A method for flattening the solidification front in directional solidification technology

Abstract

Nonplanar solidification front causes defects in directional solidification process. The transverse temperature gradient, which can be divided into radial temperature gradient and circumferential temperature gradient, is one of the reasons causing the nonplanar solidification front. This paper presents a method by varying the wall thickness of the mould to decrease the circumferential temperature gradient and hence flatten the solidification front. The equations for calculating the wall thickness were deduced by heat transfer analysis. The optimized mould contour was obtained by solving the equations numerically. It was proved by simulation that the circumferential temperature gradient can be almost reduced by 40%. Furthermore, the starting time difference of solidification at one cross section along the circumferential direction almost reduces by half. Additionally, this paper also researches the influences of parameters of the mould and the furnace etc. on the shape of the mould and the circumferential temperature gradient. The circumferential temperature gradient decreases as the thermal conductivity and the emissivity of the mould increase. And the temperature of the cooling ring impacts little on the circumferential temperature gradient. According to the development trend of the blade manufacturing, this method may be applied widely.