Study On Strengthening And Toughening Heat Treatment Of Laser-arc Hybrid Welding Of High-strength Steel

In this paper,a method of soldering based on laser-arc hybrid welding on 6mm thick high strength steel was put forward.In order to obtain hybrid welded joint with better properties of strength and toughness,a variety of post-weld heat treatment schemes were designed and analyzed the tissue,strength and toughness of no heat treatment and heat treatment.This paper designed two kinds of annealing heat treatment with different process for studying the effect of annealing process on strong change.Results showed that the hardness and strength of the welds are lower than those of the untreated one,but the plasticity is improved.Moreover,annealing can greatly improved the toughness of heat affected zone.Isothermal annealing reduced overall toughness of joint,the two kinds of annealing heat treatment failed to meet the strong purpose.In this paper,two kinds of normalizing heat treatment were designed in order to study the effect of normalizing process on strengthening and toughening.Results showed that the hardness of joint after normalizing is lower than that of the unheated joint,and the distribution is uneven,the strength is high,the plasticity is poor,the toughness is low but the homogeneity is good.Normalizing and high temperature tempering reduced the strength of joint as well as the toughness of weld,but ductility of plasticity and original heat affected zone was improved effectively,and the strengthening and toughening effect of two kinds of normalizing heat treatment was not ideal.For the above shortcomings,this paper designed eleven kinds of tempering heat treatment at different temperatures for studying the effect of tempering process on strengthening and toughening.Experiment results showed that the hardness of joint is high at low temperature,the hardness of the base metal decreases when the temperature is increased to 250?.With the increase of tempering temperature,the toughness of the weld is smaller reduced,and the toughness of the original heat affected zone is first increased and then decreased.After tempering,the hardness is lower than that without heat treatment,but the hardness increases again when the tempering temperature is increased to 450?.The tempering temperature increased the toughness of the weld,which is lower than that of the untreated weld.The toughness of the original heat affected zone is obviously increased and the toughness is better.After the high temperature tempering,the hardness is close to the unheat treatment,the homogeneity is good,and the hardness of the base metal region decreases seriously when it is greater than 600?.With the improvement of tempering temperature,the strength of the joint decreases and the plasticity increases gradually.The toughness of the weld and the original heat-affected zone are better after the high temperature tempering.The results showed that the properties of strength and toughness of the joints are better at 550?,which is attained the ideal state of forced convection.