METHOD OF CONTROLLING CRYSTALLIZATION AND SEGREGATION PROCESSES IN INGOTS

摘要

FIELD: metallurgy. SUBSTANCE: method may be efficiently used when developing and improving technology of ingot formation under action of weak magnetic field on crystallizing melt. Method consists in that, when imposing constant magnetic field with induction B = (0.5-2.0)x10^-3 Tl on mathematical model derived from paramagnetic properties of crystalline nuclei in two-phase region of "structural diffusion" before crystallization front, nucleus receives magnetic moment influencing velocity of motion and corresponding to indicated induction value. Velocity of motion of nuclei, characterizing by its projection on vertical axis of ingot and linked with crystallization parameters, increases and is determined from equation: v = + V_cz + V_zos where is projection of average velocity of collective motion of "paramagnetic nuclei" in field possessing induction gradient; V_cz velocity of axial convective flow affected by field; V_zos loss of velocity caused by oscillation of magnetization vector in alternating field, equal to zero in constant magnetic field. Crystallization and segregation parameters: growth velocity of nuclei (V_g), overcooling (ΔT), and thickness of enriched layer (δ_ef) are determined from relationships: v = k₁/V_g, ΔT = k₂/, δ_ef = D_l/Vocr, where k₁ and k₂ are coefficients depending on crystallization conditions; D_l coefficient of diffusion in liquid; Voervelocity of hardening in zero field; k_o= C_s/C_l - equilibrium distribution coefficient; C_s and C_l concentration of impurity in solid and liquid phases; V_n and v projections of average velocity on axis of nuclei, respectively, enriched with impurity and solvent. EFFECT: optimized controlling procedure. 14 dwg, 8 tbl