EFFECT OF EB.BACK-SCANNING DISTANCE ON CONTROLLED REFINEMENT OF WELDED METAL
电子束回扫间距对焊缝金属的可控细化作用

The effect of EB scanning frequency and welding speed on the refinement degree of Al-Mg alloy welded metal and the relationship between the refinement degree and the hardness of welded metal have been investigated respectively by the length of main axid in solidificaion crystal, which is expressed as the standard to evaluate the refinement degree of welded metal.The effect of EB back-scanning distance on controlled refinement of welded metal was analyzed with the introduced conception of EB back-scanning distance.It is found that the value of back-scanning distance determines the controlled refinement degree of welded metal.When optical back-scanning distance is 0.04 mm,the solidification structures change into fine exqiaxial grains from large columnar.Compared with non-scanning welding, the refinement degree of welded metal raises 5 times, and the hardness of welded metal increases 80%, which is close to the hardness of Al-Mg alloy base metal.