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

A one-domain mixture continuum model is introduced to simulate numerically solid/liquid phase transformation with a mushy region in laser surface reme lting process of a type 304 stainless steel. Emphasis is given to the compe titive influence of laser-induced alloying element vaporization and Marango ni 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 be en computed for six calculation cases corresponding to six different pool-s urface heat flux balances. The results show that the Langmuir-type vaporiza tion heat loss due to Fe, Mn, Cr, Ni elements can significantly reduce the heating surface peak temperature and the pool profile, while /partial deriv ative sigma/partial derivativeT/ is small or the buoyancy force is consider ed as one and only driving force. However, when vaporization-type heat loss and Marangoni flow are coexisting, the free surface temperature distributi on and its peak value are markedly affected by the magnitude order of surfa ce tension gradient and the nature of the relationship between surface tens ion temperature coefficient and temperature. When /partial derivative sigma /partial derivativeT/ > 3.0 x 10(-4) N/m K, the influence of Langmuir-type vaporization heat loss is very small and can be ignored. (C) 2001 Elsevier Science B.V. All rights reserved.