Influence of slag chemistry on the hydration of alkali-activated blast-furnace slag — Part I: Effect of MgO

Transient liquid phase (TLP) bonding is a relatively new bonding process that joins materials using an interlayer. On heating, the interlayer melts and the interlayer element (or a constituent of an alloy interlayer) diffuses into the substrate materials, causing isothermal solidification. The result of this process is a bond that has a higher melting point than the bonding temperature. This bonding process has found many applications, most notably the joining and repair of Ni-based superalloy components. This article reviews important aspects of TLP bonding, such as kinetics of the process, experimental details (bonding time, interlayer thickness and format, and optimal bonding temperature), and advantages and disadvantages of the process. A wide range of materials that TLP bonding has been applied to is also presented. Partial transient liquid phase (PTLP) bonding is a variant of TLP bonding that is typically used to join ceramics. PTLP bonding requires an interlayer composed of multiple layers; the most common bond setup consists of a thick refractory core sandwiched by thin, lower-melting layers on each side. This article explains how the experimental details and bonding kinetics of PTLP bonding differ from TLP bonding. Also, a range of materials that have been joined by PTLP bonding is presented.

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Overview of transient liquid phase and partial transient liquid phase bonding

Penetration and dissolution mechanisms are reviewed for predominantly single phase oxide, two phase oxide, and oxide–carbon composite refractories by liquid silicates. Theoretical models of these processes, as well as static (sessile drop, dipping, and crucible) and dynamic (rotating finger and rotary slag) experimental tests, along with their practical limitations are considered. Direct (congruent or homogeneous) attack involves dissolution of a solid into a liquid with no intermediate solid phase leading to active corrosion. Indirect (incongruent or heterogeneous) attack leads to formation of one or more new solid phases at the original solid/liquid interface. This may lead to passive corrosion. Examples of direct and indirect attack in a range of refractory–liquid systems are described highlighting the critical influence of the composition and hence viscosity of the local liquid adjacent to the solid. Penetration and corrosion can be controlled either through the local liquid composition via th...

Melt corrosion of oxide and oxide–carbon refractories

The extant data for the physical properties of BOS slags and for slag systems relevant to BOS have been collated and evaluated. Data for the following physical properties have been reviewed: phase equilibria, viscosities, densities, electrical conductivities, thermal conductivities, and the surface and interfacial tension between the metal and slag. In addition, various mathematical models have been developed for the estimation of the liquidus temperature, density, viscosity, surface tension, heat capacity, and enthalpy of slags. The efficacies of these different models have been evaluated and their reliability in predicting physical property for molten BOS slags has been assessed.

Physical properties of bos slags

Significant quantities of wastes are generated as the waste materials or byproducts every day from stainless steel processes. According to the origins and characteristics, the stainless steel wastes can be mainly classified into two categories, slags and dusts. They usually contained considerable quantities of valuable metals and materials. This paper summarized and analyzed the generation, composition, characteristics and the leaching behaviors of the most of wastes obtained from the stainless steel processes. On this basis, a review of several methods for treating the various stainless steel wastes was made. It is very essential not only for recycling the valuable metals and mineral resources but also for protecting the environment.

An overview for the utilization of wastes from stainless steel industries

The effect of MgO, TiO2, or Fe2O3 on the viscosity of 40CaO-40SiO2-20Al2O3 (mass pct) slags has been measured by the rotating crucible viscometer. Viscosity of these quaternary slags decreased with an increase in the content of additive oxide. At the same content of additive oxide, the viscosity decreases from MgO, TiO2 to Fe2O3. In addition, the effect of SiO2 or Al2O3 on the viscosity of 26.1CaO-73.9Fe2O3 (mass pct) (CF) and 14.9CaO-85.1Fe2O3 (mass pct) (CF2) slags has been measured. Viscosity of calcium ferrite slags increased with increasing SiO2 or Al2O3 content. Al2O3 was found to be more effective for increasing the viscosity at the same content of the additive oxide.

Viscosity of blast furnace type slags

The effects of revolution speed, temperature and slag composition on the dissolution rate of sintered alumina into molten CaO-SiO2-Al2O3 slags were examined by the rotating cylinder method. The slags used had 10% Al2O3 and CaO/SiO2 ratios of 0.64 to 1.25.The dissolution rate of alumina into CaO-SiO2-Al2O3 slags increased with increasing revolution speed and rising temperture. It was concluded from these results that the dissolution rate was controlled by mass transport in the slag boundary layer. The dissolution rate of alumina also increased with increasing CaO/SiO2 and an abrupt increase was observed in the vicinity of CaO/SiO2=1.The addition of 15% NaF or CaF2 to slags with CaO/SiO2 ratio of 0.80 to 1.25 increased the dissolution rate by a factor of 2 to 6 compared with those of CaO-SiO2-Al2O3 slags. Such an increase of the dissolution rate is estimated to be caused mainly by the increase of mass transport coefficient.The penetration of slag components, CaO and SiO2, into an alumina cylinder was observed in all experiments. Besides, CaO·6Al2O3 compound was formed in the slag penetration layer for CaO-SiO2-Al2O3 slags with CaO/SiO2≥1.

Kinetic Behavior of Dissolution of Sintered Alumina into CaO-SiO2-Al2O3 Slags.

Interfacial properties and adsorption behavior play an important role in the progress of heterogeneous reactions, so accurate values of these properties are required as the basic knowldge to examine the interfacial phenomena in iron- and steel-making processes. In this review, data for surface tension of liquid iron alloys and liquid slags, contact angle between solid and liquid phases, and interfacial tension between liquid and liquid phases, are briefly summarized on the basis of currently published articles.

Interfacial Properties of Liquid Iron Alloys and Liquid Slags Relating to Iron- and Steel-making Processes.

The rate of dissolu tion of solid lime in to liquid slag was determinedfrom the decrease of diameter of the lime cylillder rotated ill CaOSiO.-AI ,0 3 or FcOCa OSi02 slag. T he j)enetration of the slag to the solid phase and the distribution of componellts in liquid slag alijacent into the solidliquid inter.face were examined by the E. P.M.A. technique. The rate of dissolution increased with temperatllre and with rotating s/)eed of Ihe ~ylinder, sllptJorling the assumption that the diffilsioll of calcizlln through a slag phase boulldary layer would be the rate-determining step . The dissolution rate into the slag containing FeO was several times greater than thai into slag without FeO , because q{ the differences ill /)hysi cal /)roperties of slag and ill the morphology of 2CaO · Si02 formation . S lag componellts jJellelrated into solid lime Wire maillly AI, O , and FeO, alld the SiO, content was very little . This can be inter/lTeled by the formation of AI , O \" or FeO rich slag layer betweell solid lime alld 2CaO· SiO ,jilm.

A Fundamental Study on the Dissolution Rate of Solid Lime into Liquid Slag

Cylinders of burnt dolomite with the apparent porosities of 20 to 35% were immersed into molten FetO-CaO-SiO2 slags at temperatures of 1350 to 1425°C and rotated at 100 to 400rpm. The dissolution rates were determined by measuring the decrease in radius of cylinder.The dissolution rate increased with increases in temperature and revolutional speed of cylinder, but was not affected by the difference in apparent porosity of burnt dolomite. From the analysis of experimental results, it was concluded that the dissolution rate was controlled by the mass transport of CaO in burnt dolomite for low FetO slag (slag A) and that of MgO for other slags in the boundary layer of molten slag. Mass transport coefficients calculated were in the range of 4.7×10-4 to 1.7×10-3cm/s at 1400°C.It was found that the burnt dolomite after the experiment was widely covered with (Fe, Mg) O solid solution in the case of high FetO slag.

https://www.jstage.jst.go.jp/article/isijinternational1966/24/7/24_7_532/_pdf

Katsumi Mori

Papers

Viscosity of blast furnace type slags

Kinetic Behavior of Dissolution of Sintered Alumina into CaO-SiO2-Al2O3 Slags.

Interfacial Properties of Liquid Iron Alloys and Liquid Slags Relating to Iron- and Steel-making Processes.

A Fundamental Study on the Dissolution Rate of Solid Lime into Liquid Slag

Dissolution rate of burnt dolomite in molten FetO-CaO-SiO2 slags.