed in different regions of the cross-section of the welding seam. Also subject to observation was the mode of influence of the welding current on the geometry and dimensions of the welding seams. The welded samples were obtained using five different welding regimes whose main variable was the intensity of the welding current, which had values between 300 A and 700 A. The criterion used as a reference for comparing the effects produced by the studied welding regimes was a standard welding regime that is used in the industry for welding railway tank wagons, with a welding current intensity of 480 A. The base material used in the experiments was a fine-grained carbon steel specially intended for the manufacture of pressure vessels identified as P355 N; the semi-finished product from which the samples were made consisted of 6 mm thick laminated sheets used in the manufacture of the covers of the vessels that make up the railway tank wagon. The aim of this study was to highlight the differences that may appear through varying the current welding parameter and identify welding regimes that can provide welded joints with superior mechanical properties compared to what is currently employed in the industry. This study focused on the most widespread technology of welding pressure vessels: the submerged electric arc welding method.

The management of waste, especially ferrous waste, poses great problems in the steel industry due to strict regulations on preventing, reducing, or even eliminating the factors that generate a high degree of environmental pollution (landfills resulting from the steel industry and adjacent industries—mining, energy, etc.). The present paper presents a synthesis of the specialized literature regarding the processes used, both worldwide and nationally, regarding the transformation of raw materials (ores or concentrates) and iron-containing waste (steel mill dust, mill scale and scale, sludge from agglomeration factories, sideritic waste, etc.) into by-products that can be used in the steel industry. For technological reasons, the option of pelletizing powdered waste was applied—in laboratory conditions, according to its own recipes, with results that justify the application of the technology on an industrial scale (appearance after hardening; drop resistance). The aim of the paper was to identify a practical solution; based on this solution, original conceptual models of organizational strategies (management and processing, respectively, recovery of ferrous waste within steel companies) were developed, such as a concentration strategy, diversification, vertical integration, etc. Within graphical representations of the proposed strategies, other processing variants were mentioned: agglomeration; briquetting.

Optimizing the chemical composition of phosphorus cast iron for the manufacture of brake shoes, which are used in the rolling stock, is based on specific tests, and the results must be within the specified limits of railway standards. This paper presents the processing of data taken from an economic agent producing brake shoes—with chemical composition and hardness values determined through the Brinell method—as well as optimizing these data by obtaining optimal variation intervals. These technological intervals are useful in the case of foundries in order to obtain superior products from a qualitative point of view.

In order to apply the concepts that allow the transition from a linear to a circular economy, waste generators and/or processors must identify those variants that generate products that can be used as secondary raw materials, thus also respecting the actions governing sustainable development. This paper presents such a variant, the briquetting of waste with high iron content, waste generated on current flows in steel enterprises or deposited in industrial sites. The obtained briquettes are analyzed for chemical and mechanical characteristics so that can be used as secondary materials in the steel production. An optimization of the chemical composition using generic algorithms is also proposed in order to obtain the mechanical characteristics necessary for the proper handling of these products.

For noise rail decrease and observance of the limits in UE rolling stock must be equipped with silent brake blocks of composite material to replace the conventional cast-iron blocks. For testing composite materials test pieces have been produced according to the characteristics of the experimental installation. The paper presents the laboratory experimentation phase on obtaining composite materials for brake blocks and wear behavior of the experimental test pieces.

The paper presents the laboratory experiments and results meant for obtaining composite materials to be used in manufacturing brake pads for the drive and driven rolling stock. Six samples of composite material have been designed and obtained; each of them has been assessed in terms of tribological behavior using a tribotester and using the friction and wear parameters. Also, determinations have been made on the influence of the material factors and of the main parameters of the work conditions upon the tribological characteristics of the samples under tests and upon the processes that are going on in the superficial strata.