Mold powder technology for continuous casting of aluminum-killed steel.

Abstract

Synopsis Mold powder technology for continuous casting of aluminum-killed steel was developed to produce the clean and crack free steel slabs. The following items were investigated: 1) Mass balance of A120~ in the molten powder pool. 2) A1203 absorption capacity o f the molten powder. 3) Uniformization of heat removal through the mold during continuous casting. 4) Change in powder viscosity with absorption of A1203. 5) Design of optimum powder viscosity by consideration of A1203 absorption during continuous casting. The results obtained were as follows: (1) The A1203 content of the molten powder pool increases with the elapse of casting time in accordance with the A1203 absorption capacity of the powder, but after some time, reaches a constant value that matches the A1203 absorption capacity of the powder. (2) The A1203 absorption rate of the molten powder increases as the basicity index B; of the powder increases. (3) The viscosity of the molten powder generally increases with increasing A1203 content. (4) To uniformize heat removal through the mold during casting, it is effective to control the parameter iV over the range of 1.0 to 3.5, where 2 is the viscosity of the molten powder in poise at 1300 °C and V is the casting speed of the machine in m/min. (5) A method for designing the optimum powder viscosity that allows for the absorption of A1203 during casting has been established by the combination of the results mentioned above. (6) Powders designed by the above method have been applied to continuous slab casters to prevent the longitudinal surface cracking of mediumcarbon aluminum-killed steel slabs and to realize the hot direct rolling of unconditioned slabs.

Effect of Substituting CaO with BaO and CaO/Al2O3 Ratio on the Viscosity of CaO–BaO–Al2O3–CaF2–Li2O Mold Flux System

“…Viscosity is one of the most important indexes for evaluating the performance of mold fluxes, as it has a significant effect on the lubrication of casting blanks. In industrial production, the viscosity of mold fluxes at 1300 • C (η) and casting speed (υ) generally meet the correlation η•υ = 1.0-3.5 (Poise m•min −1 ), so as to meet the demands for adequate lubrication and heat transfer [16]. A significant amount of research regarding the effect of Al 2 O 3 on the viscosity of different slag systems has been conducted [17][18][19][20][21][22], while little research has been reported on mold fluxes in the absence of SiO 2 .…”

Fluorine‐Free Mould Powders for Billet Casting – Technological Parameters and Industrial Tests

“…It can be stated as either the V‐ratio (%CaO/%SiO 2 ) or a more complex term like Bi. It was reported that the alumina absorption rate (g cm −2 s −1 ) correlates well with the basicity index Bi10, 11 according to the following expression: …”

“…For the mould powders F‐bearing and F‐free, the alumina absorption rate is expected to be similar because they have similar Bi10, 11; see Table 1.…”

Technologies that have made direct concatenation of continuous casting and hot rolling possible.

“…Use of Uniformly Flowing Powders35- 39) Needless to say, proper selection of a casting powder in accordance with other specific casting conditions for the steel is imperative. Here, the properties required of such a powder are the lubricity between mold and solidified shell, thermal insulation and oxidation prevention of the molten steel, removal by absorption of floating alumina particles, and many others.…”