Research On The Process Of AH36 Ship Steel By Laser Arc Hybrid Welding

AH36 ship steel is a low-alloy high-strength steel.There are problems in the traditional arc welding,such as low welding efficiency,serious pollution,and large welding deformation.Laser-arc hybrid welding is a new type of high-energy beam welding method,which has the characteristics of high welding efficiency,small welding deformation,and lower requirements for assembly accuracy.It is widely used in industrial fields such as ships,aerospace,automobiles and petroleum pipelines.In order to obtain a welding process with good weld formation,good adaptability to working conditions,and good mechanical properties of the joint,this subject carried out a laser-arc hybrid welding process test study of AH36 ship steel.Aiming at the butt joint structure of 5～12mm thick AH36 ship steel,the basic process test of laser-arc hybrid welding was carried out,and the influence of process parameters such as laser power,defocusing amount,filament spacing,current,and welding speed on the weld forming quality was studied.This subject has obtained welding specimens with beautiful double-sided molding,sufficient penetration,and qualified quality.The typical process parameters of typical 7mm thick imposition laser-arc hybrid welding: laser power 7500～8000W,defocusing amount-2～0mm,laser wire pitch 1～3mm,current 240～280A,welding speed1.2～3m/min.Aiming at the problems of joint bevel errors such as uneven gaps and serious unfitness in actual ship welding,the adaptability test of laser-arc hybrid welding conditions is carried out in this paper.The results show that the lower the welding speed,the better the adaptability of the weld gap,when the welding speed is 1.2m/min,the maximum gap of the joint is 1.5mm;the faster the welding speed,the stronger the adaptability to the unfitness of the joint.when the welding speed is 2.4 m/min,the maximum allowable amount of unfitness is 1.9mm,reaching27% of the thickness of the test board.At the same time,the effects of different process parameters on the weld tumor are analyzed,and the characteristics of the weld tumor formation process are analyzed.The analysis and experiments show that the process parameters such as laser power,defocusing amount,and laser wire pitch have a greater impact on the weld tumor.The parameters and their coordination are effective means to suppress the weld tumor.This paper uses a combination of numerical simulation and experimental verification to analyze the effect of preheating on the microstructure and residual stress of the joint.The results show that the unpreheated weld seam causes a typical welded joint due to excessive cooling speed It is composed of a large amount of hardened martensite structure.As the preheating temperature increases,the cooling rate decreases and the martensite content decreases;the higher the preheating temperature,the lower the residual stress value of the weld joint.The mechanical property test of the welded joint shows that,using the best process parameters studied in this paper,the microhardness of the heat affected zone(HAZ)of the welded joint is as follows: the hardness of the weld area is about 340 HV,the microhardness of the MGHAZ is about 235 HV,and the hardness of the FGHAZ is about 345 HV,the hardness of the CGHAZ is about 360 HV,and the hardness of the base metal is about 190 HV.The hardness of the arc action area is lower than that of the laser action area.Preheating before welding can effectively reduce the hardness of the heat affected zone and the weld zone of the welded joint value.The tensile specimens at different preheating temperatures are all broken from the base material,and the tensile strength is between 544.3～556.5MPa;the impact absorption work increases first and then decreases as the preheating temperature increases.When the preheating temperature is 150℃,The impact absorption work of the weld reached a maximum of 86.63 J,and the impact absorption work of the heat-affected zone reached 51.72 J.