.30 Crmnsia Steel Laser Welding Stomatal Causes And Control

30CrMnSiA steel is a representative medium carbon hardened and tempered steel and becoming widely used in aviation and national defense industries.Porosity is apt to occur when welding 30CrMnSiA steel,brings on bad influence to the mechanical property of the welding joint,even affects the reliability of the product.It is of important theoretical and engineering significance to comprehend the mechanism of the blow holes,control the formation and improve the quality of the joint.In this article,the reasons of blow hole were investigated in the process of laser beam welding 30CrMnSiA steel,proved up the relation between welding parameters and porosity ratio and mastered the methods to control the formation.The results of this research assure the mechanical property of the welding joint.Through pulse laser beam welding experiments,metallographic analysis and energy spectrum analysis,the results indicate that in the process of the laser beam welding 30CrMnSiA steel,the unsteadiness of the keyhole brings air bubbles.Especially the technological parameters that do not match the fluctuation of the keyhole will induce the blow holes.The blow holes usually appear in the bottom of the welding seam belong to CO pore. The percentage composition of carbon increase obviously on the wall of the blow holes, because of the liquation of the liquid steel around the blow hole.It induce porosity formation tendency during laser welding 30CrMnSiA steel.The temperature field of the laser welding was simulated with MARC.Compared the heat cycle curves measured and metallographic photos,the simulated result was consistent with the actual temperature field.With the simulated temperature field,the molten pool shape and freezing time were compared under different levels of power and speed.And then the influences of power and speed on blow hole were analyzed.The results show that the depth-to-width ratio increases with the rise of power,while the freezing time of molten pool falls when the speed increased.Since the air bubbles escape difficultly,there are more blow holes appearing.Influence of welding parameters on porosity ratio and fusion penetration,and its mechanism were investigated through orthogonal test experiments.With the suitable welding parameters,pulse modulated 88Hz,power 1170W,speed 400mm/min,duty ratio 50%and focus under the work piece 0.5mm,it was effective to control the blow holes,as that the porosity ratio was only 0.05 percent.The mechanism and the controlling methods of the blow hole were mastered though this research.Consequently,the results supply greatly valuable reference basis and significance for the similar production.