Inclusion Characteristics in 95CrMo Steels with Different Calcium and Sulfur Contents

Abstract

In order to study the effect of Ca and sulfur contents on the characteristics of inclusions, industrial experiments using 95CrMo steel were conducted. SEM-EDS detections and stereological analysis were used to probe the characteristics of inclusions, including their compositions, morphologies, size, number density, and distribution. The results indicate that there were mainly three types of inclusions in 95CrMo steel billets with 6–18 ppm Ca and 30–100 ppm S: inclusions with single-phased morphology mainly composed of oxides; isolated MnS/CaS-only inclusions; inclusions with multi-phased morphology. The three-dimensional inclusion size distribution suggests that there were more Type-1 inclusions with a small size in low S containing steels. The average diameter of all types of inclusions increased with increasing Ca or S content in 95CrMo steel, indicating that the formation of MnS and CaS coarsened their size. The density distribution of inclusions indicates that the more inclusions there are, the more easily they aggregate and collide. Moreover, it is presumably concluded that the formation of sulfide in the outer layer of oxide inclusions weaken the attraction between oxide inclusions. The equilibrated transformation and formation of inclusions during the cooling process of 95CrMo steel was discussed based on thermodynamic calculation. The equilibrated transformation trajectory of inclusions in 95CrMo steel during the cooling process was Ca2SiO4 + MgO → Ca3MgSi2O8 → Spinel + CaS, which was corresponding to the detected results. The precipitation regular of sulfide was obtained. The formation mechanism for three types of inclusions was discussed.

Study on the Melting Temperature of CaF2-CaO-MgO-Al2O3-TiO2 Slag under the Condition of a Fixed Ratio of Titanium and Aluminum in the Steel during the Electroslag Remelting Process

“…In order to investigate the thermodynamic equilibrium of SUS321 steel and slag S0-F1(F2) further, the activity coefficients of Ti and Al in steel are calculated by Equation (3) and the value of is considered as −0.12. The interaction parameters [ 24 , 25 , 26 ] used in present study are listed in Table 5 . The activity coefficients of TiO 2 and Al 2 O 2 in slag are calculated based on Factsage 7.3-FToxid FactPS.…”

Characteristics and Transformation Mechanism of Nonmetallic Inclusions in 304 Stainless Steel during Heat Treatment at 1250 °C

“…Table 6 shows the average contents of the two typical inclusions and the corresponding activities calculated by FactSage 7.2. The activity coefficients f Cr and f Mn are calculated by the Wagner formula in Equation (5), where e j i is the first-order activity interaction coefficient of elements j to i relative to the diluted solution. These values are from reference [22].…”

“…There are two main types of no-inclusions in Si-killed stainless steel are CaO-SiO 2 -Al 2 O 3 -based and MnO-SiO 2 -Al 2 O 3 -based systems [1][2][3][4][5]. They have different properties and different effects on the surface quality of stainless steel strips.…”

“…They have different properties and different effects on the surface quality of stainless steel strips. Researchers [1][2][3][4][5][6][7][8][9][10] found that an effective way to improve the surface quality of stainless steel strip by controlling the nonmetallic inclusion as plasticity MnO-SiO 2 -Al 2 O 3 -based inclusion instead of CaO-SiO 2 -Al 2 O 3 -based ones. This could be realized by using different basicity refining slags and [Al] s contents during the smelting process.…”

Effect of Sulfur Content on the Inclusion and Mechanical Properties in Ce-Mg Treated Resulfurized SCr420H Steel

“…In addition, to achieve grain refinement during the gear carburizing process [6,7], grain refining elements cerium and magnesium are considered to be added into steel during the secondary refining process [8][9][10][11][12][13][14][15][16]. However, it is known that sulfur, as one of the common inclusion forming elements, can participate in inclusion formation in liquid steel [17,18] and MnS precipitation during solidification [19] and present an impact on the mechanical properties of steel finally [20]. Therefore, an in-depth understanding of the influence of sulfur content on inclusions and mechanical properties becomes necessary for designing a proper sulfur content for industrial production.…”