Study On Non-penetrating Welding Technology Of Dual Beam Laser For 304 Stainless Steel

Dual beam laser welding can increase the keyhole area and stabilize the keyhole to reduce or even eliminate the porosity,in some complex shape,non-penetrating laser welding has a wide range of applications in some welding seam of complex shape,difficult clean and precise forming.In this paper,against the keyhole-induced porosity of stainless steel non-penetrating laser welding,the pores are eliminated by the method of double beam welding including spot distance,spot diameter and energy distribution three process parameters,and also get the influence on weld quality with the three process parameters.When change the spot distance,it is found that when the spot spacing is 0.6mm and 0.8mm,there is no pores in the weld seam.For one thing,the two beams form a common larger keyhole,which increases the area of keyhole and pool,thereby stabilizing the keyhole,reducing the bubbles generated by the collapse of the keyhole,reducing the appearance of the pores,and for another thing,the cooling time of the welding pool also increases,which can help the porosity better escape even if the bubbles form in the welding pool.Also in the two sets of spot distance,the weld shape is nail shape,which is more able to support the two beams to form a common keyhole,so the weld seam appear nail sharp because the upper part of the weld seam is wide and the lower part of the weld seam is narrow.When changing the diameter of the spot,it can be found that the litter spot diameter produces dense porosity even in the condition that the two laser beam form a common larger keyhole,when the spot diameter is further increases,there has none pores at the distance 0.6mm and 0.8mm,there are pores at the distance 1.0mm,in the large spot diameter distance,there all are no porosity at the distance of 0.6mm,0.8mm and 1.0mm,which indicates that the stability of the keyhole requires the proper keyhole size.When the common keyhole area formed by the two beams is too small,the common keyhole is still equivalent to a single keyhole during the welding process.It is easy to collapse to form air bubbles and form pores.After the diameter exceeds a certain threshold,the larger the corresponding keyhole area is,the greater the range of the pitch range of the stabilized keyhole is,the more adaptable the process is to obtain the double beam welding without no porosity.When changing the energy distribution,it can be found that the spatter is severe and the weld produces a greater number of pores when the energy ratio is extremely uneven,and then there is weaken splash and a small number of chain porosity when the energy proportion is further homogenization,finally the weld seam is no splash and none pores in the energy ratio of 50%-50%.It shows that in the process of double beam welding,the more average the energy distribution ratio,the more stable the two-beam welding process,the less the porosity or even disappear.In conclusion,there is some correlation between the weld quality and keyhole stability,keyhole opening area changes directly determine the stability of the keyhole.On the one hand,the stability of the keyhole requires a certain spot diameter,so that the keyhole in the welding process is in a stable state,on the other hand by changing the spot spacing,spot diameter,energy distribution of the three core process parameters,it was found that when the variance of keyhole opening area is less than 0.5%,there is no pore in the weld;when the variance of the keyhole opening area is between 0.5% and 1.0%,the weld produces fewer porosity;when the variance of the keyhole opening area is greater than 1.0%,there is a large number of chain pores in the weld.