Mold fluxes

Mold fluxes are routinely used in both continuous casting and bottom pouring of steel. These fluxes are generally calcium silicate based compositions with alkali oxides [(Li, Na, K)20] and fluorides [CaF2, NaF] added as fluidizers. The compositions frequently use fly ash as the base material because it provides a significant concentration of silica in a prefused form easily dissolved as the powder melts on the liquid steel. 

In this paper, recent work on the viscosity of mold flux compositions is reviewed, and a relation to describe the temperature dependence of viscosity is discussed. This relation is based on the Clausius-Clapeyron Equation and was originally developed by Kirchoff and Rankine to describe the temperature dependence of vapor pressure. 

Several recent publications have discussed the effects of compositional variables on the viscosity of oxide melts for use as mold fluxes. Lanyi ( 1) measured the viscosity of several continuous casting fluxes and found that the viscosity correlated well with the combined silica and alumina content of the flux. The fluxes... 

The results indicate that, for mold flux oxide compositions, the viscosity is dependent on the quantity of network forming oxides present, principally silica and alumina. This is demonstrated by the results of McCauley ( ) in Figure 1. In this case, it is the ratio of network forming ions to total anion concentration. However, as shown in Figure 2, the viscosity/reciprocal temperature relationship is not linear and cannot be adequately represented by the Arrhenius Equation over a wide temperature range. 

Such a derivation was originally developed and used by Kirchoff [1858] and Rankine [1849] ( ) to express the temperature dependence of vapor pressure. It was also successfully used by Brostow (O to express the temperature dependence of the isothermal compressibility of a wide variety of organic liquids, some metallic liquids and water. By a similar analogy, we have used it to express the viscosity of liquid mold fluxes. 

The evaluation of the viscosity of mold fluxes has shown that the viscosity is primarily controlled by the concentration of network forming oxides, particularly the silica content. It has also been demonstrated that the temperature dependence of viscosity can be expressed by the relation, nri = Cj + C2/T + C3 nT, derived from the Clausius-Clapeyron Equation. This relation produces a better description of viscosity vs. temperature than the more familiar Arrhenius Equation. 

X. Long et al., Properties of High Basicity Mold Fluxes for Peritectic Steel Slab Casting . Journal of Iron and Steel Research, International, 19(7)(2012),39- 5. 

The CSP mold was vertical type and the 70mm thick. Two steel grades were studied, including LCAK steel and weathering steel, the compositions of which are shown in Table 1. And the mold flux powders used are listed m Table 2. The industrial production data over three months was used and analyzed. 

Table II. Composition and properties of mold fluxes used in the casting ...

Cho, J.W., et al.. Heat Transfer across Mold Flux Film in Mold during Initial Solidification in Continuous Casting of Steel. ISIJ International, 1998. 38(8) p. 834-842. 

Cast and Hand-Molded Refractories. Large shapes such as burner blocks and flux blocks, and intricate shapes such as glass feeder parts saggers are produced by casting sHps, hydraulic cement bonded mixtures, or hand-molding clay or chemically bonded materials. Because these techniques are labor intensive, they are reserved for articles that caimot be satisfactorily formed in any other way, owing to complexity or small production quantities. 

Large and small shapes may be sUp cast from both plastic and nonplastic mixes by the usual techniques. Precise shapes, such as glass feeder parts, are made in this way as well as large flux blocks. The process requkes the formulation of a sUp of suitably stable character to be poured into a plaster mold to be dewatered. After it solidifies, the mold is removed and dried further before firing. 

Table 4 also reports dependence of the mechanical tensile properties of the samples on the processing conditions. The highest tensile properties of sample 1, injection molded with a lower melt temperature and a lower volume flux, are attributed to the highest degree of fibrillation of the TLCP fibers, as shown in Fig. 12, by so-called in situ reinforcement. 

The solder (2% tin-98% lead) was molded into test specimens with a 1.27 cm diameter reduced section. The soldered lap joint specimens were prepared from the tinplate and solder. A solder flux was applied... 

Figure 5 Temperature profile in primary drying of dobutamine HCl-mannitol (1 1), 53 mg solids/mL, 10 mL fill volume. Vials are 5304 molded glass vials (8.3 cm2 cross-sectional area) which are placed in a flat aluminum tray. The heat flux is 42 cal/(cm2 hr), and the chamber pressure is 0.1 torr. (From Ref. 5.)...

Fig. 7.5 The serinyl group NHCH(CH2OH)C(=0) cut from the glycine mold represented by the intersection of its van derWaals 0.001 au isodensity surface with the -C(C=0) or C-surface at the top left and the NH- or N-surface at the bottom center. These are the complementary sides of the amidic zero-flux surface characteristic of a polypeptide. All properties of the residue are defined and make additive contributions to the molecule constructed from it. The residue has a net charge of -0.006 e.

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