Research of the formation mechanisms of nonmetallic inclusions in steel 23G2A

Abstract

Formulation of the problem. The article presents the results of studies of chemical and phase composition of nonmetallic inclusions in the cast steel 23Г2A and mechanisms of their formation after treatment in the ladle complex processing aids ДT1 proposed instead ferrotitanium brand ФTи68. Method. In the work to solve this problem it was used, except metallographic studies, volume allocation method, which is subjected by the metal anodic dissolution in the electrolyte. Ions and molecules of dissolved metal were whipped through the colloid bag. Solid particles siege nonmetallic inclusions, which are not dissolved, were investigated by X-ray phase and chemical analyzes. The siege, the resulting electrochemical dissolution of steel 23Г2A, investigated by X-ray analysis to determine the phase composition of nonmetallic inclusions. For this, solution with the precipitate was filtered and dried, separated from the filter paper and examined at the facility DRON−2.0 in the emission of chromium and copper. Microstructures of the 23Г2A steel, namely, the nonmetallic inclusion distribution features in the cast steel, studied by the methods of optical microscopy. Results. It is established that in steel, treated with ferrotitanium ФTи68, carbides manganese Mn₅C₂, chromium Cr₂₃C₆, iron Fe₃C form hard alloyed cement type (Fe, Mn, Cr)₃C, and the steel treated additive DT1, hard alloyed cement type (Fe, Cr) ₃C and titanium nitride. Using of the X-ray diffraction and petrographic methods has proved that after treatment with the addition ДT1 achieved a significant increase in quality compared to steel processing ferrotitanium ФTи68. It is istablished, the decrease in the total amount of oxygen that was part of the oxides. It is proved that there is stronger deoxidizing additive effect compared with ДT1 ferrotitanium. Scientific innovation. It is shown, that titanium grains at the origin and impact on the grain steel structure acts as a modifier of I-st kind, and in shaping the structure of dendrites and nonmetallic inclusions − as a modifier of the
II-nd kind. It is proved that there is a range of values in titanium content (0.019…0.025 %), and where the number of non-metallic inclusion in steel is insignificant: ~ (6…17) 10^-3 %). When the content of titanium < 0.019 % the number of nonmetallic inclusions peaks on the curve corresponding to ~ 26 10^-3 %. When the content of titanium >  0,025 % − the number of non-metallic inclusion
− > 40 × 10^-3 %. The practical significance. It is proved the possibility of using the waste of expensive titanium and aluminum alloys for deoxidation, micro modification microalloying of the low alloy steels to reduce the amount of harmful non-metallic inclusions and improve the quality and properties of steels processed.