This paper presents the industrial results of evaluation of efficiency of synthetic slags during the treatment of steel at the equipment of the secondary metallurgy under conditions of the steel plant VÍTKOVICE HEAVY MACHINERY a.s. The aim of the heats was to assess the influence of the briquetted and sintered synthetic slags based on Al 2 O 3 aiming the course of the steel desulphurization and slag regime during the production and treatment of steel grade 42CrMo4 with the technology EAF→LF→ VD. Within the plant experiments, basic parameters influencing the steel desulphurization and slag regime were monitored: desulphurization degree, basicity, content of easily reducible oxides, proportion of CaO/Al 2 O 3 and Mannesmann's index. Obtained results allowed to compare the steel desulphurization and to evaluate the slag regime. It was proved that the synthetic slag presenting the briquetted mixture of secondary corundum raw materials can adequately replace the synthetic slag created from the sintered mixture of natural raw materials.Keywords: synthetic slag, slag regime, desulphurization, secondary metallurgy, steel W pracy tej przedstawiono przemysłowe wyniki oceny efektywności zastosowania żużli syntetycznych podczas obróbki pozapiecowej stali w zakładzie VÍTKOVICE HEAVY MACHINERY a.s. Celem badań był a ocena wpływu brykietowanych i spiekanych żużli syntetycznych opartych na Al 2 O 3 -na przebieg odsiarczania stali i żużla podczas produkcji i obróbki stali 42CrMo4, zgodnie z technologią EAF → LF → VD. Podczas eksperymentów w zakładzie, monitorowano podstawowe parametry wpływające na odsiarczania stali i żużla: stopień odsiarczania, zasadowość, zawartość tlenków łatwo redukowalnych, stosunek CaO/Al 2 O 3 oraz indeks Mannesmann'a. Uzyskane wyniki pozwoliły na porównanie stopnia odsiarczania stali w kontekście zastosowanych żużli. Wykazano, że syntetyczny żużel składający się z brykietowanej mieszaniny wtórnego korundu, może zastąpić syntetyczny żużel otrzymywany ze spieku mieszaniny surowców naturalnych.
Synthetic slags are used during steel treatment in the ladle from the viewpoint of effective refinement. Their basic task is formation of active slag for improvement of kinetic conditions of refining processes. In the steel industry, a number of synthetic slags based on Al 2 O 3 are used which are produced from natural or secondary raw materials in different forms. However, the use of synthetic slags is influenced by the choice of used raw materials, by production technology and by final chemical composition. This paper shows plant results and experience with the utilization of briquetted synthetic slags based on Al 2 O 3 and containing different amount of Cr 2 O 3. Trial plant heats were realized during steel treatment under the conditions of steelwork VÍTKOVICE HEAVY MACHINERY a.s. The main aim of these heats was assessment of the plant results with utilization of two types of synthetic slags with different chromium content and the evaluation of the increase of chromium content in steel as well as the course of desulphurization during steel treatment.
There is a steadily increasing demand for steel grades with increased nitrogen content in a certain range. Nitrogen is an important alloying element and it has a beneficial effect on mechanical and corrosion properties of stainless steel. Increased nitrogen content has a positive effect on the increasing of the pitting resistance equivalent in case of duplex stainless steels. Nitrogen can also substitute expensive nickel that strongly supports its use. There are several ways to increase nitrogen content in the steel. One of the most used ways is the nitrogen gas injection in the ladle. Solubility of nitrogen is significantly influenced by the chemical composition of the steel. However, due to nitrogen enrichment in the remaining liquid, gas pores can be formed during solidification of nitrogen-rich stainless steels. This article describes the results obtained during production of high nitrogen steels at steel plant VÍTKOVICE HEAVY MACHINERY a.s., mainly during production of martensitic 9% chromium steels and super duplex stainless steels.
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