Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Nov 4, 2020
Al-Ti complex deoxidation equilibria in high Cr stainless steels were studied by measuring the th... more Al-Ti complex deoxidation equilibria in high Cr stainless steels were studied by measuring the thermodynamic behavior of O in the Fe-Cr-Al-O, Fe-Cr-Ti-O, and Fe-Cr-Al-Ti-O melts. The present deoxidation experiments were thermodynamically analyzed along with available data in the literature using Wagner's formalism. The compatible set of parameters for the multicomponent Fe-Cr-Al-Ti-O system was selected, and its applicable concentration and temperature limits were discussed. The parameter set successfully reproduced the present experimental results and literature data of deoxidation equilibria in the Fe-Cr-Al-O and Fe-Cr-Ti-O alloy melts over the wide Cr concentration up to 40 mass pct at 1823 K to 1996 K (1550°C to 1723°C). The validity of the parameters was also checked by carrying out the Al-Ti complex deoxidation experiments with the construction of the predominance diagram for inclusions in the Fe-Cr-Al-Ti-O melts at 1873 K (1600°C).
Sulfatizing roasting is used when separating small contents of valuable metals from sulfide and c... more Sulfatizing roasting is used when separating small contents of valuable metals from sulfide and composite ores. In sulfatizing roasting the desired constituents are selectively converted to water soluble sulfates, whilst other constituents such as iron remain as insoluble oxides. In Finland the sulfatizing roasting process has been used at the Outokumpu Oy Kokkola Works for the extraction of cobalt and nickel from roasted calcines and pyritepyrrhotite concentrates since 1967 (1).
The refining function of slags in ladle metallurgy comprises of desulphurization and capture of i... more The refining function of slags in ladle metallurgy comprises of desulphurization and capture of inclusions, which are removed from the steel melt in the course of deoxidation procedure. In that task, the interaction between the two phases, slag and steel is active and highly beneficial. Further, the slag has a passive, shrouding role when it protects steel from atmospheric oxidation and heat losses. In some cases, slag can even have negative influences as a reoxidation source and eventual origin of harmful inclusions in steel. Conventionally, inclusions in steel are understood as deoxidation products, remained in the steel after the deoxidation process. These, "intrinsic" inclusions are then related to the steel composition i.e. determined by the deoxidizing components in steel, generally Al but even Si, Mn and Ca. However, in intensive ladle treatment the role of the top slag is not only the receiver of inclusions from the steel but pronounced chemical interaction between the liquid slag and metal can take place. Consequently, a component with low activity in the slag e.g. SiO2 can intensify deoxidation by silicon. By contrast, CaO has a high activity in basic ladle slags and it can interact with steel and bring CaO into inclusions. As a consequence, the type of inclusions can remarkably change. The current paper examines the fundamentals of interaction phenomena between slag, steel and inclusions via thermodynamic calculations, experimental results from steel industry, and observations on related research in the literature.
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Nov 4, 2020
Al-Ti complex deoxidation equilibria in high Cr stainless steels were studied by measuring the th... more Al-Ti complex deoxidation equilibria in high Cr stainless steels were studied by measuring the thermodynamic behavior of O in the Fe-Cr-Al-O, Fe-Cr-Ti-O, and Fe-Cr-Al-Ti-O melts. The present deoxidation experiments were thermodynamically analyzed along with available data in the literature using Wagner's formalism. The compatible set of parameters for the multicomponent Fe-Cr-Al-Ti-O system was selected, and its applicable concentration and temperature limits were discussed. The parameter set successfully reproduced the present experimental results and literature data of deoxidation equilibria in the Fe-Cr-Al-O and Fe-Cr-Ti-O alloy melts over the wide Cr concentration up to 40 mass pct at 1823 K to 1996 K (1550°C to 1723°C). The validity of the parameters was also checked by carrying out the Al-Ti complex deoxidation experiments with the construction of the predominance diagram for inclusions in the Fe-Cr-Al-Ti-O melts at 1873 K (1600°C).
Sulfatizing roasting is used when separating small contents of valuable metals from sulfide and c... more Sulfatizing roasting is used when separating small contents of valuable metals from sulfide and composite ores. In sulfatizing roasting the desired constituents are selectively converted to water soluble sulfates, whilst other constituents such as iron remain as insoluble oxides. In Finland the sulfatizing roasting process has been used at the Outokumpu Oy Kokkola Works for the extraction of cobalt and nickel from roasted calcines and pyritepyrrhotite concentrates since 1967 (1).
The refining function of slags in ladle metallurgy comprises of desulphurization and capture of i... more The refining function of slags in ladle metallurgy comprises of desulphurization and capture of inclusions, which are removed from the steel melt in the course of deoxidation procedure. In that task, the interaction between the two phases, slag and steel is active and highly beneficial. Further, the slag has a passive, shrouding role when it protects steel from atmospheric oxidation and heat losses. In some cases, slag can even have negative influences as a reoxidation source and eventual origin of harmful inclusions in steel. Conventionally, inclusions in steel are understood as deoxidation products, remained in the steel after the deoxidation process. These, "intrinsic" inclusions are then related to the steel composition i.e. determined by the deoxidizing components in steel, generally Al but even Si, Mn and Ca. However, in intensive ladle treatment the role of the top slag is not only the receiver of inclusions from the steel but pronounced chemical interaction between the liquid slag and metal can take place. Consequently, a component with low activity in the slag e.g. SiO2 can intensify deoxidation by silicon. By contrast, CaO has a high activity in basic ladle slags and it can interact with steel and bring CaO into inclusions. As a consequence, the type of inclusions can remarkably change. The current paper examines the fundamentals of interaction phenomena between slag, steel and inclusions via thermodynamic calculations, experimental results from steel industry, and observations on related research in the literature.
Uploads
Papers by Lauri Holappa