通过对HT250灰铸铁进行激光重熔试验, 研究了不同气氛保护条件下试样重熔区气孔的产生机理。研究结果表明, 在氩气保护条件下, 重熔区中的气孔为析出性气孔;在开放条件下, 重熔区的气孔为析出性气孔和反应性气孔。在相同工艺参数下, 当扫描速度较低时, 开放条件下重熔区的气孔比氩气保护条件下的多; 当扫描速度较高时, 两种气氛保护条件下重熔区的气孔情况基本相同。当激光能量密度较低时, 灰铸铁内部气体的析出是重熔区气孔形成的主要原因。

The mechanisms of pore formation in the remelting zone under different protective atmosphere conditions are investigated by the laser remelting experiments of HT250 gray cast irons. The study results show that the pores in the remelting zone are dissolved pores under the argon shielding atmosphere, and the pores are dissolved pores and reactive pores under the open atmosphere. With the same process parameters, there are more pores in the melting zone under the open atmosphere than those under the argon shielding atmosphere at a low scanning speed, however, at a high scanning speed, the pores are basically the same under these two protective atmosphere conditions. When the laser energy density is relatively low, the main reason of pore formation in the remelting zone is the dissolving out of gasses from the gray cast irons.