Numerical analysis of the competitive influence of Marangoni flow and evaporation on heat surface temperature and molten pool shape in laser surface remelting

摘要

A one-domain mixture continuum model is introduced to simulate numerically solid/liquid phase transformation with a mushy region in laser surface remelting process of a type 304 stainless steel. Emphasis is given to the competitive influence of laser-induced alloying element vaporization and Marangoni flow on the heating surface maximum temperature and its distribution as well as the molten pool shapes. The molten pool shapes and fluid flow, the temperature distribution and its peak values on the heating surface have been computed for six calculation cases corresponding to six different pool-surface heat flux balances. The results show that the Langmuir-type vaporization heat loss due to Fe, Mn, Cr, Ni elements can significantly reduce the heating surface peak temperature and the pool profile, while |partial derivσ/partial derivT|is small or the buoyancy force is considered as one and only driving force. However, when vaporization-type heat loss and Marangoni flow are coexisting, the free surface temperature distribution and its peak value are markedly affected by the magnitude order of surface tension gradient and the nature of the relationship between surface tension temperature coefficient and temperature. When |partial deriv129L?partial derivT| ＞ 3.0 * 10~(-4) N/m K, the influence of Langmuir-type vaporization heat loss is very small and can be ignored.