Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi

Abstract

The focus of this study involved comparative investigations of non-metallic inclusions in 316L stainless steel bars without and with Ca treatments. The inclusions were extracted by using electrolytic extraction (EE). After that, the characteristics of the inclusions, such as morphology, size, number, and composition, were investigated by using a scanning electron microscope (SEM) in combination with an energy dispersive X-ray spectroscopy (EDS). The following four types of inclusions were observed in 316L steels: (1) Elongated MnS (Type I), (2) MnS with hard oxide cores (Type II), (3) Undeformed irregular oxides (Type III), and (4) Elongated oxides with a hard oxide core (Type IV). In the reference sample, only a small amount of the Type III oxides (Al2O3–MgO–MnO–TiOx) existed. However, in Ca-treated 316L steel, about 46% of the observed inclusions were oxide inclusions (Types III and IV) correlated to gehlenite and to a mixture of gehlenite and anorthite, which are favorable for the machinability of steel. Furthermore, untransformed oxide cores (Al2O3–MgO–MnO) were also found in the inclusions of Type IV. The mechanism leading to different morphologies of oxide inclusions is also discussed.

Three-dimensional Investigations of Non-metallic Inclusions in Stainless Steels before and after Machining

“…The electrolytic extraction process was used to evaluate the characteristics of NMIs in the reference steel sample and chips. As the previous study 24) shows, a EE performed with the nonaqueous electrolytes named 10% AA (10% acetylacetone -1% tetramethylammonium chloridemethanol) works well with Ca-containing inclusions in a normal-size Ca-treated 316L stainless steel sample. Thus, similar EE conditions except a much shorter extraction time were performed on steel chips in this study.…”

Manufacturing and Applications of Stainless Steels

“…The review papers focus on the state of the art and perspectives in repairing and reinforcing historic timber structures by stainless steels [1], on duplex and super-duplex stainless steel microstructures and the evolution of their properties by surface modification processes [2], on the process and properties of reversion-heated austenitic stainless steels [3] and on the 3D printing of stainless steels by the laser powder bed fusion technique [4]. A group of research papers deal with physical metallurgy and advancedcharacterization techniques [5], others with process aspects [6][7][8] or property application items related to stainless steels [9][10][11][12][13][14]. The paper by Fava et al [5] presents and discusses the results of mechanical spectroscopy tests carried out on Cr martensitic steel.…”

“…This technique permitted the authors to characterize the specific role played by point defects in the investigated phenomena. Due et al [6] investigate non-metallic inclusions in 316L stainless steel bars with and without Ca treatments. The inclusions are extracted using electrolytic extraction.…”

Silicon Determination in Stainless Steels via Inductively Coupled Plasma Optical Emission Spectrometry: An Overview based on Experimental Data

“…Silicon‐rich inclusions in stainless steel may be accidental or intentionally created: for example, metallic silicon and calcium (in the form of calcium silicide) are sometimes added to molten steel during manufacturing to modify alumina‐rich oxides to more machinable Al–Si–Ca oxides (anorthite or gelhenite). [ 12 ] However, there is the evidence that these types of inclusions are readily soluble in acid. [ 13 ]…”