【作者】 高健；

【导师】 王克鸿；

【作者基本信息】 南京理工大学 ， 材料工程（专业学位）， 2020， 硕士

【摘要】 AH36船舶钢属于低合金高强钢,传统弧焊在焊接时,存在焊接效率低、污染严重、焊接变形大等问题。激光-电弧复合焊是一种新型的高能束流焊接方法,具有焊接效率高、焊接变形小、对装配精度要求低等特点,被广泛的应用于船舶、航空航天、汽车及石油管道等工业领域。为了获得焊缝成形好、工况适应性强、接头力学性能好的焊接工艺,本课题开展了AH36船舶钢激光-电弧复合焊接工艺试验研究。针对5～12mm厚AH36船舶钢拼焊结构,开展了激光-电弧复合焊基础工艺试验,研究了激光功率、离焦量、光丝间距、电流、焊接速度等工艺参数对焊缝成形质量的影响规律,获得了双面成形美观、熔透充分、质量合格的焊接试件,典型的7mm厚拼板激光-电弧复合焊接最佳工艺参数范围:激光功率7500～8000W、离焦量-2～0mm、光丝间距1～3mm、电流240～280A、焊接速度1.2～3m/min。针对实际船体焊接中存在的间隙不均、错边严重等接头坡口误差问题,本文进行了激光-电弧复合焊工况适应性试验,结果表明:焊接速度越低对焊缝间隙的适应能力越强,焊接速度1.2 m/min,允许接头最大间隙为1.5mm;焊接速度越快对接头错边的适应能力越强,在焊接速度为2.4 m/min时,允许的最大错边量为1.9mm,达到了试板厚度的27%。同时,分析了不同工艺参数对焊瘤的影响,并分析了焊瘤形成的特征,激光功率、离焦量、光丝间距等工艺参数对焊瘤影响较大,合理的工艺参数及其配合是抑制焊瘤的有效手段。本文采用了数值模拟和试验验证结合的方法,分析研究了焊前预热对接头微观组织和残余应力的影响规律,结果表明:未预热的焊缝由于冷却速度过快,导致典型的焊接接头由大量的淬硬马氏体组织构成,随着预热温度的提高,冷却速度降低,马氏体含量降低;预热温度越高,焊缝接头的残余应力值越低。焊缝接头力学性能测试表明,采用本文研究的最佳工艺参数,焊缝接头热影响区(HAZ)显微硬度如下:焊缝区约为340HV、粗晶区硬度约为360HV、细晶区约为345HV、混晶区约为235HV、母材约为190HV,焊前预热能有效降低焊接接头热影响区和焊缝区的硬度值,预热温度越高、焊缝接头各区域硬度值均有下降;不同预热温度下的拉伸试样均断裂于母材,拉伸强度在544.3～556.5MPa之间;冲击吸收功随预热温度的升高先增大再减小,预热温度为150℃时,焊缝区的冲击吸收功达到最大值86.63J,热影响区的冲击吸收功达到了51.72J。更多还原

【Abstract】 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.更多还原