Search

Developing environmentally friendly and biodegradable corrosion inhibitors is an important research direction due to the toxicity and non-degradability of conventional carbon steel corrosion inhibitors added to circulating cooling water environments. Polysaccharides in EPSs (Exopolysaccharides) can be used as green corrosion inhibitors, but a low inhibition rate limits their practical application. Chemical modification is widely used to modify the functionality of polysaccharides by altering their physicochemical properties and structures, thereby enhancing or supplementing their functional characteristics. In this study, we employed chloroacetic acid as an esterifying agent to chemically modify Dextran and successfully synthesized a modified polysaccharide derivative with a substitution degree of 0.326. This derivative efficiently inhibited the corrosion of carbon steel in circulating cooling water environments. The carboxymethylated dextran (CM-Dextran) formed after synthesis could adsorb onto metal surfaces to form a protective film, thereby inhibiting metal surface dissolution reactions and exhibiting anodic corrosion inhibition properties. The experimental results showed that the corrosion inhibition efficiency of CM-Dextran after modification increased by up to 57.4%, with a maximum inhibition efficiency of 82.52% at a concentration of 4 mg/mL. This study provides new insights and opportunities for the development of environmentally friendly corrosion inhibitors derived from polysaccharides. [ABSTRACT FROM AUTHOR]

The sigma‐phase distribution in a 2507 super duplex stainless steel continuous casting slab is analyzed using microstructural analyses and thermodynamic calculations. The sigma phase contains high Cr and Mo contents, and precipitates along the phase boundary between austenite and ferrite and grows toward the interior of the ferrite phase in the continuously cast slab. The sigma‐phase fraction at the center of the width direction is higher than that in the one fourth width. Furthermore, the sigma‐phase fraction at the center of the thickness direction is higher than those at the upper and lower surfaces, which is due to the lower cooling rate at the center. The Brinell hardness (HB) at the center increases to 313 HB with an increasing sigma‐phase fraction. The sigma‐phase fraction at the one fourth thickness near the lower surface is higher than that at the one fourth thickness near the upper surface at the same cooling rate. Additionally, Mo and Ni are severely segregated in this zone. A higher Mo content influences the precipitation and stabilization of the sigma phase. Furthermore, Scheil–Gulliver calculations indicate that compositional segregation results in an increase in the sigma‐phase precipitation temperature range. [ABSTRACT FROM AUTHOR]

Industrial experiments and thermodynamic calculations were carried out to investigate the evolution mechanism of Ca-containing inclusions in 20Mn23AlV steel with the Al content up to 2 wt-%. After Al deoxidation in AOD, the main inclusions were spherical shape Ca–Al–Si–Mn–O inclusions. Spherical Ca–Alrich–Si–Mn–O and spherical Ca–Al–Mn–O became the main inclusions after the first Al alloying. After Ca treatment in LF, the typical inclusions were aggregate CaS–CaO inclusions. In tundish, the types of inclusions were CaS and CaSrich–CaO, and the size and quantity of inclusions were substantially decreased. Thermodynamic analysis indicated that with the Al content increase to about 2 wt-%, the inclusions containing high Al2O3 content formed, which were extremely easy to be removed in the steelmaking process. Moreover, after the second Al alloying, the decrease of oxygen content promoted the formation of CaS inclusions, and CaS or CaS–CaO inclusions were formed Lastly, the evolution mechanism of inclusions was summarized in detail. [ABSTRACT FROM AUTHOR]

Industrial experiments are carried out to investigate the precipitation and growth of AlN in Fe–23Mn–2Al–0.08 V steel with nitrogen content up to 80–92 ppm. AlN inclusions can be precipitated before solidification. The morphologies of AlN are mainly divided into hexagonal and needle‐like shapes. With the cooling rate decreasing from 36.66 to 0.71 K s−1, the equivalent diameters of typical AlN increase from 7.56 to 24.20 μm, and the total amount decreases from 203.01 to 60.00 mm−2. The relationship between the cooling rate and the number density is obtained: lnNV=29.848 + 0.453 lnRC. The element segregation analyzed by electronic probe microanalyzer shows that aluminum concentration is low in interdendritic regions but high in dendrites. Aluminum segregation is very weak, and there is almost no nitrogen segregation. Thermodynamic calculation shows that AlN can precipitate before solidification with the nitrogen content higher than 58 ppm. The predicted results of AlN growth by kinetic analysis method can well reveal the growth trend. The nitrogen content (≥58 ppm) has a negligible effect on the size of AlN when the cooling rates are 3.02 and 0.71 K s−1, while the cooling rate has a significant effect on the size of AlN. [ABSTRACT FROM AUTHOR]

Nonmetallic inclusions formed during the Ti-stabilized stainless steelmaking process can induce the clogging in the submerged entry nozzle during continuous casting. To investigate the formation mechanism of nonmetallic inclusions in Ti-stabilized stainless steel, steel specimens were taken at different stages in industrial trials. The characteristics of inclusions and the chemical compositions of steel were analysed. After 10 min of Al deoxidation, the main type of inclusions in samples was irregular MgO·Al2O3. With titanium addition after calcium treatment, the irregular dual phase CaO–TiOx–Al2O3–MgO inclusions were formed. The steel compositions of most samples were located in or close to the Al2O3–TiOx liquid oxide phase field. According to experiment and thermodynamic results, the solid CaTiO3 and/or CaO·2Al2O3 inclusions were formed during titanium addition when the molten steel contained more than 20 ppm calcium. The effect of the initial calcium content on the formation of Ca–Al–Ti–O inclusions during titanium addition was discussed. [ABSTRACT FROM AUTHOR]