TANG Ping
,
XU Chushao
,
WEN Guanghua
,
ZHAO Yanhong
,
QI Xin
钢铁研究学报(英文版)
An experimental apparatus for simulating copper mold is used to quantify the heat flux through the slag film and to obtain a solid slag for further determining its crystallization behavior. The result indicates that both the chemical composition of the mold powder and the cooling rate have an important influence on the heat flux through the slag film. With increasing the binary basicity, the heat flux of slag film decreases at first, reaches the minimum at the basicity of 14, and then increases, indicating that the maximum binary basicity is about 14 for selecting “mild cooling” mold powder. The heat transfer through the slag film can be specified in terms of the crystalline ratio and the thickness of the slag film. Recrystallization of the solid slag occurs and must be considered as an important factor that may influence the heat transfer through the solid slag layer.
关键词:
continuous casting;mold powder;slag film;heat flux;crystallization
YU Xiong
,
WEN Guanghua
,
TANG Ping
,
MA Fanjun
,
WANG Huan
钢铁研究学报(英文版)
Because of the addition of significant quantities of Al and Mn, the great challenge of casting 20Mn23Al non-magnetic steel is to design a mold slag that is chemically compatible with this steel chemistry. In this paper, a new mold slag with low melting point, low basicity was proposed. The initial slag (the base mold slag) and two corresponding spent mold slag (8min slag and 15min slag), which was sampled from the caster after 8 minutes and 15minutes of casting, were investigated, the changes of mold slag composition and properties of molten slag were discussed. The results showed that:(i) The slag quickly changed in chemistry to a slag that contained a low quantity of silica and a higher quantity of alumina, and the basicity increased obviously; (ii) Heat flux density through the slag film decreased appreciably with the time increase; (iii) Mold slag used for non-magnetic steel precipitated CaF2 crystals; (iv) The slab has good surface quality with not occurrences of longitudinal face cracks and slag inclusions; (v) The Al2O3 content in the molten slag pool increased with time, and Al2O3 concentration of the pool can be regarded as being in a practically equilibrium state after about 600sec.
关键词:
Non-magnetic steel;Continuous casting;Mold slag;Viscosity;CaF2
XU Hailun
,
WEN Guanghua
,
SUN Wei
,
et al
钢铁研究学报(英文版)
Finite element models of steady heat conduction in the meniscus region of beam blank mold were developed by using ABAQUS software. The effect of mold grinding thickness, cooling water velocity, diameter of restrictor rods and water channel design on hot face temperature was analyzed in detail. Attention was focus on the peak temperature and temperature uniformity along hot face. The results showed that the peak temperature of existing mold, about 337.2 oC, is located in the fillet, and two valleys of hot face temperature are found in flange corner and junction of wide face and narrow face, respectively. Decreasing mold thickness, increasing cooling water velocity and increasing diameter of restrictor rods can all reduce peak temperature and improve temperature uniformity along hot race at the expense of lower overall temperature. Redesigning the water channel can decrease peak temperature and thermal gradient of mold without lowering overall temperature of hot face. In particular, the small hole design can improve temperature uniformity across hot face to the best advantage.
关键词:
beam blank;continuous casting mold;thermal behavior;temperature distribution
WEN Guanghua
,
LIU Hui
,
TANG Ping
钢铁研究学报(英文版)
The isothermal and nonisothermal experiments were performed to construct the continuous cooling transformation (CCT) and temperature time transformation (TTT) diagrams of four industrial mold fluxes through visual observations in an experimental apparatus based on the single hot thermocouple technique (SHTT). The results of the CCT diagrams indicate that ① the crystallization temperature of mold fluxes lowers as the cooling rate increases, ② the mold fluxes have larger critical cooling rate, higher crystallization temperature, and less onset time of crystallization when the basicity increases or the viscosity decreases, ③ the influences of the melting points of the mold fluxes on their crystallization tendency are not significant. Isothermal tests show that the onset time of crystallization decreases at first, and then increases, and finally represents a “C” shape with increasing isothermal temperature. The TTT diagrams of four industrial mold fluxes were divided into two separate “C” shape regions. The crystal phase of C20A selected was analyzed by Xray diffraction, which is cuspidine (Ca4Si2O7F2) over 1 100 ℃ and calcium silicon oxide fluoride (Ca2SiO2F2) below 1 100 ℃. When compared with the TTT diagram, the CCT diagram can provide a more realistic estimate of the critical cooling rate of the mold fluxes. Thus, both the CCT and TTT diagrams can unambiguously describe the crystallization phenomena of the mold fluxes.
关键词:
mold flux;CCT;TTT;critical cooling rate;crystallization
