时间：2013-11-20 10:40　作者：admin　点击： 次

When the temperature drops below the freezing point, the metal changes from a liquid state to a crystalline state. This process is called crystallization or solidification. From the perspective of the internal structure of the metal, the transition of metal atoms from a short-range orderly arrangement to a long-range orderly arrangement occurs. And fixed the changes.
Steel is an iron-based alloy containing C, Si, Mn, P, S and other elements.The solidification of molten steel is actually non-equilibrium crystallization, so the crystallization of molten steel has characteristics different from pure metals.
The crystallization of molten steel is not only related to the temperature supercooling, but also related to the change of the liquid phase composition during crystallization.The selective crystallization phenomenon in the crystallization changes the composition of the liquid phase in the solidification front, causing the melting point of the liquid phase to change, thereby changing the supercooling situation in the solidification front.The crystallization of steel requires two conditions:
(1) A certain degree of supercooling, which is a thermodynamic condition;
(2) The necessary core, this is a dynamic condition.