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Review of Titanium Related Inclusions in Casting of Steel

Sheikh Ali R.

Archives of Foundry Engineering

2023

Vol. 23, iss. 2

127--136

The general area of understanding is inclusions in steel both metallic and nonmetallic in nature. This work has also used the concepts of inclusions in steel in general other than Ti however mainly the research works done on precipitation, solute segregation, grain developments and equilibrium aspects of important inclusions like Ti in steel have been probed. Interaction of inclusions with slag oxides has also been incorporated. Interdependence of elements common in-between many inclusions has been marked. TiN, TixOy and MnS inclusions have been very outstanding in the confines of present research. Ratios and effective concentration have been highlighted in certain cases around the topic. Type of steels, compositions of the constituent elements and temperature correlation has been spotted in certain environments. A suggestive relation with the steel properties has also been inferred. Hardness, corrosion behaviour and strength stand out to be the parameters of vital importance when considering Ti inclusions in the form of either TiN or TixOy. Certain inclusions like MnS seem to nucleate on TiN inclusions and there is a correlation evident certainly in case of complex alloys.

The application of the local electrochemical probes to study the corrosion behaviour of the heterogeneous alloys

Krawiec H.

Inżynieria Materiałowa

2007

Vol. 28, nr 3-4

783-787

The Electrochemical Microcell Technique was applied to study the local electrochemical behaviour of 304L-RES stainless steel and austempered ductile iron in 1M NaC104, pH=3 and pH=10 solutions. This technique revealed the local electrochemical behaviour of manganese sulphide inclusions, graphite spheres, oxide inclusions and matrix. In additional the influence of the dissolution of MnS inclusions at OCP value on the chemical composition of passive film was studied using local surface analysis technique like SIMS. The dissolution process of MnS inclusions under free corrosion was not uniform along the interface and numerous inclusions were partly dissolved. In the case of ADI the local electrochemical investigations have revealed that the matrix (ausferrite), far from spheres, undergoes passivation in 1M NaClC>4, pH=10 solution within a wide potential range, from the corrosion potential (of about -280 mV/SCE) until 800 mV/SCE. Surface observations combined with local electrochemical analysis have shown that the corrosion of ADI first occurred in the close vicinity of some graphite spheres and then at oxide inclusions. The oxidized regions are richer in oxygen than the matrix located far from spheres.

Technika lokalnej elektrochemicznej polaryzacji, znana w literaturze pod nazwą ang. Electrochemical Microcell Technique, została zastosowana do badania elektrochemicznego zachowania się stali 304 zawierającej wtrącenia siarczku manganu i żeliwa ADI w wodnym roztworze chloranu VII sodu. Za pomocą tej techniki zostało zdeterminowane elektrochemiczne zachowanie się osnowy w obu stopach, a także metalurgicznych heterogenicznosci takich jak siarczek manganu, grafit, wtrącenia tlenkowe. Lokalne badania polaryzacyjne wykazały, że wtrącenia siarczku manganu ulegają anodowemu roztwarzaniu i są prekursorami korozji lokalnej. Ponadto roztwarzanie siarczku manganu jest niejednorodne i wiele wtrąceń MnS ulega częściowemu roztwarzaniu po zanurzeniu w roztworze IM NaC104, pH=3. Lokalne elektrochemiczne badania prowadzone na żeliwie ADI, wykazały, że osnowa (ausferryt) ulega pasywacji w IM NaC104, pH=10, natomiast grafit ulega aktywnemu roztwarzaniu. Analiza powierzchni żeliwa po ekspozycji w środowisku korozyjnym wykazała, że roztwarzanie stopu zaczyna na granicy faz osnowa/grafit, osnowa/tlenkowe wtrącenia. Utleniony obszar jest bardziej wzbogacony w tlen niż osnowa znajdująca się dalej od grafitu.